Tài liệu lập trình C++ Tiếng Việt

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Hc C++ c bn v nng cao ............................................................................................... 9
i vi c gi ...................................................................................................................... 9
iu kin tin ................................................................................................................... 9
Tng quan v C++................................................................................................................ 9
Lp trnh hng i tng.............................................................................................. 10
Th vic chun C++ (C++ Standard Library) .................................................................. 10
ANSI Standard................................................................................................................ 10
Hc tp C++ nh th no? ............................................................................................. 10
Min s dng ca C++ ................................................................................................... 11
Ci t mi trng C++ ...................................................................................................... 11
Ci t mi trng ni b cho C++ ................................................................................. 11
Text Editor ...................................................................................................................... 11
C++ Compiler: ................................................................................................................ 11
Ci t GNU C/C++ Compiler......................................................................................... 12
Ci t trn UNIX/Linux .................................................................................................. 12
Ci t trn Mac OS X .................................................................................................... 12
Ci t trn Windows...................................................................................................... 12
C php C++ c bn .......................................................................................................... 13
Cu trc chng trnh C++ ............................................................................................. 13
Bin dch v thc thi chng trnh C++........................................................................... 14
Du chm phy v khi (block) trong C++ ...................................................................... 15
nh danh (Identifier) trong C++ ...................................................................................... 16
T kha trong C++ ......................................................................................................... 16
Trigraph trong C++.......................................................................................................... 17
Khong trng (Whitespace) trong C++............................................................................ 18
Comment trong C++........................................................................................................... 19
Kiu d liu trong C++ ........................................................................................................ 20
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http://vietjack.com/cplusplus/index.jsp
Kiu d liu nguyn thy trong C++................................................................................ 20

Khai bo typedef trong C++ ............................................................................................ 23
Kiu lit k enum trong C++............................................................................................ 24
Kiu bin trong C++ ............................................................................................................ 24
nh ngha bin trong C++ .............................................................................................. 25
Khai bo bin trong C++ ................................................................................................. 26
V d ............................................................................................................................... 27
Lvalue v Rvalue trong C++............................................................................................ 28
Phm vi bin trong C++ ...................................................................................................... 29
Bin cc b trong C++ .................................................................................................... 29
Bin ton cc trong C++ ................................................................................................. 30
Khi to bin cc b v bin ton cc trong C++ ............................................................ 31
Hng (Constant/Literal) trong C++ ...................................................................................... 32
Hng s nguyn trong C++............................................................................................. 32
Hng s thc trong C++ ................................................................................................. 33
Boolean literal trong C++................................................................................................. 33
Hng k t trong C++ ..................................................................................................... 34
Hng chui trong C++..................................................................................................... 35
nh ngha hng trong C++............................................................................................. 36
S dng b tin x l #define trong C++......................................................................... 36
S dng t kha const trong C++................................................................................... 37
Modifier trong C++ .............................................................................................................. 37
Qualifier trong C++.......................................................................................................... 39
Lp lu tr (Storage Class) trong C++................................................................................ 39
Lp lu tr auto trong C++ ............................................................................................. 40
Lp lu tr register trong C++......................................................................................... 40
Lp lu tr static trong C++ ............................................................................................ 41
Lp lu tr extern trong C++ .......................................................................................... 42
Lp lu tr mutable trong C++ ....................................................................................... 43
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Ton t trong C++ .............................................................................................................. 43

Ton t s hc trong C++ ............................................................................................... 44
Ton t quan h trong C++ ............................................................................................ 45
Ton t logic trong C++ .................................................................................................. 45
Ton t so snh bit trong C++ ........................................................................................ 46
Ton t gn trong C++ ................................................................................................... 49
Cc ton t hn hp trong C++ ...................................................................................... 51
Th t u tin ton t trong C++ .................................................................................... 52
Vng lp trong C++............................................................................................................. 53
Cc lnh iu khin vng lp trong C++.......................................................................... 55
Vng lp v hn trong C++ ............................................................................................. 55
iu khin lung trong C++ ................................................................................................ 56
Ton t iu kin ? : trong C++....................................................................................... 57
Hm trong C++................................................................................................................... 57
nh ngha mt hm trong C++....................................................................................... 58
V d ............................................................................................................................... 59
Khai bo hm trong C++................................................................................................. 59
Gi hm trong C++ ......................................................................................................... 60
Tham s ca hm trong C++: ......................................................................................... 61
Gi tr mc nh cho cc tham s trong C++.................................................................... 62
Number trong C++.............................................................................................................. 63
nh ngha Number trong C++........................................................................................ 63
Hm ton hc trong C++ ................................................................................................ 65
S ngu nhin (Random Number) trong C++ ................................................................. 67
Mng (Array) trong C++ ...................................................................................................... 68
Khai bo mng trong C++............................................................................................... 69
Khi to mng trong C++ ............................................................................................... 69
Truy cp cc phn t mng trong C++ ........................................................................... 70
Chi tit v mng trong C++ ............................................................................................. 71
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Chui (String) trong C++ ..................................................................................................... 72

Chui theo phong cch C ............................................................................................... 72
Lp String trong C++ ...................................................................................................... 75
Con tr trong C++ ............................................................................................................... 76
Con tr l g? .................................................................................................................. 77
Cch s dng con tr trong C++..................................................................................... 78
Chi tit v con tr trong C++............................................................................................ 79
Tham chiu trong C++ ........................................................................................................ 79
Tham chiu v con tr trong C++.................................................................................... 80
To tham chiu trong C++ .............................................................................................. 80
Date v Time trong C++...................................................................................................... 82
Date v Time hin ti trong C++...................................................................................... 84
nh dng Time bi s dng cu trc tm trong C++ ....................................................... 85
Input/Output trong C++ ....................................................................................................... 86
Header file cho I/O trong C++.......................................................................................... 86
Standard Output Stream (cout) trong C++ ...................................................................... 87
Standard Input Stream (cin) trong C++............................................................................ 87
Standard Error Stream (cerr) trong C++ .......................................................................... 88
Standard Log Stream (clog) trong C++ ........................................................................... 89
Cu trc d liu trong C++.................................................................................................. 90
nh ngha mt cu trc trong C++ ................................................................................. 90
Truy cp cc thnh vin ca cu trc trong C++ ............................................................. 91
Cu trc nh l tham s hm trong C++ ......................................................................... 93
Con tr ti cu trc trong C++ ......................................................................................... 94
T kha typedef trong C++ ............................................................................................. 97
Lp v i tng trong C++............................................................................................... 97
nh ngha Lp trong C++ .............................................................................................. 98
nh ngha i tng trong C++..................................................................................... 98
Truy cp cc thnh vin d liu trong C++...................................................................... 99
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Chi tit v Lp & i tng trong C++ .......................................................................... 100

Tnh k tha trong C++..................................................................................................... 101
Lp c s (Base Class) v Lp tha k (Derived Class) trong C++ ............................. 102
iu khin truy cp v Tnh k tha trong C++ ............................................................. 103
Kiu k tha trong C++................................................................................................. 104
a k tha trong C++ ................................................................................................... 105
Np chng ton t v Np chng hm trong C++ ............................................................ 107
Np chng hm trong C++ ........................................................................................... 107
Np chng ton t trong C++ ....................................................................................... 109
Ton t c th np chng v khng th np chng trong C++...................................... 112
V d v Np chng ton t trong C++.......................................................................... 112
a hnh trong C++ ............................................................................................................ 113
Hm virtual trong C++ ................................................................................................... 116
Hm pure virtual trong C++ ........................................................................................... 116
Tru tng ha d liu trong C++.................................................................................... 117
Nhn truy cp (Access Label) trong C++....................................................................... 118
Li ch ca Tru tng ha d liu trong C++.............................................................. 119
V d v Tru tng ha d liu trong C++ .................................................................. 119
Chin lc thit k trong C++ ....................................................................................... 120
Tnh ng gi d liu trong C++........................................................................................ 121
V d v ng gi d liu trong C++ ............................................................................. 122
Interface trong C++ (Lp tru tng)................................................................................ 123
V d v Lp tru tng trong C++............................................................................... 124
File v Stream trong C++ .................................................................................................. 127
M mt File trong C++.................................................................................................. 128
ng mt File trong C++............................................................................................... 129
Vit ti mt File trong C++............................................................................................. 129
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c mt File trong C++ ................................................................................................. 129

V d v c v Vit file trong C++................................................................................ 129
Con tr v tr File trong C++............................................................................................ 131
X l ngoi l (Exception Handling) trong C++.................................................................. 132
Nm Exception trong C++ ............................................................................................ 133
Bt Exception trong C++ ............................................................................................... 134
Standard Exception trong C++...................................................................................... 135
nh ngha Exception mi trong C++ ............................................................................ 137
B nh ng trong C++ .................................................................................................... 139
Ton t new v delete trong C++.................................................................................. 139
Cp pht b nh ng cho Mng trong C++................................................................. 141
Cp pht b nh ng cho i tng trong C++.......................................................... 141
Namespace trong C++ ..................................................................................................... 142
nh ngha mt Namespace trong C++ ........................................................................ 143
using namespace directive trong C++ ........................................................................... 144
Namespace khng k nhau trong C++ ......................................................................... 146
Namespace lng nhau trong C++ ................................................................................. 146
Template trong C++.......................................................................................................... 148
Function Template trong C++ ....................................................................................... 148
Class Template trong C++ ............................................................................................ 150
B tin x l (Preprocessor) trong C++ ............................................................................. 152
B tin x l # define trong C++ .................................................................................... 153
Function-Like Macro trong C++..................................................................................... 154
Bin dch c iu kin trong C++................................................................................... 155
Cc ton t # v ## trong C++...................................................................................... 156
Macro tin nh ngha trong C++ ................................................................................... 158
X l tn hiu (Signal Handling) trong C++......................................................................... 159
Hm signal() trong C++................................................................................................. 160
Hm raise() trong C++ .................................................................................................. 161
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a lung (Multithread) trong C++ ...................................................................................... 163

To Thread trong C++ .................................................................................................. 163
Kt thuc Thread trong C++.......................................................................................... 164
V d ............................................................................................................................. 165
Truyn tham s ti Thread trong C++ ........................................................................... 166
Kt hp v Tho g cc Thread trong C++ .................................................................. 168
Lp trnh Web trong C++ .................................................................................................. 171
CGI l g?...................................................................................................................... 171
Web Browsing .............................................................................................................. 171
S cu trc CGI ....................................................................................................... 172
Cu hnh Web Server ................................................................................................... 172
Chng trnh CGI u tin ........................................................................................... 173
Hello World! This is my first CGI program...................................................................... 174
HTTP Header ............................................................................................................... 174
Bin mi trng ca CGI.............................................................................................. 175
Th vin CGI trong C++ ............................................................................................... 178
Phng thc POST v GET ........................................................................................ 178
Truyn thng tin bi s dng phng thc GET .......................................................... 178
V d URL n gin s dng phng thc GET.......................................................... 179
V d v FORM bi s dng phng thc GET........................................................... 181
Truyn thng tin bi s dng phng thc POST ....................................................... 181
Truyn Checkbox Data ti CGI Program ...................................................................... 182
Truyn Radiobutton Data ti CGI Program ................................................................... 184
Truyn Text Area Data ti CGI Program....................................................................... 186
Truyn DropDown Box Data ti CGI Program.............................................................. 187
S dng Cookie trong CGI ........................................................................................... 189
Cch n lm vic .......................................................................................................... 189
Thit lp Cookie ............................................................................................................ 190
Thu hi Cookie.............................................................................................................. 191
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V d v File Upload...................................................................................................... 193

Th vin Template chun (STL) trong C++ ...................................................................... 195
Th vin chun C++ (C++ Standard Library) .................................................................... 198
Th vin hm chun trong C++ (Standard Function Library)......................................... 198
Th vin lp hng i tng trong C++ (Object Oriented Class Library).................... 198
Ti liu tham kho C++..................................................................................................... 199
Link hu ch v C++...................................................................................................... 199
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Hc C++ c bn v nng cao

C++ l ngn ng lp trnh bc trung (middle-level), c pht trin bi Bjarne Stroustrup nm 1979
ti Bell Labs. C++ chy trn cc nn tng a dng, nh Windows, Mac OS, v cc phin bn Unix
a dng.
Bi hng dn ny s cung cp chi tit khi nim v C++ t c bn ti nng cao, km theo cc v
d thc hnh trc tuyn a dng gip bn thch th bi hc v hiu su hn cc khi nim
c cp.
Lot bi hng dn ca chng ti da trn ngun ti liu ca: Tutorialspoint
i vi c gi
Lot bi hng dn v C++ c chun b cho ngi mi hc, gip h hiu cc khi nim C++ t
c bn ti nng cao.
iu kin tin
Trc khi bt u hc theo lot bi ny v thc hnh vi cc v d v C++ a dng, mnh gi s
rng bn bit khi nim v mt chng trnh my tnh l g v th no l mt ngn ng lp trnh
my tnh.
Tng quan v C++

C++ l mt ngn ng lp trnh kiu tnh, mc ch tng qut, phn bit kiu ch m h tr lp trnh
hng i tng, lp trnh th tc.
C++ c coi nh l ngn ng bc trung (middle-level), khi n kt hp cc c im v tnh
nng ca ngn ng bc cao v bc thp.
C++ c pht trin bi Bjarne Stroustrup nm 1979 ti Bell Labs Murray Hill, New Jersey, nh
l mt bn nng cao ca ngn ng C v vi tn gi u tin l C vi cc Lp, nhng sau
c i tn thnh C++ vo nm 1983.
C++ l mt Superset ca C, v bt k chng trnh C no cng l mt chng trnh C++.
Ghi ch: Khi ni mt ngn ng lp trnh l kiu tnh khi vic kim tra kiu c thc hin trong
thi gian bin dch (compile-time), ch khng phi l run-time.
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Lp trnh hng i tng

C++ h tr y lp trnh hng i tng, bao gm 4 tnh nng tr ct ca lp trnh hng i
tng l:
Tnh bao ng (Encapsulation)
n d liu (Data hiding)
Tnh k tha (Inheritance)
Tnh a hnh (Polymorphism)
Th vic chun C++ (C++ Standard Library)

C++ chun gm 3 phn quan trng:
Core Language cung cp tt c cc khi bao gm bin, kiu d liu (data type) v literals,
Th vin chun C++ (C++ Standard Library) cung cp tp hp hm a dng thao tc file,
string,
Standard Template Library (STL) cung cp tp hp phng thc a dng thao tc cu

trc d liu,
ANSI Standard
ANSI Standard bo m rng C++ l portable, ngha l: code bn vit cho compiler ca Microsoft
s c bin dch m khng xy ra li khi s dng mt compiler trn Mac, UNIX, v Windows box
hoc mt Alpha.
ANSI Standard tn ti trong thi gian di, v tt c C++ compiler u h tr ANSI Standard.
Hc tp C++ nh th no?
iu quan trng nht khi hc tp C++ l trng tm vo cc khi nim.
Mc ch ca vic hc mt ngn ng lp trnh l tr thnh mt lp trnh vin gii hn, tc l
thit k v thc thi cc h thng mi hiu qu hn, hoc sa i chng trnh c.
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C++ h tr cc phong cch lp trnh a dng. Bn c th vit trong Fortran, C, Smalltalk, trong
bt k ngn ng no. Mi style c th t c mc tiu ca n mt cch hiu qu trong khi duy tr
runtime v space hiu qu.
Min s dng ca C++

C++ c s dng bi hng nghn lp trnh vin trong mi lnh vc ng dng c bn.
C++ ang c s dng ph bin vit device driver v cc phn mm khc m da vo thao
tc trc tip ca phn cng di rng buc v realtime.
C++ c s dng rng ri o to, nghin cu.
Bt c hai s dng Apple Macintosh hoc mt PC chy trn Windows l gin tip s dng
C++, bi v User Interface ca cc h thng ny c vit bng C++.
Ci t mi trng C++
Ci t mi trng ni b cho C++
Nu bn mun ci t mi trng C++, bn cn hai phn mm c sn trong my sau y:
Text Editor
N s c s dng son chng trnh ca bn. V d nh Windows Notepad, OS Edit
command, Brief, Epsilon, EMACS v Vim hoc Vi.
Tn v phin bn ca Text Editor c th a dng trn cc h iu hnh khc nhau. V d, Notepad
s c s dng trn Windows v Vim hoc Vi c th c s dng trn Windows cng nh Linux
hoc UNIX.
Cc file, m bn to vi editor ny, c gi l cc source file v vi C++, chng c t tn vi
ui m rng l .cpp, .cp, hoc .c.
Trc khi bt u lp trnh, m bo rng bn c mt Text editor v bn c kinh nghim
son mt chng trnh C++.
C++ Compiler:
C++ Compiler c s dng bin dch source code ca bn thnh chng trnh c th thc thi.
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Hu ht C++ compiler khng quan tm phn ui m rng bn cung cp cho source code, nhng
nu bn khng xc nh, th theo mc nh, n s s dng ui l .cpp.
Compiler c s dng thng xuyn nht l GNU C/C++ compiler, hoc bn c th s dng cc
Compiler khc t HP hoc Solaris nu bn c H iu hnh tng ng.
Ci t GNU C/C++ Compiler

Ci t trn UNIX/Linux
Nu bn ang s dng Linux hoc UNIX, th kim tra xem GCC c ci t trn h thng
cha bng vic nhp lnh sau ti dng lnh (command line):
$ g++ -v
Nu bn ci t GCC, th n s in thng bo sau:

Using built-in specs.
Target: i386-redhat-linux
Configured with: ../configure --prefix=/usr .......
Thread model: posix
gcc version 4.1.2 20080704 (Red Hat 4.1.2-46)
Nu
GCC
cha
ci
t,
bn
cn
phi
ci
theo
hng
dn
ti:http://gcc.gnu.org/install/
Ci t trn Mac OS X
Nu bn s dng Mac OS X, cch n gin nht ci t GCC l ti mi trng pht trin Xcode
t Website ca Applet v theo cc ch dn.
Bn c th ti Xcode t: developer.apple.com/technologies/tools/.
Ci t trn Windows
ci t GCC trn Windows, bn cn ci t MinGW. ci t MinGW, bn truy
cp:www.mingw.org, v t ti trang ti MinGW. Ti phin bn mi nht ca MinGW, s c
tn l MinGW-<version>.exe.
Trong khi ci t MinGW, ti thiu bn phi ci t gcc-core, gcc-g++, binutils, v MinGW runtime.
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Thm th mc ph bin ca MinGW ti bin mi trng PATH, m bn c th xc nh cc tool

trn command line bi cc tn n gin ca chng.
Khi vic ci t hon tt, bn c th chy gcc, g++, ar, ranlib, dlltool, v mt s GNU tool khc t
Windows command line.
C php C++ c bn
Khi chng ta xem xt mt chng trnh C++, n c th c nh ngha nh l mt tp hp ca
cc i tng, m giao tip thng qua vic triu hi cc phng thc ca mi i tng . Di
y, chng ti miu t ngn gn ngha ca class (lp), object (i tng), method (phng thc)
v cc bin i tng:
Object - i tng c cc trng thi v hnh vi. V d: mt i tng dog c cc trng thi
l color, name, breed, v cc hnh vi l wagging, barking, eating. Mt i tng l mt
minh ha ca mt lp.
Class - Mt lp c th c nh ngha nh l mt template/blueprint, m miu t hnh

vi/trng thi m i tng h tr.
Methods - V c bn, mt phng thc l mt hnh vi. Mt lp c th cha nhiu phng

thc. Phng thc l ni tnh logic c vit, d liu c thao tc v tt c action c
thc thi.
Instant Variables - Mi i tng c tp hp bin i tng duy nht ca n. Trng thi

ca mt i tng c to ra bi cc gi tr c gn cho cc bin i tng ca n.
Cu trc chng trnh C++

Bn theo di mt on code n gin s in Hello World.
#include <iostream>
using namespace std;
// main() is where program execution begins.
int main()
{
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cout << "Hello World"; // prints Hello World

return 0;
}
Chng trnh trn c cc phn sau:
Ngn ng C++ nh ngha mt s header, m cha tong tin cn thit v hu ch cho

chng trnh ca bn. Vi chng trnh ny, header l <iostream> l cn thit.
Dng using namespace std; ni cho compiler s dng std namespace. Namespce l phn
b sung gn y cho C++.
Dng tip theo // main() is where program execution begins. l mt comment n dng
trong C++. Cc comment n dng bt u vi // v kt thc cui dng.
Dng int main() l hm main, ti y vic thc thi chng trnh bt u.
Dng tip theo cout << "This is my first C++ program."; lm thng bo This is my first
C++ program c hin th trn mn hnh.
Dng tip theo return 0; kt thc hm main() v lm n tr v gi tr 0 ti tin trnh ang gi.
Bin dch v thc thi chng trnh C++

Di y l cch lu file, bin dch v chy chng trnh. Bn theo cc bc sau:
M mt text editor v thm on code trn.
Lu file vi tn: hello.cpp.
M mt dng nhc lnh (command prompt) v ti th mc ni bn lu file .
Son 'g++ hello.cpp ' v nhn Enter bin dch code trn. Nu khng c li xy ra trong
code ca bn th dng nhc lnh s a bn ti dng tip theo v to a.out file c th thc
thi.
By gi, bn son a.out chy chng trnh.
Bn s thy Hello World c in trn ca s.
$ g++ hello.cpp
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$ ./a.out
Hello World
Bn chc chn rng g++ l trong path ca bn v bn ang chy n trong th mc m cha
hello.cpp file.
Bn c th bin dch chng trnh C/C++ bi s dng makefile. bit thm chi tit, bn c th
truy cp: Makefile Tutorial.
Du chm phy v khi (block) trong C++

Trong C++, du chm phy l k t kt thc lnh (statement terminator). Ngha l, mi lnh n
phi kt thc bi mt du chm phy. N ch dn s kt thc ca mt thc th logic.
Di y l v d v 3 lnh khc nhau:
x = y;
y = y+1;
add(x, y);
Mt khi (block) l mt tp hp cc lnh c kt ni mt cch logic, m c bao quanh bi cc

du ngoc mc m v ng. V d:
{
return 0;
}
Hai dng sau l tng ng, C++ khng quan tm bn t bao nhiu lnh trn mt dng. V d:
x = y;
y = y+1;
add(x, y);
L ging vi:
x = y; y = y+1; add(x, y);
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nh danh (Identifier) trong C++

Mt nh danh (Identifier) trong C++ l mt tn c s dng nhn din mt bin, hm, lp,
module, hoc bt k user-defined item no (ngi dng t nh ngha). Mt nh danh (Identifier)
bt u vi mt ch ci t A ti Z hoc t a ti z hoc mt du gch di (_) c theo sau bi 0
hoc nhiu ch ci, du gch di v k s (t 0 ti 9).
C++ khng cho php cc k t nh @, $ v % bn trong cc Identifier. C++ l ngn ng lp trnh
phn bit kiu ch. V th, Manpower v manpower l hai Identifier khc nhau trong C++.
Di y l mt s v d v Identifier (nh danh) thch hp:
mohd
zara
abc
move_name
a_123
myname50
_temp
a23b9
retVal
T kha trong C++

Bng di lit k cc t c d tr (dnh ring) trong C++. Nhng t ny khng th c s
dng nh l constant hoc bin hoc bt k tn Identifier (nh danh) no.
asm
else
new
this
auto
enum
operator
throw
bool
explicit
private
true
break
export
protected
try
case
extern
public
typedef
catch
false
register
typeid
char
float
reinterpret_cast
typename
class
for
return
union
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const
friend
short
unsigned
const_cast
goto
signed
using
continue
if
sizeof
virtual
default
inline
static
void
delete
int
static_cast
volatile
do
long
struct
wchar_t
double
mutable
switch
while
dynamic_cast
namespace
template
Trigraph trong C++

Mt Trigraph l mt dy 3 k t m biu din mt k t n v dy ny lun lun bt u vi 2 du
hi.
Cc Trigraph c m rng bt c ni u chng xut hin, bao gm bn trong String literal v
Character literal, trong comment, v trong cc preprocessor directive (cc directive tin x l).
Di y l cc dy trigraph c s dng thng xuyn nht:
Trigraph
Thay th cho
??=
??/
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??'
??(
??)
??!
??<
??>
??-
Tt c compiler khng h tr Trigraph v chng c khuyn l khng nn s dng bi v tnh kh

hiu ca n.
Khong trng (Whitespace) trong C++

Mt dng m ch cha khong trng (Whitespace), c th l mt comment, c bit n nh l
mt dng trng, v C++ hon ton b qua n.
Khong trng (Whitespace) l khi nim c s dng trong C++ miu t blank, tab, k t
newline, v comment. Khong trng (Whitespace) phn bit cc phn ca lnh v gip compiler
nhn din v tr mt phn t trong mt lnh, v d nh int, v tr phn kt thc v v tr phn t tip
theo bt u. Do , trong lnh sau:
int age;
Phi c t nht mt Whitespace (thng l khong trng) gia int v age compiler c th phn
bit chng. Trong lnh:
fruit = apples + oranges;
// Get the total fruit
Cc k t khong trng (Whitespace) gia fruit v =, hoc gia = v apples l khng cn thit; tuy
nhin, gip cho code ca bn d c hn, bn c th thm chng vo.
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Comment trong C++

Comment ca chng trnh l cc li din gii, m bn c th bao trong C++ code, v gip cho bt
k ai c source code d dng hn. Tt c ngn ng lp trnh u cho php mt s mu comment
no .
C++ h tr cc comment n dng v a dng. Tt c k t c trong comment c b qua bi
C++ compiler.
Comment trong C++ bt u vi /* v kt thc vi */. V d:
/* This is a comment */
/* C++ comments can
also
* span multiple lines

*/
Mt comment cng c th bt u vi //, ko di ti phn cui ca dng. V d:

#include <iostream>
main()
{
return 0;
}
Khi code trn c bin dch, n s b qua // prints Hello World v cui cng cho kt qu sau:
Hello World
Bn trong mt comment dng /* v */, cc k t // khng c ngha c bit g. Bn trong mt

comment dng //, cc k t /* v */ khng c ngha c bit g. V th, bn c th lng (nest) bt
k dng comment no bn trong dng khc. V d:
/* Comment out printing of Hello World:
Trang 19
*/
Kiu d liu trong C++

