Bob Withers Graphics Adventures

Bob Withers CoCo Graphics Adventures
with Source Code, Maps, Downloads, and an Interview

Welcome to my little space on the web. The picture above may appear a little fuzzy but it is actually crystal clear. I’m just a fuzzy person!

Once upon a time, in a previous life, my friend, Steve O’Dea and I developed a series of six graphic adventures for the Radio Shack Color Computer. These adventures were marketed by Mark Data Products and were considered rather revolutionary for their time. The adventures stored all images compressed in memory and were usable from cassette based systems as well as from diskette. These games were all written in MC6809 assembly language and assembled with the fantastic Micro Works MACRO-80C assembler. To this day this is one of the best assemblers I’ve ever used.

A little known fact is that these adventure games were also ported to the IBM/PC using a CGA graphic screen. These versions entered the market too late and did not take full advantage of the available hardware and were not widely distributed.

You can read an interview with me about the CoCo adventure days below. Walkthroughs of all the games have been compiled by Ricardo Mendonça Ferreira and are available here. While developing these games I would always draw a game map to work from. This map would assign a number to each room in the game and identify direction and object placement. Sadly the maps for Trekboer and Vortex Factor have been lost.

  • Before blindly grabbing all of these files: All Coco binary files have been replaced with Robert Gault’s modifications that save and load game positions from disk rather than tape as in the originals. The source code files are the originals that use tape. Also, a missing source file called ASCLNO.ASM has been recreated so the games can be assembled correctly.
  • Like MANY CoCo 1 and 2 games, these games make use of the artifact color set which causes red and blue colors to appear on a composite monitor even though only black and white pixels are actually used. Most CoCo emulators generate the same artifact colors while a real CoCo allows you to hit RESET and cause red and blue to be swapped for the generated colors. Either way, you’ll have to hit ENTER to get past the artifact color selection screen you see at the start of some of these games.

Install the VCC CoCo Emulator to play these CoCo games Right Now!

Countless legends tell of
a magnificent Pot of Gold and enormous wealth hidden by leprechauns at the
end of the rainbow. Many have attempted to find the marvelous treasure but
success has eluded tham and it remains hidden to this day. Because you are
a dedicated adventurer, eager to face danger and challenges for great rewards,
you have determined to search for that fabled Pot of Gold and succeeded
where others have failed.  SHENANIGANS (source
) (maps)
(Play Now –
Requires VCC Emulator
This game was originally named
Seq Quest but was renamed after several threatening letters from lawyers
representing ActiVision. Get your shark repellant and scuba tanks ready!
The underwater scenes in this adventure are unforgettable. You’ll run into
a pirate, a mermaid, and some hungry sharks in this colorful and unique
treasure hunt.  SEA SEARCH (source
) (maps)
(Play Now)
A valuable museum treasure
has been stolen; can you recover it? CALIXTO ISLAND is a challenging puzzle
with and occasional twist of humor. You’ll visit a laboratory, a Myan pyramid
and you’ll meet crazy Trader Jack – all in living color and exciting detail.
) (maps)
(Play Now)
Encounter the forces of black
magic as you roam around an old 18th century monastery. See all the evil
locations in this spooky adventure in full hi-res detail. If you like suspense,
you’ll love searching out and destroying the evil in this classic tale.
) (Play
This exciting adventure begins
abord the starship TREKBOER in the 21st century. Life on Earth is threatened
by a deadly virus and your mission is to search the frontiers of space for
the cure that will save mankind from disaster. But how? Where? The name
of your starship provides the first clue.  TREKBOER (source
What is it? What secrets does
it hold? The seeker of treasures through time and space must find out! From
the coliseum of ancient Rome to the futuristic world of tomorrow … join
us in this unforgettable odyssey.  VORTEX FACTOR (source
) (Play


An INTERVIEW with Bob Withers by Nickolas Marentes, October 1999

Bob Withers, currently aged 49 and living in Dallas, Texas, is
the co-creator of those popular graphic adventures from Mark Data during the
early 80’s. I remember playing these adventures till all hours of the night,
not giving up till I solved the next puzzle. I loved them! What many of us CoCo
users don’t realize though is that Bob later translated these adventures to
the IBM PC but they did not achieve the same level of success as on the CoCo.
Bob has these adventures, including the IBM PC versions, available for
download off his web page.

How and when did you become interested in computers?

