Loops, also known as iterative statements, are used in C to execute a block of code repeatedly as long as a specified condition remains true. They are fundamental for automating repetitive tasks.

C Programming: Loops / Iterative Statements 🔁

Loops allow you to write compact code that avoids redundancy. C provides three types of loops: for, while, and do-while. These are categorized into two main types:

·         Entry-controlled loops: The condition is checked before executing the loop body. The body may not execute at all if the condition is initially false. (for and while)

·         Exit-controlled loops: The condition is checked after executing the loop body. The body is guaranteed to execute at least once. (do-while)

1. The while Loop

A while loop is an entry-controlled loop that is ideal when the number of iterations is not known in advance. The loop continues as long as the condition is true.

·         Syntax:

C

while (condition) {

    // statements to execute

}

Example

This program reads numbers from the user and calculates their sum, stopping only when the user enters 0.

C

#include <stdio.h>

int main() {

    int number;

    int sum = 0;

    printf("Enter a number (enter 0 to stop): ");

    scanf("%d", &number);

    while (number != 0) {

        sum += number; // Add the number to the sum

        printf("Enter a number (enter 0 to stop): ");

        scanf("%d", &number);

    }

    printf("The sum of the entered numbers is: %d\n", sum);

    return 0;

}

2. The for Loop

A for loop is an entry-controlled loop that is perfect for when you know the number of iterations in advance. It combines initialization, condition checking, and modification into a single, compact line.

·         Syntax:

C

for (initialization; condition; modification) {

    // statements to execute

}

Example

This program prints the multiplication table for the number 5.

C

#include <stdio.h>

int main() {

    int number = 5;

    int i;

    printf("Multiplication Table for %d:\n", number);

    // Loop from 1 to 10

    for (i = 1; i <= 10; i++) {

        printf("%d x %d = %d\n", number, i, number * i);

    }

    return 0;

}

3. The do-while Loop

A do-while loop is an exit-controlled loop. Its key feature is that the loop body is guaranteed to execute at least once because the condition is checked at the end of the iteration.

·         Syntax:

C

do {

    // statements to execute

} while (condition);

Example

This program displays a menu and asks for a choice. It will keep displaying the menu until the user enters a valid choice (1, 2, or 3).

C

#include <stdio.h>

int main() {

    int choice;

    do {

        // This menu is always displayed at least once

        printf("\n--- MENU ---\n");

        printf("1. Start Game\n");

        printf("2. Load Game\n");

        printf("3. Quit\n");

        printf("Enter your choice: ");

        scanf("%d", &choice);

    } while (choice < 1 || choice > 3); // Repeat if choice is not 1, 2, or 3

    printf("You selected option %d.\n", choice);

    return 0;

}