Trong khi lm vic vi bt k ngn ng lp trnh no, bn cn s dng cc kiu bin a dng
lu gi thng tin. Cc bin, khng g khc ngoi cc v tr b nh c dnh ring lu gi tr.
Ngha l, khi bn to mt bin, bn dnh ring mt s khng gian trong b nh cho bin .
Bn c th thch lu thng tin ca cc kiu d liu (Data Type) a dng nh Character, Wide
Character, integer, floating-point, double floating point, Boolean, . Da trn kiu d liu ca mt
bin, h thng s cp pht b nh v quyt nh nhng g c th c lu gi trong b nh dnh
ring .
Kiu d liu nguyn thy trong C++

Tn ting Anh l Primitive Type, cn c th gi l kiu d liu gc, kiu d liu c sn trong C++.
Bn cnh cc kiu d liu gc ny, C++ cng cung cp cc kiu d liu user-defined. Bng di
y lit k 7 kiu d liu c bn trong C++:
Kiu d liu
T kha
Boolean
bool
Character
char
Integer
int
Floating point
float
Double floating point
double
Trang 20
Valueless
void
Wide character
wchar_t
Mt s kiu c bn c th c sa i bi s dng mt hoc nhiu modifier ny:
signed
unsigned
short
long
Bng sau hin th kiu bin, lng b nh n dng lu gi tr trong b nh, v gi tr ln nht v
nh nht c th c lu gi vi cc kiu bin :
Kiu
rng bit
Dy gi tr
char
1byte
-127 ti 127 hoc 0 ti 255
unsigned char
1byte
0 ti 255
signed char
1byte
-127 ti 127
int
4bytes
-2147483648 ti 2147483647
unsigned int
4bytes
0 ti 4294967295
signed int
4bytes
-2147483648 ti 2147483647
short int
2bytes
-32768 ti 32767
Trang 21
unsigned short int
Range
0 ti 65,535
signed short int
Range
-32768 ti 32767
long int
4bytes
-2,147,483,647 ti 2,147,483,647
signed long int
4bytes
Tng t nh long int
unsigned long int
4bytes
0 ti 4,294,967,295
float
4bytes
+/- 3.4e +/- 38 (~7 digits)
double
8bytes
+/- 1.7e +/- 308 (~15 digits)
long double
8bytes
+/- 1.7e +/- 308 (~15 digits)
wchar_t
2 or 4 bytes
1 wide character
Kch c ca cc bin c th khc vi nhng g hin th trn bng, ph thuc vo compiler v my

tnh bn ang s dng.
Di y l v d s a ra kch c chnh xc ca cc kiu d liu a dng trn my tnh ca bn.
#include <iostream>
int main()
{
cout << "Size of char : " << sizeof(char) << endl;
cout << "Size of int : " << sizeof(int) << endl;
cout << "Size of short int : " << sizeof(short int) << endl;
cout << "Size of long int : " << sizeof(long int) << endl;
cout << "Size of float : " << sizeof(float) << endl;
Trang 22
cout << "Size of double : " << sizeof(double) << endl;

cout << "Size of wchar_t : " << sizeof(wchar_t) << endl;
return 0;
}
V d ny s dng endl, m chn mt k t newline sau mi dng, v ton t << c s dng

truyn nhiu gi tr ti mn hnh. Chng ti cng s dng ton t sizeof() ly kch c ca cc
kiu d liu a dng.
Khi code trn c bin dch v thc thi, n cho kt qu sau (kt qu c th a dng ty thuc vo
compiler v my tnh bn ang s dng).
Size of char : 1
Size of int : 4
Size of short int : 2
Size of long int : 4
Size of float : 4
Size of double : 8
Size of wchar_t : 4
Khai bo typedef trong C++

Bn c th to mt tn mi cho mt kiu d liu ang tn ti bi s dng typedef trong C++. C
php n gin sau nh ngha mt kiu d liu mi bi s dng typedef:
typedef type newname;
V d sau ni cho compiler rng feet l tn khc ca int:

typedef int feet;
By gi, khai bo sau l hon ton hp l v s to mt bin integer gi l distance:

feet distance;
Trang 23
Kiu lit k enum trong C++

Kiu lit k enum khai bo mt tn kiu ty v mt tp hp ca 0 hoc nhiu Identifier (nh
danh) m c th c s dng nh l cc gi tr ca kiu . Mi Enumerator l mt constant c
kiu l kiu lit k (enumeration).
to mt Enumeration, bn s dng t kha enum trong C++. Form chung ca kiu lit k enum
l:
enum enum-name { list of names } var-list;
Ti y, enum-name l tn kiu lit k. Danh sch tn c phn bit bi du phy.

V d, code sau nh ngha mt bn lit k mu gi l color v bin c l kiu ca color. Cui cng, c
c gn gi tr blue.
enum color { red, green, blue } c;
c = blue;
Theo mc nh, gi tr ca name u tin l 0, name th hai l 1 v name th 3 l 2, . Nhng bn

c th cung cp cho mt name mt gi tr c th bng vic thm mt Initializer (gi tr khi to). V
d, trong enumeration sau, green s c gi tr l 5:
enum color { red, green=5, blue };
y, blue s c gi tr l 6 bi v mi name s c gi tr ln hn ca name trc l 1.
Kiu bin trong C++

Mt bin cung cp ni lu gi c t tn chng ta c th thao tc. Mi bin trong C++ c mt
kiu c th, m quyt nh: kch c v cch b tr b nh ca bin; dy gi tr c th c lu gi
bn trong b nh ; v tp hp hot ng c th c p dng cho bin .
Tn bin c th gm cc k t, cc k s, du gch di. N phi bt u bi hoc mt k t hoc
mt du gch di. Cc k t ch hoa v ch thng l khc nhau bi C++ l ngn ng phn bit
kiu ch.
Di y l cc kiu bin c bn trong C++ c gii thiu trong chng trc:
Trang 24
Kiu
Miu t
bool
Lu gi gi tr true hoc false
char
L mt kiu integer, kch c 1 byte
int
Kch c t nhin nht ca integer ca my tnh
float
Gi tr single floating-point
double
Gi tr double floating-point
void
Khng tr v gi tr no
wchar_t
Kiu wide character
C++ cng cho php nh ngha cc kiu bin khc, s c gii thch trong cc chng ti,
l: Enumeration, Pointer, Array, Reference, Data structure, v Class.
Tip theo l cch nh ngha, khai bo v s dng cc kiu bin a dng:
nh ngha bin trong C++

nh ngha bin trong C++ ngha l ni cho compiler ni v lng b nh cn to lu gi bin
. Mt nh ngha bin xc nh mt kiu d liu, v cha danh sch ca mt hoc nhiu bin c
kiu , nh sau:
type variable_list;
y, type phi l mt kiu d liu hp l trong C++, gm char, w_char, int, float, double, bool
hoc bt k i tng no m ngi dng t nh ngha, v variable_list c th cha mt hoc
nhiu tn Identifier (nh danh) phn bit nhau bi du phy. Sau y l mt s khai bo hp l
trong C++:
int
i, j, k;
Trang 25
char
c, ch;
float
f, salary;
double d;
Dng int i, j, k; va khai bo v nh ngha cc bin i, j, k, m ch dn compiler to cc bin vi

tn l i, j, k ca kiu int.
Cc bin c th c khi to (c gn gi tr ban u) trong cc khai bo. Initializer (phn khi
to) gm mt k hiu bng c theo sau bi mt Constant Expression (biu thc hng s), nh
sau:
type variable_name = value;
V d:
extern int d = 3, f = 5;
// declaration of d and f.
int d = 3, f = 5;
// definition and initializing d and f.
byte z = 22;
// definition and initializes z.
char x = 'x';
// the variable x has the value 'x'.
Vi nh ngha m khng c phn khi to: cc bin c khi to vi NULL (tt c byte c gi tr
0); gi tr khi to ca tt c bin khc khng c nh ngha.
Khai bo bin trong C++

Khai bo bin trong C++ chc chn vi compiler rng c mt bin ang tn ti vi kiu v tn
cho, m compiler tip tc trnh bin dch m khng cn bit y chi tit v bin . Mt khai
bo bin ch c ngha ti thi gian bin dch, compiler cn khai bo bin thc s ti thi im kt
ni chng trnh.
Khai bo bin l hu ch khi bn ang s dng nhiu file, v bn nh ngha bin ca bn mt
trong cc file m s c sn ti thi im kt ni chng trnh. Bn s s dng t kha extern
khai bo mt bin ti bt k u. Mc d, bn c th khai bo mt bin nhiu ln trong chng
trnh C++, nhng n c th ch c nh ngha mt ln trong mt file, mt hm, hoc mt khi
code.
Trang 26
V d
Trong v d sau, mt bin c khai bo ti phn u chng trnh, nhng n c nh
ngha bn trong hm main.
#include <iostream>
// Variable declaration:
extern int a, b;
extern int c;
extern float f;
int main ()
{
// Variable definition:
int a, b;
int c;
float f;
// actual initialization
a = 10;
b = 20;
c = a + b;
cout << c << endl ;
f = 70.0/3.0;
cout << f << endl ;
return 0;
}
Khi code trn c bin dch v thc thi, n cho kt qu sau:
Trang 27
30
23.3333
Ging khi nim p dng trn khai bo hm, bn cung cp tn hm ti thi im khai bo v nh
ngha thc s ca hm c th c cung cp bt c u. V d:
// function declaration
int func();
int main()
{
// function call
int i = func();
}
// function definition
int func()
{
return 0;
}
Lvalue v Rvalue trong C++

C hai loi Expression trong C++:
lvalue : y l expression lin quan ti mt v tr vng nh. Bt k lvalue c th xut hin

bn tri hoc bn phi ca mt php gn.
rvalue : Khi nim ny lin quan ti mt gi tr d liu m c lu gi ti mt s a ch

trong vng nh. Mt rvalue l mt expression m khng th c mt gi tr c gn ti n,
ngha l: rvalue c th xut hin bn phi nhng khng th xut hin bn tri ca mt php
gn.
Cc bin l lvalue c th xut hin bn tri ca php gn. Cc Numeric literal (hng s) l rvalue
khng th c gn v khng th xut hin bn tri ca php gn. Di y l mt lnh hp l
trong C++:
Trang 28
int g = 20;
Nhng lnh sau l khng hp l v s cho mt compile-time error (li ti thi im bin dch):
10 = 20;
Phm vi bin trong C++

Mt scope (phm vi) l mt khu vc ca chng trnh ni bin hot ng, v ni chung c th c 3
khu vc m bin c th c khai bo:
Bn trong mt hm hoc mt khi, c gi l bin cc b (local).
Trong nh ngha ca cc tham s hm, c gi l cc tham s chnh thc (formal).
Bn ngoi ca tt c hm, c gi l bin ton cc (global).
Chng ta s hc hm v cc tham s ca hm l g trong chng ti. Di y chng ti s gii

thch khi nim v bin cc b v bin ton cc.
Bin cc b trong C++

Cc bin c khai bo bn trong mt hm hoc khi l cc bin cc b (local). Chng ch c th
c s dng bi cc lnh bn trong hm hoc khi code . Cc bin cc b khng c bit
bn ngoi hm (tc l ch c s dng bn trong hm hoc khi code ). Di y l v d
s dng cc bin cc b:
#include <iostream>
int main ()
{
// Local variable declaration:
int a, b;
int c;
a = 10;
Trang 29
b = 20;
c = a + b;
cout << c;
return 0;
}
Bin ton cc trong C++

Bin ton cc (global) trong C++ c nh ngha bn ngoi cc hm, thng phn u chng
trnh. Cc bin ton cc gi gi tr ca n trong sut vng i chng trnh ca bn.
Mt bin ton cc c th c truy cp bi bt k hm no. Tc l, mt bin ton cc l c sn
cho bn s dng trong ton b chng trnh sau khi khai bo n. Di y l v d s dng
bin ton cc v bin ni b trong C++:
#include <iostream>
// Global variable declaration:

int g;
int main ()
{
int a, b;
a = 10;
b = 20;
g = a + b;
cout << g;
Trang 30
return 0;
}
Mt chng trnh c th c cc bin ton cc v bin cc b cng tn vi nhau, nhng trong mt

hm th gi tr ca bin cc b s c u tin. V d:
#include <iostream>
// Global variable declaration:

int g = 20;
int main ()
{
int g = 10;
cout << g;
return 0;
}

10
Khi to bin cc b v bin ton cc trong C++

Khi mt bin cc b c nh ngha, n khng c khi to bi h thng, chnh bn phi khi
to n. Cc bin ton cc c khi to t ng bi h thng khi bn nh ngha chng, nh sau:
Kiu d liu
Initializer (Gi tr khi to)
int
Trang 31
char
'\0'
float
double
pointer
NULL
Khi to bin mt cch chnh xc l mt s thc hnh tt, nu khng, i khi chng trnh s cho
kt qu khng mong i.
Hng (Constant/Literal) trong C++

Constant lin quan ti cc gi tr c nh m chng trnh khng th thay i v chng c gi
l literals.
Constant l mt kiu d liu thay th cho Literal, cn Literal th hin chnh n. Trong v d: const PI
= 3.14 th Constant y l PI, cn Literal l 3.14.
Constant c th l bt k kiu d liu c bn no trong C++, v c th c phn chia thnh gi tr
hng s nguyn, hng s thc, hng k t, hng chui v Boolean literal (tm dch: hng logic).
Ngoi ra, constant c i x ging nh cc bin thng thng, ngoi tr vic gi tr ca chng
l khng th thay i sau khi nh ngha.
Hng s nguyn trong C++

Hng s nguyn c th l decimal (c s 10), octal (c s 8) hay hexadecimal (c s 16). Gi tr
c tin t (prefix) l 0 cho octal, l 0x hay 0X cho hexadecimal v khng c g cho decimal.
Mt hng s nguyn cng c cc hu t (suffix) U hay L th hin kiu unsigned hay long. Hu t c
th l ch hoa hoc ch thng v c th trong bt k th t no.
V d v cc hng s nguyn:
212
// Legal
215u
// Legal
Trang 32
0xFeeL
// Legal
078
// Illegal: 8 is not an octal digit
032UU
// Illegal: cannot repeat a suffix
Di y l cc kiu hng s nguyn a dng:

85
// decimal
0213
// octal
0x4b
// hexadecimal
30
// int
30u
// unsigned int
30l
// long
30ul
// unsigned long
Hng s thc trong C++

Mt hng s thc bao gm phn nguyn (integer part), du chm thp phn (decimal point), phn
l (fraction part) v phn m (exponent part). Chng ta c th biu din hng s thc theo dng
decimal hay dng m.
Khi th hin dng decimal phi bao gm du chm thp phn, phn m hoc c hai. Khi th hin
dng m phi gm phn nguyn, phn l hoc c hai. Dng m i km vi k t E hoc e.
Xt cc v d sau:
3.14159
// Legal
314159E-5L
// Legal
510E
// Illegal: incomplete exponent
210f
// Illegal: no decimal or exponent
.e55
// Illegal: missing integer or fraction
Boolean literal trong C++

C hai kiu Boolean literal v chng l mt phn ca cc t kha C++:
Gi tr true
V gi tr false
Trang 33
Bn khng nn ng nht gi tr true vi 1 v gi tr false vi 0.
Hng k t trong C++

Cc hng k t trong C++ m u v kt thc bi du nhy n. Nu hng k t bt u vi L (v
d Lx) th n l kiu wchar_t. Nu khng th, n l hng k t kiu char, v d nh x.
Hng k t c th l mt k t (nh X), mt escape sequence (nh \t) hay mt k t m rng (nh
\u02c0).
Mt s k t trong C++ khi c ng trc bi du \ th chng s mang mt ngha c bit nh
bt u dng mi \n hay to mt tab \t. Chng c bit nh l escape sequence (dy thot).
Bng di y th hin mt s m escape sequence ph bin:
Escape sequence
ngha
\\
K t \
\'
K t '
\"
K t "
\?
K t ?
\a
Alert hoc bell
\b
Backspace
\f
Form feed
\n
Newline
\r
Carriage return
Trang 34
\t
tab ngang
\v
tab dc
\ooo
S h c s 8 ca mt ti 3 k s
\xhh . . .
S h c s 16 ca mt hoc nhiu k s
Di y l v d minh ha mt s k t escape sequence:

#include <iostream>
int main()
{
cout << "Hello\tWorld\n\n";
return 0;
}

Hello
World
Hng chui trong C++

Hng chui cha trong du nhy kp, v d abc. Mt chui s cha cc k t tng t hng k t,
gm cc k t thun, escape sequence, v cc k t m rng.
C th ngt mt dng di thnh nhiu dng bi s dng hng chui v phn bit chng bi s
dng khong trng (whitespace).
Xt v d mt hng chui trong C++ th hin theo 3 cch khc nhau:
"hello, dear"
"hello, \
Trang 35
dear"
"hello, " "d" "ear"
nh ngha hng trong C++

C hai cch nh ngha hng trong C++ l:
S dng b tin x l #define.
S dng t kha const.
S dng b tin x l #define trong C++

Di y l c php s dng tin x l #define nh ngha mt constant trong C++:
#define identifier value
V d sau gii thch c php trn:

#include <iostream>
#define LENGTH 10
#define WIDTH
#define NEWLINE '\n'
int main()
{
int area;
area = LENGTH * WIDTH;

cout << area;
cout << NEWLINE;
return 0;
Trang 36

50
S dng t kha const trong C++

Bn c th s dng tin t const nh ngha hng trong C++ vi mt kiu c th, nh sau:
const type variable = value;
V d sau gii thch chi tit c php trn:

#include <iostream>
int main()
{
const int
LENGTH = 10;
const int
WIDTH
= 5;
const char NEWLINE = '\n';

int area;
area = LENGTH * WIDTH;

cout << area;
cout << NEWLINE;
return 0;
}

50
Ghi ch: N l bc thc hnh tt cho bn khi nh ngha cc hng kiu ch hoa trong C++.
Modifier trong C++

Trang 37
C++ cho php cc kiu d liu char, int v double c cc Modifier t trc chng. Mt Modifier
c s dng thng bo ngha ca kiu c s, gip cho n tng s chnh xc hn vi s cn
thit ca cc tnh hung a dng.
Di y l cc Modifier trong C++:
signed
unsigned
long
short
Cc Modifier l: signed, unsigned, long, v short c th c p dng cho kiu integer. Ngoi
ra, signed v unsigned c th c p dng cho kiu char, v long c th p dng cho kiu
double.
Cc Modifier l signed v unsigned cng c th c s dng nh l tin t cho cc Modifier
l long hoc short modifiers. V d: unsigned long int.
C++ cho php kiu khai bo tt khai bo cc unsigned, short, or long integer. Bn c th ch
n gin s dng t unsigned, short, hoc long, m khng cn int. V d sau minh ha hai khai
bo l hp l trong C++ khai bo cc bin unsigned integer:
unsigned x;
unsigned int y;
phn bit s khc nhau gia hai Modifier l signed integer v unsigned integer c thng dch
bi C++, bn nn chy chng trnh sau:
#include <iostream>
/* This program shows the difference between

* signed and unsigned integers.
*/
int main()
{
Trang 38
short int i;
// a signed short integer
short unsigned int j;
// an unsigned short integer
j = 50000;
i = j;
cout << i << " " << j;
return 0;
}
N s cho kt qu:
-15536 50000
Qualifier trong C++

Qualifier cung cp thng tin b sung v cc bin theo sau n.
Qualifier
ngha
const
i tng ca kiu const khng th b thay i bi chng trnh trong khi thc thi
volatile
Modifier ny ni cho compiler rng gi tr ca bin c th c thay i mt cch

khng r rng (khng bo trc) bi chng trnh.
restrict
Mt con tr c t l restrict th c ngha l i tng n tr n c th c

truy cp. Restrict c thm vo trong chun C99.
Lp lu tr (Storage Class) trong C++

Lp lu tr (Storage Class) nh ngha phm vi v vng i ca bin v/hoc cc hm bn trong
mt chng trnh C++. Chng thng ng trc kiu d liu m chng tc ng. Di y l cc
lp lu tr c th c s dng trong C++:
auto
Trang 39
register
static
extern
mutable
Lp lu tr auto trong C++

Lp lu tr auto trong C++ l lp lu tr mc nh cho tt c bin cc b trong C++:
{
int mount;
auto int month;
}
V d trn nh ngha hai bin vi cng lp lu tr, auto ch c th c s dng bn trong cc

hn, v d: cho cc bin ni b.
Lp lu tr register trong C++

Lp lu tr register trong C++ c s dng nh ngha cc bin cc b m nn c lu gi
trong mt thanh ghi thay v RAM. Ngha l, bin c kch c ti a bng vi kch c thanh ghi
(thng l 1 t) v khng th c ton t mt ngi '&' c p dng ti n (v khng c a ch b
nh).
{
register int
miles;
Lp lu tr register nn ch c dng cho cc bin yu cu truy cp nhanh nh cc bin m

(counters). Cng cn ch rng, mt bin nh ngha vi register khng c ngha l bin c
lu tr trong thanh ghi. Tc l n c th c lu tr trong thanh ghi ph thuc vo phn cng v
gii hn thc thi.
Trang 40
Lp lu tr static trong C++

Lp lu tr static trong C++ ni vi compiler gi mt bin cc b tn ti trong ton b thi gian
sng ca chng trnh thay v to v hy bin mi ln n vo v ra khi phm vi bin. V vy, cc
bin c static cho php n duy tr gi tr gia cc ln gi hm.
Lp lu tr static cng c th c p dng cho cc bin ton cc (global). Khi p dng cho bin
ton cc, n ni vi trnh bin dch rng, phm vi ca bin ton cc b gii hn trong tp tin m n
c khai bo.
Trong C++, khi static c s dng trn thnh vin d liu ca lp, n gy ra: ch c mt bn sao
ca thnh vin c chia s bi tt c i tng trong lp ca n.
#include <iostream>
// Function declaration
void func(void);
static int count = 10; /* Global variable */
main()
{
while(count--)
{
func();
}
return 0;
}
// Function definition
void func( void )
{
static int i = 5; // local static variable
i++;
std::cout << "i is " << i ;
std::cout << " and count is " << count << std::endl;
Trang 41

i is 6 and count is 9
Lp lu tr extern trong C++

Lp lu tr extern trong C++ c dng cung cp mt tham chiu ca mt bin ton cc c
nhn thy bi TT C cc file chng trnh. Khi bn s dng extern, bin khng th c khi
to, khi n tr ti tn bin ti mt v tr lp lu tr m c nh ngha trc .
Khi bn c nhiu file v bn nh ngha mt bin hay hm ton cc trong mt file v cng mun
dng n trong cc file khc, th extern c dng trong file khc cung cp tham chiu ca bin
hay hm c nh ngha. Cn nh rng, extern dng khai bo mt bin hay hm ton cc
trong file khc.
Lp lu tr extern c dng ph bin khi c hai hoc nhiu file chia s cng bin hay hm ton
cc. Xem v d vi hai file sau:
File u tin: main.cpp
#include <iostream>
int count ;
extern void write_extern();
main()
Trang 42
{
count = 5;
write_extern();
}
File th hai: support.cpp

#include <iostream>
extern int count;
void write_extern(void)
{
std::cout << "Count is " << count << std::endl;
}
y, t kha extern ang c s dng khai bo count trong file khc. By gi bin dch hai
file ny nh sau:
$g++ main.cpp support.cpp -o write
N s to chng trnh write c th thc thi, bn th thc thi write v kim tra kt qu nh sau:
$./write
5
Lp lu tr mutable trong C++

Lp lu tr mutable trong C++ ch p dng cho cc i tng class, s c bn lun trong
chng sau. N cho php mt thnh vin ca mt i tng override (ghi ). l, mt thnh
vin l mutable c th c sa i bi mt hm thnh vin const.
Ton t trong C++

Mt ton t l mt biu tng, m ni cho compiler thc hin cc thao tc ton hc v logic c th.
C++ cung cp nhiu ton t c sn, l:
Ton t s hc
Trang 43
Ton t quan h
Ton t logic
Ton t so snh bit
Ton t gn
Ton t hn hp
Ton t s hc trong C++

Bng di lit k cc ton t s hc c h tr bi ngn ng C++:
Gi s bin A gi gi tr 10, bin B gi 20 th:
V d
Ton
t
Miu t
V d
Cng hai ton hng
A + B kt qu l 30
Tr ton hng th hai t ton hng u
A - B kt qu l -10
Nhn hai ton hng
A * B kt qu l 200
Php chia
B / A kt qu l 2
Php ly s d
B % A kt qu l 0
++
Ton t lng gia (++), tng gi tr ton

hng thm mt n v
A++ kt qu l 11
--
Ton t lng gim (--), gim gi tr

ton hng i mt n v
A-- kt qu l 9
Trang 44
Ton t quan h trong C++

Bng di y lit k cc ton t quan h c h tr bi ngn ng C++:
Gi s bin A gi gi tr 10, bin B gi 20 th:
V d
Ton
t
Miu t
V d
==
Kim tra nu 2 ton hng bng nhau hay

khng. Nu bng th iu kin l true.
(A == B) l khng ng
!=
Kim tra 2 ton hng c gi tr khc nhau

hay khng. Nu khng bng th iu kin
l true.
(A != B) l true
>
Kim tra nu ton hng bn tri c gi tr

ln hn ton hng bn phi hay khng.
Nu ln hn th iu kin l true.
(A > B) l khng ng
<
Kim tra nu ton hng bn tri nh hn

ton hng bn phi hay khng. Nu nh
hn th l true.
(A < B) l true
>=

ln hn hoc bng gi tr ca ton hng
bn phi hay khng. Nu ng l true.
(A >= B) l khng ng
<=

nh hn hoc bng ton hng bn phi
hay khng. Nu ng l true.
(A <= B) l true
Ton t logic trong C++

Bng di y ch r tt c cc ton t logic c h tr bi ngn ng C.
Trang 45
Gi s bin A c gi tr 1 v bin B c gi tr 0:
V d
Ton
t
Miu t
V
d
&&
c gi l ton t logic AND (v). Nu c hai ton t u c gi tr khc 0

th iu kin tr ln true.
(A
&&
B) l
false.
||
c gi l ton t logic OR (hoc). Nu mt trong hai ton t khc 0, th

iu kin l true.
(A ||
B) l
true.
c gi l ton t NOT (ph nh). S dng o ngc li trng thi

logic ca ton hng . Nu iu kin ton hng l true th ph nh n s l
false.
!(A
&&
B) l
true.
Ton t so snh bit trong C++

