--- title: Sinclair ZX 81 categories: - Computers types: - Home Computer origins: - United Kingdom years: - '1981' cpus: - Zilog Z80A params: name: ZX 81 company: /companies/sinclair company_name: Sinclair specs: - label: NAME value: ZX 81 - label: MANUFACTURER value: Sinclair - label: TYPE value: Home Computer - label: ORIGIN value: United Kingdom - label: YEAR value: march 1981 - label: BUILT IN LANGUAGE value: Sinclair Basic - label: KEYBOARD value: Touch-sensitive keyboard, 40 keys - label: CPU value: Zilog Z80A - label: SPEED value: 3.5 MHz - label: RAM value: 1 KB (901 bytes available, up to 64 KB) - label: ROM value: 8 KB - label: TEXT MODES value: 32 x 24 (but 2 lines are reserved for system messages and commands) - label: GRAPHIC MODES value: 64 x 44 - label: COLORS value: Black and white - label: SOUND value: None - label: SIZE / WEIGHT value: 167 x 175 x 40 mm / 350gr - label: I/O PORTS value: Z80 Bus, tape, video - label: POWER SUPPLY value: 9V DC , 600 mA (centre polarity = +ve) - label: PRICE value: 'Kit :£50 (UK, june 1981) / Ready-built : £70 (UK, june 1981)' tabs: - photos - adverts - hardware - software - emulators - links - docs photos: - title: LEFT SIDE subtitle: '' text: |- From left to right :\ \- UHF TV output,\ \- MIC & EAR (Tape interface),\ \- Power in (9v DC). image: null - title: FRONT subtitle: '' text: '' image: null - title: ZX-81 subtitle: '' text: '' image: null - title: RIGHT SIDE subtitle: '' text: '' image: null - title: REAR subtitle: '' text: The only thing here is the expansion port, which can be used for many things... image: null - title: TOP subtitle: '' text: '' image: null - title: INSIDE ZX-81 subtitle: '' text: |- **(1)** Z-80 microprocessor.\ **(2)** Peripherals and memory expansions connector.\ **(3)** RAM memory chips. One or two chips can be used.\ **(4)** 8 Kb. ROM circuit holding Basic interpreter, Input/Output routines and character generator.\ **(5)** Keyboard connectors.\ **(6)** Three jack connectors for the external power supply and tape recorder.\ **(7)** Specialized circuit named ULA in charge of the whole computer's logical management.\ **(8)** TV aerial RF modulator.\ **(9)** Keyboard. Each key can perform up to six different functions. image: null - title: '"COFFRET INITIATEUR"' subtitle: '' text: This "inititateur" box included a ZX-81 + an ABS chicklet keyboard + a BASIC book + 2 tapes with 10 games. It cost 100 Euros in 1984. image: null - title: BOX subtitle: '' text: '' image: null - title: 'BOX #2' subtitle: '' text: '' image: null - title: THE DEF 3000 subtitle: '' text: This computer was launched in 1983. It was compatible with the ZX 81 and had the same features (except the 2KB RAM). It had very limited success. The photo shows the DEF with the 'color pack' extension (color + enhanced graphic mode) image: null - title: THE LAMBDA 8300 subtitle: '' text: The Lambda 8300 is another ZX81 clone. image: null - title: ARTIST IMPRESSION subtitle: '' text: |- Sculpture made by italian ArteStudio53 using a ZX-81... From [ArteStudio53](http://www.artestudio53.it/arte/) **(Italy)** image: null adverts: - title: 'ADVERT #1' subtitle: '' text: Picture courtesy of [Steve Browning, www.sbrowning.com/vintage](http://www.sbrowning.com/vintage). image: null - title: 'ADVERT #2' subtitle: '' text: Picture courtesy of [Steve Browning, www.sbrowning.com/vintage](http://www.sbrowning.com/vintage). image: null - title: 'ADVERT #3' subtitle: '' text: Picture courtesy of [Steve Browning, www.sbrowning.com/vintage](http://www.sbrowning.com/vintage). image: null - title: US ADVERT (APRIL 1982) subtitle: '' text: '' image: null - title: 'ADVERT #6 (1982)' subtitle: '' text: |- The new sale price is $99.95 instead of 149.95 Advert said: The ZX81 represents the latest technology in microelectronics. More than 10,000 are sold every week. In fact, the ZX81 is the best selling personal computer in the world. image: null - title: KIT VERSION (1982) subtitle: '' text: '' image: null - title: MEMOTECH LEAFLET subtitle: '' text: '' image: null - title: GERMAN ADVERT subtitle: '' text: |- Einstein's face probably means: Buy a ZX-81 and you will become a new genius... Karl_Heinz - www.sharpmz.org image: null - title: SPANISH ADVERT subtitle: '' text: '' image: null - title: FRENCH ADVERT (1981) subtitle: '' text: '' image: null - title: FRENCH ADVERT (1981) subtitle: '' text: '"It has not finished to surprise you"' image: null - title: FRENCH ADVERT (FEBRUARY 1982) subtitle: '' text: '' image: null - title: FRENCH ADVERT (APRIL1982) subtitle: '' text: '"The Sinclair Phenomenon"' image: null - title: FRENCH AD (DEC. 1982) subtitle: '' text: '"Your personnal computer for 670 F"' image: null - title: FRENCH ADVERT (SEPT. 83) subtitle: '' text: '"The initiator"' image: null - title: FRENCH AD (MAY 1984) subtitle: '' text: A selection for the Initiator... at Sinclair price image: null - title: FRENCH ADVERT (JULY 1984) subtitle: '' text: '' image: null - title: FRENCH AD (JULY 1984) subtitle: '' text: '' image: null - title: 'PROMOTIONAL PICTURE #1' subtitle: '' text: '"Learn computing today to be ready for tomorrow"' image: null - title: 'PROMOTIONAL PICTURE #2' subtitle: '' text: '"The ZX-81 will soon become a precious work tool"' image: null hardware: - title: SOUND CARD subtitle: brand unknown text: '' image: null - title: VOCAL SYNTHESIZER subtitle: '' text: '' image: null - title: EPROM STORAGE subtitle: '' text: This little black box contains a 2732 EPROM on which you can save & read your data. Maximum amount is 4 KB. Programs stored in the EPROM can then be automaticaly loaded at startup. image: null - title: EPROM BURNER subtitle: brand unknown text: '' image: null - title: '"NO NAME" JOYSTICKS' subtitle: '' text: '' image: null - title: CHICKLET KEYBOARD subtitle: '' text: |- An essential option if one used the ZX81 more than 5 minutes per day. Could be stuck on top of the original keyboard in seconds. image: null - title: DK'TRONICS KEYBOARD subtitle: '' text: The Sinclair ZX-81 may be the most popular computer, but that doesn't mean people like its keyboard. Numerous add-on keyboards and enclosures were manufactured for the ZX-81. This one, from DK'tronics, includes a full-size keyboard with numeric keypad, and an enclosure large enough to fit the Sinclair board and other Sinclair peripherals. Sadly, its price (£45) was almost as much as the ZX-81 computer one. image: null - title: MEMOTECH KEYBOARD subtitle: '' text: Before manufacturing computers (MTX Series) Memotech sold various add-ons for Sinclair computers. image: null - title: 64 KB subtitle: from Suntroncis text: Suntronics T/S 1000 & ZX81 64K Memory Pack (Male Socket on Back, Female Socket on Front). image: /media/museum/hardware/timex_1000-suntronics-64k_1.jpg - title: TIMEX SINCLAIR 1016 subtitle: 16k RAM extension text: '' image: /media/museum/hardware/timex_sinclair-1000_16kram-1016.jpg - title: INDESCOMP 16K RAM EXPANSION subtitle: '' text: |- 16K RAM expansion module made by a spanish company Thanks to **www.zonadepruebas.com** image: null - title: 16 KB MEMORY EXPANSION subtitle: brand unknown text: '' image: null - title: MEMOPAK MODULES subtitle: '' text: |- Advert said: **MEMOPAK 64K RAM** The 64K RAM extends the memory of ZX-81 to a full 64 KB. The unit is user transparent and accepts such BASIC command as DIM A (9000). It does not inhibit the use of the printer or other add-on units. No additional power supply is required. **MEMOPAK 32K RAM** The 32K RAM offers your Sinclair a full 32K of directly addressable RAM. Like the 64K Memopak it is neither switched nor paged and enables you to execute sophisticated programs and store large data bases. It is also fully compatible with Sinclair's or Memotech's 16K RAM to give you a full 48K of RAM **MEMOPAK 16K RAM** The Memopak 16K RAM provides an economical way to increase the capabilities of your Sinclair. And at the same time, it enables you to continue to add on other features with its "piggy back" connectors. It is compatible with the Sinclair 16K or a second Memopak 16K or Memopak 32K to give you 32K or 48K of RAM respectively. **MEMOPAK High Resolution Graphics** The Memopak HRG contains a 2K EPROM monitor and is fully programmable for high resolution graphics. The HRG provides for up to 192 x 248 pixels resolution. **MEMOPAK Printer Interface** The Memotech Centronics parallel or RS232 printer interface packs enable your Sinclair to use a wide range of compatible printers. The resident software in the units gives the ASCII set of characters. Both Memopak printer interfaces provide lower case character capabilities. The RS232 interface is also compatible with modems. Memopak 64K Memory map:\ **0...8K:** Sinclair ROM\ **8...16K:** This section of memory switches in or out in 4 KB blocks to leave space for memory mapping, holds its content during cassette loads, allows comunication between programs and can be used to run assembly language routines.