Example: Matrix Multiplication in C

// Matrix Multiplication
#include <stdio.h>

#define ROW1 2
#define COL1 2 // Also ROW2
#define COL2 2

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

    int matrixB[COL1][COL2] = { // COL1 of matrixA must be ROW of matrixB
        {5, 6},
        {7, 8}
    };

    int matrixC[ROW1][COL2]; // Resultant matrix

    // Step 2: Check for compatibility (COL1 of A must equal ROW1 of B, which is COL1 here)
    // In this example, COL1 (2) matches ROW of matrixB (which is COL1 itself).
    // This check is often more explicit when dimensions are user-defined.
    // For fixed sizes as defined by #define, we ensure compatibility by design.

    // Step 3: Perform matrix multiplication
    // Outer loop iterates through rows of matrixA (and resultant matrixC)
    for (int i = 0; i < ROW1; i++) {
        // Middle loop iterates through columns of matrixB (and resultant matrixC)
        for (int j = 0; j < COL2; j++) {
            matrixC[i][j] = 0; // Initialize element of resultant matrix to 0
            // Inner loop iterates through columns of matrixA (and rows of matrixB)
            for (int k = 0; k < COL1; k++) { // Or ROW2, they are the same
                matrixC[i][j] += matrixA[i][k] * matrixB[k][j];
            }
        }
    }

    // Step 4: Print the resultant matrix
    printf("Resultant Matrix C (%dx%d):\n", ROW1, COL2);
    for (int i = 0; i < ROW1; i++) {
        for (int j = 0; j < COL2; j++) {
            printf("%d\t", matrixC[i][j]);
        }
        printf("\n");
    }

    return 0;
}