Ton t so snh bit lm vic trn n v bit, tnh ton biu thc so snh tng bit. Bng di y v
&, |, v ^ nh sau:
p
p&q
p|q
p^q
Trang 46
Gi s nu A = 60; v B = 13; th by gi trong nh dng nh phn chng s l nh sau:

A = 0011 1100
B = 0000 1101
----------------A&B = 0000 1100
A|B = 0011 1101
A^B = 0011 0001
~A = 1100 0011
Cc ton t so snh bit c h tr bi ngn ng C++ c lit k trong bng di y. Gi s ta
c bin A c gi tri 60 v bin B c gi tr 13, ta c:
V d
Ton
t
Miu t
V d
&
Ton t AND (v) nh phn sao chp mt bit ti kt qu nu n tn ti trong

c hai ton hng.
(A &
B) s
cho
kt
qu
l 12,
tc l
0000
1100
Ton t OR (hoc) nh phn sao chp mt bit ti kt qu nu n tn ti trong

mt hoc hai ton hng.
(A |
B) s
cho
kt
qu
l 61,
tc l
Trang 47
0011
1101
Ton t XOR nh phn sao chp bit m n ch tn ti trong mt ton hng m

khng phi c hai.
(A ^
B) s
cho
kt
qu
l 49,
tc l
0011
0001
Ton t o bit (o bit 1 thnh bit 0 v ngc li).
(~A )
s
cho
kt
qu
l 61,
tc l
1100
0011.
<<
Ton t dch tri. Gi tr ton hng tri c dch chuyn sang tri bi s cc
bit c xc nh bi ton hng bn phi.
A <<
2 s
cho
kt
qu
240,
tc l
1111
0000
(dch
sang
tri
hai
bit)
>>
Ton t dch phi. Gi tr ton hng tri c dch chuyn sang phi bi s
A >>
2 s
Trang 48
cc bit c xc nh bi ton hng bn phi.
cho
kt
qu
l 15,
tc l
0000
1111
(dch
sang
phi
hai
bit)
Ton t gn trong C++

Di y l nhng ton t gn c h tr bi ngn ng C++:
V d
Ton
t
Miu t
V d
Ton t gn n gin. Gn gi tr ton hng bn phi cho ton hng tri.
C=A
+ B s
gn
gi tr
ca A
+B
vo
trong
C
+=
Thm gi tr ton hng phi ti ton hng tri v gn gi tr cho ton

hng tri.
C +=
A
tng
ng
vi C
=C+
A
Trang 49
-=
Tr i gi tr ton hng phi t ton hng tri v gn gi tr ny cho ton

hng tri.
C -= A
tng
ng
vi C
=CA
*=
Nhn gi tr ton hng phi vi ton hng tri v gn gi tr ny cho ton

hng tri.
C *= A
tng
ng
vi C
=C*
A
/=
Chia ton hng tri cho ton hng phi v gn gi tr ny cho ton hng tri.
C /= A
tng
ng
vi C
=C/
A
%=
Ly phn d ca php chia ton hng tri cho ton hng phi v gn cho
ton hng tri.
C %=
A
tng
ng
vi C
=C%
A
<<=
Dch tri ton hng tri sang s v tr l gi tr ton hng phi.
C <<=
2
tng
ng
vi C
=C
<< 2
>>=
Dch phi ton hng tri sang s v tr l gi tr ton hng phi.
C >>=
2
tng
Trang 50
ng
vi C
=C
>> 2
&=
Php AND bit
C &=
2
tng
ng
vi C
=C&
2
^=
Php OR loi tr bit
C ^= 2
tng
ng
vi C
=C^
2
|=
Php OR bit.
C |= 2
tng
ng
vi C
=C|2
Cc ton t hn hp trong C++

Di y l mt s ton t hn hp quan trng c h tr bi ngn ng C++.
Ton t
Miu t
sizeof
Ton t sizeof trong C++ tr v kch c ca mt bin. V d:

sizeof(a), vi a l integer, s tr v 4
iu kin ? X : Y
Ton t iu kin trong C++. Nu Condition l true ? th n tr

v gi tr X : nu khng th tr v Y
Trang 51
Ton t Comma trong C++ lm cho mt dy hot ng c

thc hin. Gi tr ca ton biu thc comma l gi tr ca biu
thc cui cng trong danh sch c phn bit bi du phy
. (dot) v -> (arrow)
Ton t thnh vin trong C++ c s dng tham chiu cc

phn t n ca cc lp, cc cu trc, v union
Cast
Ton t p kiu (Casting) trong C++ bin i mt kiu d liu

thnh kiu khc. V d: int(2.2000) s tr v 2
&
Ton t con tr & trong C++ tr v a ch ca mt bin. V du:

&a; s tr v a ch thc s ca bin ny
Ton t con tr * trong C++ l tr ti mt bin. V d: *var s

tr ti mt bin var
Th t u tin ton t trong C++

Th t u tin ton t trong C++ xc nh cch biu thc c tnh ton. V d, ton t nhn c
quyn u tin hn ton t cng, v n c thc hin trc.
V d, x = 7 + 3 * 2; y, x c gn gi tr 13, ch khng phi 20 bi v ton t * c quyn u
tin cao hn ton t +, v th u tin n thc hin php nhn 3 * 2 v sau thm vi 7.
Bng di y lit k th t u tin ca cc ton t. Cc ton t vi quyn u tin cao nht xut
hin trn cng ca bng, v cc ton t c quyn u tin thp nht th bn di cng ca bng.
Trong mt biu thc, cc ton t c quyn u tin cao nht c tnh ton u tin.
V d
Loi
Ton t
Th t u tin
Postfix
() [] -> . ++ - -
Tri sang phi
Unary
+ - ! ~ ++ - - (type)* & sizeof
Phi sang tri
Trang 52
Tnh nhn
*/%
Tri sang phi
Tnh cng
+-
Tri sang phi
Dch chuyn
<< >>
Tri sang phi
Quan h
< <= > >=
Tri sang phi
Cn bng
== !=
Tri sang phi
Php AND bit
&
Tri sang phi
Php XOR bit
Tri sang phi
Php OR bit
Tri sang phi
Php AND logic
&&
Tri sang phi
Php OR logic
||
Tri sang phi
iu kin
?:
Phi sang tri
Gn
= += -= *= /= %=>>= <<= &= ^= |=
Phi sang tri
Du phy
Tri sang phi
Vng lp trong C++

C mt tnh hung m bn cn phi thc hin mt on code mt vi ln. Nhn chung, cc cu
lnh c thc hin mt cch tun t. Cu lnh u tin ca hm c thc hin trc, sau
n cu th 2 v tip tc.
Trang 53
Ngn ng lp trnh cung cp cho chng ta nhiu cu trc iu khin v cho php bn thc hin
nhng phn phc tp.
Vng lp cho php thc hin mt lnh v mt nhm lnh nhiu ln , di y l dng tng qut:
C++ h tr nhng lnh iu khin sau y. Click chut vo link xem chi tit.
Vng lp
Miu t
Vng lp while trong
Lp li mt hoc mt nhm cc lnh trong khi iu kin cho l

ng. N kim tra iu kin trc khi thc hin thn vng lp.
C++
Vng lp for trong C++
Thc thi mt dy cc lnh nhiu ln v tm tt on code m

qun l bin vng lp.
Vng
Ging lnh While, ngoi tr im l n kim tra iu kin

cui thn vng lp.
lp
do...while
trong C++
Lng vng lp trong
Bn c th s dng mt hoc nhiu vng lp trong cc vng lp

while, for hoc do..while khc.
Trang 54
C++
Cc lnh iu khin vng lp trong C++

Cc lnh iu khin vng lp thay i s thc thi lnh t dy thng thng ca n. Khi s thc thi
lnh ri khi mt phm vi, tt c cc i tng t ng m c to ra trong phm vi b hy.
C++ h tr cc lnh iu khin vng lp sau y. Click vo cc ng link sau bit thm chi
tit.
Lnh iu khin
Miu t
Lnh break trong C++
Kt thc vng lp hoc lnh switch v chuyn sang thc thi

vng lp hoc lnh switch ngay sau n.
Lnh
Khi gp lnh ny th chng trnh s b qua cc cu lnh di

n (trong cng mt cu lnh lp) thc hin vng lp mi.
continue
trong
C++
Lnh goto trong C++
Chuyn ti lnh c gn. Mc d vy, n c khuyn rng

khng nn s dng lnh goto trong chng trnh ca bn.
Vng lp v hn trong C++

Mt vng lp l vng lp v hn khi mt iu kin khng bao gi false. Vng lp for thng c
s dng cho mc ch ny. Khi bn ba biu thc iu kin trong vng lp for trng th bn s
to ra mt vng lp v hn.
#include <iostream>
int main ()
{
for( ; ; )
{
printf("This loop will run forever.\n");
Trang 55
return 0;
}
Khi biu thc iu kin vng mt, n c gi s l lun ng. Bn c th c mt biu thc khi
to v biu thc lng gia, nhng cc lp trnh vin C++ thng s dng for(;;) biu th mt
vng lp v hn.
Ghi ch: Bn c th dng (kt thc) mt vng lp v hn bi nhn Ctrl + C.
iu khin lung trong C++

Cc cu trc iu khin lung yu cu lp trnh vin xc nh mt hoc nhiu iu kin c
nh gi v kim tra bi chng trnh, cng vi cc lnh c thc hin nu iu kin c xc
nh l ng, hoc cc lnh khc c thc hin nu iu kin xc nh l sai.
Di y l mu chung ca mt cu trc iu khin lung hay gp trong ngn ng lp trnh.
Di y lit k cc lnh iu khin lung c cung cp bi C++. Bn click vo link thy chi
tit.
Trang 56
Lnh
Miu t
Lnh if trong C++
Mt lnh if bao gm mt biu thc logic theo sau bi mt

hoc nhiu lnh khc.
Lnh if...else trong C++
Mt lnh if c th theo sau bi mt lnh else (ty : c hoc

khng), m c th c thc hin khi biu thc logic c gi
tr false.
Lnh switch trong C++
Mt lnh switch cho php kim tra iu kin ca mt bin

trc khi thc thi cc lnh.
Lng cc lnh if trong C++
Bn c th s dng lnh if hoc else if bn trong lnh if

hoc else if khc.
Lng cc lnh switch trong
Bn c th s dng mt lnh switch bn trong mt lnh

switch khc.
C++
Ton t iu kin ? : trong C++

Chng ta bn v Ton t iu kin ? : trong chng trc m c th c dng thay th
cho lnh if...else. N c mu chung nh sau:
Exp1 ? Exp2 : Exp3;
Trong Exp1, Exp2 v Exp3 l cc biu thc. Ch vic s dng v t ca du hai chm.
Gi tr ca biu thc Exp1 trc du ? c gi tr true, Exp2 c thc hin, v gi tr ca n l gi
tr ca biu thc. Nu Exp1 l false th Exp3 c thc hin v gi tr ca n l gi tr ca biu
thc.
Hm trong C++
Mt hm l mt nhm cc lnh i cng nhau thc hin mt nhim v. Mi chng trnh C++ c
t nht mt hm l hm main(), v tt c hu ht cc chng trnh bnh thng u nh ngha
thm cc hm.
Trang 57
Bn c th chia on code ca bn thnh nhng hm ring bit. Cch bn chia on code ca bn

thnh cc hm khc nhau ph thuc vo bn, nhng theo tnh logic, mt hm thng c mt
nhim v nht nh.
Mt s khai bo hm thng bo vi b bin dch v tn ca hm, kiu tr v v tham s. Mt nh
ngha hm cung cp phn thn ca mt hm.
Cc th vin tiu chun ca ngn ng C++ cung cp rt nhiu hm c sn chng trnh ca
bn c th gi. V d, hm strcat() c th ni hai on chui, hm memcpy() dng copy mt
vng nh n mt vng nh khc v rt nhiu hm khc na.
Mt hm c bit n vi cc tn khc nhau nh mt phng thc, mt tuyn ph hoc mt th
tc.
nh ngha mt hm trong C++

Mu chung ca nh ngha hm trong Ngn ng C++ nh sau:
Kieu_tra_ve Ten_ham( Danh sach tham so )
{
Than ham
}
Mt nh ngha hm trong ngn ng C++ bao gm u hm v mt thn hm. Di y l cc

phn ca mt hm:
Kiu tr v: Mt hm c th tr v mt gi tr. Kieu_tra_ve l dng d liu ca gi tr m

hm tr v. Vi hm cung cp cc hot ng v khng tr v gi tr no c. l
hm void.
Tn hm: y l tn thc s ca hm. Tn hm v danh sch tham s cu to nn du

hiu hm.
Danh sch tham s: Khi hm c gi, bn phi truyn vo danh sch cc tham s. Mt
gi tr hng n mt tham s thc t. Danh sch tham s c cc kiu, th t v s lng
cc tham s ca hm. Cc tham s trong hm l ty chn, ngha l mt hm c th khng
c tham s.
Trang 58
Thn hm: Phn thn ca mt hm bao gm tp hp cc lnh xc nh nhng g m hm

thc hin.
V d
Sau y l m ngun cho mt hm c tn gi l max(). Hm ny c 2 tham s: num1 v num2 v
tr v gi tr ln nht gia hm s:
// function returning the max between two numbers
int max(int num1, int num2)

{
// local variable declaration
int result;
if (num1 > num2)

result = num1;
else
result = num2;
return result;
}
Khai bo hm trong C++

Mt khai bo hm thng bo cho trnh bin dch v tn hm v cch gi ca hm. Phn thn hm
c th nh ngha mt cch ri rc.
Mt khai bo hm c cc phn sau y:
return_type function_name( parameter list );
V d khi nh ngha hm max(), di y l cu khai bo hm:

int max(int num1, int num2);
Tn cc tham s khng quan trng trong vic khai bo hm, nhng kiu di y l cch khai bo
hp l:
Trang 59
int max(int, int);
Mt khai bo hm c yu cu khi bn nh ngha mt hm v m ngun v khi gi mt hm t

mt file ngun khc. Trong trng hp ny, bn nn khai bo hm trc khi gi hm .
Gi hm trong C++
Trong khi to mt hm, bn nh ngha nhng g hm phi lm. s dng mt hm, bn phi gi
hm thc hin mt nhim v c th.
Khi mt chng trnh gi mt hm, phn iu khin c chuyn n hm c gi. Mt hm
c gi thc hin cc nhim v c nh ngha v tr v gi tr sau khi thc hin chng trnh.
gi hm, bn n gin cn truyn cc tham s c yu cu cng vi tn ca hm v nu hm
tr v cc gi tr, bn c th d tr cc gi tr tr v ny, v d:
#include <iostream>
// function declaration
int max(int num1, int num2);
int main ()
{
// local variable declaration:
int a = 100;
int b = 200;
int ret;
// calling a function to get max value.

ret = max(a, b);
cout << "Max value is : " << ret << endl;
return 0;
}
Trang 60
// function returning the max between two numbers

int max(int num1, int num2)
{
// local variable declaration
int result;
if (num1 > num2)

result = num1;
else
result = num2;
return result;
}
Ti gi gi tr hm max() trong hm main vo bin ret. Khi chng trnh c chy, n s in ra kt

qu sau y:
Max value is : 200
Tham s ca hm trong C++:

Mt hm s dng cc danh sch tham s, n phi khai bo cc bin v chp nhn gi tr cc bin
ny. Cc bin ny c gi l cc bin chnh thc.
Cc bin chnh thc ging cc bin cc b khc bn trong hm.
Khi bn gi hm, c 2 cch bn truyn cc gi tr vo cho hm:
Kiu gi
Gi hm bi gi tr
trong C++
Gi hm bi con tr
Miu t
Phng thc ny sao chp gi tr thc s ca tham s vo trong

tham s chnh thc ca mt hm. Trong trng hp ny, cc
thay i ca bn thn cc tham s bn trong hm khng nh
hng ti cc tham s.
Phng thc ny sao chp a ch ca tham s vo trong bin
Trang 61
chnh thc. Bn trong hm ny, a ch ny c s dng truy

cp tham s thc s c s dng trong li gi hm.
trong C++
Gi
hm
bi
tham
chiu trong C++
Phng thc ny sao chp a ch ca tham s vo trong tham

s chnh thc. Bn trong hm, a ch c dng truy cp
tham s thc s c s dng khi gi hm. C ngha l cc thay
i ti tham s lm tham s thay i.
Theo mc nh, C++ s dng gi bi gi tr truyn cc tham s. Nhn chung, code trong mt
hm khng th thay i cc tham s c dng gi hm v trong v d trn, khi gi hm
max() l dng phng thc tng t.
Gi tr mc nh cho cc tham s trong C++

Khi bn nh ngha mt hm, bn c th xc nh mt gi tr mc nh cho mi tham s cui cng.
Gi tr ny s c s dng nu tham s tng ng l trng bn tri khi gi hm .
Vic ny c thc hin bi s dng ton t gn v gn cc gi tr cho cc tham s trong nh
ngha hm. Nu mt gi tr cho tham s khng c truyn khi hm c gi, th gi tr mc
nh cung cp s c s dng, nhng nu mt gi tr c xc nh, th gi tr mc nh
ny b b qua v, thay vo , gi tr truyn c s dng. Bn theo di v d sau:
#include <iostream>
int sum(int a, int b=20)

{
int result;
result = a + b;
return (result);
}
int main ()
{
// local variable declaration:
Trang 62
int a = 100;
int b = 200;
int result;
// calling a function to add the values.

result = sum(a, b);
cout << "Total value is :" << result << endl;
// calling a function again as follows.

result = sum(a);
cout << "Total value is :" << result << endl;
return 0;
}

Total value is :300
Total value is :120
Number trong C++

Thng thng, khi chng ta lm vic vi Number, chng ta s dng cc kiu d liu gc nh int,
short, long, float v double, . Cc kiu d liu s, v gi tr c th v dy gi tr ca chng,
c bn lun trong chng Kiu d liu trong C++.
nh ngha Number trong C++

Bn thy nh ngha cc s trong cc v d a dng cc chng trc. Di y l mt v d
tng hp nh ngha cc kiu s a dng trong C++:
#include <iostream>
int main ()
{
Trang 63
// number definition:
short
s;
int
i;
long
l;
float
f;
double d;
// number assignments;
s = 10;
i = 1000;
l = 1000000;
f = 230.47;
d = 30949.374;
// number printing;
cout << "short
s :" << s << endl;
cout << "int
i :" << i << endl;
cout << "long
l :" << l << endl;
cout << "float
f :" << f << endl;
cout << "double d :" << d << endl;
return 0;
}

short
s :10
int
i :1000
long
l :1000000
float
f :230.47
double d :30949.4
Trang 64
Hm ton hc trong C++

Bn cnh cc hm a dng bn c th to, C++ cng bao gm mt s hm ton hc hu ch cho
bn s dng. Nhng hm ny c sn trong cc th vin C v C++ chun, v c gi l cc
hm built-in. y l cc hm m c th c bao trong chng trnh ca bn v sau s dng.
C++ c mt tp hp hm ton hc a dng, c th c thc hin trn cc kiu s khc nhau.
Bng di lit k mt s hm ton hc c sn hu ch trong C++.
s dng cc hm ny, bn cn bao header file l <cmath>.
STT
Hm & Mc ch
double cos(double);
Hm ny tr v cosin ca mt gc (dng mt double)
double sin(double);
Hm ny tr v sin ca mt gc (dng mt double)
double tan(double);
Hm ny tr v tang ca mt gc (dng mt double)
double log(double);
Hm ny tr v logarit t nhin (ln) ca s
double pow(double, double);

Hm m vi c s l s double u tin v s m l double th hai
double hypot(double, double);

Nu bn truyn di ca hai cnh ca tam gic (ln lt l cc s double), n s tr
v di cnh huyn
Trang 65
double sqrt(double);
Tr v cn bc hai ca s double
int abs(int);
Tr v tr tuyt i ca int
double fabs(double);
Tr v tr tuyt i ca bt k s double no
double floor(double);
10
Tm s integer m nh hn hoc bng tham s truyn cho n

V d sau minh ha mt s hm ton hc trong C++:
#include <iostream>
#include <cmath>
int main ()
{
// number definition:
short
s = 10;
int
i = -1000;
long
l = 100000;
float
f = 230.47;
double d = 200.374;
// mathematical operations;
cout << "sin(d) :" << sin(d) << endl;
cout << "abs(i)
:" << abs(i) << endl;
cout << "floor(d) :" << floor(d) << endl;

cout << "sqrt(f) :" << sqrt(f) << endl;
Trang 66
cout << "pow( d, 2) :" << pow(d, 2) << endl;
return 0;
}

sign(d) :-0.634939
abs(i)
:1000
floor(d) :200
sqrt(f) :15.1812
pow( d, 2 ) :40149.7
S ngu nhin (Random Number) trong C++

Trong mt s trng hp, bn mun to mt s ngu nhin (random number). C hai hm c th
gip bn thc hin vic ny. Hm u tin l rand() c nh ngha trong th vin <cstdlib>: s
ch tr v mt s ngu nhin gi, m c th khng thay i qua cc ln chy chng trnh. gii
quyt im bt thng ny, chng ta s s dng hm srand() trong th vin <ctime>.
V d sau s to vi s ngu nhin trong C++. V d c s dng hm time() ly s giy trn
System time ca bn. Gi tr tr v t time l qua scrand, bn lu l s ngu nhin c to ra
trc li gi rand.
#include <iostream>
#include <ctime>
#include <cstdlib>
int main ()
{
int i,j;
// set the seed

srand( (unsigned)time( NULL ) );
Trang 67
/* generate 10
random numbers. */
for( i = 0; i < 10; i++ )

{
// generate actual random number
j= rand();
cout <<" Random Number : " << j << endl;
}
return 0;
}

Random Number : 1748144778
Mng (Array) trong C++

Ngn ng lp trnh C++ cung cp cu trc d liu gi l mng, c lu tr trong mt tp hp cc
d liu cng kiu vi di c nh. Mt mng c s dng lu tr tp hp d liu, nhng n
rt hu dng nu bn ngh v mt mng cc bin vi cng mt kiu.
Thay v khai bo bin mt cch ri rc, nh bin number0, number1, v number99, bn c th
khai bo mt mng cc gi tr nh numbers[0], numbers[1] v numbers[99] biu din cc gi
tr ring bit. Mt thnh vin c th ca mng c th c truy cp qua index (ch s).
Trang 68
Tt c mng u bao gm cc v tr nh lin k nhau. a ch thp nht tng ng vi thnh vin

u tin v a ch cao nht tng ng vi thnh vin cui cng ca mng.
Khai bo mng trong C++

khai bo mt mng trong ngn ng C++, bn xc nh kiu ca bin v s lng cc phn t
c yu cu bi bin nh sau:
Kieu Ten_mang [ Kich_co_mang ];
y l mng mt chiu. Kich_co_mang phi l mt s nguyn ln hn 0 v Kieu phi hp l

trong ngn ng C++. V d, khai bo mt mng 10 phn t gi l balance vi kiu double, s dng
cu lnh sau y:
double balance[10];
Khi to mng trong C++

Bn c th khi to mng trong C++ hoc tng phn t mt hoc s dng mt cu lnh nh di
y:
double balance[5] = {1000.0, 2.0, 3.4, 17.0, 50.0};
S lng cc gi tr trong du ngoc kp {} khng c ln hn s lng phn t khai bo trong

du ngoc vung [].
Nu bn b st kch c mng th mng ln gi cc gi tr c khi to: Bn s to chnh
xc mt chui c gi tr ging ht chui bn trn bng cch gn tng phn t mt. Di y l mt
v d khi gn gi tr cho mt phn t ca mng:
double balance[] = {1000.0, 2.0, 3.4, 17.0, 50.0};
Bn c th to ra cng mt mng ging nh lm trong v d trc.

balance[4] = 50.0;
Cu lnh bn trn gn gi tr th 5 ca mng gi tr 50.0. Tt c cc mng u c ch s (index)

u tin bng 0, y c gi l ch s c bn v phn t cui cng ca mng c ch s bng
ln ca mng tr i 1. Di y l cch biu din hnh ha cho chui khai bo bn trn thng qua
ch s:
Trang 69
Truy cp cc phn t mng trong C++

Mt mng c truy cp bi cch nh ch s trong tn ca mng. Di y l mt cch truy cp
mt gi tr ca mng:
double salary = balance[9];
Cu lnh trn ly phn t th 10 ca mng v gn gi tr ny cho bin salary. Di y l mt v

d v vic s dng vi tt c m t bn trn:
#include <iostream>
#include <iomanip>
using std::setw;
int main ()
{
int n[ 10 ]; // n is an array of 10 integers
// initialize elements of array n to 0

for ( int i = 0; i < 10; i++ )
{
n[ i ] = i + 100; // set element at location i to i + 100
}
cout << "Element" << setw( 13 ) << "Value" << endl;
// output each array element's value

for ( int j = 0; j < 10; j++ )
{
cout << setw( 7 )<< j << setw( 13 ) << n[ j ] << endl;
}
Trang 70
return 0;
}
Chng trnh ny s dng hm setw() trong C++ nh dng output. Khi on code ny c
bin dch v thc hin, kt qu sau y s c in ra:
Element
Value
100
101
102
103
104
105
106
107
108
109
Chi tit v mng trong C++

Mng l mt phn rt quan trng trong ngn ng C++. Di y l nhng nh ngha quan trng
lin quan n mt mng c th m c trnh by r rng hn cho cc lp trnh vin C++:
Khi nim
Miu t
Mng a chiu trong C++
C++ h tr cc mng a chiu. Mu n gin nht ca

mng ny l mng hai chiu
Con tr ti mt mng trong C++
Truyn mng ti hm nh l
tham s trong C++
Bn c th tr ti phn t u tin ca mng mt cch

n gin ch bi xc nh tn mng , ch khng phi
mt ch s
Bn c th truyn ti hm mt im tr ch ti mt
mng bi xc nh tn mng ch khng phi l mt ch
s
Trang 71
Tr v mng t hm trong C++
C++ cho php mt hm c th tr v mt mng
Chui (String) trong C++

C++ cung cp hai kiu biu din chui nh sau:
Chui theo phong cch ca ngn ng C (C-style),
Lp Chui (String) c gii thiu trong C++ chun.
Chui theo phong cch C

Dng chui ny bt ngun t ngn ng C v tip tc c h tr trong C++. Chui trong ngn ng
lp trnh C thc cht l mng mt chiu ca cc k t m kt thc bi mt k tnull \0.
Phn khai bo v khi to di y to ra mt chui bao gm mt t Hello. gi cc gi tr null
ti cui ca mng, c ca mng cc k t bao gm mt chui phi nhiu hn s lng cc k t
trong t kha Hello.
char greeting[6] = {'H', 'e', 'l', 'l', 'o', '\0'};
Nu bn theo quy tc khi to cc chui, bn c th vit lnh nh sau:

char greeting[] = "Hello";
Di y l phn biu din nh cho on chui trn trong ngn ng C/C++:
Thc t, bn khng t k t null ti v tr cui cng ca bin hng s. B bin dch C t ng thm
\0 ti v tr cui cng ca chui khi n khi to chui. Cng th v d in ra chui sau y:
#include <iostream>
Trang 72
int main ()
{
char greeting[6] = {'H', 'e', 'l', 'l', 'o', '\0'};
cout << "Greeting message: ";

cout << greeting << endl;
return 0;
}
Khi on code trn c bin dch v thc hin, kt qu in ra s nh sau:

Greeting message: Hello
Ngn ng C++ h tr nhiu hm a dng thao tc cc chui kt thc l null:

STT
Hm & Mc ch
strcpy(s1, s2);
Sao chp chui s2 cho chui s1.
strcat(s1, s2);
Ni chui s2 vo cui chui s1.
strlen(s1);
Tr v di ca chui s1.
strcmp(s1, s2);
Tr v 0 nu s1 v s2 l nh nhau; nh hn 0 nu s1<s2; ln hn 0 nu s1>s2.
Trang 73
strchr(s1, ch);
Tr v con tr ti v tr u tin ca ch trong s1.
strstr(s1, s2);
Tr v con tr ti v tr u tin ca chui s2 trong chui s1.

