Individual elements of a two-dimensional array are accessed using two indices: the first specifies the row, and the second specifies the column. Both indices start at 0.

#include <stdio.h>

int main(void)
{
    int matrix[2][3] = {
        {10, 20, 30},
        {40, 50, 60}
    };

    printf("First row, second column: %d\n", matrix[0][1]);
    printf("Second row, third column: %d\n", matrix[1][2]);

    matrix[0][1] = 99;

    printf("Updated element: %d\n", matrix[0][1]);

    return 0;
}

Example Output #

First row, second column: 20
Second row, third column: 60
Updated element: 99

Explanation #

The declaration creates an array with two rows and three columns:

int matrix[2][3] = {
    {10, 20, 30},
    {40, 50, 60}
};

The expression matrix[0][1] accesses the element in the first row and second column. The expression matrix[1][2] accesses the element in the second row and third column.

Element Index Reference #

A nested loop can access every element:

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

    printf("\n");
}

The row index must remain between 0 and 1, and the column index between 0 and 2. Accessing an element outside either dimension results in undefined behavior.