how to program a windower? : FFXI General Discussions

guys
I have just been really curious lately about how windower applications are created.
I'm not asking for a complete course of how to get one created
but I would like to know about basic knowledge I should be looking for.
If I am to look into programming, what topics should I look at?
If anyone can point me to the right direction, please help.
books, websites, or anything.
Thanks.