Di y l v d cho vic s dng mt vi hm bn trn:
#include <iostream>
#include <cstring>
int main ()
{
char str1[10] = "Hello";
char str2[10] = "World";
char str3[10];
int
len ;
// copy str1 into str3

strcpy( str3, str1);
cout << "strcpy( str3, str1) : " << str3 << endl;
// concatenates str1 and str2

strcat( str1, str2);
cout << "strcat( str1, str2): " << str1 << endl;
// total lenghth of str1 after concatenation

len = strlen(str1);
cout << "strlen(str1) : " << len << endl;
return 0;
Trang 74
Khi on code trn c bin dch v thc hin, kt qu di y s c in ra:

strcpy( str3, str1) : Hello
strcat( str1, str2): HelloWorld
strlen(str1) : 10
Lp String trong C++

Th vin chun C++ cung cp mt kiu lp String m h tr tt c hot ng lin quan ti chui
cp trn, v b sung thm nhiu tnh nng na. Chng ta s hc lp ny trong Th vin
chun C++ (C++ Standard Library), nhng lc ny, chng ta xem xt v d sau:
Lc ny, c th bn khng hiu v d ny, bi v chng ta cha bn lun v Lp v i
tng trong C++. V th, bn quan st v ghi nh chng ti khi bn hiu cc khi nim v
Hng i tng c trnh by chng sau .
#include <iostream>
#include <string>
int main ()
{
string str1 = "Hello";
string str2 = "World";
string str3;
int
len ;
// copy str1 into str3

str3 = str1;
cout << "str3 : " << str3 << endl;
// concatenates str1 and str2

str3 = str1 + str2;
Trang 75
cout << "str1 + str2 : " << str3 << endl;
// total lenghth of str3 after concatenation

len = str3.size();
cout << "str3.size() :
" << len << endl;
return 0;
}
Khi code trn c bin dch v thc thi, n s cho kt qu:

str3 : Hello
str1 + str2 : HelloWorld
str3.size() :
10
Con tr trong C++

Con tr - Pointer trong ngn ng C++ rt d hc v th v. Mt vi tc v trong ngn ng C++ c
thc hin d dng hn nh con tr, v nhng tc v khc tr nn linh hot hn, nh trong vic cp
pht b nh, khng th thc hin m khng dng con tr. Do rt cn thit phi nm vng con
tr khi tr thnh mt lp trnh vin C++ hon thin. By gi hy bt u bng nhng bc n
gin nht.
Nh bn bit, mi bin trong mt vng nh nht nh v mi vng nh ny c a ch c n c
nh ngha d dng trong vic truy cp s dng ton t (&) tng ng vi a ch ca n trong
b nh. Xem xt v d di y, s in ra a ch ca bin c nh ngha:
#include <iostream>
int main ()
{
int
var1;
char var2[10];
Trang 76
cout << "Address of var1 variable: ";

cout << &var1 << endl;
cout << "Address of var2 variable: ";

cout << &var2 << endl;
return 0;
}
Khi cc on code trn c bin dch v thc hin, n s in ra kt qu sau y:

Address of var1 variable: 0xbfebd5c0
Address of var2 variable: 0xbfebd5b6
Con tr l g?
Mt con tr l mt bin m trong gi tr ca n l a ch ca bin khc. V d nh a ch ca
vng nh. Ging nh cc bin v hng s, bn phi khai bo con tr trc khi bn c th s dng
n lu tr bt k a ch ca bin no. Dng tng qut ca vic khai bo con tr nh sau:
type *var-name;
y, type l kiu d liu c bn con tr, n l kiu hp l trong ngn ng C v var-namel tn

gi tr ca con tr. Phn k t * s dng trong khai bo con tr ging nh vic bn s dng cho
php nhn. Mc d vy, trong khai bo ny, k t * c thit k s dng cc bin ca con tr.
Di y l mt s cch khai bo hp l ca con tr:
int
*ip;
// pointer to an integer
double *dp;
// pointer to a double
float
*fp;
// pointer to a float
char
*ch
// pointer to character
Kiu d liu thc s ca gi tr ca tt c cc con tr, c th l integer, float, character, hoc kiu
khc, l ging nh, mt s long hexa biu din mt a ch b nh. im khc nhau duy nht ca
cc con tr ca cc kiu d liu khc nhau l kiu d liu ca bin hoc hng s m con tr ch ti.
Trang 77
Cch s dng con tr trong C++

C mt vi php ton quan trng, s gip chng ta lm vic vi con tr mt cch thng xuyn: a)
chng ta nh ngha bin con tr, b) gn a ch ca bin n mt con tr v c) cui cng truy cp
cc gi tr bin a ch trong bin con tr. iu ny c thc hin bi ton t * tr v gi tr cc
cc bin cha trong a ch c xc nh bi ton t ny. Di y l cc s dng nhng php
ton trn:
#include <iostream>
int main ()
{
int
var = 20;
// actual variable declaration.
int
*ip;
// pointer variable
ip = &var;
// store address of var in pointer variable
cout << "Value of var variable: ";

cout << var << endl;
// print the address stored in ip pointer variable

cout << "Address stored in ip variable: ";
cout << ip << endl;
// access the value at the address available in pointer

cout << "Value of *ip variable: ";
cout << *ip << endl;
return 0;
}
Trang 78
Value of var variable: 20

Address stored in ip variable: 0xbfc601ac
Value of *ip variable: 20
Chi tit v con tr trong C++

Con tr c nhiu khi nim nhng cng kh d hc v rt quan trng trong lp trnh ngn ng
C++. Di y l nhng khi nim quan trng v con tr trong C++, c trnh by r rng cho
bn, khi bn click vo link tng ng.
Khi nim
Miu t
Con tr Null trong C++
C++ h tr con tr null, l mt constant vi gi tr l 0

c nh ngha trong mt s th vin chun
Con tr s hc trong C++
C 4 ton t i s m c th c s dng trn cc

con tr l: ++, --, +, -
Con tr v mng trong C++
C mi lin h g gia con tr v mng. Bn kim tra

ngay.
Mng con tr trong C++
Con tr ti con tr trong C++
Truyn con tr ti hm trong

C++
Tr v con tr t hm trong C++
Bn c th nh ngha cc mng gi cc con tr.
C++ cho php bn tr ti mt con tr ...
Truyn mt tham s bi tham chiu hoc a ch: c hai

cho cc tham s c truyn kh nng c th c
thay i trong hm gi bi hm c gi.
C++ cho php mt hm tr v mt con tr ti bin cc

b, bin tnh v cng nh b nh c cp pht ng.
Tham chiu trong C++

Mt bin tham chiu l mt alias, l tn khc cho mt bin ang tn ti. Khi mt tham chiu
c khi to vi mt bin, th: hoc tn bin hoc tn tham chiu c th c s dng tham
chiu ti bin .
Trang 79
Tham chiu v con tr trong C++

S dng tham chiu c th thng gy bi ri cho bn nh vi con tr, tuy nhin, c 3 im khc
nhau gia tham chiu v con tr trong C++:
Bn khng th c tham chiu NULL. Bn lun lun phi gi s rng mt tham chiu c
kt ni vi mt phn ca kho lu tr.
Khi mt tham chiu c khi to cho mt i tng, n khng th b thay i tham

chiu ti i tng khc. Cc con tr c th c tr ti i tng khc ti bt k thi
im no.
Mt tham chiu phi c khi to khi n c to. Cc con tr c th c to ti bt k

thi im no.
To tham chiu trong C++

Bn coi mt tn bin nh l mt label c nh km vi v tr bin trong b nh. Sau , bn c
th ngh v tham chiu nh l label th hai c nh km vi v tr b nh . V th, bn c th
truy cp ni dung ca bin thng qua: hoc tn bin ban u hoc tham chiu. Gi s chng ta c
v d sau:
int
i = 17;
Bn c th khai bo cc bin tham chiu cho i nh sau:

int&
r = i;
c & trong cc khai bo ny l Tham chiu. V th, trong khai bo u tin, r l tham chiu
integer c khi to cho i v trong tham chiu th hai, s l tham chiu double c khi to cho
d. V d sau s dng cc tham chiu trong C++:
#include <iostream>
int main ()
{
// declare simple variables
Trang 80
int
i;
double d;
// declare reference variables

int&
r = i;
double& s = d;
i = 5;
cout << "Value of i : " << i << endl;
cout << "Value of i reference : " << r
<< endl;
d = 11.7;
cout << "Value of d : " << d << endl;
cout << "Value of d reference : " << s
<< endl;
return 0;
}
Khi code trn c bin dch v thc thi, n s cho kt qu sau:

Value of i : 5
Value of i reference : 5
Value of d : 11.7
Value of d reference : 11.7
Tham chiu trong C++ thng c s dng cho danh sch cc tham s hm v hm tr v cc
gi tr. Sau y l hai khi nim quan trng lin quan ti tham chiu trong C++, bn s thy chi tit
khi click vo link:
Khi nim
Miu t
Truyn tham s bi tham chiu
C++ h tr truyn cc tham chiu nh l cc tham s

hm m an ton hn so vi cc tham s
trong C++
Trang 81
Tr v gi tr bi tham chiu
Bn c th tr v tham chiu t mt hm C++ ging

nh bt k kiu d liu khc c th c tr v
trong C++
Date v Time trong C++

Th vin chun C++ (C++ Standard Library) khng cung cp mt kiu Date thch ng. C++ k
tha cu trc v hm thao tc Date v Time t C. truy cp cc hm v cu trc lin quan ti
Date v Time, bn s cn khai bo <ctime> trong chng trnh C++ ca bn.
C 4 kiu lin quan ti thi gian: clock_t, time_t, size_t, v tm. Trong cc kiu clock_t, size_t
v time_t c th biu din System date v time dng int.
Kiu cu trc tm gi Date v Time trong mu mt cu trc C c cc phn t sau:
struct tm {
int tm_sec;
// seconds of minutes from 0 to 61
int tm_min;
// minutes of hour from 0 to 59
int tm_hour;
// hours of day from 0 to 24
int tm_mday;
// day of month from 1 to 31
int tm_mon;
// month of year from 0 to 11
int tm_year;
// year since 1900
int tm_wday;
// days since sunday
int tm_yday;
// days since January 1st
int tm_isdst; // hours of daylight savings time

}
Bng di lit k cc hm quan trng trong khi bn lm vic vi Date v Time trong C hoc C++.
Tt v hm ny l mt phn ca th vin C v C++ chun v bn c th kim tra chi tit bi s
dng tham chiu ti Th vin chun C++ c cung cp di y:
STT
Hm & Mc ch
time_t time(time_t *time);

Tr v thi gian theo lch ca h thng, l s giy tri qua t 1/1/1970. Nu h
Trang 82
thng khng c thi gian, n tr v -1
char *ctime(const time_t *time);

Hm ny tr v mt con tr ti mt chui ca mu: day month year
hours:minutes:seconds year\n\0.
struct tm *localtime(const time_t *time);

struct tm *localtime(const time_t *time); Hm ny tr v mt con tr ti cu trctm biu
din local time
clock_t clock(void);
Hm ny tr v mt gi tr m xp x vi lng thi gian ca chng trnh ang gi
ang chy. Tr v -1 nu thi gian l khng c sn
char * asctime ( const struct tm * time );

Tr v mt con tr ti mt chui m cha thng tin c lu gi trong cu trc c
tr ti bi time c bin i thnh mu: day month date hours:minutes:seconds
year\n\0
struct tm *gmtime(const time_t *time);

Tr v mt con tr ti time trong mu cu trc tm. Thi gian c biu din dng
Coordinated Universal Time (UTC), v bn cht l Greenwich Mean Time (GMT).
time_t mktime(struct tm *time);

Tr v thi gian theo lch tng ng vi thi gian c tm thy trong cu trc
c tr ti bi time
double difftime ( time_t time2, time_t time1 );

Hm ny tnh ton s khc nhau v s giy ca time1 v time2
Trang 83
9
size_t strftime();
Hm ny c th c s dng nh dng Date v Time trong mt nh dng c th
Date v Time hin ti trong C++

Gi s bn mun ly date v time hin ti ca h thng: hoc local time hoc dng UTC. V d sau
thc hin cng vic trn:
#include <iostream>
#include <ctime>
int main( )
{
// current date/time based on current system
time_t now = time(0);
// convert now to string form

char* dt = ctime(&now);
cout << "The local date and time is: " << dt << endl;
// convert now to tm struct for UTC

tm *gmtm = gmtime(&now);
dt = asctime(gmtm);
cout << "The UTC date and time is:"<< dt << endl;
}

The local date and time is: Sat Jan
The UTC date and time is:Sun Jan
8 20:07:41 2011
9 03:07:41 2011
Trang 84
nh dng Time bi s dng cu trc tm trong C++

Cu trc tm l rt quan trng trong khi lm vic vi Date v Time trong C v C++. Cu trc ny gi
Date v Time trong mu ca mt cu trc C c cp trn. Hu ht cc hm lin quan ti
thi gian u s dng cu trc tm. V d sau s dng cc hm a dng lin quan ti Date v Time
v cu trc tm:
Trong khi s dng cu trc trong chng ny, mnh gi s bn hiu c bn v cu trc trong C
v cch truy cp cc thnh vin ca cu trc bi s dng ton t ->.
#include <iostream>
#include <ctime>
int main( )
{
// current date/time based on current system
time_t now = time(0);
cout << "Number of sec since January 1,1970:" << now << endl;
tm *ltm = localtime(&now);
// print various components of tm structure.

cout << "Year: "<< 1900 + ltm->tm_year << endl;
cout << "Month: "<< 1 + ltm->tm_mon<< endl;
cout << "Day: "<<
ltm->tm_mday << endl;
cout << "Time: "<< 1 + ltm->tm_hour << ":";

cout << 1 + ltm->tm_min << ":";
cout << 1 + ltm->tm_sec << endl;
}

Number of sec since January 1, 1970:1294548238
Trang 85
Year: 2011
Month: 1
Day: 8
Time: 22: 44:59
Input/Output trong C++

Th vin chun C++ cung cp nhiu kh nng input/output v s c bn lun trong cc
chng sau. Trong chng ny, chng ta tho lun rt c bn v ph bin nht v hot ng I/O
cn thit cho lp trnh C++.
I/O trong C++ din ra trong cc Stream (lung), m l dy cc byte. Nu cc byte chy t mt thit
b, nh bn phm, disk drive, hoc mt kt ni mng , ti b nh chnh, n c gi l hot
ng input. Nu cc byte chy t b nh chnh ti cc thit b, nh mn hnh hin th, my in, dist
drive, hoc mt kt ni mng , n c gi l hot ng output.
Header file cho I/O trong C++

Bng di lit k cc header file quan trng cho cc chng trnh C++:
Header File
Miu t
<iostream>
File ny nh ngha cc i tng cin, cout, cerr v clog, tng ng vi

Standard Input Stream (Lung u vo chun), Standard Output Stream
(Lung u ra chun), Un-buffered Standard Error Stream (Lung li
chun khng c m) v Buffered Standard Error Stream (Lung li
chun c m)
<iomanip>
File ny khai bo cc dch v hu ch thc hin hot ng I/O c

nh dng vi cc b thao tc lung c tham s ha
nh setw vsetprecision.
<fstream>
File ny khai bo cc dch v x l file c kim sot bi ngi dng.

Chng ta s tho lun chi tit v n trong chng File v Stream trong
C++
Trang 86
Standard Output Stream (cout) trong C++

i tng tin nh ngha cout l mt minh ha ca lp ostream. i tng cout c xem nh
c kt ni ti thit b u ra chun, thng l mn hnh. i tng cout c s dng kt hp
vi ton t chn lung (insertion operator), c vit l <<, nh v d di y:
#include <iostream>
int main( )
{
char str[] = "Hello C++";
cout << "Value of str is : " << str << endl;

}

Value of str is : Hello C++
B bin dch C++ cng quyt nh kiu d liu ca bin c output v chn ton t chn lung
thch hp hin th gi tr. Ton t << c np chng (overload) ti d liu u ra ca kiu
integer, float, double, string, v gi tr con tr c sn.
Ton t chn lung << c th c s dng nhiu hn mt ln trong mt lnh v endl c s
dng them mt dng mi ti cui dng .
Standard Input Stream (cin) trong C++

i tng tin nh ngha cin l mt minh ha ca lp isrtream. i tng cin c xem nh nh
km vi thit b u vo chun, m thng l bn phm. i tng cin c s dng kt hp vi
ton t trch lung (extraction operator), vit l >>, nh trong v d sau:
#include <iostream>
Trang 87
int main( )
{
char name[50];
cout << "Please enter your name: ";

cin >> name;
cout << "Your name is: " << name << endl;
Khi code trn c bin dch v thc thi, n s nhc bn nhp mt tn. Bn nhp mt gi tr v sau
enter thy kt qu ging nh sau:
Please enter your name: cplusplus
Your name is: cplusplus
B bin dch C++ cng quyt nh kiu d liu ca gi tr nhp v chn ton t trch lung thch
hp trch gi tr v lu gi n trong cc bin cung cp.
Ton t trch lung >> c th c s dng nhiu hn mt ln trong mt lnh. yu cu nhiu
hn mt d liu chun, bn c th s dng:
cin >> name >> age;
N tng ng vi hai lnh sau:

cin >> name;
cin >> age;
Standard Error Stream (cerr) trong C++

i tng tin nh ngha cerr l mt minh ha ca lp ostream. i tng cerr c xem nh
nh km vi thit b li chun, m cng l mn hnh hin th nhng i tng cerr l Un-buffered
(khng c m) v mi s chn lung ti cerr lm u ra ca n xut hin tc th.
i tng cerr trong C++ cng c s dng kt hp vi ton t chn lung, nh trong v d sau:
#include <iostream>
Trang 88
int main( )
{
char str[] = "Unable to read....";
cerr << "Error message : " << str << endl;

}

Error message : Unable to read....
Standard Log Stream (clog) trong C++

i tng tin nh ngha clog l mt minh ha ca lp ostream. i tng clog c xem nh
nh km vi thit b li chun, cng l mn hnh hin th nhng i tng clog l c m.
Ngha l, mi s chn lung ti clog lm u ra ca n c gi trong mt b m (buffer) ti khi
b m b in y hoc ti khi b m b flush (chuyn t m ra a).
i tng clog trong C++ cng c s dng kt hp vi ton t chn lung, nh v d sau:
#include <iostream>
int main( )
{
char str[] = "Unable to read....";
clog << "Error message : " << str << endl;

}

Error message : Unable to read....
Trang 89
Bn s khng th thy bt k im khc bit no gia cout, cerr v clog vi nhng v d nh ny,
nhng trong khi vit v thc thi cc chng trnh ln, th s khc nhau ny tr nn r rng hn. V
th, n l bi thc hnh tt cho bn hin th cc thng bo li (error message) bi s dng
lung cerr v trong khi hin th thng bo log khc, th clog nn c s dng.
Cu trc d liu trong C++

Cc mng trong C/C++ cho php bn nh ngha mt vi loi bin c th gi gi tr ca mt vi
thnh vin cng kiu d liu. Nhng structure - cu trc l mt loi d liu khc trong ngn ng
lp trnh C/C++, cho php bn kt hp cc d liu khc kiu nhau.
Cu trc c s dng biu din mt bn ghi. Gi s bn mun lu tr gi tr ca mt quyn
sch trong th vin ca bn. Bn c th lu tr cc thuc tnh ca sch sau y:
Title
Author
Subject
Book ID
nh ngha mt cu trc trong C++

nh ngha cu trc, bn phi s dng cu lnh struct. Cu lnh struct nh ngha mt kiu d
liu mi, vi hn mt thnh vin trong chng trnh ca bn. Dng tng qut ca cu lnh struct
nh sau y:
struct [structure tag]
{
member definition;
member definition;
...
member definition;
} [one or more structure variables];
y, structure tag c th ty v mt thnh vin nh ngha l cc bin thng nh int i, float j

hoc mt nh ngha bin khc . Ti phn cui cng ca nh ngha cu trc, trc du chm
phy, bn c th xc nh mt hoc nhiu bin cu trc (ty chn). Di y l cch khai bo bin
cu trc Book:
Trang 90
struct Books
{
char
title[50];
char
author[50];
char
subject[100];
int
book_id;
}book;
Truy cp cc thnh vin ca cu trc trong C++

truy cp bt k thnh vin no ca cu trc, bn s dng ton t truy cp phn t (.). Ton t
truy cp thnh vin cu trc c m ha l du chm gia tn bin cu trc v thnh vin cu
trc m bn mun truy cp. Bn s s dng t kha struct nh ngha cc bin ca kiu cu
trc. Di y l v d cho cch s dng cu trc trong C++:
#include <iostream>
#include <cstring>
struct Books
{
char
title[50];
char
author[50];
char
subject[100];
int
book_id;
};
int main( )
{
struct Books Book1;
// Declare Book1 of type Book
struct Books Book2;
// book 1 specification
strcpy( Book1.title, "Learn C++ Programming");
Trang 91
strcpy( Book1.author, "Chand Miyan");

strcpy( Book1.subject, "C++ Programming");
Book1.book_id = 6495407;
strcpy( Book2.title, "Telecom Billing");
strcpy( Book2.author, "Yakit Singha");
strcpy( Book2.subject, "Telecom");
// Print Book1 info

cout << "Book 1 title : " << Book1.title <<endl;
cout << "Book 1 author : " << Book1.author <<endl;
cout << "Book 1 subject : " << Book1.subject <<endl;
cout << "Book 1 id : " << Book1.book_id <<endl;
// Print Book2 info

cout << "Book 2 title : " << Book2.title <<endl;
cout << "Book 2 author : " << Book2.author <<endl;
cout << "Book 2 subject : " << Book2.subject <<endl;
cout << "Book 2 id : " << Book2.book_id <<endl;
return 0;
}

Book 1 title : Learn C++ Programming
Book 1 author : Chand Miyan
Book 1 subject : C++ Programming
Book 1 id : 6495407
Book 2 title : Telecom Billing
Book 2 author : Yakit Singha
Book 2 subject : Telecom
Trang 92
Book 2 id : 6495700
Cu trc nh l tham s hm trong C++

Bn c th truyn mt cu trc nh mt tham s ca hm theo cch kh ging nh khi bn truyn
bt k bin hay con tr khc. Bn s truy cp bin cu trc theo cch tng t nh bn truy cp
trong v d trn:
#include <iostream>
#include <cstring>

void printBook( struct Books book );
struct Books
{
char
title[50];
char
author[50];
char
subject[100];
int
book_id;
};
int main( )
{
struct Books Book1;
struct Books Book2;
Trang 93

// Print Book1 info

printBook( Book1 );
// Print Book2 info

printBook( Book2 );
return 0;
}
void printBook( struct Books book )
{
cout << "Book title : " << book.title <<endl;
cout << "Book author : " << book.author <<endl;
cout << "Book subject : " << book.subject <<endl;
cout << "Book id : " << book.book_id <<endl;
}

Book title : Learn C++ Programming
Book author : Chand Miyan
Book subject : C++ Programming
Book id : 6495407
Book title : Telecom Billing
Book author : Yakit Singha
Book subject : Telecom
Book id : 6495700
Con tr ti cu trc trong C++

Bn c th nh ngha con tr cu trc theo cch tng t bn nh ngha con tr ti bt k bin
no khc nh sau:
Trang 94
struct Books *struct_pointer;
By gi bn c th lu a ch ca bin cu trc trong bin con tr c nh ngha trn. tm

a ch ca mt bin cu trc, t ton t & trc tn cu trc nh sau:
struct_pointer = &Book1;
truy cp vo thnh vin ca mt structure s dng con tr ti structure , bn phi s dng

ton t -> nh sau:
struct_pointer->title;
By gi chng ta vit li v d trn s dng con tr cu trc, hy vng iu ny s d dng cho bn

hiu khi nim ny:
#include <iostream>
#include <cstring>

void printBook( struct Books *book );
struct Books
{
char
title[50];
char
author[50];
char
subject[100];
int
book_id;
};
int main( )
{
struct Books Book1;
struct Books Book2;
// Book 1 specification
Trang 95

// Book 2 specification
// Print Book1 info, passing address of structure

printBook( &Book1 );
// Print Book1 info, passing address of structure

printBook( &Book2 );
return 0;
}
// This function accept pointer to structure as parameter.
void printBook( struct Books *book )
{
cout << "Book title : " << book->title <<endl;
cout << "Book author : " << book->author <<endl;
cout << "Book subject : " << book->subject <<endl;
cout << "Book id : " << book->book_id <<endl;
}

Book title : Learn C++ Programming
Book author : Chand Miyan
Book subject : C++ Programming
Book id : 6495407
Book title : Telecom Billing
Trang 96
Book author : Yakit Singha

