JiffyDOS Problem and Memory Usage

From: doug.cotton@the-spa.com (Doug Cotton)
Subject: Re: JiffyDOS problem!
Date: Mon, 19 Feb 1996 22:05:18 -0500

> Magnus Nyman <magnus.q.nyman@telia.se> wrote:
> >When Jiffy

> >loads the direcory (@$) it uses the vector bb/bc as a pointer to a
> >temporary buffer. Normally $9f01. The system uses the same vector as a
> >temporary storage for filenames after loading. (/,%,=A3... etc).
> >Load a ML-file from $1000 to $cfff, show the dir, and a part of your code
> >is corrupted!

There are a number of zero page locations used by JiffyDOS. These locations are also used by the JiffyDOS kernal built into RAMLink and RAMDrive. It is best to avoid using these locations in your own programs in order to retain complete JiffyDOS compatibility. At the very least, you should make sure that your use of them does not interfere with JiffyDOS' usage.

JiffyDOS 64 Zero Page Variables

Location  Variable Name  Note

$26 allflag/rsize 2 $27 comsav 2 $9B keybyt 2 $9F cjla 2 $A3 ldflg/qflag 3 $A6 tflag 2 $B0/$B1 keyptr 2 $B0 sprsav 1 $B1 rassav 1 $B2 regsav 1 $BE drvbyt 2 $BF dest 2

JiffyDOS 128 Zero Page Variables

Location Variable Name Note

$26 allflag/rsize 2 $27 comsav 2 $9F cjla 2 $A3 ldflg/qflag 3 $A6 tflag/togsav 2 $B0 sprsav 1 $B1 rassav 1 $B2 regsav 1 $BE drvbyt 2 $BF dest 2

Notes

Note 1 - Saved, then restored by LOAD routine (no other usage).
Note 2 - Used only from BASIC for JiffyDOS wedge comands, device toggle, and function keys.
Note 3 - Used in all disk access and LOAD routines.

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