Do-While loop in C - W3Colleges

Prerequisite – Control Statements in C
The “do-while” loop is a loop statement in C that executes a block of code at least once, and then continues to execute the code as long as the loop condition is true.

Syntax:
The basic syntax of a “do-while” loop in C is:

do {
    // code to be executed
} while (condition);

Here, the code block within the “do” statement is executed at least once, and then the loop condition is checked. If the condition is true, the code block is executed again, and the loop continues until the condition becomes false.

Examples:
Here are some examples of using the “do-while” loop in C:

Example-1: Print the numbers from 1 to 10

#include <stdio.h>

int main() {
    int i = 1;

    do {
        printf("%d ", i);
        i++;
    } while (i <= 10);

    return 0;
}

Output:

1 2 3 4 5 6 7 8 9 10

Example-2: Read and sum a list of numbers until a negative value is encountered

#include <stdio.h>

int main() {
    int num, sum = 0;

    printf("Enter a list of positive numbers (terminate with a negative number):\n");

    do {
        scanf("%d", &num);
        if (num >= 0) {
            sum += num;
        }
    } while (num >= 0);

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

    return 0;
}

Output:

Enter a list of positive numbers (terminate with a negative number):
3
4
7
-1
Sum = 14

In this example, the “do-while” loop is used to read a list of numbers from the user and add them together until a negative value is encountered. The loop starts by executing the code block within the “do” statement, which prompts the user to enter a number and then checks if it is non-negative. If the number is non-negative, it is added to the sum variable. After each iteration of the loop, the loop condition is checked to see if the value of num is greater than or equal to 0. If num is greater than or equal to 0, the loop continues; if it is less than 0, the loop terminates and the final value of sum is printed to the console.

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