Two Questions About 80-Col HP-IL Video

[J-F Garnier]

Your code looks fine.
A small improvement, replace
X$[I9,I9]=CHR$(NUM(X$[I9,I9])+128)
with
X$[I9,I9]=CHR$(BINIOR(NUM(X$[I9,I9]),128))
in case X$ already holds a character >= 128

If you want to be faster, you can use the HGL$ function, present in the LEX3421 from the Data Acquisition Pac.
A standalone HGLLEX file is described here (slides 5, 6).
The name HGL$ (Highlight) comes from the equivalent function of the HP Series 80.

J-F