Program Control : REPETITION

Program Control : REPETITION

Sub Topics :

• Repetition Definition
• For
• While
• Do-While
• Repetition Operation
• Break vs Continue

Repitition Definition

• One or more instruction repeated for certain amount of time
• Repetition/looping operation ;
• for
• while
• do-while

Repetition : FOR

exp1 and exp3 can consist of several expression separated with comma

Example:

void reverse(char ss[])

{

    int c,i,j;

    for(i=0, j=strlen(ss)-1; i<j; i++, j--){

        c=ss[i];

        ss[i]=ss[j];

        ss[j]=c;

    }

}

• Infinite Loop
• Loop withh no stop condition can use "for-loop" by removing all parameters (exp1, exp2, exp3). To end the loop use break.
• Nested Loop
• Loop in a loop. The repetition operation will start from inner side loop.

Repetition : WHILE

while (exp) statements;

• exp is boolean expression. The result will be true (not zero) or false (zero).
• statement will be executed while the exp is not equal to zero (true).
• exp evaluation is done before the statements executed.

Repetition : DO-WHILE

Example :

     int counter=0;

     do {

          printf( "%d  ", counter );

       ++counter;

     } while (counter <= 10);

• while exp is true, keep executing
• exp evaluation done after executing the statement(s)

Repetition : OPERATION

• In while operation, statement block of statements may never be executed at all if exp value is false
• In do-while on the other hand statement block of statements will be executed min once
• To end the repetition, can be done through several ways:
• Sentinel
• Question, should the repetition continue

BREAK vs CONTINUE

• Break :
• ending loop (for, while, and do-while)
• end the switch operation
• Continue : skip all the rest of statements inside a repetition and continue normally to the next loop