Loops in C with Examples: For, While, Do..While Loops

Loops in C: An Overview

Are you interested in programming but don't know where to start? Have you ever heard the term loop? Looping is one of the key concepts behind programming, and learning how to use loops in C can open up a new world of code. Gain the foundational skills from this C tutorial and move to the advancedC training thatincludes in-depth coverage of loops and other essential programming concepts.

What are Loops in C?

Loops are a block of code that executes itself until the specified condition becomes false. In this section, we will look in detail at the types of loops used in C programming.

What is the Need for Looping Statements in C?

Here are some uses of loops in C:

• Loops allow the user to execute the same set of statements repeatedly without writing the same code multiple times.
• It saves time and effort and increases the efficiency.
• It reduces the chance of getting errors during compilation.
• Loop makes the code readable and easier to understand, especially when dealing with complex logic or large data sets.
• It promotes code reusability.
• Loops help traverse data structures like arrays or linked lists

1. for loop
2. while loop
3. do while loop

1. for loop in C

A for loop is a control structure that enables a set of instructions to get executed for a specified number of iterations. It is an entry-controlled loop.

Syntax

for(initialization; test condition; update expression){
//code to be executed
}

• Here, the initialization statement is executed first and only once.
• The test condition is checked, if false the loop terminates
• If the test condition is true, the body of the loop executes
• The update expression gets updated
• Again the test condition is evaluated
• The process repeats until the test condition becomes false.

Example

// Program to print numbers from 1 to 10
#include <stdio.h> 

int main() {
 int i;
 for (i = 0; i < 10; i++)
 {
 printf("%d\n", i+1);
 }
 return 0;
}

The above code prints the numbers from 1 to 10 using a for loop in C.

• We know it will take 10 iterations to print 10 numbers so, we have used the for loop.
• i is initialized to 0.
• The condition i<10 will be checked. It is true, therefore i+1 i.e. 1 gets printed.
• Then i increments to 1 again the condition, i<10 is evaluated.
• The process will repeat until i become 10.

Output

1
2
3
4
5
6
7
8
9
10

2. while loop in C

Syntax

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

If the test condition inside the () becomes true, the body of the loop executes else loop terminates without execution. The process repeats until the test condition becomes false.

Example

// Print numbers from 1 to 10
#include <stdio.h>
int main() 
{
 int i = 1;
 while (i <= 10) {
 printf("%d\n", i);
 i++;
 }
 return 0;
}

• In the above code, i is initialized to 1 before the start of the loop.
• The test condition, i<=10 is evaluated. If true, the body of the loop executes.
• If the condition becomes false in the beginning itself, the program control does not even enter the loop once.
• The loop executes until i becomes 10.

Output

1
2
3
4
5
6
7
8
9
10

3. do...while loop in C

Syntax

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

• The body of the loop executes before checking the condition.
• If the test condition is true, the loop body executes again.
• Again the test condition is evaluated.
• The process repeats until the test condition becomes false.

Example

#include <stdio.h>
int main() 
{
 int i = 0;
 do {
 printf("%d\n", i+1);
 i++;
 }
 while (i < 10);
 return 0;
}

• The above code prints numbers from 1 to 10 using the do while loop in C.
• It prints 1 before checking if i less than 10.
• It checks the condition i<10 and executes until i becomes 10

Output

1
2
3
4
5
6
7
8
9
10

Summary