Book subject : Telecom
Book id : 6495700
T kha typedef trong C++

C mt cch d dng hn nh ngha cc cu trc hoc bn c th alias cc kiu bn to. V
d:
typedef struct
{
char
title[50];
char
author[50];
char
subject[100];
int
book_id;
}Books;
Lc ny, bn c th s dng Books mt cch trc tip nh ngha cc bin ca kiu cu

trc Books m khng s dng t kha struct. Sau y l v d:
Books Book1, Book2;
Bn c th s dng t kha typedef trong C++ cho cc dng khng phi cu trc, nh sau:
typedef long int *pint32;
pint32 x, y, z;
Vi x, y v z l tt c con tr ti long int.
Lp v i tng trong C++

Mc ch chnh ca C++ l b sung thm tnh hng i tng (object) cho Ngn ng lp trnh C
v cc Lp (class) l tnh nng trung tm ca C++ m h tr lp trnh hng i tng v thng
c gi l cc kiu ngi dng t nh ngha (user-defined).
Mt lp c s dng xc nh form ca mt i tng v n kt ni s biu din d liu v
cc phng thc thao tc cc d liu vo trong mt package gn gng. D liu v hm bn
trong mt lp c gi l cc thnh vin ca lp .
Trang 97
nh ngha Lp trong C++

Khi bn nh ngha mt lp, bn nh ngha mt blueprint cho mt kiu d liu. iu ny khng
thc s nh ngha bt k d liu no, nhng n nh ngha ngha tn lp l g, l, nhng g
mt i tng ca lp s bao gm v nhng hot ng no c th c thc hin trn mt i
tng .
Mt nh ngha lp trong C++ bt u vi t kha class, c theo sau bi tn lp v phn thn
lp, c bao quanh trong mt cp du ngoc mc. Mt nh ngha lp phi c theo sau: hoc
bi mt du chm phy hoc mt danh sch cc khai bo. V d, chng ta nh ngha kiu d liu
Box bi s dng t kha class trong C++ nh sau:
class Box
{
public:
double length;
// Length of a box
double breadth;
// Breadth of a box
double height;
// Height of a box
};
T kha public quyt nh cc thuc tnh truy cp ca cc thnh vin lp m theo sau n. Mt
thnh vin public c th c truy cp t bn ngoi lp bt c u bn trong phm vi (scope) ca
i tng lp . Bn cng c th xc nh cc thnh vin ca lp l privatehoc protected s
c bn lun trong chng ph.
nh ngha i tng trong C++

Mt lp cung cp cc blueprint cho cc i tng, v th v c bn, mt i tng c to t mt
lp. Chng ta khai bo cc i tng ca mt lp ging ng nh chng ta khai bo cc bin ca
kiu c bn. Cc lnh sau khai bo hai i tng ca lp Box:
Box Box1;
// Declare Box1 of type Box
Box Box2;
C hai i tng Box1 v Box2 s c bn sao ca cc thnh vin d liu (Data Member) ring.
Trang 98
Truy cp cc thnh vin d liu trong C++

Cc thnh vin d liu public ca cc i tng ca mt lp c th c truy cp bi s dng
ton t truy cp thnh vin trc tip l du chm (.). Bn s thy r rng khi xem v d sau:
#include <iostream>
class Box
{
public:
double length;
// Length of a box
double breadth;
// Breadth of a box
double height;
// Height of a box
};
int main( )
{
Box Box1;
Box Box2;
double volume = 0.0;
// Store the volume of a box here
// box 1 specification
Box1.height = 5.0;
Box1.length = 6.0;
Box1.breadth = 7.0;
Box2.height = 10.0;
Box2.length = 12.0;
Box2.breadth = 13.0;
// volume of box 1
volume = Box1.height * Box1.length * Box1.breadth;
Trang 99
cout << "Volume of Box1 : " << volume <<endl;
// volume of box 2
volume = Box2.height * Box2.length * Box2.breadth;
return 0;
}

Volume of Box1 : 210
im quan trng cn nh l: cc thnh vin private v protected khng th c truy cp mt cch

trc tip bi s dng ton t truy cp thnh vin tr tip ny. Chng ta s hc cch cc thnh vin
private v protected c th c truy cp.
Chi tit v Lp & i tng trong C++

Lc ny, bn hiu kh c bn v Lp v i tng trong C++. Di y l cc khi nim kh
th v lin quan ti Lp v i tng trong C++ m bn cn quan tm. Bn click vo link xem
chi tit.
Khi nim
Hm thnh vin lp trong C++
Access Modifier cho lp trong

C++
Constructor & Destructor trong

C++
Miu t
Mt hm thnh vin ca mt lp l mt hm c nh
ngha ca n hoc prototype ca n bn trong nh
ngha lp ging nh bt k bin no khc
Mt thnh vin lp c th c nh ngha l public,
private hoc protected. Theo mc nh, cc thnh vin
s l private
Mt class constructor l mt hm c bit trong mt lp
m c gi khi mt i tng mi ca lp c
to. Mt class destructor cng l mt hm c bit m
c gi khi i tng to b hy
Trang 100
Copy Constructor trong C++
copy constructor l mt constructor m to mt i

tng bng vic khi to n vi mt i tng ca
cng lp , m c to trc
Hm Friend trong C++
Hm friend c cho php truy cp ti cc thnh vin

l private v protected ca mt lp
Hm Inline trong C++
Vi mt hm inline, trnh bin dch c gng m rng

code trong thn hm th ch cho mt li gi ti hm
Con tr this trong C++
Mi i tng c mt con tr this c bit, m tr ti

chnh i tng
Con tr ti lp trong C++
Thnh vin Static trong C++
Mt con tr ti mt lp c thc hin ging ht nh

cch mt con tr ti mt cu trc. Thc ra, mt lp l
mt cu trc vi cc hm trong n
C cc thnh vin d liu (data member) v cc thnh

vin hm (function member) c th c khai bo l
static
Tnh k tha trong C++

Mt trong nhng khi nim quan trng nht trong lp trnh hng i tng l Tnh k tha
(Inheritance). Tnh k tha cho php chng ta nh ngha mt lp trong iu kin mt lp khc,
m lm cho n d dng hn to v duy tr mt ng dng. iu ny cng cung cp mt c hi
ti s dng tnh nng code v thi gian thc thi nhanh hn.
Khi to mt lp, thay v vit ton b cc thnh vin d liu v cc hm thnh vin mi, lp trnh
vin c th nn k tha cc thnh vin ca mt lp ang tn ti. Lp ang tn ti ny c gi
l Base Class - lp c s, v lp mi c xem nh l Derived Class lp tha k.
tng ca tnh k tha trin khai mi quan h IS A (L Mt). V d: mammal IS-A animal, dog ISA mammal, v th dog IS-A animal v ....
Trang 101
Lp c s (Base Class) v Lp tha k (Derived

Class) trong C++
Mt lp c th c k tha t hn mt lp khc, ngha l, n c th k tha d liu v hm t
nhiu lp c s. nh ngha mt lp k tha (Derived Class), chng ta s dng mt danh sch
xc nh cc lp c s. Danh sch ny lit k mt hoc nhiu lp c s v c form sau:
class derived-class: access-specifier base-class
y, access-specifier l public, protected hoc private, v base-class l tn ca mt lp

c nh ngha trc . Nu access-specifier khng c s dng, th mc nh l private.
Bn xem xt v d sau vi Shape l lp c s v Rectangle l lp k tha:
#include <iostream>
// Base class
class Shape
{
public:
void setWidth(int w)
{
width = w;
}
void setHeight(int h)
{
height = h;
}
protected:
int width;
int height;
};
Trang 102
// Derived class
class Rectangle: public Shape
{
public:
int getArea()
{
return (width * height);
}
};
int main(void)
{
Rectangle Rect;
Rect.setWidth(5);
Rect.setHeight(7);
// Print the area of the object.

cout << "Total area: " << Rect.getArea() << endl;
return 0;
}

Total area: 35
iu khin truy cp v Tnh k tha trong C++

Mt lp k tha c th truy cp tt c thnh vin khng phi l private ca lp c s ca n. V
th, cc thnh vin lp c s, m l hn ch truy cp ti cc hm thnh vin ca lp k tha, nn
c khai bo l private trong lp c s.
Chng ta tng kt cc kiu truy cp khc nhau, tng ng vi ai c th truy cp chng nh sau:
Trang 103
Truy cp
public
protected
private
Trong cng lp
Lp k tha
Khng
Bn ngoi lp
Khng
Khng
Mt lp k tha (Derived Class) s k tha tt c cc phng thc ca lp c s, ngoi tr:
Constructor, destructor v copy constructor ca lp c s.
Overloaded operator (ton t np chng) ca lp c s.
Hm friend ca lp c s.
Kiu k tha trong C++

Khi k tha t mt lp c s, lp c s c th c k tha thng qua kiu k tha lpublic,
protected hoc private. Kiu k tha trong C++ c xc nh bi Access-specifier c gii
thc trn.
Chng ta him khi s dng kiu k tha protected hoc private, nhng kiu k thapublic th
c s dng ph bin hn. Trong khi s dng cc kiu k tha khc sau, bn nn ghi nh cc
quy tc sau:
Kiu k tha Public: Khi k tha t mt lp c s l public, th cc thnh vinpublic ca

lp c s tr thnh cc thnh vin public ca lp k tha; v cc thnh
vin protected ca lp c s tr thnh cc thnh vin protected ca lp k tha. Mt
thnh vin l private ca lp c s l khng bao gi c th c truy cp trc tip t mt
lp k tha, nhng c th truy cp thng qua cc li gi ti cc thnh
vin public v protected ca lp c s .
Kiu k tha protected: Khi k tha t mt lp c s l protected, th cc thnh

vin public v protected ca lp c s tr thnh cc thnh vin protected ca lp k
tha
Trang 104
Kiu k tha private: Khi k tha t mt lp c s l private, th cc thnh

vinpublic v protected ca lp c s tr thnh cc thnh vin private ca lp k tha
a k tha trong C++

Mt lp trong C++ c th k tha cc thnh vin t nhiu lp, v y l c php:
class derived-class: access baseA, access baseB....
Ti y, access l public, protected hoc private v s c cung cp cho mi lp c s, v

chng s c phn bit vi nhau bi du phy nh trn. Bn th v d sau:
#include <iostream>
// Base class Shape

class Shape
{
public:
{
width = w;
}
{
height = h;
}
protected:
int width;
int height;
};
// Base class PaintCost

class PaintCost
{
Trang 105
public:
int getCost(int area)
{
return area * 70;
}
};
// Derived class
class Rectangle: public Shape, public PaintCost
{
public:
int getArea()
{
}
};
int main(void)
{
Rectangle Rect;
int area;
Rect.setWidth(5);
Rect.setHeight(7);
area = Rect.getArea();

cout << "Total area: " << Rect.getArea() << endl;
// Print the total cost of painting

cout << "Total paint cost: $" << Rect.getCost(area) << endl;
Trang 106
return 0;
}

Total area: 35
Total paint cost: $2450
Np chng ton t v Np chng hm

trong C++
C++ cho php bn xc nh nhiu hn mt nh ngha cho mt tn hm hoc mt ton t trong
cng phm vi (scope), c gi tng ng l Np chng hm (function overloading) v Np
chng ton t (operator overloading) trong C++.
Mt khai bo np chng l mt khai bo m c khai bo vi cng tn nh mt khai bo c
khai bo trc trong cng phm vi, ngoi tr rng: c hai khai bo c cc tham s khc nhau v
nh ngha khc nhau.
Khi bn gi mt hm np chng hoc mt ton t np chng, th compiler quyt nh nh ngha
thch hp nht s dng bng vic so snh cc kiu tham s bn s dng gi hm hoc
ton t vi cc kiu tham s c xc nh trong cc nh ngha. Tin trnh la chn hm np
chng hoc ton t np chng thch hp nht ny c gi l overload resolution - phn gii
np chng.
Np chng hm trong C++

Bn c th c nhiu nh ngha cho cng tn hm trong cng phm vi. nh ngha ca hm phi
khc ln nhau v kiu v/hoc s tham s trong danh sch tham s. Bn khng th np chng cc
khai bo hm m ch khc nhau kiu tr v.
Trong v d sau, cng mt hm print() c s dng in cc kiu d liu khc nhau:
#include <iostream>
class printData
{
Trang 107
public:
void print(int i) {
cout << "Printing int: " << i << endl;
}
void print(double
f) {
cout << "Printing float: " << f << endl;

}
void print(char* c) {
cout << "Printing character: " << c << endl;
}
};
int main(void)
{
printData pd;
// Call print to print integer

pd.print(5);
// Call print to print float
pd.print(500.263);
// Call print to print character
pd.print("Hello C++");
return 0;
}

Printing int: 5
Printing float: 500.263
Printing character: Hello C++
Trang 108
Np chng ton t trong C++

Bn c th nh ngha li hoc np chng hu ht cc ton t c sn trong C++. V th, mt lp
trnh vin c th s dng cc ton t vi kiu t nh ngha (user-defined).
Np chng ton t trong C++ l cc hm vi tn c bit: Tn hm l t kha operator theo sau l
k hiu ca ton t ang c nh ngha. Ging nh bt k hm khc, mt ton t np chng c
mt kiu tr v v mt danh sch tham s.
Box operator+(const Box&);
Khai bo ton t + cng hai i tng Box v tr v i tng Box cui cng. Hu ht ton t
np chng c th c nh ngha di dng: cc hm khng c thnh vin (non-member) hoc
cc hm thnh vin lp. Trong trng hp trn, chng ta nh ngha hm dng non-member ca
mt lp, th sau chng ta phi truyn hai tham s cho mi ton hng, nh sau:
Box operator+(const Box&, const Box&);
V d sau minh ha khi nim np chng ton t bi s dng mt hm thnh vin. y, mt i

tng c truyn nh l mt tham s m cc thuc tnh ca n s c truy cp bi s dng i
tng ny, i tng m s gi ton t ny c th c truy cp bi s dng ton t this, nh
sau:
#include <iostream>
class Box
{
public:
double getVolume(void)
{
return length * breadth * height;
}
void setLength( double len )
{
length = len;
Trang 109
void setBreadth( double bre )

{
breadth = bre;
}
void setHeight( double hei )

{
height = hei;
}
// Overload + operator to add two Box objects.
Box operator+(const Box& b)
{
Box box;
box.length = this->length + b.length;
box.breadth = this->breadth + b.breadth;
box.height = this->height + b.height;
return box;
}
private:
double length;
// Length of a box
double breadth;
// Breadth of a box
double height;
// Height of a box
};
// Main function for the program
int main( )
{
Box Box1;
Box Box2;
Box Box3;
double volume = 0.0;
// Store the volume of a box here
Trang 110
Box1.setLength(6.0);
Box1.setBreadth(7.0);
Box1.setHeight(5.0);
Box2.setLength(12.0);
Box2.setBreadth(13.0);
Box2.setHeight(10.0);
// volume of box 1
volume = Box1.getVolume();
// volume of box 2
// Add two object as follows:

Box3 = Box1 + Box2;
// volume of box 3
return 0;
}

Trang 111
Ton t c th np chng v khng th np chng

trong C++
Bng di lit k danh sch cc ton t c th c np chng trong C++:
+
&
<
>
<=
>=
++
--
<<
>>
==
!=
&&
||
+=
-=
/=
%=
^=
&=
|=
*=
<<=
>>=
[]
()
->
->*
new
new []
delete
delete []
Cn y l danh sch cc ton t khng th c np chng trong C++:

::
.*
?:
V d v Np chng ton t trong C++

Di y l cc v d a dng minh ha Np chng ton t trong C++, t gip bn hiu su
hn v khi nim ny. Bn click vo link thy v d:
STT
Ton t v V d
Np chng ton t mt ngi (unary) trong C++
Trang 112
2
Np chng ton t nh phn trong C++
Np chng ton t quan h trong C++
Np chng ton t Input/Output trong C++
Np chng ton t ++ v -- trong C++
Np chng ton t gn trong C++
Np chng ton t gi hm () trong C++
Np chng ton t [] trong C++
Np chng ton t truy cp thnh vin lp -> trong C++
a hnh trong C++

a hnh (polymorphism) ngha l c nhiu hnh thi khc nhau. Tiu biu l, a hnh xut hin khi
c mt cu trc cp bc ca cc lp v chng l lin quan vi nhau bi tnh k tha.
a hnh trong C++ ngha l mt li gi ti mt hm thnh vin s lm cho mt hm khc c
thc thi ph thuc vo kiu ca i tng m triu hi hm .
Bn xem xt v d sau, y lp c s c k tha bi hai lp khc trong C++:
#include <iostream>
class Shape {
protected:
int width, height;
public:
Trang 113
Shape( int a=0, int b=0)

{
width = a;
height = b;
}
int area()
{
cout << "Parent class area :" <<endl;
return 0;
}
};
class Rectangle: public Shape{
public:
Rectangle( int a=0, int b=0):Shape(a, b) { }
int area ()
{
cout << "Rectangle class area :" <<endl;
}
};
class Triangle: public Shape{
public:
Triangle( int a=0, int b=0):Shape(a, b) { }
int area ()
{
cout << "Triangle class area :" <<endl;
return (width * height / 2);
}
};
// Main function for the program
int main( )
{
Shape *shape;
Trang 114
Rectangle rec(10,7);
Triangle
tri(10,5);
// store the address of Rectangle

shape = &rec;
// call rectangle area.
shape->area();
// store the address of Triangle

shape = &tri;
// call triangle area.
shape->area();
return 0;
}

Parent class area
Parent class area
L do cho output khng chnh xc l v: li gi ca hm area() ang c thit lp mt ln bi

compiler nh phin bn c nh ngha trong lp c s . iu ny gi l static resolution (s
phn gii tnh) ca li gi hm, hoc static linkage (s lin hp tnh) li gi hm c sa
trc khi chng trnh c thc thi. i khi n cng c gi l early binding (hoc static
binding) bi v hm area() c thit lp trong khi bin dch chng trnh.
By gi, chng ta sa chng trnh trn mt cht v t trc khai bo ca area() trong lp Shape
vi t kha virtual, khi n trng nh sau:
class Shape {
protected:
int width, height;
public:
{
Trang 115
width = a;
height = b;
}
virtual int area()
{
cout << "Parent class area :" <<endl;
return 0;
}
};
Sau khi sa i, khi code ca v d trn c bin dch v thc thi, n s cho kt qu sau:
Rectangle class area
Triangle class area
Lc ny, compiler nhn vo cc ni dung ca con tr thay v kiu ca n. V th, khi a ch ca cc

i tng ca lp tri v rec c lu gi trong *shape, th hm area() tng ng c gi.
Nh bn c th thy, mi lp con c mt trin khai hm area() ring bit. y l cch chung m a
hnh trong C++ c s dng. Bn c cc lp khc nhau vi cng mt tn hm, v c th l cng
tham s, nhng trnh trin khai l khc nhau.
Hm virtual trong C++

Mt hm virtual l mt hm trong mt lp c s m c khai bo bi s dng t kha virtual
trong C++. Vic nh ngha trong mt lp c s mt hm virtual, vi phin bn khc trong mt lp
k tha, bo cho compiler rng: chng ta khng mun Static Linkage cho hm ny.
Nhng g chng ta lm l mun vic la chon hm c gi ti bt k im no cung cp
trong chng trnh l da trn kiu i tng, m vi n c gi. Hot ng ny c th gi tt
l dynamic linkage, hoc late binding trong C++.
Hm pure virtual trong C++

N l c th nu bn mun bao mt hm virtual trong mt lp c s, m n c th c ti nh
ngha trong mt lp k tha ph hp vi cc i tng ca lp , nhng l nh ngha
khng c ngha g.
Chng ta c th thay i hm virtual l area() trong lp c s thnh nh sau:
Trang 116
class Shape {
protected:
int width, height;
public:
{
width = a;
height = b;
}
// pure virtual function
virtual int area() = 0;
};
=0 ni cho compiler rng hm khng c phn thn v hm virtual trn s c gi l hm pure

virtual function trong C++..
Tru tng ha d liu trong C++

Tru tng ha d liu (Data abstraction) lin quan ti vic ch cung cp thng tin cn thit ti
bn ngoi v n chi tit c s ca chng, v d: biu din thng tin cn thit trong chng trnh
m khng hin th chi tit v chng.
Tru tng ha d liu (Data abstraction) l mt k thut lp trnh m da trn s phn bit ca
Interface v Implementation (trnh trin khai).
Xem xt v d v mt chic TV, bn c th bt/tt, thay i knh, chnh m lng, v thm cc thit
b ngoi vi nh loa, VCR v DVD. Nhng bn khng bit cc chi tit ni vi ca n, l, bn khng
bit cch n nhn tn hiu qua khng kh hoc qua dy cp, cch phin dch chng v cui cng l
hin th chng trn mn hnh.
V th, c th ni rng mt chic TV phn bit r rng trnh trin khai ni vi ca n vi giao din
ngoi vi v bn c th thao tc vi interface vi cc nt ngun, iu khin m lng m khng cn
c bt k hiu bit v nhng g din ra bn trong n.
By gi, v mt ngn ng lp trnh C++, th cc lp C++ cung cp Tru tng ha d liu (Data
abstraction) mc tht tuyt vi. Chng cung cp cc phng thc public ti bn ngoi
Trang 117
thao tc vi tnh nng ca i tng v thao tc d liu i tng, v d: trng thi m khng
cn thc s bit v cch lp c trin khai ni ti.
V d, chng trnh ca bn c th to mt li gi ti hm sort() m khng cn bit v hm
thc s s dng thut ton g sp xp cc gi tr cho. Thc ra, trnh trin khai c s
(underlying implementation) ca tnh nng sp xp c th thay i ty vo th vin, v min l
Interface vn nh c th li gi hm ca bn vn tip tc lm vic.
Trong C++, chng ta s dng cc Lp nh ngha kiu d liu tru tng (abstract data types
(ADT)) ca ring chng ta. Bn c th s dng i tng cout ca lp ostream cho lung d liu
ti u ra chun nh sau:
#include <iostream>
int main( )
{
cout << "Hello C++" <<endl;
return 0;
}
Ti y, bn khng cn hiu cch cout hin th vn bn trn mn hnh. Bn ch cn bit Public

Interface v Underlying Implementation ca cout l sn sng thay i.
Nhn truy cp (Access Label) trong C++

Trong C++, chng ta s dng Access Label nh ngha Abstract Interface (Giao din tru
tng) cho lp. Mt lp c th cha 0 hoc nhiu Access Label.
Cc thnh vin c nh ngha vi mt nhn public l c th truy cp cho tt c cc phn

ca chng trnh. Tru tng ha d liu ca mt kiu c nh ngha bi cc thnh vin
public ca n.
Cc thnh vin c nh ngha vi mt nhn private l khng th truy cp cho code m s

dng lp . Khu vc private n trnh trin khai ny vi code m s dng kiu .
Khng c hn ch v tn sut m mt nhn truy cp (Access Label) c th xut hin. Mi Access

Label xc nh truy cp (Access Level) ca s nh ngha thnh vin tip theo. truy cp
Trang 118
xc nh cn tn ti hiu qu ti khi gp Access Label k tip hoc gp du ngoc mc ng ca

thn lp.
Li ch ca Tru tng ha d liu trong C++

Tru tng ha d liu trong C++ mang li hai li th quan trng:
Phn ni vi hay bn trong lp c bo v trnh khi cc li do ngi dng v , m c th

gy h hng trng thi ca d liu.
Trin khai lp c th tin hnh qua thi gian p ng yu cu thay i hoc bug cc bo
co m khng yu cu thay i trong code ca ngi dng.
Bng vic nh ngha cc thnh vin d liu ch trong khu vc private ca lp, tc gi ca lp c
th t do to cc thay i trong d liu. Nu trnh trin khai thay i, th ch m ha lp l cn kim
tra bit kha cnh no em li thay i. Nu d liu l public, th khi bt k hm no m truy
cp mt cch trc tip ti cc thnh vin d liu ca php biu din c c th b ph v.
V d v Tru tng ha d liu trong C++

Trong bt k chng trnh C++ no, ni bn trin khai mt lp vi cc thnh vin l public v
private, th l mt v d ca tru tng ha d liu. Bn xem xt v d sau:
#include <iostream>
class Adder{
public:
// constructor
Adder(int i = 0)
{
total = i;
}
// interface to outside world
void addNum(int number)
{
total += number;
}
Trang 119

int getTotal()
{
return total;
};
private:
// hidden data from outside world
int total;
};
int main( )
{
Adder a;
a.addNum(10);
a.addNum(20);
a.addNum(30);
cout << "Total " << a.getTotal() <<endl;

return 0;
}

Total 60
Lp trn cng hai s v tr v tng ca chng. Cc thnh vin public l addNum vgetTotal l cc
Interface ti bn ngoi v mt ngi s dng cn bit chng s dng lp . Thnh vin
private l total l ci g m ngi s dng khng cn bit n, nhng l cn thit cho lp
hot ng mt cch chnh xc.
Chin lc thit k trong C++

Tru tng ha d liu phn bit code thnh Interface v Implementation. V th, trong khi thit k
thnh phn ca bn, bn phi gi Interface c lp vi Implementation, m nu bn thay i
underlying implementation th Interface s vn cn tn ti nh c.
Trang 120
Trong trng hp ny, bt k chng trnh no ang s dng cc Interface ny, chng s khng b
nh hng v s cn mt s ti bin dch vi Implementation mi nht ny.
Tnh ng gi d liu trong C++

Tt c chng trnh C++ bao gm hai thnh phn nn tng l:
Cc lnh (code) chng trnh: y l phn chng trnh m thc hin cc hnh ng v
cng c gi l cc hm.
D liu chng trnh: D liu l thng tin ca chng trnh m tc ng n cc hm

chng trnh.
Tnh ng gi (Encapsulation) l mt khi nim ca lp trnh hng i tng m rng buc d

liu v cc hm m thao tc d liu , v gi chng an ton bi ngn cn s gy tr ngi v s
lm dng t bn ngoi. Tnh ng gi d liu dn n khi nim OOP quan trng l Data Hiding.
Tnh ng gi d liu - Data encapsulation l mt k thut bao ng d liu, v cc hm m s
dng chng v tru tng ha d liu l mt k thut ch trng by ti cc Interface v n
Implementation Detail (chi tit trnh trin khai) ti ngi s dng.
C++ h tr cc thuc tnh ca ng gi v n d liu thng qua vic to cc kiu t nh ngha
(user-defined), gi l classes. Chng ta hc rng mt lp c th cha cc thnh vin private,
protected v public. Theo mc nh, tt c thnh phn c nh ngha trong mt lp l private.
V d:
class Box
{
public:
double getVolume(void)
{
return length * breadth * height;
}
private:
double length;
// Length of a box
double breadth;
// Breadth of a box
double height;
// Height of a box
Trang 121
};
Cc bin length, breadth, v height l private. Ngha l chng ch c th c truy cp bi cc

thnh vin khc ca lp Box, v khng th bi bt k phn khc trong chng trnh ca bn. y
l mt cch thc hin tnh ng gi trong C++.
lm cho cc phn ca lp l public (v d: c th truy cp ti cc phn khc trong chng trnh
ca bn), bn phi khai bo chng sau t kha public. Tt c bin v hm c nh ngha sau t
kha public l c th truy cp cho tt c cc hm trong chng trnh ca bn.
V d v ng gi d liu trong C++

Trong bt k chng trnh C++ no, ni bn trin khai mt lp vi cc thnh vin l public v
private th l v d ca ng gi d liu v Tru tng ha d liu trong C++. Bn xem xt v
d sau:
#include <iostream>
class Adder{
public:
// constructor
Adder(int i = 0)
{
total = i;
}
void addNum(int number)
{
total += number;
}
int getTotal()
{
return total;
};
Trang 122
private:
// hidden data from outside world
int total;
};
int main( )
{
Adder a;
a.addNum(10);
a.addNum(20);
a.addNum(30);
cout << "Total " << a.getTotal() <<endl;

return 0;
}

Total 60
Lp trn cng hai s v tr v tng ca chng. Cc thnh vin public l addNum vgetTotal l cc
Interface ti bn ngoi v mt ngi s dng cn bit chng s dng lp . Thnh vin
private l total l ci g m ngi s dng khng cn bit n, nhng l cn thit cho lp
hot ng mt cch chnh xc.

