The cartridge starts in EDIT mode. The programmer enters lines of assembly source into the Atari BASIC-like editor. Source text must be prefixed with a line number, or it is interpreted as a command. Like Atari BASIC, Assembler Editor included an codice_1 command that could be used to combine files together into a single larger program listing. Unlike Atari BASIC, Assembler Editor included a number of commands for automatically creating spaced-out line numbers, as well as renumbering lines and deleting them "en masse". The editor also had a codice_2 command, which was very useful when working with labels.