HP-42 Program Critique - Kinematic Equations (first program)

[Dave Britten]

You might have been running into issues with the KEY XEQ instructions since your menu doesn't loop back to itself. Typically, after MENU, STOP, you'll want a GTO that jumps back to the same menu. This can either be a LBL directly before the MENU instruction, or all the way before the CLMENU (sometimes it depends on the program and whether it needs to refresh the contents of the menu every time it's displayed).

By doing that, and also leaving out the KEY 9 GTO... (i.e. not moving the program pointer when closing the menu), the user can redisplay the last menu by simply pressing R/S. Of course, there are plenty of times where you DO want to handle the EXIT key and RTN or GTO, particularly if you're building a tree of submenus and you want EXIT to go back up a level.