Looping Structures

Loops are used to repeat a block of code multiple times.

In this lesson, you will learn about for, while, and do-while loops.

The for loop repeats code a fixed number of times.

Syntax:

for (initialization; condition; update) { // Code to execute }

This program prints numbers from 1 to 5 using a for loop.

#include <stdio.h>

int main() {
    for (int i = 1; i <= 5; i++) {
        printf("%d\n", i);
    }
    return 0;
}

The while loop repeats code while a condition is true.

Syntax:

while (condition) { // Code to execute }

This program prints numbers from 1 to 5 using a while loop.

#include <stdio.h>

int main() {
    int i = 1;
    while (i <= 5) {
        printf("%d\n", i);
        i++;
    }
    return 0;
}

The do-while loop always executes the code at least once before checking the condition.

Syntax:

do { // Code to execute } while (condition);

This program prints numbers from 1 to 5 using a do-while loop.

#include <stdio.h>

int main() {
    int i = 1;
    do {
        printf("%d\n", i);
        i++;
    } while (i <= 5);
    return 0;
}

An infinite loop runs forever if the condition never becomes false.

Example:

while (1) { printf("This loop runs forever!\n"); }

Always ensure there is a way to exit the loop.

In this lesson, you learned:

• How to use for, while, and do-while loops.
• The differences between each type of loop.
• How to prevent infinite loops.

Next, we will explore logical and comparison operators in C!