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On this Day in 1981: Launch of the Sinclair ZX81

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On this Day in 1981: Launch of the Sinclair ZX81

Posted by Lisa Miles on Mar 5, 2019 12:02 pm

Okay, own up.... Who had a Sinclair ZX81 and what was the first thing you programmed on it...?¬†ūüė鬆‚Ć®
Lisa Miles - Online Community Manager, Engineering Communities

Re: On this Day in 1981: Launch of the Sinclair ZX81

Posted by Julie Hudson on Mar 5, 2019 1:33 pm

Me! We used them in Computer Studies in school so I remember I did quite a bit of programming in Basic on it. First thing I remember programming on it was trying to create a random number generator - can't remember if I succeeded or not! I do remember destroying the keyboard quite quickly playing Daley Thompson's Decathlon...my dad quickly bought me a joystick after forking out for its repair.
Julie Hudson | Local Network Manager | The IET

Re: On this Day in 1981: Launch of the Sinclair ZX81

Posted by Kenneth McNaught on Mar 6, 2019 12:14 pm

I had one of the very first before they were on general release, purchased from the Timex factory shop in Dundee, where they were made. I still have it, along with the 16K RAM pack, but cannot remember what I programmed on it.
Ken McNaught

Re: On this Day in 1981: Launch of the Sinclair ZX81

Posted by Alasdair Anderson on Mar 6, 2019 2:07 pm

My brother worked for a time in a store which starting selling the ZX81 and brought one home to learn how to use it for demonstration purposes (though it might have been a ZX80). I had a go, having learned both Basic programming and Fortran at school (rather unusually for the seventies), but my attempts to program it were foiled by the rather meagre (1Kb) memory as I kept coming up against error messages about lack of memory. When I did finally get the program into memory, there was insufficient memory to run the damn thing.....
I don't remember what it was supposed to do, but possibly find prime numbers.
Julie,
Are you sure that it was the ZX81 you are thinking of and not the Sinclair Spectrum? The ZX81 had a near indestructible (and difficult to use) keyboard and is still the only coffee-proof computer I have ever come across.
Alasdair

Re: On this Day in 1981: Launch of the Sinclair ZX81

Posted by Lisa Miles on Mar 6, 2019 2:12 pm

Alasdair Anderson:

Are you sure that it was the ZX81 you are thinking of and not the Sinclair Spectrum? 

Ahhhh the Sinclair Spectrum....ūü§ó

We had one of those after we'd grown out of the ZX81 and then the Spectrum 2 as well which, if I remember rightly, came with an integrated tape deck to load the programs.¬†ūü§ď
Lisa Miles - Online Community Manager, Engineering Communities

Re: On this Day in 1981: Launch of the Sinclair ZX81

Posted by Roy Bowdler on Mar 6, 2019 3:39 pm

I was an adult by this time just buying my first property, so any spare resources after mortgage payments etc, went elsewhere. A video recorder was much more desirable to me than a ‚Äútoy‚ÄĚ computer and I eventually rented one by the mid-80s. From around 1985 PLCs came onto my radar at work gradually replacing the 1960s relay and electronic based controls that I had become familiar with. So I got involved with them, although not on a major scale, so ladder logic is probably the closest I ever got to coding/programming. I was a very early adopter of the Psion Series 3 and still have at least one tucked away at home somewhere. I learned spreadsheet basics and found the add on spellchecker package especially useful when we were still handwriting much of the time. ¬†A laptop came along within a couple of years and eventually a digital mobile telephone, but the original and a later reserve Psion still earned their keep until the late 90s. ¬†I first gained internet access in 1993 via my employer to support a part-time MSc I was doing, but it didn‚Äôt become really useful at home until broadband came to my street this century. I remember complaining in the early noughties that Watford Central Library had dropped the OAG Flight Guide, which you needed if you didn‚Äôt rely on a travel agent along with Hotel Gazetteers, guide books etc. ¬†Remember the dot-com bubble - its premise is coming true now.¬† ¬† ¬† ¬† ¬†¬†
 

Re: On this Day in 1981: Launch of the Sinclair ZX81

Posted by Moshe W on Mar 7, 2019 3:50 am


I never owned ZX81 but I purchased my first PC The ZX Spectrum ( "ZX81 Colour") an 8-bit personal home computer that was released in the United Kingdom in 1982 by Sinclair .
While originally called the "ZX81 Colour" and "ZX82" during development, the system was renamed the ZX Spectrum in order to promote its colour display, which was a significant upgrade from its black and white predecessor, the ZX81. It proved immensely popular in various incarnations over the years and remains the most successful British computer ever made.
I used it to interface to a water irrigation controller that I constructed with a friend. But mostly we used it for games.    



