Array in C Programming – Explained for Beginners

Introduction

In C programming, an array is a collection of elements of the same data type stored at contiguous memory locations.

It helps you store multiple values in a single variable, instead of declaring separate variables for each value.

Example: Instead of writing

int num1 = 10, num2 = 20, num3 = 30;

You can use an array:

int numbers[3] = {10, 20, 30};

Why Use Arrays?

To store large amounts of data easily.
To access data quickly using an index.
To perform operations (sorting, searching) on bulk data.
To avoid writing multiple variables.

Declaration of Arrays

datatype array_name[size];

- datatype → Type of data (int, float, char, etc.)
- array_name → Name of the array
- size → Number of elements in the array
Example:

int marks[5];   // Array to store 5 integers

Initialization of Arrays

At Declaration

int marks[5] = {90, 85, 70, 95, 100};

Without Size (Compiler counts automatically)

int marks[] = {90, 85, 70, 95, 100};

Partial Initialization (remaining elements set to 0)

int marks[5] = {90, 85};   // → {90, 85, 0, 0, 0}

Accessing Array Elements

Array elements are accessed using an index (starting from 0).

#include <stdio.h>
int main() {
    int marks[5]  {90, 85, 70, 95, 100};
    printf("First mark = %d\n", marks[0]);   // Output: 90
    printf("Third mark = %d\n", marks[2]);   // Output: 70
    return 0;
}

Traversing an Array (Using Loop)

#include <stdio.h>
int main() {
    int marks[5] = {90, 85, 70, 95, 100};
    for(int i = 0; i < 5; i++) {
        printf("marks[%d] = %d\n", i, marks[i]);
    }
    return 0;
}

Output:

Types of Arrays in C

One-Dimensional Array (1D)

Linear list of elements.
Example: int arr[5] = {1, 2, 3, 4, 5};

Two-Dimensional Array (2D)

Like a table (rows & columns).
Example:

int matrix[2][3] = {
    {1, 2, 3},
    {4, 5, 6}
};

Accessing element: matrix[1][2] = 6

Multi-Dimensional Array

More than 2 dimensions (rare in beginner-level).

Example Program – Sum of Array Elements

#include <stdio.h>
int main() {
    int numbers[5] = {10, 20, 30, 40, 50};
    int sum = 0;
    for(int i = 0; i < 5; i++) {
        sum += numbers[i];
    }
    printf("Sum = %d", sum);
    return 0;
}

Output: