Originally Posted by Turbulent Bill
CNC covers the whole spectrum of automation, from line-by-line input of code (basically an automated version of manual machining) right through to fully-automatic part creation of parts. In my (very limited) experience of CNC there's always some level of manual intervention to check/correct paths etc. before production starts. It also helps a lot if the designer has an understanding of the machining process, so the part is manufacturable.
That's a good description of it alright.
Non-CNC machines require buttons to be pressed or levers to be pulled for them to operate.
CNC machines operate by reading a program called Computer Numerical Code, hence CNC.
M codes are direct functions.
i.e. M8/M9 are coolant on/off
M3/4/5 are spindle forward/reverse/stop
G codes are preparitary functions. They prepare the machine to perform a specific machining function.
i.e. G76:thread cutting,G32 tapping,G71 turning cycle,etc
X,Y,Z are used for positioning tools.
A lathe will have 2 axes, X & Z, whereas a milling machine will have 3 axes, X,Y & Z.
The Z axis will follow the forward/reverse direction of the tool.
I always program using the keyboard & monitor on the machine.
In my experiance most CNC programmers tend to learn on the job, though there must be courses out there to learn about it .
EDIT; I think modern ZEUS books have a couple of pages in them dedicated to some of the more common codes, to give you an idea of it.