Fred Nachbaur's ZX81Page

It's been a long, long, time...

Exclusive to Tech/Worlde - here is a selection of long lost work from ZX81 old-timer, Fred Nachbaur! Fred wrote some of finest software for the ZX81 and now after many years, his programs are again available to you. Without further ado - over to Fred...

Skip the chatter... click to jump straight to:

• Program Descriptions List with download links
• Download Table For heavy-duty downloading

Greetings, All!

Rev 1

• Programs that use more than 24 rows (e.g. HRCHESS) lose the bottom two input lines.
• Programs that combine 22 hi-res rows with 2 low-res rows will show corruption of the low-res input line.
• At least one program (ZX-TERM-80) doesn't run at all. This may be because of the use of the latest version of WRX16, which eliminates the need of the "ghost dummy display file" in high memory.
• Programs that reverse the dummy display file (set bit 7 high) to get an inverse screen do not show up in reverse video on ZX Emulator. Don't know about Xtricator2. Rather too bad, because this could be a spectacular effect in some programs (e.g. "Hi-res Invaders".
• On faster computers, some games run too fast to be playable. One option is to use "MO-SLO" to trim processor speed as needed.

Program Descriptions

• "3-D Fractals" (16, WRX) This is an interesting little program by Gregory C. Harder, my main "partner in crime" during the Great WRX16 Explosion of '86-'87. Adapted to ZX81 from an article in Creative Computing. I sure hope he doesn't mind my posting his stuff here, Greg if you're reading this please give me a shout!
  
  
• "Graphics Archiver" (16, WRX) Greg put together this little graphics archiver to store/ retrieve WRX16 graphics screens. "Upload" transfers existing high-res screen into program for saving, "Download" transfers from loaded program into high-res display file for viewing.
  
  
• "Bi-Plot demo" (16, WRX) This is a demonstration of a cool WRX16 display option. The 8K hi-res display file is divided into two 4K chunks, which are displayed on alternate frames to give a neat overlay effect. The lower six lines are standard low-res. Doesn't work as expected on ZX Emulator, needs a real ZX81 or TS1000/1500.
  
  
• "Blackjack" (16, WRX) "Blackjack" was written by myself in 1986. The game logic was adapted from a similar game I had written earlier for the first "TRS-80 Pocket Computer". This is a direct application of Greg Harder's "SRAM Hi-Res Extended BASIC" (aka SHREB) that demonstrates just a few of the cool things you can do with this package. Runs in a standard 16K ZX81 or equivalent, plus 8K SRAM. Works fine in ZX Emulator, except the input lines are a bit messed up.
  
  
• "Block-Buster" (16, WRX) By Greg Harder. This was adapted from a Spectrum program, and is an interesting game in the "puzzle" genre. It's a bit sluggish on a real ZX81, and benefits from a moderate speed increase, as is possible using emulators. Loads in two parts.
  
  
• "Calendar" (16, WRX) "Year-at-a-Glance" was a neat little program using tape-storage, but might actually be useful on a hard-disk system! It calculates any given year, showing the whole year on a single screen. Press "M" to give the "month" legends, "D" for day- of- the- week. Move the cursor around the calendar to highlight any date, then press ENTER - you're shown your appointments or other significant events for that date. Move the cursor to a non-date field, and you can peruse the entire database. Better documentation to follow as soon as I find it. Comes with the calendar for 1987 (which was when I wrote it) for you to play with. And yes, your ZX81 is Y2K compliant!
  
  
• "CE Amplifier" (16, STD) This is an oldie (from 1983) which takes you through the entire design process, and subsequently analyses, the populor Common-emitter transistor amplifier. Mainly of interest to electronics enthusiasts, but sports some interesting features such as self-changing BASIC code to simulate VAL$ - i.e. given a string representation of a variable name, INPUT to or PRINT that variable.
  
  
• "Dragons" (16, WRX) The classic fractal dragons program, written by Greg Harder. Runs in 16K, but 32K recommended for larger dragons.
  
  
• "Dungeon of Ymir" (16, WRX) This is one of my all-time favourite games, and not just because I wrote it. It's your basic D&D style game, but more action-oriented. Nine levels that get harder as you go along, 8 kinds of monsters (each in two variants), objects, spells, an oracle, all the usual stuff. And all in a mere 16K of very compact Z80 machine code. Considering it's interrupt driven monster-move system, it's amazing it runs in ZX Emulator, albeit sometimes a bit choppy compared to a real ZX81. Also download YM-DUNGN.ZIP which lets you design your own dungeon layout.
  