\ **16...32K:** This area can be used for BASIC programs and assembly language routines.\ **32...64K:** 32 KB of RAM memory for BASIC variables and large arrays. image: null - title: MEMOPAK 32 subtitle: '' text: '' image: null - title: PANDA 16K subtitle: '' text: One of the numerous second-source 16 KB memory expansion modules image: null - title: 8 INPUTS/OUTPUTS CARD subtitle: brand unknown text: '' image: null - title: 8 INPUTS CARD subtitle: brand unknown text: '' image: null - title: MODEM CARD subtitle: by Timex text: This is a modem card developed by Timex around 1982, originally for the Timex-Sinclair 1000 system. image: null - title: ZX THERMAL PRINTER subtitle: '' text: |- This is a small thermal printer (of very poor quality !). It can print all graphical characters of the ZX-81 and can print 9 lines of text per inch. It was possible to do a hard copy of the screen thanks to the "Copy" command. This tiny thermic printer can also be used with the ZX-Spectrum. image: null - title: ZX PRINTER'S BOX subtitle: '' text: '' image: null screenshots: - title: SURVIVOR subtitle: '' text: '' image: null - title: CRAZY KONG subtitle: '' text: '' image: null - title: NIGHT DRIVER subtitle: '' text: '' image: null - title: OLYMPIADE subtitle: '' text: '' image: null - title: PAC MAN subtitle: '' text: '' image: null - title: RABBITS subtitle: '' text: '' image: null - title: REDANTS subtitle: '' text: '' image: null - title: RISEHIVE subtitle: '' text: '' image: null - title: SHORT CIRCUIT subtitle: '' text: '' image: null - title: SNAKE subtitle: '' text: '' image: null - title: STARTREK subtitle: '' text: '' image: null - title: STEINSCH subtitle: '' text: '' image: null - title: SULTAN subtitle: '' text: '' image: null - title: COMPUTACALC subtitle: '' text: A speadsheet made in England by Silicon Tricks and written in BASIC language... image: null emulators: - title: EightyOne url: http://www.chuntey.com/eightyone/ platform: Windows text: Excellent emulator emulating nearly all ZX computers (80, 81, Spectrums, Timex, etc.). As well as emulating the machines themselves, numerous addon cards are supported, including hi-res graphics, custom character sets, sound and colour cards. - title: VB81 url: http://freestuff.grok.co.uk/vb81/ platform: Windows text: Sinclair ZX81 Emulator (with Visual Basic sources). Excellent emulator - title: X-Tender url: http://www.delhez.demon.nl/ platform: Windows text: The best ZX emulator for PC compatibles - title: ZX 81 Homepage url: http://www.maxon.de/homes/r_kurz/ platform: Windows text: '' - title: ZX81 url: http://www.w-4.de/~kurz/ platform: Apple text: '' - title: XZ81 url: http://www.zx81.nl/ platform: Unix / Linux text: And other ZX-81 emulators there... - title: ZX-81 Emulator 2.1 url: http://www.hh.schule.de/hhs/mjaap/ftp/zx81_v21.zip platform: Atari text: '' - title: Java ZX81 Emulator url: http://home.clara.net/rsergeant/ platform: Other platform text: Java emulator - title: Timex/Sinclair 1000 Emulator (Java) url: http://www.vavasour.ca/jeff/trs80.html#ts1000 platform: Other platform text: With this JAVA emulator, you'll be able to run a Timex/Sinclair 1000 in your browser window - title: zx81emu url: http://www.tlienhard.com/ap800.shtml platform: Other platform text: ZX-81 Emulator for the SonyEricsson P800 Smart Phone - title: MESS url: http://www.mess.org platform: Multiplatform text: MESS emulates the ZX-81, Lambda 8300, Power 3000 and other clones ! links: - title: Achromic's ZX81 Site url: http://zx81.achromic.co.uk/ text: A small, ZX81 fan site. With games and links to some emulators - title: DOCUMENTATION url: http://www.8bit.ht.st/ text: The Lil Old Sinclair Computer Technical Information Repository - title: DOCUMENTATION url: http://web.ukonline.co.uk/sinclair.zx81/ text: ZX-81 on-line manual. Great work ! - title: Jame's Sinclair ZX-81 Page url: http://james.istop.com/zx81/ text: Some technical infos and links - title: Planet Sinclair url: http://www.nvg.ntnu.no/sinclair/computers/zx81/zx81.htm text: Planet Sinclair has very interesting information on the ZX-81 - title: Sinclair ZX Hardware Website url: http://www.xs4all.nl/~echorod/zx/index.htm text: Features designs to build your own Sinclair computer - title: The ZX81 Hardware and Software Collection url: http://zx81.atspace.com/ text: Online museum for ZX81 hardware, software and literature - title: TS1000.US url: http://www.ts1000.us/ text: Documentation, software, hardware tips and more - title: Zebra Systems, Inc. url: http://www.zebrasystems.com/zebrasystems/zx81/index.html text: Website where you can buy Timex/Sinclair products including ZX-81 kits ! - title: ZX81 Collection url: http://www.zx81stuff.org.uk/ text: Online collection of ZX81 tapes, books and hardware - title: ZX-81 forum url: http://zx81.tlienhard.com/ text: A new ZX-81 forum. cool. - title: ZX81 Home Page url: http://www.honneamise.u-net.com/zx81/ text: FAQ and ZX81 Charts. - title: ZX-81 The Archive url: http://www.imarshall.karoo.net/zx81/zx81technical.htm text: Lot of info here - title: ZX-81 webring url: http://www.zx81.de/webring/index.htm text: Very useful to explore other ZX-81 related sites - title: ZX-Team Homepage url: http://www.zx81.de/ text: Quite a reference for the ZX-80, ZX-81, TS1000-1500, PC8300, Lambda and Jupiter Ace ! - title: ZX-TEAM-homepage & ZX-81 Web-Ring url: http://www.zx81.de/ text: Logically useful - title: Web Wiz CAPTCHA url: http://www.webwizcaptcha.com text: Sinclair computers docs: - title: SINCLAIR ZX-81 BASIC PROGRAMMING url: ftp://ftp.worldofspectrum.org/pub/sinclair/books/ZX81BASICProgramming.pdf cover: /media/museum/docs/couvs/sinclair_zx81_basic-programming.jpg text: |- [**SINCLAIR ZX-81 BASIC PROGRAMMING**](ftp://ftp.worldofspectrum.org/pub/sinclair/books/ZX81BASICProgramming.pdf)written by Sinclair Research Limited / Steven Vickers  compiled/archived by Robin Stuart\  type of document : PDF\  size : 5,2 MB\  source : [www.worldofspectrum.org](http://www.worldofspectrum.org/) **... READ THE ONLINE VERSION BY CLICKING BELOW :** - title: TIMEX SINCLAIR 1000 - USER MANUAL url: http://www.ts1000.us/usermanuals.htm cover: /media/museum/docs/couvs/timex-sinclair_1000_user-manual.jpg text: |- [**TIMEX SINCLAIR 1000 - USER MANUAL**](http://www.ts1000.us/usermanuals.htm)written by Timex / Sinclair / Steven Vickers  compiled/archived by Bill Hicks\  type of document : PDF\  size : 3.5 MB\  source : [www.ts1000.us](http://www.ts1000.us/) **... READ THE ONLINE VERSION BY CLICKING BELOW :** - title: THE COMPLETE TIMEX TS1000 & SINCLAIR ZX81 ROM DISASSEMBLY url: null cover: /media/museum/docs/couvs/sinclair_zx81_rom-disasembly.jpg text: |- **THE COMPLETE TIMEX TS1000 & SINCLAIR ZX81 ROM DISASSEMBLY**\ written by Dr. Ian Logan & Dr. Frank O'Hara  compiled/archived by Bill Hicks\  type of document : PDF\  size : 5 MB\  source : [www.ts1000.us](http://www.ts1000.us/) **... READ THE ONLINE VERSION BY CLICKING BELOW :** - title: TIMEX SINCLAIR 2020 COMPUTER PROGRAM RECORDER url: null cover: /media/museum/docs/couvs/ts2020_tape-recorder_manual.jpg text: |- **TIMEX SINCLAIR 2020 COMPUTER PROGRAM RECORDER**\ written by Timex Computer Corporation  compiled/archived by Bill Hicks / www.ts1000.us\  type of document : Online reader **... READ THE ONLINE VERSION BY CLICKING BELOW :** comments: - author: Ean Bowman (Earth) date: Tuesday 16th January 2007 text: |- This was my very first personal computer. I still remember when my father brought this home, I was about three!!! Most people don't seem to keep powerful memories this early in life but I guess I do. This thing was truly archaic but sleek and tiny at the same time. It used cassette tapes like many systems of it's day. It hooked up to the black and white Candle television, the first TV my family ever had. Wrath of Khan is another first memory that stuck pretty vivdly with the bugs... the bugs! Anyway, I digress... I remember my father making some kind of alternate connection for the video. Only a year or two after buying this system my father found something better for his job, which required better graphing capabilities and printing. He eventually bought a COCO 2, the Disk Drive and DMP-100 dot matrix printer. The Sinclair became a toy for us, although I was fascinated by the colours of the new computer and quickly ditched this little thing. The most I ever did on it was create simple text-based BASIC programs once I was a little older. - author: Numanoid (Norway) date: Wednesday 8th September 2021 text: What I think has been lost in hindsight, is that the ZX81 at the time was a powerful calculator at a very friendly price. To think of ZX81 in relation to games I think is missing the point. At the price 1K was a lot compared to contemporary calculators, and a user was not locked to a tiny calculator display, but could draw full graphs on a TV screen - author: Timothy Heider (Portland Oregon USA) date: Monday 1st August 2016 text: I bought this mail order as a kit and built it as a teenager in 