matrix-multiply.c

#include <stdio.h>

void print_matrix(int m, int n, int matrix[m][n]);
void multiply(int n, int m, int p, int a[n][m], int b[m][p], int c[n][p]);

int main() {

    int x[3][2] = {
        {1, 2},
        {3, 4},
        {5, 6}
    };
    int y[2][4] = {
        { 7,  8,  9, 10},
        {11, 12, 13, 14}
    };
    int m[3][4] = {
        {0, 0, 0, 0},
        {0, 0, 0, 0},
        {0, 0, 0, 0}
    };

    print_matrix(3, 2, x);
    printf("---------\n");
    print_matrix(2, 4, y);
    printf("---------\n");

    multiply(3, 2, 4, x, y, m);
    print_matrix(3, 4, m);
    printf("\n");

    return 0;
}

void print_matrix(int m, int n, int matrix[m][n]) {
    int i;
    int j;

    for (i = 0; i < m; i++) {
        for (j = 0; j < n; j++) {
            printf("%5d", matrix[i][j]);
        }
        printf("\n");
    }
}

void multiply(int n, int m, int p, int a[n][m], int b[m][p], int c[n][p]) {
    int i;
    int j;
    int k;
    int sum;

    for (i = 0; i < n; i++) {
        for (j = 0; j < p; j++) {
            sum = 0;
            for (k = 0; k < m; k++) {
                sum += a[i][k] * b[k][j];
            }
            c[i][j] = sum;
        }
    }
}