Using C Libraries From Assembly

Linux Assembly Programmers,

I had posted an earlier message about adding graphics to an assembly
language program. After some research the past couple of days it seems
that most available, open source graphics libraries provide a C API. I
would like to add graphics capabilities to the simple programming
language I want to write in assembly.

So, my next question is this:

Can you call C functions from a program written in assembly language?
I've googled this subject, but was only able to find one paragraph that
didn't seem to help much. Most information seems to deal with going the
other direction, that is, calling assembly from C functions. However,
I'm guessing that it is possible, since both languages end up as machine
code at some point. Are there any resources that explain how to do this?

Thanks for all the help.

Landon