Problem in G-Code...!!

Hi there!!

This is myfirst message to any group. I 've a prob.
with CNC milling's gcode. But first I should tell u
that I am new to CAM.
The problem is...

We generated the gcode (from dxf) with the software
came along the m/c. but the tool didn't go back to it
original position (although same xy coords) once
moved.
e.g. when I try to make circle, it didn't close
the circle instead the dia is shorttened. infact the
the co-ordinates are not remaining same. (I think :)

Plz. help me in this prob and tell me from where
could I learn gcode.

Bye

Hammad