A chessboard is merely a two-dimensional array — a matrix — one where the rows and columns are the same size. As long as you can write code to output an 8-by-8 board, you can modify the code to reset the board’s size to any value.

When I wrote my solution, I started with code that output a standard 8-by-8 board. I realized that the board was simply the same row repeated 8 times. Here’s the basic row:

 --- --- --- --- --- --- --- ---
|   |   |   |   |   |   |   |   |

A final line is drawn under the last row, which makes the board look better for my chosen approach.

Then I recognized that each cell in the row is basically the same thing over and over:

 ---
|   

The last cell in the row has a right side to it. So the code could just repeat the above cell chunk 8 times, cap the row with another | character. Then repeat that row 8 times, followed by output of the final line:

 --- --- --- --- --- --- --- ---
|   |   |   |   |   |   |   |   |
 --- --- --- --- --- --- --- ---
|   |   |   |   |   |   |   |   |
 --- --- --- --- --- --- --- ---
|   |   |   |   |   |   |   |   |
 --- --- --- --- --- --- --- ---
|   |   |   |   |   |   |   |   |
 --- --- --- --- --- --- --- ---
|   |   |   |   |   |   |   |   |
 --- --- --- --- --- --- --- ---
|   |   |   |   |   |   |   |   |
 --- --- --- --- --- --- --- ---
|   |   |   |   |   |   |   |   |
 --- --- --- --- --- --- --- ---
|   |   |   |   |   |   |   |   |
 --- --- --- --- --- --- --- ---

To make the size adjustable, I replaced the value 8 with the variable size. Then I added a simple check to determine whether a command line argument was present:

    if(argc <= 1)

When no argument is present, argc equals one, so the value of variable size is set to 8. Otherwise, size is assigned the value of argv[1], the first argument. The atoi() function handles the conversion.

The rest of the code consists of the loops required to output the board. Oh! And I added initial output that announces the board’s dimensions.

Here is my solution:

#include <stdio.h>
#include <stdlib.h>

int main(int argc, char *argv[])
{
    int size,row,column;

    if(argc <= 1)
        size = 8;
    else
        size = atoi(argv[1]);

    printf("%d x %d Chessboard:\n",size,size);
    for(row=0;row<size;row++)
    {
        /* Draw the top line */
        for(column=0;column<size;column++)
            printf(" ---");
        putchar('\n');
        /* Draw the squares */
        for(column=0;column<size;column++)
            printf("|   ");
        printf("|\n");
    }
    /* Draw the bottom line */
    for(column=0;column<size;column++)
        printf(" ---");
    putchar('\n');

    return(0);
}

Your solution doesn’t need to look exactly like this. The output must resemble a chess board in some way, and the code must react properly to the command line option. I tested my code for a 1 square chess board as well as a 40 square board and various values in between. It worked! If your code works as well, then you’re good.