Chess Program

Hello. I am having some difficulty making a chess program. I've tried searching for tutorials but I've not found any that help. They are just words but no practical help. And the are almost entirely about AI. Don't chess programs need collision checks and legal move checks, or am I doing something wrong!? I have some basics in place, but (among other problems) I'm having difficulty with collision detection. That is, if i want to move bishop from here to there, how do I check the coast is clear? My one doesn't work all the time but it's rubbish anyway. What is the best way? Thanks.