Trying to add numbers to the rows

[BinaryGeek]

As stated above, when I try to go beyond 9 the compiler complains and gives me a warning. Exactly how can I add the 10-15 without that warning? Part of my code is up to that point (there's more but I felt its not necessary to post it all). If you need it all to determine feel free to ask. And if you need the code with the line numbers, kindly tell me how, I'm not all that familiar to this site yet.

#include <iostream>
#include <cmath>
#include <iomanip>
#include <fstream>
using namespace std;

const int n_of_rows = 15;
const int n_of_columns = 5;
char choose (char seat[][n_of_columns]);
void available (char seat[][n_of_columns]);
void show_seats(char seat[][n_of_columns]);

int main(void)
{
char seat[n_of_rows][n_of_columns] = { {'1', 'A', 'B', 'C','D'},
{'2', 'A', 'B', 'C', 'D'},
{'3', 'A', 'B', 'C', 'D'},
{'4', 'A', 'B', 'C', 'D'},
{'5', 'A', 'B', 'C', 'D'},
{'6', 'A', 'B', 'C', 'D'},
{'7', 'A', 'B', 'C', 'D'},
{'8', 'A', 'B', 'C', 'D'},
{'9', 'A', 'B', 'C', 'D'},
{'A', 'B', 'C', 'D'},
{'A', 'B', 'C', 'D'},
{'A', 'B', 'C', 'D'},
{'A', 'B', 'C', 'D'},
{'A', 'B', 'C', 'D'},
{'A', 'B', 'C', 'D'}, };

[vlad from moscow]

Warning is not an error. So you can ignore a warning.
By the way could you show the text of the warning?