Multiply Two Matrices Using Multi-dimensional Arrays in C

Exercise:

Write a C Program to multiply two matrices using multi-dimensional arrays.

Click Here to View the Solution!
#include <stdio.h>

// function to get elements entered by the user
void getMatrixElements(int matrix[][10], int row, int column) {
    printf("\nEnter elements: \n");
    for (int i = 0; i < row; ++i) {
        for (int j = 0; j < column; ++j) {
            printf("Enter a%d%d: ", i + 1, j + 1);
            scanf("%d", &matrix[i][j]);
        }
    }
}

// function to multiply two matrices
void multiplyMatrices(int first[][10],int second[][10],int result[][10],int r1, int c1, int r2, int c2) {
    // Initializing elements of matrix mult to 0.
    for (int i = 0; i < r1; ++i) {
        for (int j = 0; j < c2; ++j) {
            result[i][j] = 0;
        }
    }
    // Multiplying first and second matrices and storing it in result
   for (int i = 0; i < r1; ++i) {
       for (int j = 0; j < c2; ++j) {
           for (int k = 0; k < c1; ++k) {
               result[i][j] += first[i][k] * second[k][j];
           }
       }
    }
}

// function to display the matrix
void display(int result[][10], int row, int column) {
    printf("\nOutput Matrix:\n");
    for (int i = 0; i < row; ++i) {
        for (int j = 0; j < column; ++j) {
            printf("%d  ", result[i][j]);
            if (j == column - 1) {
                printf("\n");
            }
         }
    }
}

int main() {
    int first[10][10], second[10][10], result[10][10], r1, c1, r2, c2;
    printf("Enter rows and column for the first matrix: ");
    scanf("%d %d", &r1, &c1);
    printf("Enter rows and column for the second matrix: ");
    scanf("%d %d", &r2, &c2);

    // Taking input until
    // 1st matrix columns is not equal to 2nd matrix row
    while (c1 != r2) {
        printf("Error! Enter rows and columns again.\n");
        printf("Enter rows and columns for the first matrix: ");
        scanf("%d%d", &r1, &c1);
        printf("Enter rows and columns for the second matrix: ");
        scanf("%d%d", &r2, &c2);
    }

    // get elements of first matrix
    getMatrixElements(first, r1, c1);

    // get elements of second matrix
    getMatrixElements(second, r2, c2);

    // multiply matrices.
    multiplyMatrices(first, second, result, r1, c1, r2, c2);
    display(result, r1, c2);
    return 0;
}
Click Here to View the Output!
 Enter rows and column for the first matrix: 2
 2
 Enter rows and column for the second matrix: 2
 2
 Enter elements: 
 Enter a11: 1
 Enter a12: 2
 Enter a21: 3
 Enter a22: 4
 Enter elements: 
 Enter a11: 5
 Enter a12: 6
 Enter a21: 7
 Enter a22: 8
 Output Matrix:
 19  22  
 43  50   
Click Here to View the Explanation!
  • This program is used to calculate the product of two matrices by using multidimensional arrays.
  • The program first initializes a user-defined function getMatrixElements that requests the user to enter elements for a matrix and stores them in a 2D matrix by iterating between the rows and columns.
  • A second function multiplyMatrices is initialized that declares three generic 2D matrices and row and columns for each matrix.
  • The result[i][j] matrix which will hold the product of the two matrices is initialized to 0.
  • The first and second matrices are then multiplied, and their result is stored in a resultant matrix result[i][j].
  • The final function display is initialized that takes the resultant matrix, the row and column as its arguments.
  • result[i][j] is then finally printed row-wise. And once the inner loop reaches to the (column – 1)th value, the loop exits and the outer loop starts executing again for the second row.
  • In main(), the program requests the user to enter the rows and columns for both the first and second matrix separately and stores them in the variable r1,c1,r2 and c2 respectively.
  • The program will continue requesting the user for rows and columns input until the first matrix columns are not equal to the second matrix row.
  • The getMatrixElements function is called twice to get the elements of the first and second matrix.
  • Then the multiplyMatrices function is called to multiply the first and second matrices.
  • Finally, the display function is called to display the result[i][j] matrix.