c – How to check if the seat is free and if not ask the user to type again by inserting an "X" in the occupied space?

I need the user to insert where he wants to sit, informing the row and the column that he wants, where he chooses the position 0-1 the program will register and write to a txt file later on this information, and enter into a endlessly to register a new user, where he will enter what position he wants and s? he enters a position where he is already occupied by another user of the program will not accept place a X in place to demonstrate that he is busy.

Follow the code …

void main () {

printf (" n  nChoose your seat:  n  n");
int m, n, row, seat;
int places[10][16];

for (m = 1, m <10, m ++)
for (n = 1; n <16; n ++) {
printf ("[%d- %d]", m, n);
printf (" n");

printf (" N desired file:");
scanf ("% d", & row);
printf ("desired seat:");
scanf ("% d", & seat);

system ("pause");