C do while Loop

Summary: in this tutorial, you will learn about the C do...while loop statement to execute a code block repeatedly based on a checked condition at the end of each iteration.

Introduction to the C do…while loop statement #

The do...while loop statement allows you to execute the statement repeatedly until the expression become false:

do 
{
    statement;
} while (expression);Code language: C++ (cpp)

How the do...while loop works.

• First, the statement inside the do...while statement executes.
• Second, the do...while statement evaluates the expression. If the result is non-zero (or true), it executes the statement again. This cycle is repeated until the expression is zero (or false).

Unlike the while loop statement:

• The statement inside the do...while is always executed at least once.
• The expression is checked at the end instead of at the beginning of each iteration.

The following flowchart illustrates how the do...while loop works:

C do…while loop examples #

Let’s take some examples of using the do...while loop statement.

1) Simple C do…while loop statement example #

The following example uses the do...while loop statement to display 5 numbers from 0 to 4:

#include <stdio.h>

int main()
{
    int n = 0;
    do
    {
        printf("%d ", n);
        n++;
    } while (n < 5);

    return 0;
}Code language: C++ (cpp)

Output:

0 1 2 3 4Code language: C++ (cpp)

2) Using C do while loop to calculate the sum of input numbers #

The following example uses the do...while statement to allow users to enter multiple numbers. If users enter 0, the loop stops and displays the sum of all the entered numbers:

#include <stdio.h>

int main()
{
    int n = 0,
        total = 0;

    printf("Enter some numbers (0 to stop): ");
    do
    {
        scanf("%d", &n);
        total += n;
    } while (n != 0);

    printf("Sum = %d", total);

    return 0;
}Code language: C++ (cpp)

Output:

Enter some numbers (0 to stop): 1 2 3 4 5 0
Sum = 15   Code language: plaintext (plaintext)

Summary #

• Use the C do...while loop statement to execute a block of code repeatedly based on a condition that is checked at the end of each iteration.