For

After learning while, a very commonly used structure appears when the repetition has a more compact and controlled form: for.

In this lesson you will learn:

• how for works
• what parts it has
• how it relates to initial state, condition, and update
• when it’s worth using for
• how to use break and continue inside a for

What does for do?

The for statement repeats a block of code and concentrates in a single line three very important elements of the loop:

• initialization
• condition
• update

Syntax

for (initialization; condition; update) {
    instructions;
}

Basic example

#include <stdio.h>

int main() {
    int i;

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

    return 0;
}

Correct reading of for

Initialization

i = 1

Executes only once, at the beginning.

Condition

i <= 5

Evaluated before each iteration.

Update

i = i + 1

Executes at the end of each round.

When is for worth using?

for is great when the repetition is associated with a counter or a fairly clear number of steps.

For example:

• display numbers from 1 to 10
• repeat an action 5 times
• traverse numbered positions

for and while: same idea, different form

A for and a while can often express the same logic.

The main difference is how the reading is organized.

for is usually more comfortable when you want to see initialization, condition, and update together.

Using break in for

for (i = 1; i <= 10; i = i + 1) {
    if (i == 6) {
        break;
    }
    printf("%d\n", i);
}

The loop cuts off when i is 6.

Using continue in for

for (i = 1; i <= 5; i = i + 1) {
    if (i == 3) {
        continue;
    }
    printf("%d\n", i);
}

When i is 3, that iteration jumps directly to the next step of the loop.

Frequent conceptual error

Many students believe for is “another kind of magic” different from while.

No.

The deep idea is the same: repeat a block while a condition allows it.

What changes is the form of organizing the expression of the loop.

Summary

• for organizes initialization, condition, and update in a single line
• it’s very useful when working with a counter or a clear number of repetitions
• break can cut off the loop
• continue can jump to the next iteration
• conceptually, for and while share the same controlled repetition logic

Final idea

If while teaches you the general logic of repetition, for teaches you to write it in a more compact and readable way when the structure of the loop is well defined.