ZXSpectrum48k.jpg
Moshe Waserman BEET, MCGI, CEng MBCS, FEDIPAdvPra, MIET.

Re: On this Day in 1981: Launch of the Sinclair ZX81

Posted by Howard Warren on Mar 18, 2019 1:08 pm

I owned a ZX81! I've actually still got it up in the loft. The basic machine came with a whole 1K of RAM - and there was the RAM pack that took it up to a mind-boggling 16K. I also had the thermal printer, which produced its output on what resembled a silver toilet roll. I seem to recall it needed a beefed-up power supply for the printer. I also invested in a Kempston keyboard - it stuck over the ZX81's touch pad and had "clicky" keys that seemed to work intermittently. I vaguely remember the first thing I programmed was a formula that plotted a sine wave. Anything more than a few lines of Basic required the 16K Ram Pack - and does anybody else recall that you had to keep the machine completely still while typing, otherwise the TV screen would flicker and you'd lose the lot and have to start again?

And let's hear it for the ZX81's contemporaries, like the Commodore PET, VIC 20, Oric 1, BBC Micro, ZX Spectrum etc. (Cue the background music from the Hovis advert...)

Re: On this Day in 1981: Launch of the Sinclair ZX81

Posted by Alasdair Anderson on Mar 18, 2019 1:47 pm

Howard Warren:
And let's hear it for the ZX81's contemporaries, like the Commodore PET, VIC 20, Oric 1, BBC Micro, ZX Spectrum etc. (Cue the background music from the Hovis advert...)

Now you're talking! I remember looking at the TRS-80 while at college (1977?) and a couple of friends got themselves early Acorn computers (Acorn System 1 and Acorn Atom respectively) but I stayed out of the computer revolution until I got a BBC micro. I also remember using either a Commodore Pet or an Apple II in the 80's at university, before we got to use IBM PCs for Pascal programming.
However the beauty of the ZX81 was its affordability, which brought computers into homes for the first time which probably fired up the enthusiasm to upgrade and sparked the market for the later computers mentioned.

Re: On this Day in 1981: Launch of the Sinclair ZX81

Posted by Bill Shepherd on Apr 30, 2019 4:54 pm

Yes, my rather perceptive Aunt purchased me a ZX81 as a 12-yr old. it spawned my career.

My Aunt was from the era that had programmed "for the government" in the 40s and 50s during the early days of computing. (whatever that meant) As a woman she was prevented from continuing to make computing her career. These days programming for the government in the very early days counjours up all sorts of exciting exploits but that may just be romantic nonsense. 
In any case, my Aunt purchased me a ZX81 mostly to give me an outlet for my interest in code and electronics. Although it clearly gave her a kick to think that computers could be purchased for the home and that her young nephew was excited and interested.

Re: On this Day in 1981: Launch of the Sinclair ZX81

Posted by Kevin Field on Apr 30, 2019 4:57 pm

I have got one of those. Built it myself as I was fascinated to see the micro electronic components inside. Still at school, much of the electronics I had exposure to still had thermionic vacuum tubes in them.  May have cleared it out of my mothers loft quite recently. It went with me to university, Big mistake as did not have much credibility with an 8 bit processor. 
 

Re: On this Day in 1981: Launch of the Sinclair ZX81

Posted by Rupert Brun on Apr 30, 2019 5:07 pm

The ZX81 was my first computer, before this I had only programmed a Texas Instruments calculator. The first thing I programmed was a simple slalom game but I later programmed it to play Othello reasonably well, using machine code to calculate the best move and Basic to draw the board on the screen. I remember the "floppy ram" 16KB RAM pack which plugged on the back in a very insecure way and was prone to falling off at a crucial moment. I also remember using a cassette deck to record and load software, and I had a printer which sparked through the aluminium coating on black paper to print. I later added a proper keyboard. All very elementary but it got me started and I gained a reaonable understanding of the Z80 processor. My next computer was an Amstrad PCW, which also had a Z80 and to which I also added a lot of extras including a mouse and rudimentary scanner.

Re: On this Day in 1981: Launch of the Sinclair ZX81

Posted by John Bregazzi on Apr 30, 2019 5:43 pm

I was Manufacturing Director at AB Electronics where we assembled them for Sinclair.  Usual story - product launched before all the bugs were cleared out, so no easy task.
Johnbreg

Re: On this Day in 1981: Launch of the Sinclair ZX81

Posted by Richard Farthing on Apr 30, 2019 5:55 pm

Oh yes, I soldered mine together from the kit - £50 as I recall. I think I got the resistor networks back to front, but it still worked, with its 1K of RAM. Still have it, and I think it might still work! I used it to calculate the coefficients of a chebyshev filter for an audio crossover - a real use!. Rather simplified as it kept running out of memory. Oh the pain...the pain

Re: On this Day in 1981: Launch of the Sinclair ZX81

Posted by RhysE on Apr 30, 2019 11:46 pm

I had a ZX Spectrum and used an audio cassette to store programmes. I did not even have a colour television to use as a monitor - had to use a small b/w tv. My first programme was a very basic assembler which I used to do simple animations - very simple!
Unfortunately I did a clearout some years ago and gave it to charity in its original box. I am sorry now.

