Gcode standards (Was: easy to learn use cad/cam cnc software?)

At 2:52 PM -0700 10/31/04, Kim Lux wrote:

>Truthfully, I would recommend NOT using any drafting or especially CNC
>software until you can program the machine manually.
>
>[snip]
>
>Once you understand how to manually program a CNC machine you can move
>on to using automatic toolpath generation software. It will be a lot
>easier to understand and troubleshoot the generated code if you
>understand first hand how to do it manually yourself.

This makes sense to me and is the path that I have chosen, but one
thing bothers me. From what I understand there is not common gcode
standard. And the machinists seem to accept this.

I do not understand why there has not an attempt at formally defining
the gcode language. Seems like it would benefit everyone. Perhaps as
a naive newbie there is a history here that I do not know yet that
prevents it.

How standard and how different are the various gcode formats. Is
there a table on the web that shows what command-words are common and
where the various packages differ? Is there a standard "test" gcode
file that all cnc machines should be able to process to say that they
use "standard" gcode? -Chuck-