188. Master/Arc scroll quirk
     ~~~~~~~~~~~~~~~~~~~~~~~
This tip applies to a Master/Compact and the Archimedes, but it has a nasty
'twist' on the Arc in particular.

If you set *CONFIGURE NOSCROLL, ie enable the scroll-protect option, and
print a character on the last position (column) of a line on the screen, a
LineFeed is not generated in the usual way. Instead, the cursor sits under
the last character on the line until you print another character, in which
case it moves down to the next line as normal. When the cursor is 'hanging'
in this way, it returns a POS of 20/40/80 etc. depending on the screenmode,
rather than 0 or 19/39/79 etc.. As soon as another character is printed, POS
becomes 1 (not 0) as the cursor has moved down onto the next line.
This can produce some strange results on programs written under the
assumption that the cursor behaves as on a BBC B and B+. The cure is to set
*CONFIGURE SCROLL, ie scroll protect is disabled.

OK, now the booby-trap for Arc-lovers. You may have disabled the scroll
protect on your Arc, but the desktop enables it again when called up, and it
stays on. Thus when you run a program after using the desktop, the scroll
protect is enabled whether you like it or not!

On both machines, using VDU23,16| once in a program will disable the scroll
protect, and VDU23,16,1| will enable it; problem solved. (Note the "|".)

Just for fun, load any BASIC program, and then try LISTing it after first
typing VDU23,16,n| , where n is 2/3/4 etc.. The results are MOST
entertaining!