While in high school I took a brand new course offered in our
school named “Data Processing”. This was the late 60’s so the course consisted
of an IBM 082 card sorter, an 029 keypunch, and a 405 accounting machine. I
can’t tell you how many hours I spent wiring the logic board of that 405. Pretty
mundane by today’s standards but I was hooked and decided to make some form
of computing my career.

What made you choose the Color Computer?

I had been doing work on earlier TRS-80 computers, the Model
I & III. I’d developed some communication software and was asked to port
one of the programs to the Color Computer. So I picked up a gray 16K CoCo1.
I found the 6809 chip vastly superior to the Z-80’s I’d been working with and
just fell in love with it.

What computers have you owned and currently own?

I’ve owned most of the TRS-80 line with the exception of a Model
12 and 16. I also have 10-15 Macs and a couple of Apple IIgs machines. I have
an Osborne I, a Kaypro II, and a Poqet handheld. I also have four Pentiums that
are split between Windows and Linux. For a long time I was providing refuge
to abandoned computers but I’ve run out of room and only take in pocket computers
and the like these days. I probably have 50-60 machines stuffed in various places
around the house.

What companies have you worked for?

– U.S. Dep. of the Army I was a computer operator for mainframe systems.
– Chrysler Corporation COBOL programmer for pre-production auto design system.
– Volkswagen COBOL programmer for VW hourly payroll system.
– Texas Instruments Mostly workstation and PC development. OS/2, Unix, and DOS.
– Knowledge Data Systems Developed health care systems under Windows and Unix.
– Answersoft Software Interfaced to PBX systems using LAN to Windows, OS/2, Unix.
– Mastercard International Realtime middleware development under NT and Unix.
– MCI Worldcom Team lead for data base development under Unix.

Were you an adventure game fan?

Yes, I love adventure games. Not that I’m that good at them
but I just love to play them. I used to spend hours playing Colossal Cave and
I still think it’s one of the best I’ve seen. I ported a CP/M version of it
to DOS once and really had a good time with it.

Why did you choose to create ‘graphic’ adventures?

Steve and I were both big fans of adventure games. We had played
many of the Infocom games together and I had been riveted by the early Scott
Adams adventures for the TRS-80 Model I. Steve had been playing several graphic
adventures on his Atari 800 and wanted to do one for the CoCo. I agreed but
I didn’t like the way the Atari games kept accessing the disk drive during play.
I suggested that we try to make as complete a game as possible that could be
contained within RAM. This presented a lot of challenges along the way but made
game play smoother and opened the market for graphic adventures to people without
disk drives.

Shenanigans Screenshot


What was your involvement with the programming of the graphic adventures?

At the time Steve and I were both mainframe programmers. We
coded COBOL during the day and played with home computers at night. Steve is
also a very talented graphic artist so he was responsible for designing and
drawing all the game pictures. We generally would meet for an hour or two to
layout a game map and discuss various traps and puzzles. We would each then
work alone, I would write all the code to support the game and Steve would draw
the graphics. As Steve finished each room he would give me the pictures along
with any animation instructions and I would add them to the game.

What software tools were used to develop
these programs?

All the CoCo games were written with the Macro-80C assembler
package developed by The Micro Works.

Steve was using the Radio Shack cartridge Art Gallery for initial
drawings and Micro*Painter for close up work. At first it was very tedious switching
between these as the picture had to be saved, the cartridge switched, and the
picture reloaded. I pulled the code from both of these ROM packs and patched
it together so both programs would be in memory at the same time working on
the same image. I used the CLEAR key to switch between Micro*Painter and Art
Gallery. This worked great and really sped things up.

After images were drawn we used a small Basic program I’d written
to compress them using a simple RLE encoding scheme and then write out the image
using assembly pseudo-ops so it could be directly included in the source code.

Steve came up with an ingenious method of drawing the screens
in small sections we called overlays. Each screen then consisted of a background
and a number of small overlays. Overlays were also used for animation by placing
them over top of each other at regular intervals. I was constantly amazed at
how Steve could draw such nice scenes and have them compress down to almost

What was your favourite adventure of
the series?

My personal favorite was Trekboer. I had just finished reading
James Michener’s “The Covenant” when we were starting it. We used some of the
terms from the book in the game but in a futuristic setting.

How did you get into contact with Mark

When we finished our first game, Shenanigans, I made a demo
version that included four or five rooms. We dug out a Rainbow magazine and
sent off a copy to 5 or 6 companies that were advertising CoCo software. We
never heard from most of them although we did get a very nice letter from Tom
Mix telling us that he was not interested but encouraging us to submit work
in the future. The only positive response we got was a phone call from Ron Krebs
at Mark Data. Ron had written the text versions of Calixto Island and Black
Sanctum and was really excited about distributing graphic adventures. We made
a deal right there on the phone and I’ve never regretted it. Ron and his wife
Mona are wonderful people and Steve and I had a long and friendly relationship
with them.

