2.5) Loops

Loops in C are essential for repeating a set of instructions multiple times. They help automate repetitive tasks and perform iterations over a range of values.

There are three main types of loops in C:

while,
for, and
do-while.

Let’s delve into each type with detailed explanations and code examples.

Table of Contents

1. while Loop

The while loop repeatedly executes a block of code as long as a given condition remains true.

while (condition) {
    // Code to be executed repeatedly while the condition is true
}

Example:

#include <stdio.h>

int main() {
    int count = 1;

    while (count <= 5) {
        printf("Count: %d\n", count);
        count++;  // Increment count for the next iteration
    }

    return 0;
}

Explanation:

The loop starts with the count variable initialized to 1.
The loop continues executing as long as the count is less than or equal to 5.
Inside the loop, the value of count is printed, and then it’s incremented by 1 using count++.
This loop will print the numbers from 1 to 5.

2. for Loop

The for loop is used for executing a block of code a specific number of times, controlled by an initialization, condition, and an increment/decrement.

for (initialization; condition; increment/decrement) {
    // Code to be executed repeatedly as long as the condition is true
}

Example:

#include <stdio.h>

int main() {
    for (int i = 1; i <= 5; i++) {
        printf("Square of %d is %d\n", i, i * i);
    }

    return 0;
}

Explanation:

The loop starts with the initialization of the i variable to 1.
The loop continues executing as long as the value of i is less than or equal to 5.
After each iteration, the value of i is incremented by 1 (i++).
This loop calculates and prints the squares of the numbers from 1 to 5.

3. do-while Loop

The do-while loop executes a block of code at least once and then repeatedly as long as a given condition remains true.

do {
    // Code to be executed at least once and then repeatedly while the condition is true
} while (condition);

Example:

#include <stdio.h>

int main() {
    int num;

    do {
        printf("Enter a positive number: ");
        scanf("%d", &num);
    } while (num <= 0);

    printf("You entered a positive number: %d\n", num);

    return 0;
}

Explanation:

The loop starts by executing the block of code within the do section.
After the code execution, the condition (num <= 0) is checked.
If the condition is true, the loop continues, and the user is prompted to enter a positive number again.
The loop repeats until the user enters a positive number.