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There are several control statements available in C. They are; 'while', 'for', 'do', 'if', conditional, 'switch', and the infamous 'goto'. Syntax for these statements are:
while( expr ) statement for( init; test; update ) statement do // statement executed at least once statement while( expr ); if( expr ) statement else if( expr ) statement else statement expr ? expr : expr // conditional switch( expr ) { case const1: statement break; // without break, control case const2: statement // continues to next break; // statement. case const3: statement break; default : statement } goto label; . . . label:statement
The following program provides some basic examples of each control statement. One of the more common typos is to use commas instead of semi-colons in 'for' statements. Although the goto statement is provided in C, it is usually avoided and most books advise against its use. The conditional statement is shorthand for an if-then statement, but it can decrease code readability (so it is also not recommended).
// control.cp #include <iostream.h> void main() { int a = 1; int b = 2; int i = 1; cout << "start while loop" << endl; // while while( i<4 ) { cout << "i = " << i << endl; i++; } cout << "start for loop" << endl; // for for( i = 1; i<4; i++ ) cout << "i = " << i << endl; cout << "start do loop" << endl; // do i = 1; do { cout << "i = " << i << endl; i++; } while( i<4 ); cout << "start if" << endl; // if i = 2; if( i==a ) cout << "answer is a" << endl; else if( i==b ) cout << "answer is b" << endl; else cout << "neither a or b" << endl; cout << "conditional" << endl; // conditional i = 10; i = ( i>b ) ? b : i; cout << "i = " << i << endl; cout << "switch statement" << endl; // switch switch( i ) { case 1: cout << "one\n"; break; case 2: cout << "two\n"; break; case 3: cout << "three\n"; break; default: cout << "error\n"; } cout << "goto statement" << endl; // goto if( i==b ) goto skip; // functional scope cout << "zero\n"; cout << "one\n"; skip: cout << "two\n"; cout << "three\n"; } // end control.cp
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