  
• "Fontkit for WRX16" (16, WRX) Various high-res fonts developed by myself and Greg Harder, including Sanserif Bold, Olden, Olden Bold, Machine Bold, Fancy, a general- purpose lower- case- only set, even a proportional character set that looks like the "Sinclair" logo on our favourite high-tech doorstopper. Various ways of "packaging" the fonts, you shouldn't have too much trouble figuring them out.
  
  
• "Fourier Analysis" (32, WRX) This one started life as an ordinary low-res program in late 1982, and was later upgraded to WRX16 format. It lets you input the data points of any waveform (assumed repetitive) and computes the Fourier transform. Or give it the transform (Fourier co-efficients) and it computes the wave. You can even do two independent waveforms, plotted X vs Y (such as Lissajous figures). Sample run contains such an X-Y plot in the shape of Mickey Mouse; by taking various numbers of harmonics into account, you can see Mickey transform from an egg into a mouse... (Where else could you ever find a program so useless?)
  
  
• "F-Scapes" (48, WRX) "F-Scapes" was the last program I wrote for the ZX81, during a short stint as an accountant's assistant (!) in 1988. Would you believe pull-down windows, 3-D rendering, 2-D topo maps, even 3-D fractals? Believe it! It's really quite something, if I say so myself, and I strongly encourage you to read the extensive documentation either in Text-format or in Write-format (also readable with MS Word). The documentation is also included in the main ZIP file as FS-DOCx.P, which are ASCII "Big REMs" intended for reading using ZX-TERM-80. Also included are FS-FIGx.P, the figures referenced in the documentation. Before running (either on a real machine or on an emulator) POKE 16389,255 then NEW, and only then LOAD "FSCAPES.P". The program really does need a full 48K of dynamic RAM!
  
  
• "Hi-Res Chess" (16, WRX) This one was a real bugger. It's the classic Psion Chess game, with actual chess pieces on an actual (or rather, virtual) board! Only problem - ZX Emulator doesn't show the bottom two input lines, because I stretched Wilf's routine to give 26 display rows... 24 for the board, and 2 for the input lines. So you have to key your moves in blind... not too much of a handicap, if you've played the original. To exit, press DELETE (shift 0) when it's your turn, followed by STOP (shift A) then ENTER. btw - to get out of Wilf's high-res mode from immediate mode you can (almost) always get out with PAUSE 0.
  
  
• "Invaders" (16, WRX) "Hi-Res Invaders" was my Christmas present to my customers in 1987. This one's claim to fame is that it used the SHREB package, but most of the program runs in machine-code, demonstrating that the SHREB package is a useful library of graphics routines as well as a BASIC extension. This program has a bug that's so charming I left it in. If you sideswipe an invader, it kills it but it doesn't vaporise... it just sort of hangs there in space. The same bug also causes occasional rocket shrapnel to stay in place. Warning; this game is addictive, and hard to beat. Too bad the "reverse video" mode doesn't work on ZX81 Emulator... (wish, wish!)
  
  
• "Julia Sets" (16, WRX) This is the Julia set equivalent to "Mandelbrot FFP". See below.
  
  
• "L-Systems" (16, WRX) "L-Systems" is a type of fractal using rules of generation to produce self-similar space-filling curves. This implementation by Greg Harder is true to the original specification, and it's recommended that you look up the reference provided in the program. From a ZX81 standpoint, this one is interesting in that it uses our "QUIK" display mode. This is sort of a hybrid between FAST and SLOW; by mucking with system variable MARGIN and display timing, you get varying degrees of speed improvement traded off with dim or flickery displays. But at least you could see what was going on! No guarantees what emulators will do with this...
  
  
• "Macro-Life" (16 or 32, WRX) Greg Harder was a real Master at adapting program listings in magazine into our High-Res BASIC environment. This Life simulation is an example. The zipfile contains both a 16K and a 32K version, the 32K version saves the screen in high memory for improved speed and more options.
  
