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From: grant@hp-pcd.UUCP (grant)
Newsgroups: net.micro.cbm
Subject: Re: Next print location on the screen
Message-ID: <18900003@hp-pcd.UUCP>
Date: Sat, 12-Jan-85 15:21:00 EST
Article-I.D.: hp-pcd.18900003
Posted: Sat Jan 12 15:21:00 1985
Date-Received: Sat, 5-Jan-85 03:58:14 EST
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Organization: Hewlett-Packard - Corvallis, OR
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Nf-From: hpcvrd!grant    Jan  2 12:21:00 1985

{}

you can set/clear the carry for a BASIC SYS call by writing an 
appropriate value (0 for clear, 1 for set, I think) into the PSW
location (similar to the X, Y, and A locations).  I think its address
is 784, but I don't have my documentation here.  When you do a SYS,
the X, Y, A registers and the PSW are all loaded from their respective 
locations before the user routine is called.  When the routine is
finished, the registers and PSW are saved back into their locations
before BASIC resumes.  This means that BASIC can both send and receive
parameters to/from the ML.

For example, if you set the carry before calling PLOT, the cursur's
row and column will be returned to you.

One warning:  PLOT may give funny results if the cursor is on.  It
may move to a new spot while the screen is reversed, leaving an
inverse character and possibly a funny color under its old position.
(It is possible that I am confusing PLOT with just trying to turn the
cursor on in BASIC.)