Example: Matrix Multiplication Program

// Matrix Multiplication
#include <stdio.h>

#define ROW1 2 // Rows of matrix1
#define COL1 3 // Columns of matrix1
#define ROW2 3 // Rows of matrix2 (must be equal to COL1)
#define COL2 2 // Columns of matrix2

// Function to print a matrix
// Note: This print function is generic, adapted for dynamic sizes in main for clarity.
void printMatrix(int rows, int cols, int matrix[rows][cols]) {
    for (int i = 0; i < rows; i++) {
        for (int j = 0; j < cols; j++) {
            printf("%d ", matrix[i][j]);
        }
        printf("\n");
    }
}

int main() {
    // Step 1: Define matrices A and B
    int matrixA[ROW1][COL1] = {
        {1, 2, 3},
        {4, 5, 6}
    }; // 2x3 matrix

    int matrixB[ROW2][COL2] = {
        {7, 8},
        {9, 10},
        {11, 12}
    }; // 3x2 matrix

    // Resultant matrix will be ROW1 x COL2 (2x2)
    int prodMatrix[ROW1][COL2];

    printf("Matrix A (%dx%d):\n", ROW1, COL1);
    printMatrix(ROW1, COL1, matrixA);
    printf("\nMatrix B (%dx%d):\n", ROW2, COL2);
    printMatrix(ROW2, COL2, matrixB);

    // Step 2: Perform multiplication
    // Condition: Number of columns in matrixA must equal number of rows in matrixB.
    if (COL1 != ROW2) {
        printf("\nError: Matrices cannot be multiplied. Column of first matrix must equal row of second matrix.\n");
        return 1; // Indicate an error
    }

    printf("\nPerforming Matrix Multiplication (A * B):\n");
    // Initialize product matrix with zeros
    for (int i = 0; i < ROW1; i++) {
        for (int j = 0; j < COL2; j++) {
            prodMatrix[i][j] = 0;
        }
    }

    // Main multiplication logic
    for (int i = 0; i < ROW1; i++) { // For each row of matrixA
        for (int j = 0; j < COL2; j++) { // For each column of matrixB
            for (int k = 0; k < COL1; k++) { // For each element in the row/column
                prodMatrix[i][j] += matrixA[i][k] * matrixB[k][j];
            }
        }
    }

    // Step 3: Print the result
    printf("Product Matrix (%dx%d):\n", ROW1, COL2);
    printMatrix(ROW1, COL2, prodMatrix);

    return 0;
}