Vortext Factor Screenshot


What was the royalty scheme you had with
Mark Data and how did you do financially with programming for the CoCo?

We received 30% of the net which Steve and I split evenly. For
a couple of years the games produced a nice supplementary income but it was
never anything that could support even one person.

Did you program for the CoCo primarily
as a means of income or were you a hobbyist that found how to make money while
having fun?

Programming the CoCo was always a hobby for me. The extra income
was nice but really never amounted to as much as people would imagine.

Why did you leave the CoCo market?

At the time Steve and I left there really didn’t seem to be
much of a CoCo market. The CoCo 1 was stagnating and the 2 and 3 had not even
been announced. Creating and testing the adventures took a lot of our personal
time and we just decided the dwindling income wasn’t worth it.

Do you feel software piracy was to blame
for the “dwindling income” later on?

I expect it had some impact but probably not a major one. My
guess is that we had just saturated our market and sales began to drop off.
At the time, between the CoCo 1 and 2, I think this was happening all over.
It was a major reason that Mark Data wanted to move more into the IBM market.

How did the decision to port the adventures to
the IBM PC come about?

At the time I knew nothing about the IBM machine or market.
Ron Krebs at Mark Data called me one day and said he’d like to have the games
ported to an IBM machine. I said, “Sure”. About a week later a big box arrived
from Mark Data containing an IBM XT with a CGA card and a color monitor. It
had 256K RAM and two 360K disk drives. I later bought this machine from Mark
Data and I still have it sitting here in working condition.

I ran out and bought some books on 8086/88 assembly language
and the IBM PC in general and started learning. I bought the IBM Assembler and
started porting code. We didn’t have any graphic tools for the PC and at the
time Steve had moved on to other things and wasn’t particularly interested in
redrawing all the pictures. As a result I used the CoCo images adjusted for
the CGA screen resolution. They looked OK but weren’t great.

The IBM Assembler was the pits, it was horrible at assembling
data pseudo ops which comprised a large portion of my code. It used to take
a couple of hours to assemble one adventure! I later bought a version of MASM
from Microsoft which eliminated this problem.

By the time I owned an IBM video card with a higher resolution
than CGA the adventures were dead and I’d moved on to other things.

Are these adventures still available

No but they can all be downloaded, including source, from my
web site. Adventure Survivors (email: gtch30b [at] prodigy [dot] com) also sells disk and
tape versions of them (and others) for media and shipping charges only. They
also publish a nice, but infrequent, newsletter featuring game maps, gossip,

What is your opinion on Software Piracy?

Well, of course, I think it’s very wrong. I think the term piracy
is far too romantic a title for this activity. It is theft plain and simple.
To me there is no difference between stealing a program and stealing a book,
or a painting, or a car for that matter. On the other hand I am violently opposed
to copy protection. I was very upset when Mark Data decided to copy protect
our games and tried hard to convince them not to do it. I believe copy protection
punishes honest people while doing very little to stop piracy.

Did you ever consider going into game
development as a career?

No, never. I’m just not much of a visual programmer. By that
I mean that most of the work I do is server oriented, behind the scenes type
of coding. I’ve never been very good at designing graphic displays. That type
of disability would quickly kill a game writing career.

What are some of your favourite CoCo
products of all time?

My favorites include Zaxxon,  Bedlam,  Tut’s Tomb,
The Sands of Egypt,  Micro Painter,  Art Gallery,  Macro-80C
Assembler,  Color Forth.

What is your opinion of the CoCo 1 that
you were using?

I loved the 6809 and VDG chips. I hated the chiclet keyboard
and bit banger RS232. I just thought the screen resolution was so-so, not really
up to snuff with the Atari machines of the time.

As for the CoCo 2 and 3, I own a couple of each and, other than
booting them up to see if they worked, I’ve never done anything with them. I
was pretty much out of Color Computer development before the CoCo2 came out
so I’ve never used either machine.

What was
your impression of Tandy in those days?

I felt that Tandy was making a huge mistake in their efforts
to stamp out third party software. Rather than working with developers to build
a software base they made it hard to learn technical details. I always felt
that Tandy wanted 100% control of all software and hardware for their machines.
Looking back it’s a real shame, had they produced an open system and encouraged
third party development we might all be using “Tandy clones” now rather than
“IBM clones”.