1983. You had to solder the parts onto the board. Seeing it work after the painstaking assembly process was pure joy. I will never forgot that. I learned Z80 assembly on this which was like magic after doing a lot of 6502 on the Apple II. It also had a nice BASIC interpreter and the graphics mode was fun. - author: Régis Schmidt (France) date: Monday 1st August 2016 text: It was my first home computer, bought in 1982. I bougth a kit version. Not really easy to use, especially for saving programs on mini-K7 devices. - author: David Tattersall (France) date: Thursday 7th April 2016 text: At the time I was going to build my own computer, but it would have cost more in bits than the ZX81! I did a lot of programming on it including using assembler language. I added 16K memory and I/O port for controlling external devices. I went on to the BBC B. - author: GIl (Canada) date: Monday 28th September 2015 text: |- That was the first and only one at our secondary school in France in the 80s. We (2 of us) could program basic games and a calculator of distance Earth/Sun on that machine!\ The tape recorder was a life saver. I guess that was the machine that gave me the thirst to learn more about PCs.\ That was a great machine. - author: David (Scotland) date: Friday 19th December 2014 text: We bought one of these in kit form, where we had to build it ourself. - author: Nathan (Australia) date: Friday 24th January 2014 text: My first introduction to computers was this little machine when I was about 5 years old. I loved being able to type-in all the BASIC game programs on the membrane keyboard, until I eventually wore the keyboard out. Also played some great little 1K games on cassette, although the load errors were fairly common! Eventually we got a 16K expansion cartridge, but sure enough, between the cartridge wobble and the difficulty of getting a good load and save from the cassette mean that lots of typing was often lost! - author: Chuck (Vermont USA) date: Thursday 6th September 2012 text: |- The ZX 81 was the first computer that I ever actually owned. I bought it with money received as gifts upon graduation. I even had enough to by the 16k RAM expansion. I was really quite familiar with computers at the time as I had studied them extensively in a high school vocational program (although we used DEC PDP-8''s in that program.\ I wrote extensive programs for the ZX 81 and of course experienced the ''memory module shift'' that crashed the computer losing everything not previously saved. It taught me to save often! - author: Andy (England) date: Sunday 1st July 2012 text: I bought a ZX81 in 1981 and was astonished by the feeling of power that being able to programme in BASIC gave me. Sure it was slow with almost non-existent graphics, but it gave me the urge to learn more. I wrote several very simple games and utilities on it before moving up to the BBC-B, and what a machine that was! Great memories. - author: lodger (Germany) date: Saturday 20th August 2011 text: |- In 1985, we had a VIC-20 "for the whole family" at home with scheduled acces times, when a neighbour of ours bought himself a very expensive PC system. Since he knew I was interested in computers he gave me his old ZX81 along with a book that contained 100 1K game listings (My own computer! That day, I was the luckiest kid in town). Today, I have a functional ZX81 and 32K Mempack setup, along with the usual dictaphone and b/w screen that I showed on a retro expo a few years ago. There were to 18-year-olds, to who I showed the machine and one of the 1K games I prepared for the expo. They enjoyed playing (it was a simple racing game). When I told them the specs of the ZX81 (without the mempack) they couldn''t believe it. They were very impressed by the fact that even a very simple machine can be so much fun to use. The ZX81 is one true 8 bit legend. - author: Mark Cardy date: Monday 25th April 2011 text: The ZX81 was my first computer, Christmas 1982. I was realy hooked. But it was a bit slow, bad graphics, no sound,etc. But I loved it, and belive it or not, but our school only had one computer (i think it was something like a ZEON1 ?). So using my ZX81, I did, and passed City$Guilds Computer Programing Exam. i wish i had of picked the ZX Spectrum, - author: Shadow (USA) date: Friday 8th April 2011 text: |- I got one of these new and it is still part of my collection (along with it''s aftermarket keyboard with REAL keys), I never had a dedicated tape deck for it, but