From TechnoDocs
G and M codes describe a tool path and tool path operations for CNC control. For a list of all the codes, see the g-code reference.
G-Code Examples
The following examples may help provide a better understanding of how to write and manipulate g-code.
Follow a Circle
Copy this code to a file and name it circle.nc. When you load it into the Control Software, your router will follow a circle shape in the X and Y plane.
G90 G2 I2 F100 M30