In programming, loops are used to repeat a block of code until a specified condition is met.
C programming has three types of loops.
- for loop
- while loop
- do…while loop
In the previous tutorial, we learned about for
loop. In this tutorial, we will learn about while
and do..while
loop.
while loop
The syntax of the while
loop is:
while (testExpression) {
// the body of the loop
}
How while loop works?
- The
while
loop evaluates thetestExpression
inside the parentheses()
. - If
testExpression
is true, statements inside the body ofwhile
loop are executed. Then,testExpression
is evaluated again. - The process goes on until
testExpression
is evaluated to false. - If
testExpression
is false, the loop terminates (ends).
To learn more about test expressions (when testExpression
is evaluated to true and false), check out relational and logical operators.
Flowchart of while loop

Example 1: while loop
// Print numbers from 1 to 5
#include <stdio.h>
int main() {
int i = 1;
while (i <= 5) {
printf("%d\n", i);
++i;
}
return 0;
}
Output
1 2 3 4 5
Here, we have initialized i to 1.
- When
i = 1
, the test expressioni <= 5
is true. Hence, the body of thewhile
loop is executed. This prints1
on the screen and the value of i is increased to2
. - Now,
i = 2
, the test expressioni <= 5
is again true. The body of thewhile
loop is executed again. This prints2
on the screen and the value of i is increased to3
. - This process goes on until i becomes 6. Then, the test expression
i <= 5
will be false and the loop terminates.