I was one of the few kids on my block with a printer for it. Thermal, I love thermal printers, like going to the store and getting a receipt :-) My parents used to do the taxes and the budget on it, all I ever did was play games. - author: Kevin (Scotland) date: Wednesday 19th January 2011 text: Got my ZX81 as a hand-me-down in the family when my cousins upgraded to a Spectrum....will always remember the anticipation of watching the black and white stripes flashing across the screen during loading - hoping that you would get a game at the end of it.....and got either a whiteout or a screen full of dodgy glitchart because you got the volume setting wrong. Don''t get me started on the rampack - several times I was just about to beat my highscore on a game when it disconnected itself and I lost the lot! - author: John (Canada) date: Monday 4th October 2010 text: This was also my first computer. Had lots of fun programming this thing and the first time I had programmed in machine code. Got fried during an electrical storm but it was fun while it lasted. - author: Chris (Greece) date: Tuesday 31st August 2010 text: |- My first computer too!!\ then i got zx spectrum\ then atari stfm\ and final, it comes the PC :( - author: PENFOLD (Whittier CA USA Terra Sol System) date: Monday 30th August 2010 text: |- I had this one as my first computer. No On/OFF switch, you just unplugged it.\ I learned BASIC from the ZX-81 which almost ruined me. When I took BASIC in college it was right in the middle of the GOTO Considered Harmful era as well as the ZX-81 manual taught me Spaghetti Code!\ A friend killed my ZX-81 by unplugging the 16K expansion module while the computer was still on.\ I took advantage of a trade-in offer when I bought my Radio Shack Model 100 - author: Kenn (Denmark) date: Tuesday 13rd July 2010 text: My first computer!!!, and i have i still. After that i got the Spectrum, uhhh i miss the days with them, I was younger, and life simpler.... - author: Scott (Upland, CA, USA) date: Tuesday 26th August 2008 text: My very first computer. I still have the popular mechanics ad from when I filled out the order to receive the kit in the mail. I built it in one evening and haven''t stopped building PC''s since!! Later on I added a full keyboard and an in-line VU meter to get a balanced load from my cassette deck. I also created an analog to digital adapter that bypassed the modulator so I could get crystal clear resolution on a green-screen magnavox monitor. Boy I had fun. I still have the original shell and save it just for memories sake. - author: Anadin96 date: Monday 11th August 2008 text: |- This was the first computer I ever owned. The very best thing about it was the user manual, which explained absolutely everything you could possibly need to know, from a full B.A.S.I.C. tutorual right down to all the internal configuration paramaters, and even had an intro to machine code programming. I've been a professional programmer ever since. Thanks Sir Clive - author: David (Dallas, TX) date: Sunday 30th December 2007 text: The year 1981. $149 brings me my first computer that is mine. I had taking a programing school in high school and I wanted to do that for a profression, but I never had my own computer. I was 17, and my mother was saying...you will get sick of the damn things when you get into college...The get sick of them never happened. I just got deeper into them. With this one I put a external keyboard on it. I added first 16k and then 32k extra memory. I wrote missile command in basic. That impressed a software company puting out games for this computer. But they wanted games in machine langauge. And educational games at that. So off I went in that direction. I even tried to add high res graphics to the computer. That is where things started to break down. The graphics module would not work. It would show the higher res screen for a split second then it was gone. I called them. Well, a bigger power supply was what I needed. So off I went to get one fo those. I got one...but I had to wire it up. That is where things went bad. I read the diagram 3 times. I wired it up. I plugged it in...bam...crack pop and smoke...the component where the 9 volt dc comes into the computer and is converted to 5 volts dc was fried. Like burned up. I had crossed things up and shot 110 AC into that component. I only did that once. I never tried to wire up another power supply for one of these. I swapped mine for a TS1000 which was basically