Example 1: how to do matrix multiplication in c
double[][] c = new double[N][N];
for (int i = 0; i < N; i++)
{
for (int j = 0; j < N; j++)
{
for (int k = 0; k < N; k++)
{
c[i][j] += a[i][k] * b[k][j];
}
}
}
Example 2: matrix multiplication in c
#include <stdio.h>
void enterData(int first[][10], int second[][10], int r1, int c1, int r2, int c2);
void multiplyMatrices(int first[][10], int second[][10], int multResult[][10], int r1, int c1, int r2, int c2);
void display(int mult[][10], int r1, int c2);
int main() {
int first[10][10], second[10][10], mult[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);
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);
}
enterData(first, second, r1, c1, r2, c2);
multiplyMatrices(first, second, mult, r1, c1, r2, c2);
display(mult, r1, c2);
return 0;
}
void enterData(int first[][10], int second[][10], int r1, int c1, int r2, int c2) {
printf("\nEnter elements of matrix 1:\n");
for (int i = 0; i < r1; ++i) {
for (int j = 0; j < c1; ++j) {
printf("Enter a%d%d: ", i + 1, j + 1);
scanf("%d", &first[i][j]);
}
}
printf("\nEnter elements of matrix 2:\n");
for (int i = 0; i < r2; ++i) {
for (int j = 0; j < c2; ++j) {
printf("Enter b%d%d: ", i + 1, j + 1);
scanf("%d", &second[i][j]);
}
}
}
void multiplyMatrices(int first[][10], int second[][10], int mult[][10], int r1, int c1, int r2, int c2) {
for (int i = 0; i < r1; ++i) {
for (int j = 0; j < c2; ++j) {
mult[i][j] = 0;
}
}
for (int i = 0; i < r1; ++i) {
for (int j = 0; j < c2; ++j) {
for (int k = 0; k < c1; ++k) {
mult[i][j] += first[i][k] * second[k][j];
}
}
}
}
void display(int mult[][10], int r1, int c2) {
printf("\nOutput Matrix:\n");
for (int i = 0; i < r1; ++i) {
for (int j = 0; j < c2; ++j) {
printf("%d ", mult[i][j]);
if (j == c2 - 1)
printf("\n");
}
}
}