$1.$ In problem $1,$ if the square is occupied, you need to give the error message. $\%$c has played $\%$d$,\%$d

$($where $\%$c$$ is either $$X$$ or $$O$,$ whichever is already in the square, and $\%$d$,\%$d$$ are the co$-$ordinates of the occupied square$).$

$2.$ In problem $1,$ the dimensions of the $$O$$ was added; it is to be $5\backslash$times $5$ centered in the square.

$3.$ For all problems, the exit status code is $0.$Enhance the tic$-$tac$-$toe game so $2$ people can play. To do this, you need to add an$$O$$ that, like the $$X$,$ is drawn in the square. Then prompt the user for a square identifier, and alternate between drawing $$X$$s and $$O$$s at those locations on the board. The first move is for $$X$.$ You need to detect and reject when a user plays a square that is already taken. Stop after the board is full $($that is$,9$ plays$).$ You do not have to worry about who wins.

The $$O$$ is to be $5\backslash$times $5,$ centered in the middle of the square.

Here are the messages your program should print to the standard output:

The tic$-$tac$-$toe board, with $$X$$s and $$O$$s as appropriate;

When it is $$X$$s turn, print $$X$$s turn $>($note the space after the $>)$; and

When it is $$O$$s turn, print $$O$$s turn $>($again$,$ note the space after the $>).$

Here are the error messages; all are to be printed on the standard error:

When the user enters only $1$ co$-$ordinate: $$Need $2$ co$-$ordinates

$($the $$

$$ is a newline$)$;

When there is an illegal character in the input: $$Illegal character in input $"\%$c$"$

$($the $\%$c$$ is to print the offending character$)$; and

When the square is already occupied: $\%$c has played $\%$d$,\%$d

$($where $\%$c$$ is either $$X$$ or $$O$,$ whichever is already in the square, and $\%$d$,\%$d$$ are the co$-$ordinates of the occupied square$)$; and

When an invalid set of co$-$ordinates are entered: $\%$d$,\%$d$$ is not a valid square; the numbers must be between $1$ and $3$ inclusive

$($each $\%$d is one of the invalid numbers$).$

If the program reads an end of file at the prompt, print a newline and quit.

The program should exit with an exit status code of $0.$

Please call your program ttt$4$a$.$c and submit it through Gradescope. A sample executable, used to generate the Gradescope validation outputs, is available on the CSIF at $/$home$/$bishop$/$hw$4/$ttt$4$a$.$