Did you ever meet with any other CoCo
industry “heroes” ?

Well, I know Tim Purves who developed a number of fine programs
for Michtron (formerly Computer Shack). I sold a file transfer program called
Color DFT to Gordon Monnier at Michtron and Tim took over it’s enhancement.
I met Tim once or twice back then, circa 1982/83. Then ten years later I accepted
a job in Larkspur, Ca. and I find Tim already working there. We worked together
for about nine months. He’s a bright guy and an exceptional programmer.

I met Steve Bjork at a Rainbowfest once. I was a big admirer
of his work and it was nice to meet him. We both thought he was a great programmer
so we got along. :-)

I’ve met Lonnie Falk a couple of times. I’ve often heard people
say that Lonnie was just a businessman in it for the money but I never saw this.
Lonnie had a genuine fondness for Radio Shack machines in general and the CoCo
in particular. For a number of years he was certainly at the center of the CoCo
revolution and it would have been a very different community without Rainbow

I’ve never met Marty Goodman but I have spoken to him on the
phone several times. It’s hard to question Marty’s impact on the CoCo community,
his contributions are everywhere and continue even today. Marty once sent me
a board to allow my CoCo1 to work with a color composite monitor. Marty, if
you ever read this, thanks a bunch – it made all the difference in the world.

Do you have any interesting stories
from your CoCo days?

Well, I recall one time we were at a Rainbowfest and Mark Data
was approached by a group of people who made the Dragon. They were interested
in distributing the adventures in the UK but they wanted a demo of the games
we had available. I had never run any of the games on a Dragon, I’d never even
seen one, but they assured me it was 100% CoCo compatible. I went up to a hotel
suite where there were several Dragons setup with about 20-25 people gathered
for the demo. I fired up the first game, I think it was Calixto Island, and
the animation was running about 20 times too fast, I mean things were whizzing
by so fast you could hardly make out what they were. Everyone in the room just
stared dumbfounded at the screen until one gent, in a crisp British accent,
said “Are they arcade games as well?”. It turned out that I had based the timing
for all the animation off how long the keyboard scan ROM routine took to poll
for a key. The Dragon routine was much faster and caused everything to run fast.
I was up all night switching all the animation to use the timer interrupt rather
than the keyboard scan loop and the following day the demo ran much better.

Do you have any “philosophical words”
to say about your experiences with the CoCo?

It was a great time, I’ve never been sorry I was involved. Back
then people were intimately involved with the development of programs. They
would agonize for hours over how to cut a couple of processor cycles. They also
were generally very willing to share ideas and technical information. Today
a lot of programming is done by drawing a picture of a screen and answering
a bunch of questions posed by a software *wizard*. The wizard then spits out
a program which generally operates in a manner completely unknown to the programmer.
Somehow, I think we’ve lost an important part of the programming process.

I’m very pleased to see the CoCo hacker (original meaning) ethic
still alive on the Internet. It’s nice to know that the flame is still burning
even if it isn’t catching the world on fire.

Thanks for taking the time to conduct this interview. It brought
back many fond memories that had been long forgotten.


Bob Withers holds the following
programming certifications:


Bob Withers’  Programming Achievements

Disk Download System (DDS) TRS-80 Model I/III Big Systems Software 1980 Full function terminal program
Tape Download System (TDS) TRS-80 Model I/III Big Systems Software 1980 Full function terminal program
Direct File Transfer (DFT) TRS-80 Model I/III Big Systems Software 1981 Binary file transfer utility
Color DFT TRS-80 Color Computer I BSS/Michtron 1982 Binary file transfer utility
Shenanigans TRS-80 Color Computer I Mark Data Products 1983 Graphic Adventure
Sea Search TRS-80 Color Computer I Mark Data Products 1983 Graphic Adventure
Calixto Island TRS-80 Color Computer I Mark Data Products 1983 Graphic Adventure
The Black Sanctum TRS-80 Color Computer I Mark Data Products 1984 Graphic Adventure
Trekboer TRS-80 Color Computer I Mark Data Products 1984 Graphic Adventure
The Vortex Factor TRS-80 Color Computer I Mark Data Products 1985 Graphic Adventure
CoCo-UTIL TRS-80 Color Computer I Mark Data Products 1985 MS-DOS to CoCo disk transfer utility

NOTE: All graphic adventures were co-developed with Steve O’Dea