Looping

Loops provide a way to repeat commands and control how many times they are repeated. C provides a number of looping way.

while loop
The most basic loop in C is the while loop. A while statement is like a repeating if statement. Like an If statement, if the test condition is true: the statements get executed. The difference is that after the statements have been executed, the test condition is checked again. If it is still true the statements get executed again. This cycle repeats until the test condition evaluates to false.

Basic syntax of while loop is as follows:
Show Example

while ( expression ) { Single statement or Block of statements; }

for loop
for loop is similar to while, it's just written differently. for statements are often used to process lists such a range of numbers:

Basic syntax of for loop is as follows:
Show Example

for( expression1; expression2; expression3) { Single statement or Block of statements; }

In the above syntax:

• expression1 - Initializes variables.

• expression2 - Conditional expression, as long as this condition is true, loop will keep executing.

• expression3 - expression3 is the modifier which may be simple increment of a variable.

do...while loop
do ... while is just like a while loop except that the test condition is checked at the end of the loop rather than the start. This has the effect that the content of the loop are always executed at least once.

Basic syntax of do...while loop is as follows:
Show Example

do { Single statement or Block of statements; }while(expression);

break and continue statements
C provides two commands to control how we loop:

• break -- exit form loop or switch.

• continue -- skip 1 iteration of loop.

You already have seen example of using break statement. Here is an example showing usage of continue statement.

#include main() { int i; int j = 10; for( i = 0; i <= j; i ++ ) { if( i == 5 ) { continue; } printf("Hello %d\n", i ); } }

This will produce following output:

Hello 0 Hello 1 Hello 2 Hello 3 Hello 4 Hello 6 Hello 7 Hello 8 Hello 9 Hello 10