Loops in C

Imagine you want to print "Hello" 100 times.

Writing printf() 100 times would be a terrible idea!

Instead, we can tell the computer:

"Repeat this task until a certain condition is met."

This is exactly what loops do.

What is a Loop?

A loop is a programming structure that repeatedly executes a block of code as long as a specified condition is satisfied.

For example:

for (int i = 1; i <= 5; i++)
{
    printf("Hello\n");
}

Output:

Hello
Hello
Hello
Hello
Hello

Instead of writing the same statement five times, we wrote it once and used a loop.

Types of Loops in C

C provides three main types of loops:

1. for Loop

The for loop is commonly used when we know the number of repetitions.

Syntax

for (initialization; condition; update)
{
    // code
}

Example:

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

Output:

1
2
3
4
5

Here:

• int i = 1 → initialization

• i <= 5 → condition

• i++ → update

2. while Loop

A while loop executes the code as long as its condition is true.

int i = 1;

while (i <= 5)
{
    printf("%d\n", i);
    i++;
}

Output:

1
2
3
4
5

The condition is checked before each iteration.

3. do-while Loop

The do-while loop is slightly different.

It executes the code at least once, because the condition is checked after the code runs.

int i = 1;

do
{
    printf("%d\n", i);
    i++;
}
while (i <= 5);

Output:

1
2
3
4
5

Even if the condition is initially false, the code inside do executes once.

For example:

int i = 10;

do
{
    printf("Hello");
}
while (i < 5);

Hello is still printed once.

for vs while vs do-while

Loop Control Statements

C also provides break and continue to control loops.

break

break immediately stops the loop.

for (int i = 1; i <= 5; i++)
{
    if (i == 3)
        break;

    printf("%d\n", i);
}

Output:

1
2

continue

continue skips the current iteration and moves to the next one.

for (int i = 1; i <= 5; i++)
{
    if (i == 3)
        continue;

    printf("%d\n", i);
}

Output:

1
2
4
5

In Simple Words

A loop allows us to repeat a block of code without writing the same code again and again.

The three main loops in C are:

for → known number of repetitions

while → condition-based repetition

do-while → executes at least once

Once you understand loops, you'll be able to solve many repetitive programming problems much more efficiently.