This command removes a given keyword from the name table so that SuperBASIC is no longer aware of its existence. The code remains in memory so no memory is freed. A ZAPped keyword cannot be recovered without re-loading the code or resetting the system.
You try to run a SuperBASIC program but it stops at the following line:
1120 er=2: es=.9: ET=1.4: eu=0
with error -17. The author used et as a variable because the ET command was not present when (s)he wrote that program. The more resident keywords that are present, the more it is likely that such collisions may occur. ZAP “ET” and re-loading the program will cure the problem.
It is okay to ZAP incompatible and bug-ridden keywords, but removing essential keywords like ED, EDIT, AUTO, LIST to stop the user from editing a program will decrease the QL’s multitasking abilities. Yes, multitasking depends on this general rule: the more a program influences the whole system and may affect other programs, the less the computer can multitask.