X/Open Functions

[Dark Mage]

I've been coding in C/C++ for a very long time on the Window's platform, mostly for non-internet usage.  Now I find myself in a position where I need to do things in the Unix world and I'm unfamiliar with most of the functions of X/Open  Is there a place I can learn there usage?  Like what the function takes as parameters and what it fives back?  I have the list of the functions printed out, but find myself not knowing a great deal of them, though some seem self explanitory.

Thanks...