Re: Using Applesoft Internal Error Messages in a BASIC Error Handler

Path	csiph.com!tncsrv06.tnetconsulting.net!usenet.blueworldhosting.com!diablo1.usenet.blueworldhosting.com!feeder.usenetexpress.com!tr1.iad1.usenetexpress.com!69.80.99.27.MISMATCH!Xl.tags.giganews.com!local-2.nntp.ord.giganews.com!news.giganews.com.POSTED!not-for-mail
NNTP-Posting-Date	Wed, 17 Jan 2024 07:19:40 +0000
User-Agent	NewsTap/5.5 (iPhone/iPod Touch)
Cancel-Lock	sha1:O309nFECNS/s0WOhB/SdHgufosY=
Newsgroups	comp.sys.apple2.programmer
Subject	Re: Using Applesoft Internal Error Messages in a BASIC Error Handler
Content-Type	text/plain; charset=UTF-8
Mime-Version	1.0
Content-Transfer-Encoding	8bit
From	Michael J. Mahon <mjmahon@aol.com>
References	<010cc230-427a-485e-9a90-bcd294ba96b5n@googlegroups.com> <95461d63-9b7a-47b8-b433-c31432d43d24n@googlegroups.com>
Message-ID	<HOKdnXI0TYkR4jr4nZ2dnZfqnPWdnZ2d@giganews.com> (permalink)
Date	Wed, 17 Jan 2024 07:19:40 +0000
Lines	31
X-Usenet-Provider	http://www.giganews.com
X-Trace	sv3-KV9UunyTOgZcff0+Rq20TQSey1kq8GqPhGGkO/5plWUo8AzlhL8B/jkEiZ0HCVee/iDXNz+eTY6fDKU!nw7Cznu3jgy4+tmnkcENslXL39vbwzJQCwr1gl0iSz6ilOpzMslJYQVKsnVxtV6UF4Yzrs74GGhh!nQ==
X-Complaints-To	abuse@giganews.com
X-DMCA-Notifications	http://www.giganews.com/info/dmca.html
X-Abuse-and-DMCA-Info	Please be sure to forward a copy of ALL headers
X-Abuse-and-DMCA-Info	Otherwise we will be unable to process your complaint properly
X-Postfilter	1.3.40
Xref	csiph.com comp.sys.apple2.programmer:6302

Show key headers only | View raw

fadden <fadden@fadden.com> wrote:
> The error code, passed in the X register, is just the index of the start
> of the error text (table at $d260).  The error routine prints "?", then
> the error text, then "ERROR" and a bell (from $d350).  If the code was
> running, it prints the line number, and does the Applesoft error handling.
> 
> So for example, SYNTAX ERROR is error code 16.  $d260 + 16 = $d270, which
> is the string "SYNTAX".  The last letter has the high bit set (Dextral
> Character Inverted format, or DCI), which is how the code knows when to
> stop printing characters.
> 
> Try this:
> 
>  100 BASE = 53856: REM $D260
>  110 ERRCODE = 16: GOSUB 1000: REM SYNTAX ERROR
>  120 ERRCODE = 53: GOSUB 1000: REM ILLEGAL QUANTITY
>  130  END 
>  1000 PTR = BASE + ERRCODE
>  1010 L =  PEEK (PTR): IF L >  = 128 THEN  PRINT  CHR$ (L - 128);: PRINT " ERROR": RETURN 
>  1020  PRINT  CHR$ (L);:PTR = PTR + 1: GOTO 1010
> 

When writing the NadaNet ampersand extension for Applesoft, I needed a
“standard” way to signal a data packet error. Since there is no easy way to
extend the error message table, I chose to piggyback on an existing message
by choosing an error number that points to the last word in the “OUT OF
DATA” error, creating a “DATA” error message for NadaNet communication
errors. ;-)

-- 
-michael - NadaNet 3.1 and AppleCrate II:  http://michaeljmahon.com

Back to comp.sys.apple2.programmer | Previous | Next — Previous in thread | Find similar

Thread

Using Applesoft Internal Error Messages in a BASIC Error Handler Bill Chatfield <billchatfield1@gmail.com> - 2023-11-29 10:31 -0800
  Re: Using Applesoft Internal Error Messages in a BASIC Error Handler fadden <fadden@fadden.com> - 2023-11-29 22:23 -0800
    Re: Using Applesoft Internal Error Messages in a BASIC Error Handler Bill Chatfield <billchatfield1@gmail.com> - 2023-11-30 07:14 -0800
      Re: Using Applesoft Internal Error Messages in a BASIC Error Handler Jerry Penner <jerry+a2@jpen.ca> - 2023-11-30 11:00 -0700
        Re: Using Applesoft Internal Error Messages in a BASIC Error Handler fadden <fadden@fadden.com> - 2023-11-30 13:23 -0800
        Re: Using Applesoft Internal Error Messages in a BASIC Error Handler Bill Chatfield <billchatfield1@gmail.com> - 2023-12-01 07:10 -0800
    Re: Using Applesoft Internal Error Messages in a BASIC Error Handler Michael J. Mahon <mjmahon@aol.com> - 2024-01-17 07:19 +0000

csiph-web