is BigJohn here??about the interpreter

I want to ask if I can find some meterials about how the interpreter works?

since now I only get the RS274/NGC_3.pdf, but this only told me the input & output result of the interpreter, not how the interperter interpret the G code, can anyone help me?

and I also notice that some of the files in the source code, saicanon.cc/rs274ngc.cc, for example, do the interpreting job.
but if there are docs about the interpretation, things may be much better~

hey,hey!! I made a big big mistake. I got down to reading the file, and found what I really want ,hah hah~

glad to meet you. now I'm studying the interpreter. well, a rough job~