the same machine. The machine was funny because it would crash about once a day because it got too hot. But it was fun to learn z80 assembly on. It is strange to look back and realize who much trouble I put up with just to do some programming. But it was great fun. - author: Christian (Cumbria, UK) date: Thursday 5th April 2007 text: Funny,I never had a problem saving / loading from tape either on the zx81 or the spectrum!!!! The c2n on the C64 on the other hand...................... - author: Kealan (UK) date: Sunday 25th February 2007 text: Man I used to type for days on this thing out of the mags to get a crap fishing prog or something like that, it used to white out on me after days of copying, I couldnt save as the cassette never worked, but as a 10yr old this was the best thing since sliced bread, I cant wait til they rerelease it :) - author: paul williams (canada) date: Tuesday 20th February 2007 text: |- just found a sinclaire zx spectrum in the garbage along with a horizons softwre pack (cassette). No power supply, but thanks to this site I know what to look for. Will this machine work with a Radioshack cassette player (for the TRS-80)?\ Also if anyone knows of software to store the data from cassette to PC that would be great. - author: de sagazan (France) date: Sunday 26th March 2006 text: |- je posséde une cate d'extension 8 ES (8 binaries in /out) pour ZX 81, en emballage d'origine.\ Si cela vous interesse je puis vous en faire cadeau (for gift). - author: Veg (UK) date: Monday 13rd June 2005 text: |- An inventive Sinclair magazine (possibly Sinclair Programs) noticed that rapid switching between FAST and SLOW modes generated "musical tones" out of the white noise that was heard when you turned up the volume on the TV.\ The "note" could be altered by switching at different rates. They published a BASIC program that mapped keys to notes, thus creating a "sinclair organ". Amazingly, this didn't affect the Bontempi sales at the time. - author: Ivan Rozanoff (Rusia) date: Sunday 5th June 2005 text: |- Hello!(In Russia I will say "goîd morningnow" now, but I don\`t know what time is in New York).\ I have read a very intersting russian book about computers. The book was printed in 1989. And here is somting interesting about Sinklair ZX81.\ 1)On the back side Sinclair has a port for memory or other cartrijes. They (cartridjes) has got at the back side a port to. So you can take with this computer a lot of cartrijes.\ 2)On the motherboard there were 4 chips. One of them was a special controling chip, built on Ferranti fyrm. Nobody know, what Ferranti fyrm makes a lot of details for english war airplanes and helicopters (Harrier, for exsample).\ Sorry for a such long letter.\ Sertanly your,Ivan. - author: Chris Rutherford (UK) date: Thursday 24th March 2005 text: I paid £9 for my ZX81, and that was with a 16K ram pack! - author: Gary (UK) date: Wednesday 26th January 2005 text: The ZX81 had a memory expansion slot on the rear corner - it was basically an extension of the printed circuit board. Memory expansion modules plugged-in using ordinary PCB edge-connectors that were notoriously unreliable. Users often experienced unexpected reboots and lost everythng they had been typing in, thanks to small movements of the expansion unit relative to the base unit. - author: Tom (Switzerland) date: Monday 28th June 2004 text: Here is a Forum for all ZX81 friends with many useful informations. Have Fun! - author: george (canada) date: Sunday 21st September 2003 text: |- Dad built one of the kits, I remember 'typing' in programs on that bad 'keyboard' It was out first computer and i remember the excitement as if it were yesterday. - author: Al (Canada) date: Thursday 7th March 2002 text: |- My 1st computer. Built from a kit. Upgraded my RAM with 2 piggyback memory cards (had to duct tape them on or they kept falling off). I remember the hassle of searching for my programs by sound, on the cassette tape storage. My power supply box was larger than the computer! And I still have everything in working condition including a large stack of books and magazines about the ZX81. The first time I plugged it in after building the kit, I was in awe of the flashing cursor on my TV.