freeCodeCamp/guide/english/c/for/index.md

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For Loop

For Loop

The for loop executes a block of code until a specified condition is false. Use while loops when the number of iterations are variable, otherwise use for loops. A common use of for loops are array iterations. It is also known as an 'entry-controlled loop' since the condition is checked before the next iteration. Another example of an 'entry-controlled loop' is a while loop.

Syntax of For Loop

for ( init; condition; increment ) {
   statement(s);
}

The for loop consists of 3 sections, the initialization section, a specific condition and the incremental or decremental operation section. These 3 sections control the for loop.

The initialization statement is executed only once. Then, the test expression is evaluated. If the test expression is false (0), for loop is terminated. But if the test expression is true (nonzero), codes inside the body of for loop is executed and the update expression is updated. This process repeats until the test expression is false.

The for loop is commonly used when the number of iterations is known.

Example

#include <stdio.h>

int main () {

    int array[] = {1, 2, 3, 4, 5};

    for (int i = 0; i < 5; i++) {
    	printf("Item on index %d is %d\n", i, array[i]);
    }
}

Output:

> Item on index 0 is 1
> Item on index 1 is 2
> Item on index 2 is 3
> Item on index 3 is 4