G-code files must be in ASCII format. Capital and non capitalised letters can be read. Numbers are in decimal format, leading and trailing zeroes can be omitted. G-codes do not require leading zeroes. I use the MS-DOS Edit program that ships with DOS 5 and above. Windows95 has an improved version. With some exceptions, only one G-code per line is permitted, and only one M-code per line should be used.

G00 Rapid traverse.
G01 Linear Feed Move.
G02 Clockwise arc.
G03 Counter Clockwise arc.
G04 P##.# Dwell in seconds.
G17 Arcs in X-Y plane.
G18 Arcs in the X-Z plane.
G19 Arcs in the Y-Z plane.
G50 Cancel Scaling.
     SPECIAL NOTE: Scaling is as yet not well tested, and has known problems.
G51 Call Scaling.
G53 Machine Coordinate System.
G54 Work Coordinate System #1.
G55 Work Coordinate System #2.
G90 Absolute Positioning.
G91 Incremental Positioning.
G92 Relocate Absolute Zero.

                                           Other Letters Read

       \T## L#.####  Specify tool length offset. 11 tools are supported, though T0 should be reserved for spindle full retract (for tool changes, rapid moves, program end, etc.). Each tool offset command must be on a separate line. Tool offsets are based on G53, the machine coordinate system. Tool offsets can be set in manual mode, MDI mode, or imbedded in a part file.
       T## Call Tool Offset. To avoid confusion this command should be on a
seperate line.

       F### Feedrate Command. Feedrates are .1 to 100, and the current feedrate stays in effect until a new feedrate is read. The first G01 command MUST include a feedrate command or the control will default to F1. Backlash takeup is at F100, but the default accel/ decel parameters are in effect so large amounts of backlash will cause a noticible dwell.

       S#### Spindle Speed Command. This has no effect, though the value will
be displayed and can be used to alert the operator to change speeds.