\ Great memories! - author: Tom (USA) date: Sunday 3rd March 2002 text: I remember that adverts for this computer at the time proudly proclaimed that if you were to spill anything on the keyboard, you can just wipe it off! - author: Robert Kelly (World) date: Thursday 31st January 2002 text: |- The ZX81 was rumored to have handled (part or whole) a mission at NASA, the rumore also went on to state that the ZX81 had the fastest number crunching ability at the time, weather or not this is true is hard to tell. Also this machine was available with 4KB ram (kit form). This was also my first venture into real computers (aged 11), given to me by an uncle, 4Kb Kit form in 1981 related: - /museum/czerweny-cz-1000 - /museum/czerweny-cz-1000-plus - /museum/lambda-electronics-ltd-pc-8300 - /museum/microace - /museum/sinclair-zx-80 - /museum/timex-sinclair-1000 - /museum/tonel-pc oc_id: 263 source: url: https://web.archive.org/web/20230528020450/http://www.old-computers.com/museum/computer.asp?c=263 date: '2023-05-28' --- The Sinclair ZX 81 was the successor of the [ZX 80](/museum/sinclair-zx-80/), and can be regarded as an evolution of it. The ZX80 could not handle floating point numbers or cassette data files, but the ZX-81 could. The ZX-80 had 4k ROM : the ZX-81 had 8K ROM with 30 additional functions and some instructions to drive the printer. Thanks to a higher level of integrations (the total number of chips in the basic system was 4, against the ZX80's 21), the ZX-81 cost £30 less than the ZX-80. The plastic case was also different. Whereas the ZX-80 looked cheap in it lightweight white case, the ZX-81 was beautifully designed in its black ABS plastic case. The keyboard was still formed by an underprinted plastic, but this one was made of non-reflective material. Even with this slight improvement it was quite horrible to use, that's why a lot of additional keyboards appeared quickly on the market. Some of the keys sported up to 5 functions, right in the Sinclair tradition, accessible through the "GRAPHICS", "SHIFT" and "FUNCTION" keys. Here are the functions added over the ZX-80 : ASN, ACS, ATN COS, EXP, INKEY$, PI, SGN, SIN SQR, INT, LEN, LN, TAN, VAL, <=, >=, < >, COPY, DIM A$, FAST, FOR ... TO ... STEP, LLIST, LLIST n, LPRINT, PAUSE, PLOT, PRINT AT, PRINT TAB, SCROLL, SLOW, UNPLOT. Some are quite useful and make you wonder how it was possible to make anything on the ZX-80 !? However, one function disappeared: TL$ which was used to return a string minus its first character. The ZX-81 could be operated in two modes, SLOW and FAST. The FAST mode which was the only mode available on the ZX-80, only refreshed the display when the system had completed computing, resulting in a painful screen flicker! It was a useful mode when you had to do a lot of calculation without the need to see what's going on all the time on the screen. The SLOW mode, which was indeed quite slooooowwww, behaved like all other computers did, refreshing the screen all the time. The ZX81 contained only four main chips : the ROM, Z80A CPU, 1K RAM and the Ferranti custom-made chip! It is as simple as that. The machine was assembled by Timex Corporation in their Scottish plant. This computer was a very great success in Europe in the beginning of the 80's. It was very cheap and a lot of people who now are working on modern PCs or Macs, made their first move on a ZX 81 even though its performance was actually poor! A very great range of peripherals were developed for this computer, among them : 3.5" floppy disk units, keyboards, high resolution graphic cards, RS232 or Centronics interfaces, RAM expansions, etc... In fact, it was possible to make a pretty good computer from the ZX 81! The range of expansion options was quite extraordinary. For instance, Memotech created a whole range of modules which would piggy-back, one after another (and using velcro pads to secure to each other and the to the ZX81, as there was no mechanical locking on the edge connector). So, for instance, you could have additional memory (up to 128k!), high-resolution graphics, disc controllers, joystick controllers, serial ports, and so on. Popular add-ons also included replacement keyboards - one was a series of mechanical keys which stuck over the membrane keyboard, others involved re-housing the ZX81 inside a new, larger case with a "proper" keyboard. In fact, the options were - seemingly - endless. Sadly the power supply wasn't particularly stable, so "glitches" were common, resulting in a system reset and the loss of hours of painstaking coding! It was followed by the [ZX-Spectrum](/museum/sinclair-zx-spectrum/) and was also sold as the [Timex Sinclair 1000](/museum/timex-sinclair-1000/) in the USA. **Contributors:** Silas Denyer