Arrays are one of the most fundamental data structures in C. They allow you to store multiple values of the same data type under a single variable name. This makes data processing easier, especially when working with lists, tables, or large sets of numerical values.

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1. Defining Arrays in C

An array is a collection of elements stored in contiguous memory locations. All elements must be of the same data type.

Syntax

data_type array_name[size];

Example

int marks[5];   // array of 5 integers
char name[20];  // array of characters (string)
float prices[10];

Initialization

Arrays can be initialized at the time of declaration.

int nums[5] = {10, 20, 30, 40, 50};

If you omit the size, C automatically adjusts:

int nums[] = {10, 20, 30, 40, 50};

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2. Processing Arrays

Processing means accessing and manipulating array elements using indexing.
Index starts from 0 and goes up to size-1.

Example: Reading & Printing Array Elements

#include <stdio.h>

int main() {
    int i, arr[5];

    printf("Enter 5 numbers:\n");
    for (i = 0; i < 5; i++) {
        scanf("%d", &arr[i]);
    }

    printf("You entered:\n");
    for (i = 0; i < 5; i++) {
        printf("%d ", arr[i]);
    }

    return 0;
}

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3. Passing Arrays to Functions

In C, arrays are always passed by reference, meaning the function receives the memory address of the first element.

Function Declaration

void display(int arr[], int size);

Example

#include <stdio.h>

void display(int arr[], int size) {
    for (int i = 0; i < size; i++) {
        printf("%d ", arr[i]);
    }
}

int main() {
    int nums[5] = {10, 20, 30, 40, 50};
    display(nums, 5);
    return 0;
}

Key Point

• Any changes inside the function affect the original array.

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4. Multi-Dimensional Arrays

A multi-dimensional array is an array of arrays.
The most commonly used is the 2-D array, similar to matrices or tables.

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4.1 Defining a 2-D Array

Syntax

data_type array_name[rows][columns];

Example

int matrix[3][3];

Initialization

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

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4.2 Accessing 2-D Array Elements

printf("%d", matrix[1][2]);  // Output: 6

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4.3 Processing a 2-D Array (Nested Loops)

#include <stdio.h>

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

    for (int i = 0; i < 2; i++) {
        for (int j = 0; j < 3; j++) {
            printf("%d ", matrix[i][j]);
        }
        printf("\n");
    }

    return 0;
}

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4.4 Passing a 2-D Array to a Function

You must specify the column size.

void printMatrix(int arr[][3], int rows);

Example

#include <stdio.h>

void printMatrix(int arr[][3], int rows) {
    for (int i = 0; i < rows; i++) {
        for (int j = 0; j < 3; j++) {
            printf("%d ", arr[i][j]);
        }
        printf("\n");
    }
}

int main() {
    int matrix[2][3] = {{1,2,3},{4,5,6}};
    printMatrix(matrix, 2);
    return 0;
}

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Summary

Concept	Description
Defining Arrays	Declaring a list of items of the same type
Processing Arrays	Access using loops and indices
Passing Arrays to Functions	Arrays passed by reference
Multi-Dimensional Arrays	Arrays of arrays, commonly 2-D arrays

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📚 Citations

🔗 View other articles about C Programming:
https://savanka.com/category/learn/c-programming/

🔗 External C Documentation:
https://www.w3schools.com/c/