notes-shivam

LOOPING STATEMENTS

3 min read

Looping statements in C are used to execute a block of code repeatedly as long as a specified condition is true. The three main types of loops in C are while, do while, and for loops.

1. while Loop

The while loop executes a block of code as long as the specified condition is true. The condition is evaluated before the execution of the loop’s body.

Syntax:

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

Example:

#include <stdio.h>
 
int main() {
    int i = 0;
 
    while (i < 5) {
        printf("i = %d\n", i);
        i++;
    }
 
    return 0;
}

In this example, the loop prints the value of i from 0 to 4.

2. do while Loop

The do while loop is similar to the while loop, but the condition is evaluated after the execution of the loop’s body. This guarantees that the loop’s body is executed at least once.

Syntax:

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

Example:

#include <stdio.h>
 
int main() {
    int i = 0;
 
    do {
        printf("i = %d\n", i);
        i++;
    } while (i < 5);
 
    return 0;
}

In this example, the loop prints the value of i from 0 to 4. The body of the loop is executed at least once even if the condition is false initially.

3. for Loop

The for loop is used when the number of iterations is known beforehand. It has three parts: initialization, condition, and increment/decrement.

Syntax:

for (initialization; condition; increment/decrement) {
    // code to be executed
}

Example:

#include <stdio.h>
 
int main() {
    for (int i = 0; i < 5; i++) {
        printf("i = %d\n", i);
    }
 
    return 0;
}

In this example, the loop prints the value of i from 0 to 4. The initialization (int i = 0), condition (i < 5), and increment (i++) are all included in the for loop statement.

Comparison and Use Cases

  • while loop: Best used when the number of iterations is not known beforehand and the condition needs to be checked before executing the loop’s body.
  • do while loop: Best used when the loop must execute at least once, regardless of whether the condition is true initially.
  • for loop: Best used when the number of iterations is known beforehand or can be determined from the start.

Examples of Each Loop

while Loop Example:

#include <stdio.h>
 
int main() {
    int n = 10;
    while (n > 0) {
        printf("n = %d\n", n);
        n--;
    }
 
    return 0;
}

This loop counts down from 10 to 1.

do while Loop Example:

#include <stdio.h>
 
int main() {
    int n = 10;
    do {
        printf("n = %d\n", n);
        n--;
    } while (n > 0);
 
    return 0;
}

This loop also counts down from 10 to 1, but ensures the loop body executes at least once.

for Loop Example:

#include <stdio.h>
 
int main() {
    for (int n = 10; n > 0; n--) {
        printf("n = %d\n", n);
    }
 
    return 0;
}

This loop counts down from 10 to 1 using a for loop.

Summary

Looping statements are essential in C programming for performing repetitive tasks efficiently. Understanding the differences and appropriate use cases for while, do while, and for loops will help you write better, more efficient code.

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