Looping statementsTopics for statement while statement do…while statement

Why looping When similar task is performed repeatedly

then we suppose to use looping statement. Ex: 1+2+3+…………………+100 We can directly add two or three numbers

but 100 or more !!!!!!!! In this case we can use one addition

operator and then repeat the process.

For statement The for statement is the most commonly used

looping statement in C. The general form of for statement:

for( initialization; condition; increment/decrement) statement (s);

Initialization of control variables is done first, using assignment statements such as i=1.

The value of the control variable is tested using the condition. If the condition is true then the statement(s) will be executed; otherwise the loop is terminated.

The value of control variable is incremented or decremented in the last section.

Continue… Ex: for(x=0;x<=9;x=x+1)

printf(“%d”,x);

This for loop is executed 10 times and prints the digits 0 to 9 in one line.

The for statement allows for negative increments.

for(x=9; x>=0; x=x-1)

printf(“%d”,x);

This loop is also executed 10 times but output would be from 9 to 0.

Continue… More than one variable can be initialized at

a time in the for statement.

for (p=1,n=0;n<17;n++)

printf(“%d”,n); The increment section may have more than

one part.

for(n=1,m=50; n<=m;n++,m--)

printf(“%d”,m+n);

Continue… The condition may have any compound

relation and the testing need not be limited only to the loop control variable.

for(i=1; i<20 && sum<100; ++i)

{

sum = sum + i;

printf(“%d\n”, sum);

}

Continue… One or more sections of for loop can be omitted.

m = 5;

for (; m!=100;)

{

printf(“%d ”,m);

m = m + 5;

} In for loop there can have no statements.

for(j=1000; j>0;j--)

; The above statement can be written as

for(j=1000;j>0;j--);

while statement The basic format of the while statement is

while(test-condition)

{

body of the loop

} The test-condition is evaluated first and if

the condition is true, then the body of the loop is executed. This process of repeated execution of the body continues until the test-condition finally becomes false.

Continue… Ex: 1+2+3+…………………….+100 Sum=0;

i = 1;

while(i<=100)

{

sum = sum + i;

i++;

}

printf(“Sum = %d”, sum);

Do…while statement The general format:

do

{

body of the loop

}while(test-condition); The program proceeds to evaluate the body of the

loop first. At the end of the loop, the test-condition in the while statement is evaluated. If the condition is true, the program continues to evaluate the body of the loop once again. This process continues as long as the condition is true.

Continue… Ex: 1+2+3+…………………….+100 Sum=0;

i = 1;

do

{

sum = sum + i;

i++;

} while(i<=100);

printf(“Sum = %d”, sum);