++ .
2. Ͳ ²Ҳ
, , , .
. . , - -. ³ () , . , , .
, . , , . , . , , . , () ( ) .
- , - . , :
Ø ( );
Ø (- );
Ø - ( );
Ø ( ).
, , . , , , . , , .
. , . , . ++. , , ++.
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-. - . . - , . 璺 , . , , , , ( ). - , . - ʳ. - , 璺 (). - , . , , , , , ( ). , , , . . , , , . , - .1.
1.
璺 | ᒺ | |
/ |
. , - , , . . - - , , , . 璺 . . .
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ϳ , - . , . , . , .
, - , , . ++. , , , .
++ : if , if/else switch . ++ : while, do/while for. . ++ : , . ++ , .
2.2. ++
if , , 䳿, . :
if (<>) <>;
<>, , (, ), 0 (, ). ++ , TRUE FALSE ( ). TRUE ++ - , FALSE 0. , if : <> , <>, <> , , if .
if , ++ , , , , . ֳ , , 1, , , 0 . , , (, 䒺, ) n. , . , .
#include <iostream>
#include <conio.h>
void main()
{
using namespace std;
int n;
cout<<"Enter n:";
cin>>n;
if (n) cout<<"TRUE"<<endl; // ++ !
if (n>0) cout<<"n is positive"<<endl;
if (n<0) cout<<"n is negative"<<endl;
if (n==0) cout<<"n is zero"<<endl;
cout<<"Value of operation > is "<<(n>0)<<endl;
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|
cout<<"Value of operation < is "<<(n<0)<<endl;
cout<<"Value of operation == is "<<(n==0)<<endl;
_getch();
}
, , if/else, :
if (<>) <1>; else <2>;
, <>, ( ), <1>, ( ), <2>. - .1 .
.1. if ++
<1> <2> - ++, . if/else, . , else if. , , x=1; y=-1,
if (x>0) if (y>0) z=1; else z=2;
z 2. , else z=2; if (y>0), if (x>0), :
if (x>0) {if (y>0) z=1;} else z=2;
++ <1> <2> . , { }, . , ++ , . :
{ <1>; <2>;... <N> }
if/else, .
#include <iostream>
#include <conio.h>
#include <math.h>
void main()
{
using namespace std;
double x,y;
cout<<" x:"<<endl;
cin>>x;
if (x<0)
cout<<" <0 !"<<endl;
else {
y=0.75*sqrt(x)-0.5*pow(4, 1.0/3);
cout<<"y="<<y<<endl;
}
_getch();
}
2.3. ?:
++, / . ++ : && ( ), || ( ) ! ( ). , .2.
2.
&& | || | |||||
:!0=1 !1=0.
if/else. , x b :
(x>=a && x<=b)
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|
++ ?:, if/else. , , . ֳ , :
<>? <1>: <2>.
, , , , , . ,
cout<< (grade>=50? : );
, , grade>=50 , , . , 䳿, i f/else:
if(grade>=50)cout<<; else cout<< ;
, .
䳿. ,
grade>=50? cout<<: cout<< ;
: grade 50, , .
switch
. if/lse. - switch, :
switch (switch_expression)
{ case constant1: statement1; [ break;]
case constanti: statementi; [ break;]
......
case constantN: statementN; [ break; ]
[ default: statementN+1; ] }
switch . switch__expression. - char, int, unsigned int, long int long unsigned. constant1,..., constantN. . switch_expression constanti statementi. switch, i- break ( break switch). i+1, i+2 , break statement n+1.
switch_expression constanti,..., constantN, , default. switch .
, .
#include <iostream>
#include <conio.h>
void main()
{
using namespace std;
char ch;
cout<<"Enter letter:";
cin>>ch;
switch (ch) {
case 'r': cout<<"Stop! RED"<<endl; break;
case 'y': cout<<"Attention! YELLOW"<<endl; break;
case 'g': cout<<"Go! GREEN"<<endl; break;
default: cout<<"Wrong letter!"<<endl;
}
_getch();
}
goto. goto:
goto <>;
M
<>: <>;
̳ . , goto, ++. , . ֳ .