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From: 6101695@pucc.BITNET (Raymond Chen)
Newsgroups: net.micro.apple
Subject: Re: ROM to RAM (really ProDOS and CHARGET)
Message-ID: <608@pucc.BITNET>
Date: Wed, 21-May-86 21:39:58 EDT
Article-I.D.: pucc.608
Posted: Wed May 21 21:39:58 1986
Date-Received: Sat, 24-May-86 21:15:44 EDT
References: <2620@sdcc6.UUCP> <3440@reed.UUCP> <203@neoucom.UUCP>
Reply-To: 6101695@pucc.BITNET
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Organization: Princeton University Computing Center
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hayes@UCSD.EDU (Jim Hayes) says in <2620@sdcc6.UUCP>
 
> . . . I beleive
>PRODOS modifies CHARGET to look for HGR, HGR2, LOMEM, HIMEM and the
>like, so it can modify it's on memory map.
>
Pre-releases of ProDOS may have twiddled with CHARGET, but the
current release does not, as far as I can tell.  The Apple people
decided to use the TRACE flag to keep tabs on Applesoft.  TRACE is
always ON, but ProDOS watches COUT for a '#', traps it, and does its
own pre-line processing.  One thing I know it does is count the number of
assignment statements.  When it hits a certain number (determined by
the amount of FREe memory), ProDOS executes its own fast-FREe routine
so Applesoft never uses its (slow) FREe routine.  It probably does
other stuff, but I didn't bother to disassemble it that much.
 
>I can't remember the charget address off hand, but I beleive it
>lives near $10-$20.
 
CHARGET hangs out at $B1.  CHRGOT re-fetches the last token ($B7)
and TXTPTR ($B8, $B9) points to the current token.
 
Now I KNOW that I've confused the matter beyond recognition.
(What was the original topic again?)
Raymond Chen, BITNET: 6101695@PUCC   "Don't look at me.  I'm new here."