Hu ht chng ta c t nhiu kinh nghim v vic lm cho cc thnh vin lp l private theo mc
nh, tr khi chng ta thc s cn thit phi trng by chng. l mt kinh nghim v tnh ng
gi tt.
Kinh nghim ny c p dng thng xuyn nht cho cc thnh vin d liu, nhng n p dng
nh nhau cho tt c thnh vin, bao gm c cc hm virtual trong C++.
Interface trong C++ (Lp tru tng)

Trang 123
Mt Interface miu t hnh vi hoc kh nng ca mt lp trong C++ m khng k thc ti mt trnh
trin khai c th ca lp .
Interface trong C++ c trin khai bi s dng cc Lp tru tng (Abstract class) v nhng
lp tru tng ny khng nn b nhm ln vi Tru tng ha d liu, m l mt khi nim ca
vic gi Implementation Detail phn bit vi d liu c lin kt.
Mt lp c to l abstract bng vic khai bo t nht mt ln cc hm ca n l hm pure
virtual. Mt hm pure virtual c xc nh bng vic t = 0 trong khai bo ca n, nh sau:
class Box
{
public:
// pure virtual function
virtual double getVolume() = 0;
private:
double length;
// Length of a box
double breadth;
// Breadth of a box
double height;
// Height of a box
};
Mc ch ca mt Lp tru tng (thng gi tt l ABC) l cung cp mt lp c s thch hp

t cc lp khc c th k tha. Cc lp tru tng khng th c s dng thuyt minh
cc i tng v ch phc v nh l mt Interface. N lc thuyt minh mt i tng ca mt
lp tru tng trong C++ s to ra mt li bin dch (compilation error).
V th, nu mt lp ph ca mt ABC cn c thuyt minh, n phi trin khai cc hm virtual,
ngha l n h tr Interface c khai bo bi ABC. Tht bi trong vic ghi mt hm pure virtual
trong mt lp k tha, th vic n lc thuyt minh cc i tng ca lp , l mt li bin dch.
Cc lp, m c th c s dng thuyt minh i tng, c gi l Concrete Classtrong
C++.
V d v Lp tru tng trong C++

Bn xem xt v d sau: lp cha cung cp mt Interface ti lp c s trin khai mt
hmgetArea() trong C++:
Trang 124
#include <iostream>
// Base class
class Shape
{
public:
// pure virtual function providing interface framework.
virtual int getArea() = 0;
{
width = w;
}
{
height = h;
}
protected:
int width;
int height;
};
// Derived classes
class Rectangle: public Shape
{
public:
int getArea()
{
}
};
class Triangle: public Shape
Trang 125
{
public:
int getArea()
{
return (width * height)/2;
}
};
int main(void)
{
Rectangle Rect;
Triangle
Tri;
Rect.setWidth(5);
Rect.setHeight(7);
cout << "Total Rectangle area: " << Rect.getArea() << endl;
Tri.setWidth(5);
Tri.setHeight(7);
cout << "Total Triangle area: " << Tri.getArea() << endl;
return 0;
}

Total Rectangle area: 35
Total Triangle area: 17
Bn c th thy cch mt lp tru tng nh ngha mt Interface vi hm getArea() ny v hai lp

khc trin khai cng mt hm nhng vi thut ton khc nhau tnh ton din tch c th cho
hnh.
Trang 126

Mt h thng hng i tng c th s dng mt lp c s cung cp mt Interface chung v
chun ha thch hp cho tt c cc ng dng ngoi vi. V th, thng qua k tha t lp c s tru
tng , cc lp k tha c thit lp theo cch tng t.
Cc kh nng (v d: cc hm public), c cung cp bi cc ng dng ngoi vi, c cung cp
dng cc hm pure virtual trong lp c s tru tng. Trnh trin khai ca cc hm pure virtual ny
c cung cp trong cc lp k tha tng ng vi cc kiu ng dng c th.
Cu trc ny cng cho php cc ng dng mi c thm vo h thng mt cch d dng, ngay
c sau khi h thng c nh ngha.
File v Stream trong C++

Ti by gi, chng ta s dng th vin chun iostream, cung cp cc phng
thc cinv cout c t Standard Input v vit ti Standard Output tng ng.
Chng ny s hng dn bn cch c v vit t mt file. iu ny cn mt Th vin chun C++
khc l fstream, m nh ngha 3 kiu d liu mi:
Kiu d liu
Miu t
ofstream
Kiu d liu ny biu din Output File Stream v c s dng

to cc file v vit thng tin ti cc file
ifstream
Kiu d liu ny biu din Input File Stream v c s dng

c thng tin t cc file
fstream
Kiu d liu ny ni chung biu din File Stream, v c cc kh

nng ca c ofstream v ifstream, ngha l n c th to file, vit
thng tin ti file v c thng tin t file
thc hin tin trnh x l file trong C++, bn bao cc header file l <iostream> v <fstream>
trong source file ca chng trnh C++ ca bn.
Trang 127
M mt File trong C++

Mt file phi c m trc khi bn c th c thng tin t n hoc vit thng tin ti n. Hoc i
tng ofstream hoc i tng fstream c th c s dng m mt file vi mc ch vit
hoc i tng ifstream c s dng m file ch vi mc ch c.
Di y l c php chun cho hm open(), l mt thnh vin ca cc i tng fstream, ifstream
v ofstream trong C++:
void open(const char *filename, ios::openmode mode);
Ti y, tham s u tin xc nh tn v v tr ca file c m v tham s th hai ca hm

thnh vin open() nh ngha ch m file nn c m.
Ch
Miu t
ios::app
Ch Append. Tt c output ti file c ph thm vo cui

file
ios::ate
M mt file cho outpur v di chuyn iu khin read/write ti cui

ca file
ios::in
M mt file c
ios::out
M mt file vit
ios::trunc
Nu file ny tn ti, ni dung ca n s c ct (truncate)

trc khi m file
Bn c th kt hp hai hoc nhiu gi tr ny bng vic hoc chng cng vi nhau (s dng (|). V
d, nu bn mun m mt file trong ch vit v mun ct (truncate) n trong trng hp n
tn ti, bn theo c php sau:
ofstream outfile;
outfile.open("file.dat", ios::out | ios::trunc );
Theo cch tng t, bn c th m mt file vi mc ch c v vit nh sau:
Trang 128
fstream
afile;
afile.open("file.dat", ios::out | ios::in );
ng mt File trong C++

Khi mt chng trnh C++ kt thc, n t ng ng tt c Stream, gii phng tt c b nh
cp pht v ng tt c file m. Nhng n l bi thc hnh tt cho mt lp trnh vin nn ng
tt c file m trc khi kt thc chng trnh.
Di y l c php chung cho hm close() trong C++, l mt thnh vin ca cc i tng
fstream, ifstream v ofstream trong C++:
void close();
Vit ti mt File trong C++

Trong khi lp trnh C++, bn vit thng tin ti mt file t chng trnh ca bn bi s dng ton t
chn lung l (<<), ging nh khi bn s dng ton t to thng tin u ra ti mn hnh. Ch
c mt im khc nhau l bn s dng mt i tng ofstream hocfstream trong C++ thay cho
i tng cout trong C++.
c mt File trong C++

Bn c thng tin t mt file trong chng trnh C++ ca bn bi s dng ton t trch lung l
(>>), ging nh bn s dng ton t nhp thng tin u vo t bn phm. im khc nhau l
bn s dng mt i tng ifstream hoc fstream thay v s dng i tng cin trong C++.
V d v c v Vit file trong C++

Chng trnh C++ sau m mt file trong ch c v vit. Sau khi vit thng tin c nhp vo
bi ngi s dng ti mt file l afile.dat, chng trnh c thng tin t file v to kt qu u
ra trn mn hnh:
#include <fstream>
#include <iostream>
int main ()
{
Trang 129
char data[100];
// open a file in write mode.

ofstream outfile;
outfile.open("afile.dat");
cout << "Writing to the file" << endl;

cout << "Enter your name: ";
cin.getline(data, 100);
// write inputted data into the file.

outfile << data << endl;
cout << "Enter your age: ";

cin >> data;
cin.ignore();
// again write inputted data into the file.

outfile << data << endl;
// close the opened file.

outfile.close();
// open a file in read mode.

ifstream infile;
infile.open("afile.dat");
cout << "Reading from the file" << endl;

infile >> data;
// write the data at the screen.

cout << data << endl;
Trang 130
// again read the data from the file and display it.
infile >> data;
cout << data << endl;
// close the opened file.

infile.close();
return 0;
}
Khi code trn c bin dch v thc thi, n s cho input v output nh sau:
$./a.out
Writing to the file
Enter your name: Zara
Enter your age: 9
Reading from the file
Zara
9
V d trn s dng cc hm b sung t i tng cin, nh hm getline() c dng t bn ngoi

v hm ignore() b qua cc k t ph bn tri lnh read trc .
Con tr v tr File trong C++

C hai i tng istream v ostream u cung cp cc hm thnh vin xc nh li v tr ca
con tr v tr file (file-position pointer). Cc hm thnh vin ny l seekg (vit tt ca seek get) cho
istream v seekp (vit tt ca seek put) cho ostream trong C++.
Tham s cho seekg v seekp thng l mt long int. Tham s th hai c th c xc nh ch
dn hng tm kim. Hng tm kim c th l ios::beg (mc nh) xc nh v tr lin quan ti
phn bt u ca mt Stream, l ios::cur xc nh v tr lin quan ti v tr hin ti trong mt
Stream hoc l ios::end xc nh v tr lin quan ti phn kt thc ca mt Stream trong C++.
Con tr v tr file l mt gi tr integer m xc nh v tr trong file, tnh ton l s byte t v tr bt u
ca file . Di y l mt s v d xc nh v tr ca con tr v tr file trong C++:
Trang 131
// position to the nth byte of fileObject (assumes ios::beg)

fileObject.seekg( n );
// position n bytes forward in fileObject

fileObject.seekg( n, ios::cur );
// position n bytes back from end of fileObject

fileObject.seekg( n, ios::end );
// position at end of fileObject

fileObject.seekg( 0, ios::end );
X l ngoi l (Exception Handling) trong

C++
Mt Exception (ngoi l) l mt vn xut hin trong khi thc thi mt chng trnh. Mt
Exception trong C++ l mt phn hi v mt tnh hung ngoi l m xut hin trong khi mt
chng trnh ang chy, v d nh chia cho s 0.
Exception cung cp mt cch truyn iu khin t mt phn ca mt chng trnh ti phn
khc. Exception Handling (X l ngoi l) trong C++ c xy dng da trn 3 t kha l: try,
catch, v throw.
throw: Mt chng trnh nm mt Exception khi mt vn xut hin. Vic ny c thc

hin bi s dng t kha throw trong C++.
catch: Mt chng trnh bt mt Exception vi mt Exception Handler ti v tr trong mt

chng trnh ni bn mun x l vn . T kha catch trong C++ ch dn vic bt mt
exception.
try: Mt khi try c th c bt bi mt s lng c th exception. N c theo sau bi

mt hoc nhiu khi catch.
Gi s mt khi s to mt Exeption, mt phng thc bt mt exception bi s dng kt hp cc

t kha try v catch. Mt khi try/catch c t xung quanh code m c th to mt exception.
Trang 132
Code bn trong mt khi try/catch c xem nh l code c bo v, v c php s dng

try/catch trong C++ nh sau:
try
{
// protected code
}catch( ExceptionName e1 )
{
// catch block
}catch( ExceptionName e2 )
{
// catch block
}catch( ExceptionName eN )
{
// catch block
}
Bn c th lit k nhiu lnh catch bt cc kiu exception khc nhau trong trng hp
khi try ca bn xut hin nhiu hn mt exception trong cc tnh hung khc nhau.
Nm Exception trong C++

Exception c th b nm bt c u bn trong mt khi code bi s dng cc lnh throwtrong
C++. Ton hng ca lnh throw quyt nh kiu cho exception v c th l bt k biu thc no v
kiu kt qu ca biu thc quyt nh kiu ca exception b nm.
V d sau minh ha vic nm mt exception khi chia cho s 0 trong C++:
double division(int a, int b)
{
if( b == 0 )
{
throw "Division by zero condition!";
}
return (a/b);
}
Trang 133
Bt Exception trong C++

Khi catch theo sau khi try trong C++ s bt bt k exception no. Bn c th xc nh kiu ca
exception bn mun bt v iu ny c xc nh bi khai bo exception m xut hin trong cc
du ngoc n theo sau t kha catch trong C++.
try
{
// protected code
}catch( ExceptionName e )
{
// code to handle ExceptionName exception
}
Code trn s bt mt exception c kiu l ExceptionName. Nu bn mun xc nh rng mt khi

catch nn x l bt k kiu exception no b nm trong mt khi try, bn phi t mt du ba chm
() trong cc du ngoc n theo sau t kha catch, nh sau:
try
{
// protected code
}catch(...)
{
// code to handle any exception
}
V d sau nm mt exception khi chia cho s 0 v chng ta bt n trong khi catch.

#include <iostream>
double division(int a, int b)

{
if( b == 0 )
{
throw "Division by zero condition!";
Trang 134
}
return (a/b);
}
int main ()
{
int x = 50;
int y = 0;
double z = 0;
try {
z = division(x, y);
cout << z << endl;
}catch (const char* msg) {
cerr << msg << endl;
}
return 0;
}
Bi v chng ta ang to mt exception c kiu const char*, v th trong khi bt exception ny,
chng ta phi s dng const char* trong khi catch. Nu chng ta bin dch v chy code trn, n
s cho kt qu sau:
Division by zero condition!
Standard Exception trong C++

C++ cung cp mt danh sch cc Standard Exception c nh ngha trong <exception>m
chng ta c th s dng trong cc chng trnh. Nhng exception ny c sp xp theo cu trc
th t cha-con nh sau:
Trang 135
Bng di l miu t ngn gn v mi exception c cp trong s trn:

Exception
Miu t
std::exception
Mt exception v lp cha ca tt c Standard Exception trong C++
std::bad_alloc
C th c nm bi new
std::bad_cast
C th c nm bi dynamic_cast
std::bad_exception
y l thit b hu ch x l Unexpected Exception trong mt

chng trnh C++
Trang 136
std::bad_typeid
C th c nm bi typeid
std::logic_error
Mt exception m theo l thuyt c th c pht hin bi vic c

code
std::domain_error
y l mt exception c nm khi mt min ton hc khng hp l

c s dng
std::invalid_argument
c nm do cc tham s khng hp l
std::length_error
c nm khi mt std::string qu ln c to ra
std::out_of_range
C th c nm bi mt phng thc, v d std::vector v

std::bitset<>::operator[]().
std::runtime_error
Mt exception m theo l thuyt khng th c pht hin bi vic

c code
std::overflow_error
c nm nu mt s trn lung ton hc (mathematical overflow)

xut hin
std::range_error
Xut hin khi bn c gng lu gi mt gi tr bn ngoi dy gi tr
std::underflow_error
c nm nu mt mathematical underflow (s trn di) xut hin
nh ngha Exception mi trong C++

Bn c th nh ngha cc exception cho ring bn bng vic k tha v ghi tnh nng lp
exception trong C++. V d sau minh ha cch bn c th s dng lp std::exception trin khai
exception ca ring bn theo mt cch chun trong C++:
#include <iostream>
#include <exception>
Trang 137
struct MyException : public exception

{
const char * what () const throw ()
{
return "C++ Exception";
}
};
int main()
{
try
{
throw MyException();
}
catch(MyException& e)
{
std::cout << "MyException caught" << std::endl;
std::cout << e.what() << std::endl;
}
catch(std::exception& e)
{
//Other errors
}
}
N s cho kt qu sau:
MyException caught
C++ Exception
y, what() l mt phng thc public c cung cp bi lp exception trong C++ v n

c ghi bi tt c cc lp exception con. V d ny tr v nguyn nhn ca mt exception
trong C++.
Trang 138
B nh ng trong C++
Mt s hiu bit su v cch b nh ng thc s lm vic trong C++ l ct yu tr thnh mt
lp trnh vin C++ gii. B nh trong chng trnh C++ ca bn c phn thnh hai phn:
Stack: Tt c bin c khai bo bn trong hm s nhn b nh t stack trong C++.
Heap: c s dng cp pht b nh ng khi chng trnh chy.
Nhiu khi, bn khng bit trc bao nhiu b nh bn s cn lu thng tin c th trong mt
bin c nh ngha v kch c b nh cn thit c th c quyt nh ti run time.
Bn c th cp pht b nh ti run time bn trong Heap cho bin vi mt kiu cho bi s
dng mt ton t c bit trong C++ m tr v a ch ca khng gian cp pht. Ton t ny gi
l ton t new trong C++.
Nu bn khng cn thit b nh ng cp pht na, bn c th s dng ton t deletetrong
C++, s gii phng b nh c cp pht trc bi ton t new.
Ton t new v delete trong C++

y l c php chung s dng ton t new cp pht b nh ng cho bt k kiu d liu
no trong C++:
new data-type;
y, data-type c th l bt k kiu d liu c sn no v d nh mng hoc cc kiu d liu t

nh ngha nh lp hoc cu trc. u tin, chng ta xt cc kiu d liu c sn. V d, chng ta
c th nh ngha mt con tr ti kiu double v sau yu cu rng b nh c cp pht ti thi
gian thc thi. Chng ta c th lm iu ny bi s dng ton t newtrong C++ vi cc lnh sau:
double* pvalue
pvalue
= NULL; // Pointer initialized with null
= new double;
// Request memory for the variable
B nh c th cha c cp pht thnh cng, nu phn b nh ri (free store) c s dng.

V th, y l bi thc hnh tt cho bn khi kim tra nu ton t new tr v con tr NULL v thc
hin hnh ng thch hp, nh sau:
double* pvalue
if( !(pvalue
= NULL;
= new double ))
Trang 139
{
cout << "Error: out of memory." <<endl;
exit(1);
Hm malloc() t C, vn tn ti trong C++, nhng ti ngh bn trnh s dng hm malloc() ny.

Li th ln nht ca ton t new so vi hm malloc() l ton t new khng ch cp pht b nh, n
cn xy dng i tng theo mc ch chnh ca C++.
Ti bt k thi im, khi bn cm thy mt bin c cp pht ng l khng cn thit na, bn
c th gii phng b nh m n chim gi trong phn b nh ri vi ton tdelete trong C++,
nh sau:
delete pvalue;
// Release memory pointed to by pvalue
By gi, da vo cc khi nim trn chng ti to mt v d minh ha cch ton t new v delete
trong C++ lm vic:
#include <iostream>
int main ()
{
double* pvalue
pvalue
= NULL; // Pointer initialized with null
= new double;
*pvalue = 29494.99;
// Request memory for the variable
// Store value at allocated address
cout << "Value of pvalue : " << *pvalue << endl;
delete pvalue;
// free up the memory.
return 0;
}
Trang 140
Value of pvalue : 29495
Cp pht b nh ng cho Mng trong C++

Gi s bn mun cp pht b nh cho mt mng k t, v d mt chui 20 k t. Bn s dng
cng c php s dng trn, nh sau:
char* pvalue
pvalue
= NULL;
// Pointer initialized with null
= new char[20]; // Request memory for the variable
xa mng m chng ta va to, c php trong C++ l:

delete [] pvalue;
// Delete array pointed to by pvalue
y l c php chung ca ton t new, bn c th s dng cp pht b nh cho mt mng a

chiu trong C++:
double** pvalue
pvalue
= NULL;
// Pointer initialized with null
= new double [3][4]; // Allocate memory for a 3x4 array
Tuy nhin, c php gii phng b nh cho mng a chiu vn ging trn:
delete [] pvalue;
// Delete array pointed to by pvalue
Cp pht b nh ng cho i tng trong C++

i tng khng khc cc kiu d liu n gin. V d: bn xem xt code sau, trong chng ta
ang s dng mt mng i tng lm r khi nim ny:
#include <iostream>
class Box
{
public:
Box() {
cout << "Constructor called!" <<endl;
}
~Box() {
Trang 141
cout << "Destructor called!" <<endl;

}
};
int main( )
{
Box* myBoxArray = new Box[4];
delete [] myBoxArray; // Delete array
return 0;
}
Nu bn chun b cp pht b nh cho mt mng 4 i tng Box, constructor n gin trn s

c gi 4 ln v tng t trong khi xa cc i tng, destructor cng s c gi vi s ln
tng t.
Bin dch v thc thi code trn s cho kt qu:
Constructor called!
Constructor called!
Constructor called!
Constructor called!
Destructor called!
Destructor called!
Destructor called!
Destructor called!
Namespace trong C++

Xt mt tnh hung, khi chng ta c hai ngi cng tn l Zara, trng cng lp. Bt c khi no
chng ta cn phn bit h mt cch trc tip, chng ta phi s dng thng tin b sung cng vi tn
ca h, v d: v tr h sng v tn cha m ca h,
Trang 142
Tnh hung tng t xy ra trong C++. V d: C th bn ang vit mt code m c mt hm l

xyz() v c th vin khc c sn m cng c cng hm xyz() ny. By gi, compiler khng bit
phin bn no ca hm xyz() bn mun s dng trong code ca bn.
Mt namespace trong C++ gip bn vt qua tnh hung ny v c s dng nh l thng tin b
sung phn bit cc hm, lp, bin, cng tn c sn trong cc th vin khc nhau. S dng
namespace trong C++, bn c th nh ngha bi cnh trong cc tn c nh ngha. V bn
cht, mt namespace nh ngha mt phm vi (scope) trong C++.
nh ngha mt Namespace trong C++

Mt nh ngha namespace bt u vi t kha namespace c theo sau bi tn ca
namespace , nh sau:
namespace namespace_name {
// code declarations
}
gi phin bn namespace ca hm hoc bin, bn ph thm vo sau tn ca namespace, nh

sau:
name::code;
// code could be variable or function.
V d sau minh ha cch namespace nh ngha phm vi ca bin v hm trong C++:

#include <iostream>
// first name space

namespace first_space{
void func(){
cout << "Inside first_space" << endl;
}
}
// second name space
namespace second_space{
void func(){
Trang 143
cout << "Inside second_space" << endl;

}
}
int main ()
{
// Calls function from first name space.

first_space::func();
// Calls function from second name space.

second_space::func();
return 0;
}

Inside first_space
Inside second_space
using namespace directive trong C++

Bn c th trnh vic ph thm vo sau tn ca namespace bng vic s dng using
namespace directive trong C++. Directive ny ni cho compiler rng dy code sau ang s dng
cc tn c xc nh trong namespace xc nh . Bn xt v d:
#include <iostream>
// first name space

void func(){
}
}
Trang 144
void func(){
}
}
using namespace first_space;
int main ()
{
// This calls function from first name space.

func();
return 0;
}

Inside first_space
using namespace directive trong C++ cng c th c s dng tham chiu mt item c th
trong mt namespace. V d, nu bn ch c nh s dng mt phn cout ca std namespace,
bn c th tham chiu n nh sau:
using std::cout;
Phn code theo sau c th tham chiu ti cout m khng cn ph thm vo sau namespace,
nhng cc item khc trong std namespace vn cn phi r rng, nh sau:
#include <iostream>
using std::cout;
int main ()
{
cout << "std::endl is used with std!" << std::endl;
Trang 145
return 0;
}

std::endl is used with std!
Cc tn c gii thiu trong mt using namespace directive tun theo cc qui tc phm vi
(scope rule). Tn l nhn thy bt u t v tr ca using namespace directive ti phn cui ca
phm vi m trong directive ny c thy. Cc thc th vi cng tn c nh ngha trong
phm vi bn ngoi b n.
Namespace khng k nhau trong C++

Mt namespace c th c nh ngha thnh mt s phn v v th mt namespace c to t
mt tp hp cc phn c nh ngha ring bit. Cc phn ring bit ny ca mt namespace c
th nhiu file khc nhau.
V th, nu mt phn ca namespace yu cu mt tn c nh ngha file khc, th tn
vn phi c khai bo. nh ngha namespace sau hoc nh ngha mt namespace mi hoc
thm cc phn t mi ti namespace tn ti:
namespace namespace_name {
}
Namespace lng nhau trong C++

Trong C++, namespace c th lng vo nhau, tc l bn c th nh ngha mt namespace bn
trong mt namespace khc, nh sau:
namespace namespace_name1 {
namespace namespace_name2 {
}
}
Trang 146
Bn c th truy cp cc thnh vin ca namespace lng nhau ny bi s dng ton t phn gii
phm vi (resolution operator) trong C++, nh sau:
// to access members of namespace_name2
using namespace namespace_name1::namespace_name2;
// to access members of namespace:name1

using namespace namespace_name1;
Trong cc lnh trn, nu bn ang s dng namespace_name1, th n s lm cho cc phn t ca

namespace_name2 c sn trong phm vi , nh sau:
#include <iostream>
// first name space

void func(){
}
void func(){
}
}
}
using namespace first_space::second_space;
int main ()
{
// This calls function from second name space.

