Graphics for Assembly Language Program

I'm think about creating a simple computer language that I will write
with assembly language and I was curious about something.

Is it possible to access the X-Window System from assembly language? Is
there a way to call c functions from Assembly language? What is the
other alternatives to providing graphics functions to a computer
language written in assembly? Working directly with the graphics card
and keyboard/mouse sounds kind of nasty. Is that the other route? Has
anyone successfully used a graphics library like GTK from assembly?

Thanks,

Landon

P.S. - I'd like to thank Joshua for his suggestion about NASM. I have
downloaded the doc, and I hope to get started with some assembly
programming soon. I have also downloaded the Intel manuals.