Three items are three modes defining the range of atoms on which automated procedures (MAIN_MENU:auto_stuff.html, MAIN_MENU:trace.html) are applied.
Procedures will be applied on segments names included in the variable "WORK_SEGM".
To inspect the contents click "SHOW_SEG" on page 9.
Procedures will be applied on the "active" key atoms.
Procedures will be applied on the last one or two clicked atoms from the history list.