  
• "Mandelbrot-FFP" (16, WRX) This is the classic Mandelbrot set fractal. The program is pretty much self-documenting, its claim to fame is the use of the ZX81's calculator language directly, to give about a 3x speed increase over straight BASIC. However, it's still pretty slow... be forewarned. A addition is MAND4-FP.P which is a quadric Mandelbrot in medium-res dithered greyscale (needs 32K)
  
  
• "NIM - 2K" (2, STD) A two-player Nim game for the 2K TS1000 (sorry, it won't run in a 1K ZX81). Demonstrates what's possible in just 2K of RAM, using only standard Sinclair BASIC. Because it uses the characteristics of the compressed display file, if you want to run it in a 16K ZX81 or emulator, you first have to POKE 16389, 72 then NEW before loading.
  
  
• "SRAM Hi-Res Extended BASIC" (16, WRX) This is the full SHREB package, written by myself and Greg Harder. I tended to write the core routines (parser, tape routines, that sort of stuff) and Greg specialized in the cool graphics commands. Contains the lastest version of the core only, plus a couple demos. Documentation to follow as soon as I find it. (I know it's on one of those rotten old floppies... but where?)
  
  
• "Snorth Games" (16, STD) These wonderful games were written in an odd subset of Sinclair BASIC, then compiled using a program I've forgotten the name of, by a professional comedian named Steve North. He wrote these for his own amusement in 1983, then licensed them to me for distribution in 1985. LOAD "SNORTH", the loader gives you the option to load one of four games: "NFLX Football," "Miner's Revenge," "Super Slide," or "Storm Lander 3." Technically only legal if you own the original, since I haven't been able to get hold of Steve to get his permission.
  
  
• "Spirograph" (16, WRX) Yet another cool graphics program adapted from a magazine article by Greg Harder. This one simulates the popular "Spirograph" toy, you define the sizes of the gears and the program does the rest. Includes yet another method of kinda- seeing the display while drawing in FAST mode (this feature doesn't work properly in ZX Emulator.)
  
  
• "VDAQ1-HR" (16, QHR, OTH) "VDAQ1-HR" stands for "Votem Data Acquisition - Hi-res." It was written originally for the "Votem", which was a simple voltage-to-frequency converter designed for single-channel analog data acquisition using the ZX81. My implementation allows multi-screen acquisition, variable scale and timebase, all that sort of thing. Even without a Votem it was useful for frequency measurement, via the tape input jack. It still could be used for such purposes with a real ZX81, but it's only "something pretty to look at" on an emulator. Although... I suppose you could sample your waveform with your PC, export it to emulator.... naw.. Ain't worth it.
  
  
• "Voyage of Peril" (32, WRX) "Voyage of Peril" was adapted by Greg Harder from a Spectrum program in a British mag, if I remember correctly. It's a cool little adventure game, that nicely shows off his SHREB sprites, among other things. Requires 32K of RAM, but no need to poke RAMTOP higher; it only uses high memory for data storage. This is a bit sluggish on a real ZX81, and really benefits from a moderate speed-up using an emulator.
  
  
• "Wa-Tor" (16, QHR) "Wa-Tor" was based on a "Computer Recreations" piece in Scientific American (from which I used to get some of my best ideas...). It's a predator vs. prey simulator, kind of like "Life" but way cooler. You have to populate a planet with fish and sharks... the idea being to keep both species alive on a long-term basis. This uses Nissim Elmaleh's "SHR" for the cover screen and graphing routines, being before the days (1985) when Wilf's WRX16 routines really took off. Program is pretty much self-documenting.
  
  
• "ZX-PAINT" (16 up, WRX) This is truly one of those "Oh, Wow!" programs. Greg Harder wrote some awesome stuff, but with this one he really out-did himself. I remember in those productive days of 1987, I'd get a new version from him about every other week... each version better than the one before. This is the final one. Too bad there was no longer anyone around to sell it to... I Don't have a clue where the docs are, but with this program it's almost better to play around and figure it out yourself.
  
