This mini forum is intended to provide a simple means of discussion about the Sinclair  ZX 81 computer. If you want to share your own experience or memories, or add relevant information about this system: post a message!

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.

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

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.

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.

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.

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.

We bought one of these in kit form, where we had to build it ourself.

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!

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!

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.

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.

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,

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.

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!

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.

My first computer too!!
then i got zx spectrum
then atari stfm
and final, it comes the PC :(

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

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....

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.

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

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.

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......................

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 :)

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.

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).

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.

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.

I paid £9 for my ZX81, and that was with a 16K ram pack!

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.

Here is a Forum for all ZX81 friends with many useful informations. Have Fun!

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.

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!

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!

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