Example: Matrix Multiplication in C

// Matrix Multiplication
#include <stdio.h>

#define ROW1 2
#define COL1 3
#define ROW2 3
#define COL2 2

int main() {
    // Step 1: Declare and initialize matrices
    int matrix1[ROW1][COL1] = {
        {1, 2, 3},
        {4, 5, 6}
    };

    int matrix2[ROW2][COL2] = {
        {7, 8},
        {9, 1},
        {2, 3}
    };

    int resultMatrix[ROW1][COL2]; // Resultant matrix dimensions

    // Step 2: Check for multiplication compatibility
    // Number of columns in matrix1 must be equal to number of rows in matrix2
    if (COL1 != ROW2) {
        printf("Error: Matrices cannot be multiplied. Number of columns in first matrix must equal number of rows in second matrix.\n");
        return 1; // Indicate error
    }

    // Step 3: Perform matrix multiplication
    printf("Multiplying Matrix 1 (%dx%d) by Matrix 2 (%dx%d):\n", ROW1, COL1, ROW2, COL2);

    // Loop through rows of result matrix
    for (int i = 0; i < ROW1; i++) {
        // Loop through columns of result matrix
        for (int j = 0; j < COL2; j++) {
            resultMatrix[i][j] = 0; // Initialize element to 0
            // Loop through elements for dot product
            for (int k = 0; k < COL1; k++) { // Or k < ROW2, since COL1 == ROW2
                resultMatrix[i][j] += matrix1[i][k] * matrix2[k][j];
            }
        }
    }

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

    return 0;
}