Multi-dimensional Arrays

Multi-dimensional Arrays

C supports arrays of arrays -- multi-dimensional arrays. The most common is the 2D array:

Declaration

int matrix[2][3] = {
    {1, 2, 3},
    {4, 5, 6}
};

This creates a 2-row, 3-column matrix. In memory, the rows are stored contiguously.

Holodeck grids: a 2D array of emitters creating a 3D world. Every matrix[row][col] is one photon emitter in the grid.

Accessing Elements

int val = matrix[0][2];  // row 0, column 2 = 3
matrix[1][0] = 99;       // set row 1, column 0 to 99

Iterating

Use nested loops:

for (int row = 0; row < 2; row++) {
    for (int col = 0; col < 3; col++) {
        printf("%d ", matrix[row][col]);
    }
    printf("\n");
}

Memory Layout

A 2D array int m[R][C] is laid out as R*C contiguous integers. m[i][j] is at offset (i * C + j) * sizeof(int).

Your Task

Create a 3x3 identity matrix (1s on the diagonal, 0s elsewhere) and print it row by row. Each row should have numbers separated by spaces, followed by a newline.