G-code programming is a component of the numerical control programming language used to provide operational instructions to automated machines. The code instructs machines on what action they need to perform to accomplish a task.
The first version of G-code lacked essential components such as conditional operators, loops and programmer-declared variables. It required programmers to start all codes with a zero and was unable to encode the logic associated with automated machines. Over time, developers improved on the programming language to include all the necessary components, making G-code a high-level programming language.
As of 2015, all codes in the G-code programming language start with the letter G. Each code carries instructions to change the state of machines through initiating movement and causing clockwise or anticlockwise rotation. The programming environment that started with initial tape punches has developed to encompass to the latest environments that combine computer-aided design, computer-aided manufacturing and editors that are analogous to the XML programming environment.
Common G-code programming codes include G00, G01 and G03. G00 causes the machine to operate at high speed, while G01 makes the machine move in a straight line to perform a milling or cutting task. G02 and G03 make the machine move in a clockwise or anticlockwise direction respectively.