tic-tac-toe

I'm sure you all know what tic-tac-toe is. Well at least i hope you do. But that's kind of off topic. So i wrote this program for tic-tac-toe from my programing book my dad gave me. He said if i finish at least half of the book he'll get me a new and way better computer. So the only problem is you can't win diagonally. I guess here's a problem with the code. I probably didn't write enough code. I guess ill just ask my dad about it. But there's only 1 more chapter to go and then i get my new computer.