RIGHT!

I am embarking now on my final project in college (UK). What I am making is a robotic arm simulation that shows a robotic arm on screen and the user can give commands in a console of what to move for how long or how much, etc.

ANYWAY, the problem comes with the graphic of the arm. It will be very simply drawn, prolly made out of a collection of lines... possibly fill in if there is time. BUT I really havn't got a clue as to how you map 3d coords onto a 2d surface.
E.g. point 1,1,0 and point 1,1,2 are the same on a 2d surface, but if you look at a 3d perspective, depending where abouts the 'camera' is situated the 2nd point will look offset from the first. What I need to know is how you can use the coords from point 1, point 2 and the camera position to map that onto a 2d surface (VDU) and make it look right. PHEW this is hard to explain. I hope someone out there gets what I am bangin' on about!