  
• "ZX*TERM*80" (16 up, WRX, MOD) Though this was one of my best (and best-selling) programs, I almost didn't post it here. For one thing, it's hardware dependent (either Byte-Back or Timex/Westridge modem). For another, the hardware is long gone. Thirdly, you'd be hard- pressed to find any 300 baud BBS's anymore. Lastly, though it runs fine on a real ZX81 or TS1500 with appropriate "Wilf board", it won't run in hi-res mode on ZX Emulator. All that being said, it would still be useful as an ASCII text reader. What's more, it used some truly remarkable innovations - like hooking into the interrupt to do fast keyboard sensing (and buffering!) while not missing a byte of incoming data. It was really something to be typing away as fast as you can, while data is coming in, and nary a beat is missed. It also featured separate windows for input, output and control, Xmodem and ASCII down/ uploads, full relocatability... and all that in 4K of machine-code. I'm posting it mainly for historical and study interest, perhaps someone can figure out why it won't work with emulators.

Download Table

Program	Type	Load Name	Year	Memory	Hi-Res	Docs	Other Info
3-D Fractals	Fractals	3DFRAC.P	1986?	16	WRX	Reference given	by G. C. Harder
Graphics Archiver	Graphics	ARCHIVE.P	1986	16	WRX	Self- documenting	Store/ retrieve WRX16 images
Bi-Plot	Graphics	BIPLOT.P	1987	16	WRX	Self- documenting	Real ZX81 only
Blackjack	Card game	BLACKJAC.P	1986	16	WRX	N/A	N/A
Block Buster	Puzzle game	BLOCK1.P	1986	16	WRX	Self- documenting	Good on ZX emulator
Calendar	Application	CALENDAR.P	1987	16	WRX	To Follow	1987 sample
CE Amplifier	Electronics	CE.P	1983	16	STD	maybe one day...	Transistor amplifier design
Dungeon of Ymir	Advent. game	YMIR.P	1985	16	WRX	To Follow	Design your own Dungeons
Fourier Analysis	Maths App.	FOURIER.P	1982, 87	32	WRX	To follow if found	sample data included
Hi-res Font Kit	Fonts	various	1986-7	16	WRX	Self- documenting	incl. Prop. font demo
F-Scapes	Math diversion	FSCAPES.P	1988	48	WRX	Text Format Write Format	Illustrations incl. in ZIP file
Hi-res Chess	Psion chess	HRCHESS.P	1985?	16	WRX	N/A	legal only if you own original
Invaders	Arcade game	HRINVADR.P	1987	16	WRX	N/A	Merry Christmas!
Julia Sets	Fractal	JUL-FFP.P	1987	16	WRX	Self- documenting	N/A
L-Systems	Fractal	L-SYSTMS.P	1987	16	WRX	Reference given	by G. C. Harder
Macro-Life	Simulation	MACRO-16.P MACRO-32.P	1986	16 32	WRX	Self- documenting	by G. C. Harder
Mandelbrot set	Fractal	MAND-FFP.P MAND4-FP.P	1987	16 32	WRX	Self- documenting	includes quadric version
NIM-2K	Strategy game	NIM-2K.P	1984?	2	STD	Self- documenting	POKE 16389,72 on 16K machines
SRAM HR Ext. BASIC	Program Language	various	1987	16	WRX	To Follow	with G. C. Harder
Snorth Games	Games Pak	SNORTH.P	1983	16	STD	May follow later	incl. NFLX Football, Miner's Revenge, Super Slide, Storm Lander 3
Spirograph	Simulator	SPIRO.P	1987	16	WRX	Self- documenting	by G. C. Harder
VDAQ1-HR	Data acquisition	VDAQ1-HR.P	1985	16	QHR	lost	N/A
Voyage of Peril	Advent. game	VOYAGE.P	1987?	32	WRX	N/A	by G.C. Harder
Wa-Tor	Simulator	WATOR.P	1985	16	QHR	Can't find it	N/A
ZX-Paint	Graphics	ZX-PAINT.P	1987	16	WRX	N/A	Oh, wow! by G. C. Harder
ZX*TERM*80	Xmodem Terminal	ZXT80-25.P	1987	16 up, MOD	WRX	May follow later if worth retyping	see description

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All content ©1999 Fred Nachbaur.

This page was last updated on February 14th, 1999.

If you have any questions or comments on this site to pass onto Fred, you can contact him below.

Fred also runs his own excellent website which is well worth a visit at:

http://dogstar.beyondtheweb.com or http://www3.bc.sympatico.ca/dogstar

Thank You.

 

e-mail: fred_nachbaur@bc.sympatico.ca

You are visitor number: since 21st January, 1999.

 

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