func();
Trang 147
return 0;
}

Inside second_space
Template trong C++

Template l nn tng ca lp trnh tng qut (generic programming), tc l vit code theo cc m
c lp vi bt k kiu c th no.
Mt Template l mt blueprint hoc l phng thc to mt lp hoc mt hm tng qut. Cc
Library Container nh Iterator v cc thut ton l cc v d ca lp trnh tng qut v c
pht trin bi s dng khi nim Template.
Mi container c mt nh ngha n, v d vector, nhng chng ta c th nh ngha nhiu lot
vector khc nhau, v d: vector <int> hoc vector <string>.
Template l t kha trong C++, chng ta c th hiu rng l n mt kiu d liu tru tng, c
trng cho cc kiu d liu c bn. Template l t kha bo cho trnh bin dch rng on m sau
y nh ngha cho nhiu kiu d liu v m ngun ca n s c bin dch sinh ra tng ng
cho tng kiu d liu trong qu trnh bin dch. C hai kiu Template trong C++:
Function Template: l mt khun mu hm, cho php nh ngha cc hm tng qut thao
tc cho nhiu kiu d liu.
Class template: l mt khun mu lp, cho php nh ngha cc lp tng qut cho nhiu
kiu d liu
Function Template trong C++

Di y l c php chung ca mt nh ngha Function Template trong C++:
template <class type> ret-type func-name(parameter list)
{
// body of function
}
Trang 148
y, type l mt tn mt kiu d liu c s dng bi hm. Tn ny c th c s dng bn

trong nh ngha hm.
Sau y l mt v d v Function Template tr v gi tr ln nht ca hai gi tr:
#include <iostream>
#include <string>
template <typename T>

inline T const& Max (T const& a, T const& b)
{
return a < b ? b:a;
}
int main ()
{
int i = 39;
int j = 20;
cout << "Max(i, j): " << Max(i, j) << endl;
double f1 = 13.5;
double f2 = 20.7;
cout << "Max(f1, f2): " << Max(f1, f2) << endl;
string s1 = "Hello";
string s2 = "World";
cout << "Max(s1, s2): " << Max(s1, s2) << endl;
return 0;
}
Bin dch v chy code trn s cho kt qu:
Trang 149
Max(i, j): 39
Max(f1, f2): 20.7
Max(s1, s2): World
Class Template trong C++

Ging nh khi chng ta c th nh ngha Function Template, chng ta cng c th nh ngha
Class Template trong C++. C php chung ca nh ngha Class Template trong C++ l:
template <class type> class class-name {
.
.
.
}
y, type l tn kiu, m s c xc nh khi mt lp c khai bo. Bn c th nh ngha

nhiu hn mt kiu d liu tng qut (generic) bi s dng mt danh sch phn bit nhau bi du
phy.
V d sau nh ngha lp Stack v trin khai cc phng thc tng qut push v pop cc phn
t t Stack . (Stack: ngn xp, push: thm nt mi vo nh stack, pop: thao tc ly 1 phn t t
nh stack).
#include <iostream>
#include <vector>
#include <cstdlib>
#include <string>
#include <stdexcept>
template <class T>

class Stack {
private:
vector<T> elems;
// elements
Trang 150
public:
void push(T const&);
// push element
void pop();
// pop element
T top() const;
// return top element
bool empty() const{
// return true if empty.
return elems.empty();
}
};
template <class T>

void Stack<T>::push (T const& elem)
{
// append copy of passed element
elems.push_back(elem);
}
template <class T>

void Stack<T>::pop ()
{
if (elems.empty()) {
throw out_of_range("Stack<>::pop(): empty stack");
}
// remove last element
elems.pop_back();
}
template <class T>

T Stack<T>::top () const
{
if (elems.empty()) {
throw out_of_range("Stack<>::top(): empty stack");
}
// return copy of last element
Trang 151
return elems.back();
}
int main()
{
try {
Stack<int>
intStack;
Stack<string> stringStack;
// stack of ints
// stack of strings
// manipulate int stack

intStack.push(7);
cout << intStack.top() <<endl;
// manipulate string stack

stringStack.push("hello");
cout << stringStack.top() << std::endl;
stringStack.pop();
stringStack.pop();
}
catch (exception const& ex) {
cerr << "Exception: " << ex.what() <<endl;
return -1;
}
}
Bin dch v chy code trn s cho kt qu:

7
hello
Exception: Stack<>::pop(): empty stack
B tin x l (Preprocessor) trong C++

B tin x l (Preprocessor) l cc directive (ch th), cung cp ch lnh ti b bin dch tin x
l thng tin trc khi bt u bin dch thc s.
Trang 152
Tt c ch th tin x l (Preprocessor directive) bt u vi #, v ch c cc k t khong trng

trng (white-space) l c th xut hin trc mt ch th tin x l trn mt dng. Ch th tin x l
khng l cc lnh trong C++, v th chng khng kt thc vi mt du chm phy.
Bn thy mt ch th tin x l l #include trong tt c v d. Macro ny c s dng bao
mt Header file vo trong source file.
C mt s ch th tin x l c h tr bi C++ nh #include, #define, #if, #else, #line, Di
y, chng ti s trnh by cc ch th tin x l quan trng trong C++:
B tin x l # define trong C++

Ch th tin x l #define to cc biu tng hng. Biu tng hng l mt macro v mu chung
ca ch th tin x l ny trong C++ l:
#define macro-name replacement-text
Khi dng ny xut hin trong mt file, tt c macro xut hin theo sau trong file ny s c thay
th bi replacement-text trc khi chng trnh c bin dch. V d:
#include <iostream>
#define PI 3.14159
int main ()
{
cout << "Value of PI :" << PI << endl;
return 0;
}
Gi s chng ta c source file, sau bin dch n vi ty chn E v hng kt qu ti test.p.

By gi, nu bn kim tra test.p, n s c nhiu thng tin v ti di cng, bn s tinh chnh gi tr
c thay th nh sau:
$gcc -E test.cpp > test.p
Trang 153
...
int main ()
{
cout << "Value of PI :" << 3.14159 << endl;
return 0;
}
Function-Like Macro trong C++

Bn c th s dng ch th tin x l #define trong C++ nh ngha mt macro m s nhn tham
s nh sau:
#include <iostream>
#define MIN(a,b) (((a)<(b)) ? a : b)
int main ()
{
int i, j;
i = 100;
j = 30;
cout <<"The minimum is " << MIN(i, j) << endl;
return 0;
}
Bin dch v thc thi code trn s cho kt qu sau:

The minimum is 30
Trang 154
Bin dch c iu kin trong C++

C mt s ch th tin x l c th s dng bin dch c s tuyn chn gia cc phn trong
source code ca bn. Tin trnh ny c gi l bin dch c iu kin.
Ch lnh tin x l c iu kin kh ging vi cu trc la chn if. Bn xt code sau:
#ifndef NULL
#define NULL 0
#endif
Bn c th bin dch mt chng trnh vi mc ch debug v c th tt hoc bt vic debug ny

bi s dng mt macro trong C++, nh sau:
#ifdef DEBUG
cerr <<"Variable x = " << x << endl;
#endif
Lnh cerr c bin dch trong chng trnh nu biu tng hng DEBUG c nh ngha
trc ch th #ifdef DEBUG. Bn c th s dng lnh #if 0 ch thch mt phn ca chng
trnh, nh sau:
#if 0
code prevented from compiling
#endif
Bn th v d sau:
#include <iostream>
#define DEBUG
#define MIN(a,b) (((a)<(b)) ? a : b)
int main ()
{
int i, j;
i = 100;
Trang 155
j = 30;
#ifdef DEBUG
cerr <<"Trace: Inside main function" << endl;
#endif
#if 0
/* This is commented part */
cout << MKSTR(HELLO C++) << endl;
#endif
cout <<"The minimum is " << MIN(i, j) << endl;
#ifdef DEBUG
cerr <<"Trace: Coming out of main function" << endl;
#endif
return 0;
}
Bin dch v thc thi code trn s cho kt qu sau:

Trace: Inside main function
The minimum is 30
Trace: Coming out of main function
Cc ton t # v ## trong C++

Cc ton t tin x l # v ## l c sn trong C++ v ANSI/ISO C. Ton t # thng bo rng on
vn bn thay th s c chuyn i sang mt chui bao quanh bi du ngoc kp.
Bn xt nh ngha macro sau:
#include <iostream>
#define MKSTR( x ) #x
Trang 156
int main ()
{
return 0;
}
Bin dch v chy code trn s cho kt qu sau:

HELLO C++
By gi, chng ta xt cch n lm vic. N l n gin hiu rng b tin x l C++ chuyn
dng sau:
Thnh dng:
cout << "HELLO C++" << endl;
Ton t ## c s dng ni chui hai token. V d:

#define CONCAT( x, y )
x ## y
Khi CONCAT xut hin trong chng trnh, cc tham s ca n c ni chui v c s dng
thay th cho macro. V d, CONCAT(HELLO, C++) c thay th bi "HELLO C++" trong
chng trnh sau:
#include <iostream>
#define concat(a, b) a ## b
int main()
{
int xy = 100;
cout << concat(x, y);

return 0;
Trang 157

100
Gi chng ta xt cch chng lm vic. n gin l b tin x l C++ chuyn dng sau:
cout << concat(x, y);
Thnh dng:
cout << xy;
Macro tin nh ngha trong C++

C++ cung cp mt s macro c nh ngha trc nh lit k di y:
Macro
Miu t
__LINE__
Cha s dng hin ti ca chng trnh khi n ang c bin

dch
__FILE__
Cha tn file hin ti ca chng trnh khi n ang c bin

dch
__DATE__
Cha mt chui month/day/year l ngy source code c bin

dch
__TIME__
Cha mt chui hour:minute:second l thi gian chng trnh

c bin dch
Di y l v d cho tt c macro trn trong C++:

#include <iostream>
int main ()
Trang 158
{
cout << "Value of __LINE__ : " << __LINE__ << endl;
cout << "Value of __FILE__ : " << __FILE__ << endl;
cout << "Value of __DATE__ : " << __DATE__ << endl;
cout << "Value of __TIME__ : " << __TIME__ << endl;
return 0;
}

Value of __LINE__ : 6
Value of __FILE__ : test.cpp
Value of __DATE__ : Feb 28 2011
Value of __TIME__ : 18:52:48
X l tn hiu (Signal Handling) trong C++

Tn hiu (Signal) l cc ngt (interrupt) c phn phi ti mt tin trnh x l bi h iu hnh
m c th kt thc mt chng trnh. Bn c th to cc ngt bng vic nhn CTRL+C trn h
thng UNIX, LINUX, Mac OS hoc Windows.
C cc signal m khng th b bt bi chng trnh, nhng cng c signal m bn c th bt trong
chng trnh ca bn, v c th thc hin cc hnh ng thch hp da trn signal . Nhng
signal ny c nh ngha trong Header file ca C++ l <csignal>.
Signal
Miu t
SIGABRT
S kt thc bt thng ca chng trnh, v d mt li gi ti abort
SIGFPE
Mt hot ng s hc khng ng, v d nh chia cho s 0 hoc mt hot

ng lm trn lung (overflow)
SIGILL
S pht hin mt ch lnh khng hp l
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SIGINT
Nhn mt tn hiu tng tc
SIGSEGV
Mt truy cp khng hp l ti storage
SIGTERM
Mt yu cu kt thc c gi ti chng trnh
Hm signal() trong C++

Th vin x l tn hiu trong C++ cung cp hm signal by cc s kin khng c mong i.
Di y l c php ca hm signal() trong C++:
void (*signal (int sig, void (*func)(int)))(int);
Hm ny nhn hai tham s: tham s u tin l mt integer m biu din s hiu tn hiu (signal
number) v tham s th hai l mt con tr ti hm x l tn hiu.
By gi, vit mt chng trnh C++ n gin bt tn hiu SIGINT bi s dng
hmsignal() trong C++. Bt c tn hiu no bn mun bt trong chng trnh, bn phi ghi tn hiu
bi s dng hm signal v lin kt n vi mt Signal Handler. Bn xt v d:
#include <iostream>
#include <csignal>
void signalHandler( int signum )

{
cout << "Interrupt signal (" << signum << ") received.\n";
// cleanup and close up stuff here

// terminate program
exit(signum);
Trang 160
int main ()
{
// register signal SIGINT and signal handler
signal(SIGINT, signalHandler);
while(1){
cout << "Going to sleep...." << endl;
sleep(1);
}
return 0;
}

Going to sleep....
Going to sleep....
Going to sleep....
By gi, nhn CTRL+C ngt chng trnh v bn s thy rng chng trnh s bt tn hiu ny
v s in ci g nh sau:
Going to sleep....
Going to sleep....
Going to sleep....
Interrupt signal (2) received.
Hm raise() trong C++

Bn c th to cc tn hiu bi hm raise() trong C++, m nhn mt s integer biu din signal
number nh mt tham s v c c php nh sau:
int raise (signal sig);
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y, sig l signal number gi bt k loi tn hiu no: SIGINT, SIGABRT, SIGFPE, SIGILL,
SIGSEGV, SIGTERM, SIGHUP. Di y l v d to mt tn hiu ni ti bi s dng hm raise()
trong C++, nh sau:
#include <iostream>
#include <csignal>
void signalHandler( int signum )

{
cout << "Interrupt signal (" << signum << ") received.\n";
// cleanup and close up stuff here

// terminate program
exit(signum);
int main ()
{
int i = 0;
// register signal SIGINT and signal handler
signal(SIGINT, signalHandler);
while(++i){
cout << "Going to sleep...." << endl;
if( i == 3 ){
raise( SIGINT);
}
sleep(1);
}
Trang 162
return 0;
}
Bin dch v thc thi code trn, n s cho kt qu sau:

Going to sleep....
Going to sleep....
Going to sleep....
Interrupt signal (2) received.
a lung (Multithread) trong C++

a lung (Multithreading) l mt form chuyn dng ca a nhim (multitasking) v mt a nhim
l tnh nng cho php my tnh ca bn chy hai hoc nhiu chng trnh ng thi. Ni chung, c
hai kiu a nhim l: process-based v thread-based tng ng: da trn tin trnh v da trn
lung.
a nhim da trn tin trnh x l vic thc thi ng thi ca cc chng trnh. a nhim da trn
lung x l vic thc thi ng thi cc phn ca cng mt chng trnh.
Mt chng trnh a lung cha hai hoc nhiu phn m c th chy ng thi. Mi phn ca
chng trnh c gi l mt thread, v mi thread nh ngha mt path ring bit ca s thc
thi.
C++ khng cha bt k h tr c sn no cho cc ng dng a lung. Thay vo , n da hon
ton vo H iu hnh cung cp tnh nng ny.
Chng ny gi s bn ang lm vic trn H iu hnh Linux v chng ti ang chun b vit
chng trnh a lung trong C++ bi s dng POSIX. POSIX Threads hoc Pthreads cung cp
API m c sn trn nhiu h thng nh FreeBSD, NetBSD, GNU/Linux, Mac OS X v Solaris.
To Thread trong C++

y l chng trnh chng ta s dng to mt POSIX thread:
#include <pthread.h>
pthread_create (thread, attr, start_routine, arg)
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y, pthread_create to mt thread mi v lm n c th thc thi. Chng trnh ny c th

c gi bt c thi im no bt c u trong code ca bn. Di y l miu t cc tham s:
Tham s
Miu t
thread
Mt nh danh duy nht cho thread mi c tr v bi chng trnh

con
attr
Mt thuc tnh m c th c s dng thit lp cc thuc tnh ca

thread. Bn c th xc nh mt i tng thuc tnh thread, hoc
NULL cho cc gi tr mc nh
start_routine
Chng trnh C++ m thread ny s thc thi mt khi n c to
arg
Mt tham s n m c th c truyn ti start_routine. N phi

c truyn bi tham chiu dng mt con tr ca kiu void. NULL c
th c s dng nu khng c tham s no c truyn
S thread ti a c th c to bi mt tin trnh l ph thuc vo trnh trin khai

(Implementation). Mt khi c to, cc thread l ngang hng, v c th to cc thread khc.
Khng c s ph thuc gia cc thread trong C++.
Kt thuc Thread trong C++

Chng trnh sau c s dng kt thc mt POSIX thread trong C++:
pthread_exit (status)
y pthread_exit c s dng kt thc mt thread. Chng trnh pthread_exit() c gi

sau khi mt thread hon thnh cng vic ca n v khng cn thit phi tn ti na.
Nu main() kt thc trc cc thread n to, v kt thc chng trnh pthread_create(), th cc
thread khc s tip tc thc thi. Nu khng th, chng s t ng c kt thc khi main() hon
thnh.
Trang 164
V d
V d n gin sau to 5 thread vi chng trnh pthread_create(). Mi thread in mt thng bo
Hello World!, v sau kt thc vi mt li gi ti pthread_exit() trong C++:
#include <iostream>
#include <cstdlib>
#define NUM_THREADS
void *PrintHello(void *threadid)

{
long tid;
tid = (long)threadid;
cout << "Hello World! Thread ID, " << tid << endl;
pthread_exit(NULL);
}
int main ()
{
pthread_t threads[NUM_THREADS];
int rc;
int i;
for( i=0; i < NUM_THREADS; i++ ){
cout << "main() : creating thread, " << i << endl;
rc = pthread_create(&threads[i], NULL,
PrintHello, (void *)i);
if (rc){
cout << "Error:unable to create thread," << rc << endl;
exit(-1);
}
Trang 165
}
pthread_exit(NULL);
}
Bin dch chng trnh trn s dng th vin lpthread nh sau:

$gcc test.cpp -lpthread
By gi, thc thi chng trnh s cho kt qu:

main() : creating thread, 0
Hello World! Thread ID, 0
Truyn tham s ti Thread trong C++

V d ny minh ha cch truyn nhiu tham s thng qua mt cu trc. Bn c th truyn bt k
kiu d liu no trong mt Thread callback, bi v n tr ti void nh c gii thch trong v d
sau:
#include <iostream>
#include <cstdlib>
#define NUM_THREADS
struct thread_data{
int
thread_id;
Trang 166
char *message;
};
void *PrintHello(void *threadarg)

{
struct thread_data *my_data;
my_data = (struct thread_data *) threadarg;
cout << "Thread ID : " << my_data->thread_id ;

cout << " Message : " << my_data->message << endl;
pthread_exit(NULL);
}
int main ()
{
struct thread_data td[NUM_THREADS];
int rc;
int i;

cout <<"main() : creating thread, " << i << endl;
td[i].thread_id = i;
td[i].message = "This is message";
rc = pthread_create(&threads[i], NULL,
PrintHello, (void *)&td[i]);
if (rc){
exit(-1);
}
}
Trang 167
pthread_exit(NULL);
}

Thread ID : 3 Message : This is message
Kt hp v Tho g cc Thread trong C++

Hai c php sau c s dng kt hp (joining) hoc tho g (detaching) cc Thread trong
C++:
pthread_join (threadid, status)
pthread_detach (threadid)
Chng trnh con pthread_join() ng khi thread ang gi ti khi threadid kt thc. Khi mt thread
c to, mt trong cc thuc tnh nh ngha n l joinable hoc detached. Ch cc thread c
to vi dng joinable c th c kt hp. Nu mt thread c to vi dng detached, n khng
bao gi c kt hp.
V d sau minh ha cch i cho cc thread kt thc bi s dng chng trnh kt hp Pthread
trong C++:
#include <iostream>
#include <cstdlib>
#include <unistd.h>
Trang 168
#define NUM_THREADS
void *wait(void *t)

{
int i;
long tid;
tid = (long)t;
sleep(1);
cout << "Sleeping in thread " << endl;
cout << "Thread with id : " << tid << "
...exiting " << endl;
pthread_exit(NULL);
}
int main ()
{
int rc;
int i;
pthread_attr_t attr;
void *status;
// Initialize and set thread joinable

pthread_attr_init(&attr);
pthread_attr_setdetachstate(&attr, PTHREAD_CREATE_JOINABLE);

cout << "main() : creating thread, " << i << endl;
rc = pthread_create(&threads[i], NULL, wait, (void *)i );
if (rc){
Trang 169

exit(-1);
}
}
// free attribute and wait for the other threads

pthread_attr_destroy(&attr);
rc = pthread_join(threads[i], &status);
if (rc){
cout << "Error:unable to join," << rc << endl;
exit(-1);
}
cout << "Main: completed thread id :" << i ;
cout << "
exiting with status :" << status << endl;
cout << "Main: program exiting." << endl;

pthread_exit(NULL);
}

Sleeping in thread
Thread with id : 0 .... exiting
Sleeping in thread
Sleeping in thread
Trang 170
Sleeping in thread
Sleeping in thread
Main: completed thread id :0
exiting with status :0
Main: program exiting.
Lp trnh Web trong C++

CGI l g?
Common Gateway Interface hoc CGI l mt tp hp cc chun m nh ngha cch thng

tin c trao i gia Web Server v mt Custom Script.
CGI Specification hin ti c duy tr bi NCSA v NCSA nh ngha CGI nh sau:

Common Gateway Interface hoc CGI l mt chun cho cc chng trnh kt ni d mng
ngoi vi (external gateway programs) ti Interface vi thng tin t Server nh HTTP
Server.
Phin bn hin ti l CGI/1.1 v CGI/1.2 ang trong qu trnh pht trin.
Web Browsing
hiu khi nim v CGI, chng ta xem nhng g xy ra khi chng ta nhn vo mt hyperlink
ti mt Webpage hoc URL c th.
Trnh duyt ca bn lin h HTTP Web Server v yu cu mt URL, v d: filename.
Web Server s parse URL v s tm kim filename. Nu n tm thy file yu cu, th

Web Server gi file tr li trnh duyt, nu khng th, n gi mt thng bo li ch rng
bn yu cu mt wrong file.
Trnh duyt Web nhn phn hi t Web Server v hin th file nhn c hoc thng bo
li da trn phn hi nhn.
Trang 171
Tuy nhin, n l c th thit lp HTTP Server theo cch m bt c khi no mt file trong mt th
mc c th c yu cu, th file khng c gi tr li; thay cho vic n c thc thi nh l
mt chng trnh v output c to t chng trnh gi ti trnh duyt hin th.
Common Gateway Interface hoc CGI l mt giao thc chun cho cc ng dng (c gi l CGI
program hoc CGI script) kh nng tng tc vi Web Server v vi Client. Nhng CGI program
ny c th c vit bng Python, PERL, Shell, C hoc C++
S cu trc CGI
Di y l s mt cu trc n gin ca CGI:
Cu hnh Web Server

Trc khi bn tip tc vi lp trnh CGI, m bo rng Web Server ca bn h tr CGI v n c
nh cu hnh x l CGI Program. Tt c CGI program c thc thi bi HTTP Server c
gi trong mt th mc c nh cu hnh trc. Th mc ny c gi l CGI directory, v theo
Trang 172
qui c, n c t tn l /var/www/cgi-bin. Theo qui c, CGI file c ui l .cgi, v th chng l

c th thc thi trong C++.
Theo mc nh, Apache Web Server c nh cu hnh chy CGI Program trong /var/www/cgibin. Nu bn mun xc nh bt k th mc khc chy CGI script ca bn, th bn phi sa i
khu vc sau trong httpd.conf file:
<Directory "/var/www/cgi-bin">
AllowOverride None
Options ExecCGI
Order allow,deny
Allow from all
</Directory>
<Directory "/var/www/cgi-bin">
Options All
</Directory>
Chng trnh CGI u tin

Xt ni dung chng trnh C++ sau:
#include <iostream>
int main ()
{
cout << "Content-type:text/html\r\n\r\n";

cout << "<html>\n";
cout << "<head>\n";
cout << "<title>Hello World - First CGI Program</title>\n";
cout << "</head>\n";
cout << "<body>\n";
cout << "<h2>Hello World! This is my first CGI program</h2>\n";
cout << "</body>\n";
Trang 173
cout << "</html>\n";
return 0;
}
Bin dch code trn v t tn l cplusplus.cgi. File ny c gi trong th mc /var/www/cgi-bin

v n c ni dung nh sau. Trc khi chy CGI Program ca bn, bo m rng bn chuyn
ch ca file bi s dng lnh chmod 755 cplusplus.cgi trn UNIX lm file c th thc thi. By
gi, nu bn nhn vo cplusplus.cgi, th n s cho kt qu:
Hello World! This is my first CGI program

Chng trnh C++ trn l mt chng trnh n gin m ang vit output trn STDOUT file, v d:
mn hnh. C mt tnh nng quan trng c sn dng u tin c in l Contenttype:text/html\r\n\r\n. Dng ny gi tr li trnh duyt v xc nh kiu ni dung c hin th
trn mn hnh trnh duyt. By gi bn hiu khi nim c bn v CGI v bn c th vit nhiu
CGI Program phc tp bi s dng C++. Mt CGI Program trong C++ c th tng tc vi bt k
h thng ngoi vi khc nh RDBMS, trao i thng tin.
HTTP Header
Dng Content-type:text/html\r\n\r\n l mt phn ca HTTP Header, m c gi ti trnh duyt.
Tt c HTTP Header c form sau:
HTTP Field Name: Field Content
For Example
Content-type: text/html\r\n\r\n
Di y l mt s HTTP Header quan trng, m bn s s dng thng xuyn trong Lp trnh

CGI.
Header
Miu t
Content-type:
Mt chui MIME nh ngha nh dng ca file ang c tr v.

