2D Arrays: Rows and Columns

An array can have rows and columns, like a table or a chess board. This is a 2D array:

#include <stdio.h>

int main() {
    int grid[2][3] = {
        {1, 2, 3},
        {4, 5, 6}
    };
    printf("Row 0, column 2: %d\n", grid[0][2]);
    printf("Row 1, column 0: %d\n", grid[1][0]);
    return 0;
}

Output

Row 0, column 2: 3
Row 1, column 0: 4

• [2][3] means 2 rows and 3 columns.
• grid[row][column] picks one cell. Both start at 0.

Think of it like this: A 2D array is like seats in a cinema: you need the row and the seat number to find your place.

Looping over a 2D array

Use one loop for the rows and one inside it for the columns:

#include <stdio.h>

int main() {
    int sales[3][4] = {
        {5, 3, 8, 2},
        {1, 0, 4, 6},
        {7, 7, 2, 9}
    };
    for (int r = 0; r < 3; r++) {
        int rowTotal = 0;
        for (int c = 0; c < 4; c++) {
            printf("%3d", sales[r][c]);
            rowTotal += sales[r][c];
        }
        printf("  | total %d\n", rowTotal);
    }
    return 0;
}

Output

  5  3  8  2  | total 18
  1  0  4  6  | total 11
  7  7  2  9  | total 25

Common mistake: Swapping rows and columns. grid[2][3] has rows 0–1 and columns 0–2, so grid[2][0] is outside the array.