G-code and M-code are the foundational languages that drive CNC (Computer Numerical Control) machinery and 3D printers.

At this point, you can basically track any G-Code command and also insert arbitrary new G-codes, for example G1 printing moves (for wipe towers) or M280 commands to control a servo.

And if you want to see another example a DIY G-Code generator, check out this free 3D-modelling software Blender add-on called Blender CAM. Thanks [Martin] for the tip!