V d: Content-type:text/html
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Expires: Date
Ngy thng tin ht hiu lc. N nn c s dng bi trnh

duyt quyt nh khi no mt trang cn c refresh. Mt
chui date hp l nn trong nh dng 01 Jan 1998 12:00:00
GMT
Location: URL
URL m nn c tr v thay cho URL yu cu. Bn c th

s dng trng ny redirect mt yu cu ti bt k file no
Last-modified: Date
Ngy sa i cui cng ca ngun
Content-length: N
di, bng byte, ca d liu ang c tr v. Trnh duyt s

dng gi tr ny bo co lng thi gian download c lng
cho mt file
Set-Cookie: String
Thit lp cookie truyn thng qua string
Bin mi trng ca CGI

Tt c CGI Program s c truy cp ti cc bin mi trng sau y. Nhng bin ny ng vai tr
quan trng trong khi vit bt k CGI Program no:
Tn bin
Miu t
CONTENT_TYPE
Kiu d liu ca ni dung. c s dng khi Client gi ni dung

nh km ti Server. V d: file upload
CONTENT_LENGTH
di ca thng tin truy vn. N ch c sn cho cc yu cu

POST
HTTP_COOKIE
Tr v cc cookie thit lp trong form l cp key/value
HTTP_USER_AGENT
Trng request-header l User-Agent cha thng tin v User

Agent bt u yu cu . N l tn ca trnh duyt web
Trang 175
PATH_INFO
L path cho CGI script
QUERY_STRING
Thng tin m ha URL c gi vi phng thc GET
REMOTE_ADDR
a ch IP ca host t xa to yu cu . N c th l hu ch
cho mc ch log hoc authentication
REMOTE_HOST
Tn y ca host to yu cu . Nu thng tin ny khng c

sn, th REMOTE_ADDR c th c s dng ly a ch IP
REQUEST_METHOD
Phng thc c s dng to yu cu. Cc phng thc

ph bin l GET v POST
SCRIPT_FILENAME
Path y ti CGI script
SCRIPT_NAME
Tn ca CGI script
SERVER_NAME
Hostname hoc a ch IP ca Server
SERVER_SOFTWARE
Tn v phin bn ca phn mm m Server ang chy
Sau y l chng trnh CGI nh lit k tt c bin CGI. Bn click vo y xem kt qu:Get
Environment
#include <iostream>
#include <stdlib.h>
const string ENV[ 24 ] = {
Trang 176
"COMSPEC", "DOCUMENT_ROOT", "GATEWAY_INTERFACE",

"HTTP_ACCEPT", "HTTP_ACCEPT_ENCODING",
"HTTP_ACCEPT_LANGUAGE", "HTTP_CONNECTION",
"HTTP_HOST", "HTTP_USER_AGENT", "PATH",
"QUERY_STRING", "REMOTE_ADDR", "REMOTE_PORT",
"REQUEST_METHOD", "REQUEST_URI", "SCRIPT_FILENAME",
"SCRIPT_NAME", "SERVER_ADDR", "SERVER_ADMIN",
"SERVER_NAME","SERVER_PORT","SERVER_PROTOCOL",
"SERVER_SIGNATURE","SERVER_SOFTWARE" };
int main ()
{

cout << "<html>\n";
cout << "<head>\n";
cout << "<title>CGI Envrionment Variables</title>\n";
cout << "<body>\n";
cout << "<table border = \"0\" cellspacing = \"2\">";
for ( int i = 0; i < 24; i++ )

{
cout << "<tr><td>" << ENV[ i ] << "</td><td>";
// attempt to retrieve value of environment variable
char *value = getenv( ENV[ i ].c_str() );
if ( value != 0 ){
cout << value;
}else{
cout << "Environment variable does not exist.";
}
cout << "</td></tr>\n";
}
Trang 177
cout << "</table><\n";

return 0;
}
Th vin CGI trong C++

Vi cc v d thc t, bn s cn thc hin nhiu hot ng bi CGI Program ca bn. C mt th
vin CGI c vit cho chng trnh C++, m bn c th ti v t:ftp://ftp.gnu.org/gnu/cgicc/ v
theo cc bc sau ci t th vin ny:
$tar xzf cgicc-X.X.X.tar.gz
$cd cgicc-X.X.X/
$./configure --prefix=/usr
$make
$make install
Bn c th kim tra Documentation c sn ti: C++ CGI Lib Documentation.
Phng thc POST v GET

Bn gp mt s tnh hung khi bn cn truyn mt s thng tin t trnh duyt ti Web Server v
sau cng ti CGI Program ca bn. Hai phng thc c s dng thng xuyn nht bi trnh
duyt truyn cc thng tin ny ti Web Server l Phng thc GET v Phng thc POST.
Truyn thng tin bi s dng phng thc GET

Phng thc GET gi thng tin ngi dng m ha c ph thm ti trang yu cu. Trang v
thng tin m ha c phn bit bi k t ? nh sau:
http://www.test.com/cgi-bin/cpp.cgi?key1=value1&key2=value2
Phng thc GET l phng thc mc nh truyn thng tin t trnh duyt ti Web Server v
n to ra mt chui di xut hin trong Location:box ca trnh duyt. ng bao gi s dng
phng thc GET nn bn c mt khu hoc thng tin nhy cm khc truyn ti Server.
Phng thc GET c gii hn kch c v bn c th truyn 1024 k t trong mt Request String.
Trang 178
Khi s dng phng thc GET, thng tin c truyn bi trng HTTP Header l
QUERY_STRING v s l c th truy cp trong CGI Program thng qua bin mi trng
QUERY_STRING.
Bn c th truyn thng tin bng vic ni chui cc cp key/value cng vi bt k URL hoc bn c
th s dng cc th HTML <FORM> truyn thng tin bi s dng phng thc GET.
V d URL n gin s dng phng thc GET

y l mt URL n gin s truyn hai value ti chng trnh hello_get.py bi s dng phng
thc GET.
/cgi-bin/cpp_get.cgi?first_name=ZARA&last_name=ALI
Di y l chng trnh to CGI Program l cpp_get.cgi x l input c cung cp bi
trnh duyt web. Chng ta ang s dng th vin CGI trong C++, lm cho n d dng hn
truy cp thng tin truyn:
#include <iostream>
#include <vector>
#include <string>
#include <stdio.h>
#include <stdlib.h>
#include <cgicc/CgiDefs.h>
#include <cgicc/Cgicc.h>
#include <cgicc/HTTPHTMLHeader.h>
#include <cgicc/HTMLClasses.h>

using namespace cgicc;
int main ()
{
Cgicc formData;
Trang 179
cout << "<html>\n";

cout << "<head>\n";
cout << "<title>Using GET and POST Methods</title>\n";
cout << "<body>\n";
form_iterator fi = formData.getElement("first_name");
if( !fi->isEmpty() && fi != (*formData).end()) {
cout << "First name: " << **fi << endl;
}else{
cout << "No text entered for first name" << endl;
}
cout << "<br/>\n";
fi = formData.getElement("last_name");
if( !fi->isEmpty() &&fi != (*formData).end()) {
cout << "Last name: " << **fi << endl;
}else{
cout << "No text entered for last name" << endl;
}
cout << "<br/>\n";

return 0;
}
By gi, bin dch chng trnh trn nh sau:

$g++ -o cpp_get.cgi cpp_get.cpp -lcgicc
To cpp_get.cgi v t n trong th mc CGI ca bn.

N s cho kt qu:
Trang 180
First name: ZARA

Last name: ALI
V d v FORM bi s dng phng thc GET

V d n gin sau s truyn hai value bi s dng HTML FORM v nt submit. Chng ta ang s
dng cng CGI Program l cpp_get.cgi x l input ny.
<form action="/cgi-bin/cpp_get.cgi" method="get">
First Name: <input type="text" name="first_name">
<br />
Last Name: <input type="text" name="last_name" />

<input type="submit" value="Submit" />
</form>
y l output thc s ca form trn. Bn c th nhp First v Last Name v sau click nt
Submit xem kt qu:
First Name:
Last Name:
Submit
Truyn thng tin bi s dng phng thc POST

Mt phng thc chung ng tin cy hn truyn thng tin ti mt CGI Program l phng thc
POST. N ng gi thng tin theo cch ging phng thc GET, nhng thay v gi n dng mt
chui vn bn sau mt du ? trong URL, n gi dng mt thng bo ring bit. Thng bo ny
ti CGI Script trong form u vo chun.
Cng s dng CGI Program l cpp_get.cgi x l phng thc POST. Chng ta s dng cng v
d nh trn, m s truyn hai value bi s dng HTML FORM v nt Submit, nhng ln ny vi
phng thc POST nh sau:
<form action="/cgi-bin/cpp_get.cgi" method="post">
First Name: <input type="text" name="first_name"><br />
Last Name: <input type="text" name="last_name" />
Trang 181

</form>
y l output thc s ca form trn. Bn nhp First v Last Name v sau nhn nt Submit
xem kt qu:
First Name:
Submit
Last Name:
Truyn Checkbox Data ti CGI Program

Checkbox c s dng khi c nhiu hn mt ty chn l cn thit c la chn:
HTML code sau l v d cho mt form vi hai checkbox:
<form action="/cgi-bin/cpp_checkbox.cgi"
method="POST"
target="_blank">
<input type="checkbox" name="maths" value="on" /> Maths
<input type="checkbox" name="physics" value="on" /> Physics
<input type="submit" value="Select Subject" />
</form>
Kt qu ca code ny l form sau:
Maths
Physics
Select Subject
Chng trnh C++ sau s to cpp_checkbox.cgi x l input c cung cp bi trnh duyt

thng qua nt checkbox:
#include <iostream>
#include <vector>
#include <string>
Trang 182
#include <stdio.h>
#include <stdlib.h>

int main ()
{
Cgicc formData;
bool maths_flag, physics_flag;

cout << "<html>\n";
cout << "<head>\n";
cout << "<title>Checkbox Data to CGI</title>\n";
cout << "<body>\n";
maths_flag = formData.queryCheckbox("maths");
if( maths_flag ) {
cout << "Maths Flag: ON " << endl;
}else{
cout << "Maths Flag: OFF " << endl;
}
cout << "<br/>\n";
physics_flag = formData.queryCheckbox("physics");
if( physics_flag ) {
Trang 183
cout << "Physics Flag: ON " << endl;

}else{
cout << "Physics Flag: OFF " << endl;
}
cout << "<br/>\n";
return 0;
}
Truyn Radiobutton Data ti CGI Program

Radio Button c s dng khi ch c mt ty chn l cn thit la chn.
HTML code sau l v d cho form vi hai radio button:
<form action="/cgi-bin/cpp_radiobutton.cgi"
method="post"
target="_blank">
<input type="radio" name="subject" value="maths"
checked="checked"/> Maths
<input type="radio" name="subject" value="physics" /> Physics
<input type="submit" value="Select Subject" />
</form>
Kt qu ca code trn l form sau:
Maths
Physics
Select Subject
Chng trnh C++ sau s to cpp_radiobutton.cgi x l input c cung cp bi trnh duyt

web thng qua cc radio button:
#include <iostream>
#include <vector>
#include <string>
#include <stdio.h>
Trang 184
#include <stdlib.h>

int main ()
{
Cgicc formData;

cout << "<html>\n";
cout << "<head>\n";
cout << "<title>Radio Button Data to CGI</title>\n";
cout << "<body>\n";
form_iterator fi = formData.getElement("subject");
cout << "Radio box selected: " << **fi << endl;
}
cout << "<br/>\n";

return 0;
}
Trang 185
Truyn Text Area Data ti CGI Program

Phn t TEXTAREA c s dng khi vn bn nhiu dng phi c truyn ti CGI Program.
HTML code sau l v d cho mt form vi mt TEXTAREA box:
<form action="/cgi-bin/cpp_textarea.cgi"
method="post"
target="_blank">
<textarea name="textcontent" cols="40" rows="4">
Type your text here...
</textarea>
</form>
y l kt qu ca form trn:
Submit
Chng trnh C++ sau s to cpp_textarea.cgi x l input c cung cp bi trnh duyt web
thng qua text area:
#include <iostream>
#include <vector>
#include <string>
#include <stdio.h>
#include <stdlib.h>
Trang 186
int main ()
{
Cgicc formData;

cout << "<html>\n";
cout << "<head>\n";
cout << "<title>Text Area Data to CGI</title>\n";
cout << "<body>\n";
form_iterator fi = formData.getElement("textcontent");
cout << "Text Content: " << **fi << endl;
}else{
cout << "No text entered" << endl;
}
cout << "<br/>\n";

return 0;
}
Truyn DropDown Box Data ti CGI Program

DropDown Box c s dng khi c nhiu ty chn c sn, nhng ch c mt hoc hai s c
chn:
HTML code sau l v d cho mt form vi mt Dropdown box:
<form action="/cgi-bin/cpp_dropdown.cgi"
Trang 187
method="post" target="_blank">
<select name="dropdown">
<option value="Maths" selected>Maths</option>
<option value="Physics">Physics</option>
</select>
<input type="submit" value="Submit"/>
</form>
Kt qu ca code trn l form sau:

Maths
Submit
Chng trnh C++ sau s to cpp_dropdown.cgi x l input c cung cp bi trnh duyt

web thng qua dropdown box:
#include <iostream>
#include <vector>
#include <string>
#include <stdio.h>
#include <stdlib.h>

int main ()
{
Cgicc formData;

cout << "<html>\n";
Trang 188
cout << "<head>\n";

cout << "<title>Drop Down Box Data to CGI</title>\n";
cout << "<body>\n";
form_iterator fi = formData.getElement("dropdown");
cout << "Value Selected: " << **fi << endl;
}
cout << "<br/>\n";

return 0;
}
S dng Cookie trong CGI

HTTP Protocol l mt giao thc Stateless. Nhng vi mt Website thng mi, n l cn thit
duy trnh thng tin session gia cc trang khc nhau. V d, mt tin trnh ng k ca ngi s
dng c th kt thc sau khi hon thnh qua nhiu trang. Nhng cch duy tr thng tin session
ca ngi dng khi h duyt qua nhiu trang l nh th no.
Trong nhiu tnh hung, s dng Cookie l phng thc hiu qu nht ghi nh v theo du vic
t hng, mua hng, hng ha a thch,
Cch n lm vic
Server ca bn gi mt s d liu ti trnh duyt khch truy cp trong form ca mt Cookie. Trnh
duyt c th chp nhn Cookie ny. Nu n chp nhn, n c lu gi dng mt bn ghi thun
vn bn trn Hard drive ca khch truy cp. By gi, khi khc truy cp ti trang khc trn site ca
bn, Cookie ny l c sn thu hi. Khi c thu hi, Server ca bn bit/nh nhng g c lu
gi:
Cookie l mt bn ghi d liu thun vn bn ca 5 trng bin:
Trang 189
Expires : Ngy m Cookie s ht hn. Nu trng, Cookie s ht hn khi khch truy cp

thot khi trnh duyt.
Domain : Tn min ca site ca bn
Path : Path ti th mc hoc Webpage m thit lp Cookie . N c th l trng nu bn

mun thu nhn Cookie t bt k th mc hoc trang no.
Secure : Nu trng ny cha t secure, th Cookie ch c th c thu hi vi mt

Secure Server. Nu trng ny trng, s khng tn ti hn ch no.
Name=Value : Cookie c thit lp v thu hi trong form cc cp key/value.
Thit lp Cookie
Rt d dng gi Cookie ti trnh duyt. Nhng Cookie ny c gi cng vi HTTP Header
trc trng Content-type. Gi s bn mun thit lp UserID v Password dng Cookie. Th
thit lp Cookie s c thc hin nh sau:
#include <iostream>
int main ()
{
cout << "Set-Cookie:UserID=XYZ;\r\n";

cout << "Set-Cookie:Password=XYZ123;\r\n";
cout << "Set-Cookie:Domain=www.tutorialspoint.com;\r\n";
cout << "Set-Cookie:Path=/perl;\n";
cout << "<html>\n";

cout << "<head>\n";
cout << "<title>Cookies in CGI</title>\n";
cout << "<body>\n";
Trang 190
cout << "Setting cookies" << endl;
cout << "<br/>\n";

return 0;
}
T v d ny, bn phi hiu cch thit lp Cookie. Chng ta s dng HTTP Header l SetCookie thit lp cc Cookie.
y, n l ty thit lp cc thuc tnh ca Cookie nh Expires, Domain, v Path. Bn nh
rng, Cookie c thit lp trc khi gi dng sau: "Content-type:text/html\r\n\r\n.
Bin dch chng trnh trn to setcookies.cgi. N s thit lp 4 Cookie ti my tnh ca bn.
Thu hi Cookie
Vic thu hi tt c Cookie thit lp l kh d dng. Cookie c lu gi trong bin mi trng
CGI l HTTP_COOKIE v chng s c form sau:
key1=value1;key2=value2;key3=value3....
Di y l v d v cch thu hi cc Cookie:

#include <iostream>
#include <vector>
#include <string>
#include <stdio.h>
#include <stdlib.h>
Trang 191

int main ()
{
Cgicc cgi;
const_cookie_iterator cci;

cout << "<html>\n";
cout << "<head>\n";
cout << "<title>Cookies in CGI</title>\n";
cout << "<body>\n";
cout << "<table border = \"0\" cellspacing = \"2\">";
// get environment variables

const CgiEnvironment& env = cgi.getEnvironment();
for( cci = env.getCookieList().begin();

cci != env.getCookieList().end();
++cci )
{
cout << "<tr><td>" << cci->getName() << "</td><td>";
cout << cci->getValue();
cout << "</td></tr>\n";
}
cout << "</table><\n";
cout << "<br/>\n";

Trang 192
return 0;
}
By gi, bin dch chng trnh trn to getcookies.cgi, v th ly danh sch tt c Cookie c
sn ti my tnh ca bn.
N s cho mt danh sch gm 4 Cookie c thit lp phn trc v tt c Cookie khc
c thit lp ti my tnh ca bn:
UserID XYZ
Password XYZ123
Domain www.tutorialspoint.com
Path /perl
V d v File Upload
ti mt file ln, HTML code phi c thuc tnh enctype c thit lp l multipart/form-data.
Th input vi kiu file ny s to mt nt Browse.
<html>
<body>
<form enctype="multipart/form-data"
action="/cgi-bin/cpp_uploadfile.cgi"
method="post">
<p>File: <input type="file" name="userfile" /></p>
<p><input type="submit" value="Upload" /></p>
</form>
</body>
</html>
Kt qu ca code trn s l form sau:

File:
Upload
Ghi ch: V d trn b v hiu ha trnh ngi dng Upload file ln Server ca chng ti.
Nhng bn c th th code trn vi Server ca bn.
Trang 193
y l chng trnh cpp_uploadfile.cpp x l upload file:

#include <iostream>
#include <vector>
#include <string>
#include <stdio.h>
#include <stdlib.h>

int main ()
{
Cgicc cgi;

cout << "<html>\n";
cout << "<head>\n";
cout << "<title>File Upload in CGI</title>\n";
cout << "<body>\n";
// get list of files to be uploaded

const_file_iterator file = cgi.getFile("userfile");
if(file != cgi.getFiles().end()) {
// send data type at cout.
cout << HTTPContentHeader(file->getDataType());
// write content at cout.
Trang 194
file->writeToStream(cout);
}
cout << "<File uploaded successfully>\n";
return 0;
}
V d trn ang vit ni dung ti cout stream, nhng bn c th m file stream ca bn v gi ni

dung ca upload file trong mt file ti v tr mong mun.
Th vin Template chun (STL) trong

C++
Hy vng bn hiu khi nim v Template trong C++ c chng ti trnh by trong chng
v Template. Standard Tamplate Library (STL) trong C++ l mt tp hp cc lp Template mnh
m trong C++ cung cp cc lp v cc hm c to theo khun mu cho mc ch lp trnh
tng qut, m trin khai nhiu thut ton v cu trc d liu c s dng ph bin v thng dng
nh vector, list, queue v stack.
C ba thnh phn mang tnh cu trc mnh m ca Standard Tamplate Library (STL) trong C++ l:
Thnh phn
Miu t
Containers
Containers c s dng qun l cc tp hp i tng ca

mt kiu c th. C mt s kiu Containers khc nhau nh list,
vector, map,
Algorithms
Algorithms hot ng trn containers. Chng cung cp cc

phng thc m theo bn s thc hin vic khi to, sp
xp, tm kim ni dung ca Containers
Iterators
Iterators c s dng duyt qua cc phn t trong tp hp

cc i tng. Nhng tp hp ny c th l Containers hoc
Subset ca Containers
Trang 195
Chng ta s cp v 3 thnh phn ca STL trong C++ trong chng tip theo khi bn lun v
Th vin chun C++ (C++ Standard Library). By gi, bn ghi nh rng, 3 thnh phn ny c mt
tp hp cc hm c nh ngha trc, m gip chng ta trong vic thc hin cc tc v phc tp
tr nn n gin hn.
Xt v d sau minh ha vector containers (l mt Template chun trong C++), m ging nh mt
mng vi mt exception m t ng x l cc nhu cu v storage ca ring n khi n cn:
#include <iostream>
#include <vector>
int main()
{
// create a vector to store int
vector<int> vec;
int i;
// display the original size of vec

cout << "vector size = " << vec.size() << endl;
// push 5 values into the vector

for(i = 0; i < 5; i++){
vec.push_back(i);
}
// display extended size of vec

cout << "extended vector size = " << vec.size() << endl;
// access 5 values from the vector

for(i = 0; i < 5; i++){
cout << "value of vec [" << i << "] = " << vec[i] << endl;
}
Trang 196
// use iterator to access the values

vector<int>::iterator v = vec.begin();
while( v != vec.end()) {
cout << "value of v = " << *v << endl;
v++;
}
return 0;
}

vector size = 0
extended vector size = 5
value of vec [0] = 0
value of v = 0
value of v = 1
value of v = 2
value of v = 3
value of v = 4
Di y l cc im quan trng cn ghi nh lin quan ti cc hm a dng c s dng

trong v d trn:
Hm thnh vin push_back() chn gi tr ti phn cui ca vector, m rng kch c ca n

khi cn.
Hm size() hin th kch c ca vector.
Hm begin() tr v mt iterator ti phn u ca vector.
Hm end() tr v mt interator ti phn cui ca vecor.
Trang 197
Th vin chun C++ (C++ Standard

Library)
Th vin chun C++ (C++ Standard Library) c th chia thnh hai phn:
Th vin hm chun trong C++ (Standard Function Library): Th vin ny gm cc

hm mang mc ch tng qut m khng l mt phn ca bt k lp no. Th vin hm
chun l k tha t C.
Th vin lp hng i tng trong C++ (Object Oriented Class Library): y l mt

tp hp ca cc lp v cc hm lin kt.
Th vin chun C++ cng kt hp cht ch Th vin chun C, vi mt s b sung v thay i nh

h tr tnh an ton kiu (type safety).
Th vin hm chun trong C++ (Standard Function

Library)
Th vin hm chun trong C++ c phn chia thnh:
I/O
X l chui v k t
Ton hc
Date, Time v v tr
Cp pht ng
Hn hp
Cc hm cho wide-character
Th vin lp hng i tng trong C++ (Object

Oriented Class Library)
Th vin hng i tng chun C++ nh ngha mt tp hp rng ri cc lp m cung cp s h
tr cho cc hot ng ph bin, gm x l I/O, String, s. Th vin ny bao gm:
Trang 198
Cc lp I/O chun C++
Lp String
Lp thuc s
Lp STL Container
Lp STL Algorithm
Cc i tng STL Function
STL Iterator
STL Allocator
Th vin Localization
Cc lp Exception Handling
Th vin h tr hm hn hp
Ti liu tham kho C++

Di y l cc ngun cha cc ti liu tham kho v C++ hu ch. Mong bn s dng chng
hiu su hn cc khi nim c trnh by trong lot bi ny.
Link hu ch v C++
Tutorialspoint Lot bi hng dn ca chng ti xy dng da trn ngun ny.
C++ Programming Language Tutorials Lot bi hng dn v Ngn ng lp trnh C++
C++ Programming Sch ny v C++ v tnh tng tc ca n vi thit k phn mm v

s s dng ngn ng C++ trong cuc sng thc.
C++ FAQ Cu hi thng xuyn v C++
Free Country Cung cp source code v C++ min ph v th vin C++ cho mt s
chng trnh nh lp trnh game, th vin Template chun v lp trnh GUI.
Trang 199
C and C++ Users Group Cung cp source code t cc d n v C++ trong cc lnh vc
lp trnh a dng: AI, Animation, Compiler, Database, Debugging, Encryption, Game,
Graphics, GUI,
Trang 200

Tài liệu lập trình C++ Tiếng Việt

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Kiu d liu nguyn thy trong C++................................................................................ 20

Ton t trong C++ .............................................................................................................. 43

Chui (String) trong C++ ..................................................................................................... 72

Chi tit v Lp & i tng trong C++ .......................................................................... 100

c mt File trong C++ ................................................................................................. 129

a lung (Multithread) trong C++ ...................................................................................... 163

V d v File Upload...................................................................................................... 193

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Hc C++ c bn v nng cao

Tng quan v C++

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Lp trnh hng i tng

Tnh bao ng (Encapsulation)

n d liu (Data hiding)

Tnh k tha (Inheritance)

Tnh a hnh (Polymorphism)

Th vic chun C++ (C++ Standard Library)

Standard Template Library (STL) cung cp tp hp phng thc a dng thao tc cu

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Min s dng ca C++

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Ci t GNU C/C++ Compiler

Nu bn ci t GCC, th n s in thng bo sau:

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Thm th mc ph bin ca MinGW ti bin mi trng PATH, m bn c th xc nh cc tool

Class - Mt lp c th c nh ngha nh l mt template/blueprint, m miu t hnh

Methods - V c bn, mt phng thc l mt hnh vi. Mt lp c th cha nhiu phng

Instant Variables - Mi i tng c tp hp bin i tng duy nht ca n. Trng thi

Cu trc chng trnh C++

// main() is where program execution begins.

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cout << "Hello World"; // prints Hello World

Chng trnh trn c cc phn sau:

Ngn ng C++ nh ngha mt s header, m cha tong tin cn thit v hu ch cho

Dng int main() l hm main, ti y vic thc thi chng trnh bt u.

Bin dch v thc thi chng trnh C++

M mt text editor v thm on code trn.

Lu file vi tn: hello.cpp.

M mt dng nhc lnh (command prompt) v ti th mc ni bn lu file .

By gi, bn son a.out chy chng trnh.

Bn s thy Hello World c in trn ca s.

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Du chm phy v khi (block) trong C++

Mt khi (block) l mt tp hp cc lnh c kt ni mt cch logic, m c bao quanh bi cc

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nh danh (Identifier) trong C++

T kha trong C++

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Trigraph trong C++

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Tt c compiler khng h tr Trigraph v chng c khuyn l khng nn s dng bi v tnh kh

Khong trng (Whitespace) trong C++

// Get the total fruit

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Comment trong C++

/* C++ comments can

* span multiple lines

Mt comment cng c th bt u vi //, ko di ti phn cui ca dng. V d:

Bn trong mt comment dng /* v */, cc k t // khng c ngha c bit g. Bn trong mt

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cout << "Hello World"; // prints Hello World

Kiu d liu trong C++

Kiu d liu nguyn thy trong C++