C Program to Multiply Two Matrices Using Multi-dimensional Arrays

@codevarsity
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A sample C program that takes two matrices of order r1*c1 and r2*c2 respectively. Then, the program multiplies these two matrices (if possible) and displays it on the screen.

Code

#include <stdio.h>

int main()
{
    int a[10][10], b[10][10], result[10][10], r1, c1, r2, c2, i, j, k;

    printf("Enter rows and column for first matrix: ");
    scanf("%d %d", &r1, &c1);

    printf("Enter rows and column for second matrix: ");
    scanf("%d %d",&r2, &c2);

    // Column of first matrix should be equal to column of second matrix and
    while (c1 != r2)
    {
        printf("Error! column of first matrix not equal to row of second.\n\n");
        printf("Enter rows and column for first matrix: ");
        scanf("%d %d", &r1, &c1);
        printf("Enter rows and column for second matrix: ");
        scanf("%d %d",&r2, &c2);
    }

    // Storing elements of first matrix.
    printf("\nEnter elements of matrix 1:\n");
    for(i=0; i<r1; ++i)
        for(j=0; j<c1; ++j)
        {
            printf("Enter elements a%d%d: ",i+1, j+1);
            scanf("%d", &a[i][j]);
        }

    // Storing elements of second matrix.
    printf("\nEnter elements of matrix 2:\n");
    for(i=0; i<r2; ++i)
        for(j=0; j<c2; ++j)
        {
            printf("Enter elements b%d%d: ",i+1, j+1);
            scanf("%d",&b[i][j]);
        }

    // Initializing all elements of result matrix to 0
    for(i=0; i<r1; ++i)
        for(j=0; j<c2; ++j)
        {
            result[i][j] = 0;
        }

    // Multiplying matrices a and b and
    // storing result in result matrix
    for(i=0; i<r1; ++i)
        for(j=0; j<c2; ++j)
            for(k=0; k<c1; ++k)
            {
                result[i][j]+=a[i][k]*b[k][j];
            }

    // Displaying the result
    printf("\nOutput Matrix:\n");
    for(i=0; i<r1; ++i)
        for(j=0; j<c2; ++j)
        {
            printf("%d  ", result[i][j]);
            if(j == c2-1)
                printf("\n\n");
        }
    return 0;
}

Output

Enter rows and column for first matrix: 3
2
Enter rows and column for second matrix: 3
2
Error! column of first matrix not equal to row of second.

Enter rows and column for first matrix: 2
3
Enter rows and column for second matrix: 3
2

Enter elements of matrix 1:
Enter elements a11: 3
Enter elements a12: -2
Enter elements a13: 5
Enter elements a21: 3
Enter elements a22: 0
Enter elements a23: 4

Enter elements of matrix 2:
Enter elements b11: 2
Enter elements b12: 3
Enter elements b21: -9
Enter elements b22: 0
Enter elements b31: 0
Enter elements b32: 4

Output Matrix:
24  29

6  25

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