O makes use of a number of socalled major menus that expand into minor menus.
A maximum of 10 minor menus or commands can be associated with each major menu. The keywords appear on the screen with colours that vary according to which major menu the keyword belongs. These colours are defined in the O database, initially from the file menu.o . The arrangement of commands in major menus is not really important to the user of the program, except in that the grouping is made according to functionality. The real advantage of this design is in the ease of adding new groups of commands to the program that do not interfere a lot with what is already there.