Example: Matrix Multiplication in C

// Matrix Multiplication
#include <stdio.h>

#define ROW1 2 // Rows of first matrix
#define COL1 3 // Columns of first matrix
#define ROW2 3 // Rows of second matrix
#define COL2 2 // Columns of second matrix

int main() {
    // Step 1: Declare matrices and result matrix
    int matrixA[ROW1][COL1] = {
        {1, 2, 3},
        {4, 5, 6}
    };

    int matrixB[ROW2][COL2] = {
        {7, 8},
        {9, 10},
        {11, 12}
    };

    int resultMatrix[ROW1][COL2]; // Resulting matrix dimensions: ROW1 x COL2

    // Check if multiplication is possible
    if (COL1 != ROW2) {
        printf("Error: Matrix multiplication not possible. Number of columns in Matrix A must be equal to number of rows in Matrix B.\n");
        return 1; // Indicate an error
    }

    // Step 2: Initialize result matrix elements to 0
    for (int i = 0; i < ROW1; i++) {
        for (int j = 0; j < COL2; j++) {
            resultMatrix[i][j] = 0;
        }
    }

    // Step 3: Perform matrix multiplication
    // i iterates through rows of matrixA (and resultMatrix)
    for (int i = 0; i < ROW1; i++) {
        // j iterates through columns of matrixB (and resultMatrix)
        for (int j = 0; j < COL2; j++) {
            // k iterates through columns of matrixA (and rows of matrixB)
            for (int k = 0; k < COL1; k++) { // Or ROW2, they must be equal
                resultMatrix[i][j] += matrixA[i][k] * matrixB[k][j];
            }
        }
    }

    // Step 4: Display the result matrix
    printf("Resultant Matrix C (A * B):\n");
    for (int i = 0; i < ROW1; i++) {
        for (int j = 0; j < COL2; j++) {
            printf("%d\t", resultMatrix[i][j]);
        }
        printf("\n");
    }

    return 0;
}