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# 2018-01-27 - Ladybug Quest
I read a document with sample Logo code, and chose to try it out in
FreeDOS. First i tried Ladybug Logo, the Logo that i had used as a
kid. This brings back a few memories.
In middle school i checked out an spy adventure book from the school
library. It involved typing in BASIC code to decrypt hidden messages
and solve various puzzles. I had fun typing it into an Apple II
during lunch break. Then i took the book home. Dad let me type code
into GW-BASIC on an IBM XT. He also helped me debug it when i made
mistakes.
Later that year, i took a course designed to explore our interests.
We would spend each week on a new subject. During the computer
science subject, i learned to use Logo on the Apple II. This was the
first time i was officially taught to use a computer at school.
In case you are interested, below are links to Logo books:
Introducing Logo: for the Apple II, TI 99/4A and Tandy Color Computer
Computer Art and Animation: A User's Guide to Atari LOGO
LogoWorks: Challenging Programs In Logo
The Great Logo Adventure
The Great Logo Adventure Files
Computer Science Logo Style: Symbolic Computing
Computer Science Logo Style: Advanced Techniques
Turtle Geometry
Logo memos from 1974
History of Logo
And below are a couple of links to browser-based versions of Logo.
These require Javascript.
JS LOGO
Turtle Academy
Dad downloaded Ladybug Logo from Compuserve or a BBS and let me use
that at home. Ladybug Logo was hard-coded to use a CGA graphics
adapter. Since the IBM XT had a Hercules monochrome graphics adapter,
it would not run out of the box. Dad set it up with a clever TSR
named SIMCGA, which made the necessary video BIOS and memory map
changes to emulate CGA on a Hercules card. This enabled Ladybug Logo
to run on our hardware.
Download LADYBUG.ZIP
Download SIMGGA41.ZIP
I installed Ladybug Logo in FreeDOS 1.2 on VirtualBox. Ladybug is a
software engineering marvel because of its well organized
documentation and the capabilities that it DOES offer, considering
that it fits within the constraints of a real mode compiled BASIC
application and a single floppy disk. It is also interesting to note
that the documentation uses a mixture of feminine and masculine
pronouns, which seems progressive for 1984.
The software's author was an interesting character. He was humble
and did not expect to get rich. His corporate job paid the grocery
bills and Ladybug was offered on a donations accepted basis to fund
his hobby. Below is a magazine article about Ladybug Logo.
* Ladybug article page 1
* Ladybug article page 2
* Ladybug article page 3
* Ladybug article page 4
From PC Magazine, May 14, 1984
Ladybug ran fine in FreeDOS, but it would not execute the sample Logo
code, which used list processing primitives and variadic procedures.
Ladybug Logo must have internal list processing in order to run Logo
code. However, it does not expose its internal list primitives as
Logo commands. It also lacks variadic procedures. Ladybug didn't
even offer enough functionality to build my own primitives.
Next i downloaded UCBLogo 5.3 for DOS, which could run the sample
code. Success! Let's go deeper. On the same page the author also
offers three textbooks free of charge, which use Logo to teach deep
concepts in computer science. Thinking this might be fun, i began to
read the manual and tinker with commands. The EDALL command spawns
the JOVE full screen editor, which is a clone of Emacs, which is a
depraved editor indeed. (Of course i am a completely objective
observer in the emacs versus vi dichotomy.) The manual says that i
can use any editor i wish by setting the EDITOR environment variable.
So i set it to vi.
SET EDITOR=C:\BEN\BIN\VI.EXE
Calvin 2.3
Calvin 2.3 source code
My DOS vi of choice was Calvin 2.3, which is tiny, fast, and
functional. It works perfectly in DOSBox but screen navigation
produces artifacts and glitches in VirtualBox. Calvin comes with
source code and it is compiled using Borland Turbo C 2.0 and A86
4.02. Reading the source code, my guess is that the glitches come
from CGA BIOS bugs in VirtualBox, specifically around INT10h AH=05h
SELECT ACTIVE PAGE. Rather than try to fix or work around this BIOS
bug myself, i thought i would try another editor.
## 2024-03-23 follow-up
I should have read the documentation, not the source code. Calvin
includes VI.DOC, which says:
> vidcompat (default 0)
> Indicates the compatibility level for video operations.
> Setting it to a higher value may cause some screen-related
> problems to go away if you have slightly non-standard hardware.
> With vidcompat=1, Calvin does not use the alternate screen
> feature of CGA adapters, and with vidcompat=2, it does not save
> and restore the screen after editing.
Just as i thought! The problem is CGA BIOS bugs. Calvin already
includes a workaround. I just need to set the following environment
variable.
SET EXINIT=set vidcompat 2
I verified that this does indeed resolve my problem in VirtualBox.
* * *
Note that UCBLogo is compiled using the Zortech C Compiler. I
couldn't find any place to download this compiler. It has been
superseded by Digital Mars, but that compiler suite no longer runs on
DOS.
On a tangent, i am pleased with how well the latest DJGPP works on
FreeDOS 1.2. Combined with the DOSLFN driver i get long file names
and a Unix style shell. FreeDOS has come a long way and promises to
be a fun toy to play with.
By the way, i have a follow-up article that mentions printing from
Ladybug LOGO on DOS.
2022-05-15 - Print Quest
* * *
> Pavel Boytchev's meticulously researched Logo Tree Project
> [Boytchev 2014] lists just over 300 dialects of Logo, most but not
> all of which trace their ultimate ancestry to the 1968 BBN PDP-1
> Logo. Some of the listed dialects are Logo in name only, restricted
> to a turtle graphics library.
> --From: History of Logo
>
> Proc. ACM Program. Lang., Vol. 4, No HOPL, Article 79, Jun 2020
Ladybug Logo is one of these implementations of "Logo in name only,"
restricted to a turtle graphics library and lacking the list
manipulation primitives necessary to write real programs.
* * *
Good Logo implementations for DOS:
* IBM Logo 1.0
https://winworldpc.com/product/ibm-logo/100
* IBM Logo Manual
https://archive.org/details/ibm_logo_manual
* IBM Logo VGA patch
ftp://retronn.de/mirrors/garbo/pc/programming/logopat.zip
* PC Logo 4.01.04 by Harvard Associates
https://archive.org/details/pclogo4dos
* UCB Logo
http://people.eecs.berkeley.edu/~bh/logo.html
* UCB Logo 5.3 for DOS (32-bit)
http://people.eecs.berkeley.edu/~bh/downloads/blogo.exe
* UCB Logo 5.3 source code
ftp://ftp.mirrorservice.org/pub/minix/distfiles/backup/ucblogo-5.3.tar.gz
tags: bencollver,retrocomputing,technical
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bencollver
retrocomputing
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