I also had a Sinclair programmable calculator which allowed for a programme of 50 key clicks (one key click was one step in the programme).
Was very proud of myself when I programmed the calculator to do the factorial function - it just fitted in 50 steps! There was no way to store the programme for transmission to the calculator, so I had to write it down on paper and type it in if I wanted to run it. So only a geek like myself would bother writing a 50 step programme for this device!!
I still have this calculator.


 

Re: On this Day in 1981: Launch of the Sinclair ZX81

Posted by David Lee on May 1, 2019 8:10 am

I bought a ZX81 second hand when I was around 14 years old. I knew nothing about computers! I booted it up and after a short while, a default message appeared on the screen. It read
"Well press something then" I really did think it was alive!

Re: On this Day in 1981: Launch of the Sinclair ZX81

Posted by Gareth Jenkins on May 1, 2019 3:55 pm

First computer I ever programmed.
Anyone remember the books you could get of "games for your ZX81" - they were basically source code listings you had to copy (and debug if you'd mistyped).  I never had the 16k RAM pack so would try and fit games (always the better ones) that required the 16k RAM pack into my modest 1K RAM.  It was usually just about possible if you decided what to leave out, most games only required an extra 0.5k or so as if they were too long nobody would ever have the patience to type them in (especially with that finger bruising keyboard).  I learned a lot about programming from that.
I still have a ZX81 and a BBC Micro Model B (not my original ones, got them on eBay), they are proudly displayed on my office wall.

Re: On this Day in 1981: Launch of the Sinclair ZX81

Posted by G3NGD on May 1, 2019 4:41 pm

When the ZX81 was introduced, it was also made available in kit form. The components could be purchased from Sinclair.
Having purchased a kit, I built a Sinclair ZX81 computer and realized that it needed a printer and a 16K RAM Pack.
I found the Keyboard a little awkward to use and decided to build the complete package into a self-contained unit.
I also purchased a Keyboard Kit from Maplin and fitted it with the ZX81 Computer, Printer and RAM Pack into the unit.
One can find more details including the Keyboard Circuit Diagram on my Website: www.g3ngd.freevar.com/zx81.html
The first Programming I did was: Antennas & Feeders using ZX81; Resonant Frequency of a Tuned Circuit using ZX81;
Winding Single Layer Coils using ZX81; Radio Range calculations; Designing Meters (Multipliers and Shunts).
My software was published in a "Computing in Radio Special Supplement (ZX81)" in Practical Wireless Magazine - December 1983.


 

Re: On this Day in 1981: Launch of the Sinclair ZX81

Posted by Lisa Miles on May 1, 2019 4:58 pm

Gareth Jenkins:

Anyone remember the books you could get of "games for your ZX81" 

ūüėĮ Now you tell me!¬†

Never knew there was a book! 

Maybe my Dad didn't want me to have it otherwise I'd never go play outside...¬†ūü§£
Lisa Miles - Online Community Manager, Engineering Communities

Re: On this Day in 1981: Launch of the Sinclair ZX81

Posted by Howard Warren on May 2, 2019 10:01 am

I'm starting this post by going a little off-topic here but bear with me... G3NGD - now there's a great pseudonym! There's a separate topic out there about pseudonyms, and this one has a ring to it that shouts engineering and technology.

Stepping back into the discussion at hand, I was really into electronics construction when the ZX81 came out. As a 12 year old who voluntarily stayed back after school for electronics tuition and computer programming (which was quite progressive for a comprehensive in the Thatcher years!), and spending most of my spare time with a soldering iron in my hand building projects from my Dad's collection of Practical Electronics magazines, I suppose these days I'd be called a geek. Or words to that effect... Back then I was just a weirdo, but I really didn't care and I stuck with it. I only found out the ZX81 was available in kit form after I'd been using it for some time, and remember feeling a bit deflated that I hadn't built my own.

But the memories are flooding back! Remember fast mode? Useful to an extent, but I couldn't get away with it, the screen flickered every time you pressed a key. And for some reason, nearly 40 years on, I remember the command "poke 16510 0" - I used to use it every time I wrote a basic programme, it set memory location 16510 (corresponding to the first line number of the programme) to zero. And if you wanted to programme in machine code, because the 81 was set up for basic, you had to "hide" the code in a REM statement at the start of the programme, containing the same amount of characters as your machine code (thinking about it now, it was to all intents and purposes an early Trojan...). Then you'd have to type the code in letter by letter. I seem to think that the memory location of the first character of the REM statement was at 16514, so you had to use the command RAND USR 16514 to tell the machine where the code was. Told you I was a geek...

