HP NonStop G-Series - Manual (Page 286)

Editing With the Numbered Function Keys
Page Mode Editing
C–16 058061 Tandem Computers Incorporated
When you press a function key:
If the cursor is in column 80 of the first screen line, EDIT VS assumes
that you have NOT changed the text on the screen since you pressed
the previous function key. This means EDIT VS does not save the
changes if you have changed the text on the screen and if the cursor is
in column 80 of the first screen line.
If the cursor is not in column 80 of the first screen line, EDIT VS
compares each line on the screen with the EDIT file. EDIT VS flags the
lines that differ and puts them into the EDIT file.