If all you're actually trying to do is find the first empty space and replace it with an O then this would do it:

//Set all spaces to ' ' when you initialize the board
for (int i = 0; i < 8; ++i)	 //Where 8 is the size of the board
{
	 board[i] = ' ';
}
//Then when you're wanting to replace the first empty space wth 'O'
for (int i = 0; i < 8; ++i)
{
	 if (board[i] == ' ')
		 board[i] = 'O';
}

if you do not put a break in that if statement, it will change ALL empty spaces into O's, rather than the first one you find

If (board[i] =='')
{
   board [i] = 'O';
  break;
}

that way only one empty is changed

also i think you may want 9 instead of 8; arent there 9 tiles in TTT?

If all you're actually trying to do is find the first empty space and replace it with an O then this would do it:

//Set all spaces to ' ' when you initialize the board
for (int i = 0; i < 8; ++i)	 //Where 8 is the size of the board
{
	 board[i] = ' ';
}

//Then when you're wanting to replace the first empty space wth 'O'
for (int i = 0; i < 8; ++i)
{
	 if (board[i] == ' ')
	   {		   
		   board[i] = 'O';
		   [b]break; [/b]
		}

if you do not put a break in that if statement, it will change ALL empty spaces into O's, rather than the first one you find

If all you're actually trying to do is find the first empty space and replace it with an O then this would do it:

//Set all spaces to ' ' when you initialize the board
for (int i = 0; i < 8; ++i)	 //Where 8 is the size of the board
{
	 board[i] = ' ';
}

//Then when you're wanting to replace the first empty space wth 'O'
for (int i = 0; i < 8; ++i)
{
	 if (board[i] == ' ')
	   [color=#ff0000] { [/color]
		   board[i] = 'O';
		   [color=#ff0000]break; [/color]
	    [color=#ff0000]} [/color]
}

if you do not put a break in that if statement, it will change ALL empty spaces into O's, rather than the first one you find