How to Iterate Over Array in C: Simple Syntax and Example

In C, you iterate over an array using a for loop by running an index from 0 to the array's length minus one. Inside the loop, you access each element with array[index] to process or print it.

Syntax

Use a for loop with an index variable starting at 0 and running up to one less than the array size. Access elements with array[index].

• index: loop counter starting at 0
• array_size: total number of elements in the array
• array[index]: element at current position

c

for (int index = 0; index < array_size; index++) {
    // Use array[index] here
}

Example

This example shows how to print all elements of an integer array using a for loop.

c

#include <stdio.h>

int main() {
    int numbers[] = {10, 20, 30, 40, 50};
    int size = sizeof(numbers) / sizeof(numbers[0]);

    for (int i = 0; i < size; i++) {
        printf("Element at index %d is %d\n", i, numbers[i]);
    }

    return 0;
}

Output

Element at index 0 is 10
Element at index 1 is 20
Element at index 2 is 30
Element at index 3 is 40
Element at index 4 is 50

Common Pitfalls

Common mistakes include:

• Using an index that goes beyond the array size, causing undefined behavior.
• Starting the index at 1 instead of 0, which skips the first element.
• Not calculating the array size correctly.

Always ensure the loop runs from 0 up to but not including the array size.

c

/* Wrong: index starts at 1, misses first element */
for (int i = 1; i < size; i++) {
    printf("%d\n", numbers[i]);
}

/* Correct: index starts at 0 */
for (int i = 0; i < size; i++) {
    printf("%d\n", numbers[i]);
}

Quick Reference

Concept	Description
Index Start	Always start at 0 to access first element
Loop Condition	Use < array size to avoid overflow
Access Element	Use array[index] inside the loop
Calculate Size	Use sizeof(array) / sizeof(array[0]) for static arrays

Key Takeaways

Use a for loop with index from 0 to array size minus one to iterate arrays in C.

Access each element inside the loop with array[index].

Calculate array size correctly using sizeof for static arrays.

Avoid going beyond array bounds to prevent errors.

Starting index at 0 is essential to include all elements.