G - code – a standardized programming language designed for CAM machine control. In simple instructions, a G-Code sequence contains the exact commands for the machine, eg. in which way, how fast and in which axis to move. G-Code for 3D printers is generated by the cutting software (slicer). It consists of the followings data: temperatures of the hotend and the heatbed, rotation of motors in a precise sequence, which affects the movement and behaviour of the hotend. Commands are sent line by line to the CPU of the 3D printer during the printing process. Processor, based on its firmware, interprets the code and sends appropriate signals to the respective components.