G Codes

Some useful G-Codes
* G0 - Rapid Motion
* G1 - Coordinated Motion
* G2 - Arc - Clockwise
* G3 - Arc - Counter Clockwise
* G4 - Dwell
* G10 - Create Coordinate System Offset from the Absolute one
* G17 - Select XY plane (default)
* G18 - Select XZ plane (not implemented)
* G19 - Select YX plane (not implemented)
* G20 - Inches as units
* G21 - Millimeters as units
* G28 - Home given Axes to maximum
* G30 - Go Home via Intermediate Point (not implemented)
* G31 - Single probe (not implemented)
* G32 - Probe area (not implemented)
* G53 - Set absolute coordinate system
* G54-G59 - Use coordinate system from G10 P0-5
* G90 - Absolute Positioning
* G91 - Relative Positioning
* G92 - Define current position on axes
* G94 - Feed rate mode (not implemented)
* G97 - Spindle speed rate
* G161 - Home negative
* G162 - Home positive
G-Codes can have all kinds of arguments. Only a few of those are actually used here:
* X absolute position
* Y absolute position
* Z absolute position
* A position (rotary around X)
* B position (rotary around Y)
* C position (rotary around Z)
* U Relative axis parallel to X
* V Relative axis parallel to Y
* W Relative axis parallel to Z
* M code (another "action" register or Machine code(*)) (otherwise referred to as a "Miscellaneous" function")
* F feed rate
* S spindle speed
* N line number
* R Arc radius or optional word passed to a subprogram/canned cycle
* P Dwell time or optional word passed to a subprogram/canned cycle
* T Tool selection
* I Arc data X axis
* J Arc data Y axis.
* K Arc data Z axis, or optional word passed to a subprogram/canned cycle
* D Cutter diameter/radius offset
* H Tool length offset

## Examples
G1 X5 Y-5 Z6 F3300.0 (Move to postion <x,y,z>=<5,-5,6> at speed 3300.0)
G21 (set units to mm)
G90 (set positioning to absolute)
G92 X0 Y0 Z0 (set current position to <x,y,z>=<0,0,0>)