HP 3000 Manuals

HPTOOLSET XL Reference Manual

Clear Mark Function Key 

Is available while you are in visual mode.  It clears all active marks
that have been set with the Mark key for the current process.

This key is valid only while you are doing a visual mode edit or read.
To clear marks in the Show Files, Show Debug, or Show Source menus, type
a blank in the box on every line where you wish to clear mark and press
enter.

MPE/iX 5.0 Documentation