Matrix Addition in C for Absolute Beginners

Beginner-friendly blog post explaining how to add two 2D matrices in C

Introduction

In this blog post, we’ll learn how to add two 2D matrices in C programming. Matrix addition is a basic operation, often seen in mathematics and programming, where corresponding elements from two matrices are added to create a new matrix.

Let’s start by understanding what a matrix is and how to perform matrix addition in C with a step-by-step explanation.

What is a Matrix?

A matrix is a rectangular array of numbers arranged in rows and columns. In programming, we usually use a 2D array to represent a matrix.

For example, a 2×2 matrix can look like this:

1 2
3 4

If we add another 2×2 matrix to it, we get:

Matrix 1:     Matrix 2:     Result:
1 2           5 6           6 8
3 4           7 8           10 12

Steps for Matrix Addition

First, make sure both matrices have the same dimensions (same number of rows and columns).
Then, add each element in Matrix 1 to the corresponding element in Matrix 2.
Store the result in a third matrix.

Let’s see how we can write this in a C program.

Matrix Addition Code in C

#include <stdio.h>

int main() {
    int rows, cols;

    // Step 1: Get matrix dimensions
    printf("Enter the number of rows and columns of the matrices: ");
    scanf("%d %d", &rows, &cols);

    int matrix1[rows][cols], matrix2[rows][cols], sum[rows][cols];

    // Step 2: Input elements for the first matrix
    printf("Enter elements of first matrix:\n");
    for (int i = 0; i < rows; i++) {
        for (int j = 0; j < cols; j++) {
            printf("Enter element at position (%d, %d): ", i + 1, j + 1);
            scanf("%d", &matrix1[i][j]);
        }
    }

    // Step 3: Input elements for the second matrix
    printf("Enter elements of second matrix:\n");
    for (int i = 0; i < rows; i++) {
        for (int j = 0; j < cols; j++) {
            printf("Enter element at position (%d, %d): ", i + 1, j + 1);
            scanf("%d", &matrix2[i][j]);
        }
    }

    // Step 4: Add corresponding elements of both matrices
    for (int i = 0; i < rows; i++) {
        for (int j = 0; j < cols; j++) {
            sum[i][j] = matrix1[i][j] + matrix2[i][j];
        }
    }

    // Step 5: Display the resultant matrix
    printf("Resultant matrix after addition:\n");
    for (int i = 0; i < rows; i++) {
        for (int j = 0; j < cols; j++) {
            printf("%d ", sum[i][j]);
        }
        printf("\n");
    }

    return 0;
}

Explanation of Code, Line by Line

Let’s go through the code step-by-step to understand each line.

1. Including the Standard I/O Library

#include <stdio.h>

This line includes the standard input-output library in C, which allows us to use functions like printf and scanf.

2. Declaring `main` Function

int main() {

Here, we start our main function where the execution of the program begins.

3. Declaring Variables for Rows and Columns

int rows, cols;

We declare two integer variables, rows and cols, to store the number of rows and columns for the matrices.

4. Taking Matrix Dimensions from the User

printf("Enter the number of rows and columns of the matrices: ");
scanf("%d %d", &rows, &cols);

We ask the user to enter the number of rows and columns for the matrices. The scanf function reads the input values and stores them in rows and cols.

5. Declaring Matrices

int matrix1[rows][cols], matrix2[rows][cols], sum[rows][cols];

We declare three 2D arrays: matrix1 and matrix2 for the input matrices and sum to store the result of the addition.

6. Taking Input for First Matrix

printf("Enter elements of first matrix:\n");
for (int i = 0; i < rows; i++) {
    for (int j = 0; j < cols; j++) {
        printf("Enter element at position (%d, %d): ", i + 1, j + 1);
        scanf("%d", &matrix1[i][j]);
    }
}

Here, we prompt the user to enter the elements of the first matrix.
We use two for loops to iterate over each element in the matrix.
Inside the inner loop, we take input for each element and store it in matrix1 at the specified position.

7. Taking Input for Second Matrix

printf("Enter elements of second matrix:\n");
for (int i = 0; i < rows; i++) {
    for (int j = 0; j < cols; j++) {
        printf("Enter element at position (%d, %d): ", i + 1, j + 1);
        scanf("%d", &matrix2[i][j]);
    }
}

This block of code is similar to Step 6, but here we store the values in matrix2.

8. Adding Corresponding Elements

for (int i = 0; i < rows; i++) {
    for (int j = 0; j < cols; j++) {
        sum[i][j] = matrix1[i][j] + matrix2[i][j];
    }
}

After we have both matrices, we use two nested loops to add each corresponding element.
For each position (i, j), we add matrix1[i][j] and matrix2[i][j] and store the result in sum[i][j].

9. Displaying the Resultant Matrix

printf("Resultant matrix after addition:\n");
for (int i = 0; i < rows; i++) {
    for (int j = 0; j < cols; j++) {
        printf("%d ", sum[i][j]);
    }
    printf("\n");
}

Finally, we display the result by iterating over the sum matrix.
Each row is printed on a new line to maintain the matrix format.

10. Ending the Program

return 0;
}

The return 0; statement indicates that the program finished successfully.

Output Example

If the user enters matrices like:

Matrix 1:         Matrix 2:
1 2               5 6
3 4               7 8

The output will be:

Resultant matrix after addition:
6 8
10 12

Conclusion

Matrix addition is a straightforward concept where you add each corresponding element of two matrices. In this program, we learned how to take input for matrices, add them element-by-element, and display the result. This code serves as a foundation for more advanced matrix operations in C programming.