Cutting out 30-odd years... many years later I discovered Microsoft QBasic hiding away in a Windows 95 CD ROM and was instantly transported back to the 80's. It had so many similarities to ZX Basic you could pick it up in minutes. The geek was back! I wrote some cracking little personalised programmes with it to help my kids with their maths.

Re: On this Day in 1981: Launch of the Sinclair ZX81

Posted by Laurent Galea on May 2, 2019 7:39 pm

I worked for a start-up called Electrak and wrote a program to forecast various component quantities in given installations for manufacturing runs.
I had the thermal printer for output but unfortunately that faded with time so I no longer have a copy.

I had a black and white TV on my desk for a monitor, and when I was off one day, my boss 'borrowed it' to  watch at home!

It was a fantastic intro to programming which led to my running a small business using a Commodrore 64 with 2 disk drives attached.

Re: On this Day in 1981: Launch of the Sinclair ZX81

Posted by jak-g on May 3, 2019 11:14 am

I still have my ZX81 along with 16k ram and also a 16 I/O port which I used to read a punch tape, was able to edit the reading and produce a fresh tape.

Re: On this Day in 1981: Launch of the Sinclair ZX81

Posted by G3NGD on May 5, 2019 5:05 pm

Occasionally, I found loading and saving files to and from the ZX81 a problem, especially when interference was present. Don't let people use a Vacuum cleaner near the room at that time! The Printer paper was expensive and poor quality. Let us remember, the ZX81 was a good start for people to become interested in computing and the reason why it took-off.

After writing many programs for the ZX81 computer, I decided to purchase a 'BBC B' Computer as it had more memory, more functions and a good disc-drive.
I wrote a lot of software (written in BBC BASIC) to supplement textbooks and notes for students studying on City & Guilds and BTEC courses.
A great advantage of using computers in schools and colleges is the ability to give every student a different question. There is always a limitation on the number of questions given in the text book, occasionally the answers are wrong. Using computers, it is possible to give every student a different question and afterwards an immediate correct answer. In this way students cannot copy from one another, and also, provision is made for the ‚Äėhigh fliers‚Äô, and more time can be spent helping those much slower to learn.
I found that my students were so excited using my software that they wouldn't take their break and I couldn't leave them unattended in the classroom; (Not ideal for me!)
A list of my Education Software can be seen on my Website.
Later, I started using 'Z BASIC' and converted my software to run on all versions of Windows 95 to Windows XP inclusive. Here, the screen size is smaller and the graphics origin is inverted. Also, the VDU Commands are not available.
I still have my home built ZX81, Printer, keyboard and RAM-pack. I still have a few rolls of printer paper, but it may have dried up a little over the years.
 

Re: On this Day in 1981: Launch of the Sinclair ZX81

Posted by Spectras on Nov 21, 2019 7:33 pm

Lisa Miles:
Okay, own up.... Who had a Sinclair ZX81 and what was the first thing you programmed on it...?¬†ūüė鬆‚Ć®

Hello from Croatia !
I'm the one, too ! At the time, I think 1982, my father had some old car (yellow Renault 4) and after he had sold it, he bought me ZX81, 2x16k RAM and BI-PAK ZON X-81 sound generator from some guy in Zagreb. I was 12 then, a bit too young to keep it alive'n'kicking for a long time¬†ūüėä Anyway, my destiny has been sealed from that moment. Today I am a collector of the Sinclair computers, peripherals and software. It is really amazing what an industry it was !¬†

Re: On this Day in 1981: Launch of the Sinclair ZX81

Posted by AncientMariner on Dec 12, 2019 7:47 pm

I too built my ZX81 from a kit.  Bought the RAM pack and the thermal printer.
As for programming, I joined a ship in 1983 and the Second Officer had brought his ZX81 and a RAM pack along with him.  We spent a few interesting hours/days writing a program to calculate the Great Circle Distance and Initial Bearing between any two points in the world.  This was in part a navigational type calculation, but you would not normally go that distance as a pure great circle, my interest, as Radio Officer, was related to HF radio communication.  We had two problems, one the wobbly RAM pack and the other the unreliability of saving and then reloading the program using a cassette recorder. There was a third problem in that on a least one occasion the Steward had unplugged the ZX81 in order to Hoover the carpet.....  Luckily we were not developing anything to do with life support.  
I still have the ZX81 plus RAM pack and printer. I also have both PSUs, although the larger one has a terminal block to facilitate using it to power my pcb drill.

Clive
Clive S Carver GCGI IEng MIET MITP

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