
5 March 1981: The ZX81 home computer launches with 1kb memory - open-source-ux
https://en.wikipedia.org/wiki/ZX81
======
iam-TJ
My first computer. Ordered the day it was released after saving up 50% of the
£70 and my father added the other 50%.

Finished secondary school whilst waiting for it to be delivered, it arrived
the following week - the first week of June 1981.

I spent the intervening months teaching myself BASIC programming from the
total of 3 books on programming in the local library.

I remember the day it arrived well; I was busy cleaning house and didn't
realise the postman had left the parcel in the kitchen until I stopped for a
break a couple of hours later.

Had it unboxed and connected in a flash and I was still to be found lying on
the lounge carpet in front of the television programming it (in BASIC) at
midnight.

Started my agricultural apprenticeship the following week and continued
programming late into the nights, quickly moving to write pure Z80 assembly
language code.

Dropped the apprenticeship a year later, went self-employed, and been hacking
ever since.

I still miss those days of actually counting the clock cycles of different
instruction combinations to find the most efficient code via the look-up
tables in the back of Rodnay Zak's "Programming the Z80".

Oh, and we had to manually enter the hex codes of the instructions to write
those programs - before there was a decent assembler available.

I recall adding a full-size mechanical keyboard, a 16KB RAM-pack, and a weird
multi-port expansion dock that had add-on modules (like a light pen) built
into cassette tape cases and connected via a single-in-line pin connection.

I still have that original ZX81 along with a UHF<->VGA signal adapter. Time to
fetch it out of its shoe box and fire up the nostalgia.

~~~
duncan_bayne
The Zaks book! I remember thinking it was such a weighty tome when I was a
child, then being surprised to discover as an adult that it was just a regular
sized book.

------
david-given
The ZX81 was best described as a terrifying bundle of hacks flying in close
enough formation that from a distance it looks like a computer... a real
masterpiece of hardware design, in a disturbingly twisted sort of way.

Also, the official manuals had some of the best cover art ever seen on a
computer book, by science fiction artist John Harris:

[http://www.alisoneldred.com/imageJohnHarris-
Prints-2-2508.ht...](http://www.alisoneldred.com/imageJohnHarris-
Prints-2-2508.html)

[http://www.alisoneldred.com/imageJohnHarris-
Prints-2-2064.ht...](http://www.alisoneldred.com/imageJohnHarris-
Prints-2-2064.html)

[http://www.alisoneldred.com/imageJohnHarris-
Prints-3-1214.ht...](http://www.alisoneldred.com/imageJohnHarris-
Prints-3-1214.html)

------
pmontra
My first computer.

To give an idea of the state of computing back then, the manual states (I
checked now)

> to get '+' you must hold down the key SHIFT and while you are still doing
> that, press the key K.

Not something you find in user manuals now.

My English was so bad back them that I couldn't understand the full meaning of
the sentence and I couldn't go through the example. I asked my classmates at
school the day after. My mother was a touch typist but she didn't realize that
the tiny keyboard of the ZX81 could work like the one of a typewriter.
Computers were beyond geeky.

~~~
rdtsc
The reason I learned English was to read manuals and program my Soviet clone
of ZX80.

~~~
jesuslop
There should still be Berlin wall. Love to see genuinely good things
spreading.

~~~
jesuslop
I wrote it wrong, I wanted to say that I vaguely remembered that the
whenabouts of 1981 were wall's times, and referred to the computer design
spreading.

------
tomcam
My dad ordered it when it hit the States for, I think, $300. He was an English
teacher and suppressed gadget freak (we weren't rich). He returned it because
he couldn't see a practical use for it. I wasn't interested in computers. He
died two years later. I went on to become a successful programmer and very
successful businessdude. I deeply regret not being able to buy him every
single PC, Mac, iPhone, and iPad that came out those many years later.

------
hal9000xp
My first computer was ZX Spectrum (a successor of ZX81). By coincidence, a few
days ago, I've finished reading the book "It's behind you" about development
of R-Type, a top-notch arcade which pushed ZX Spectrum to its limits.

Here is a link to official free copy of this book:

[http://bizzley.imbahost.com/](http://bizzley.imbahost.com/)

About game:

[https://en.wikipedia.org/wiki/R-Type](https://en.wikipedia.org/wiki/R-Type)

Gameplay of R-Type on ZX Spectrum:

[https://www.youtube.com/watch?v=-6lvAXSGBpI&t=90s](https://www.youtube.com/watch?v=-6lvAXSGBpI&t=90s)

I'm _still_ playing ZX Spectrum games once in a while in the urge of
nostalgia.

~~~
stevekemp
> I'm still playing ZX Spectrum games once in a while in the urge of
> nostalgia.

Me too. Was playing Horace Goes Skiing earlier this week, but my all time
favourite game is "Chaos: The Battle of Wizards":

[https://en.wikipedia.org/wiki/Chaos:_The_Battle_of_Wizards](https://en.wikipedia.org/wiki/Chaos:_The_Battle_of_Wizards)

(This is available to play in your browser, online. Fun!)

Back in the day I used to hack games for infinite lives, and received a bunch
of swag from Your Sinclair, and Sinclair User for posting them.

I credit the 48k Spectrum with getting me into programming, first BASIC then
Z80 machine code. (Largely because the "bundle" we received had a dead tape-
deck, so for the first couple of weeks the only thing we _could_ do with it
was read the manual(s) and type in simple programs..)

~~~
digi_owl
I swear i ran into a clone of that game for either DOS or early Windows at
some point. Would love to find it again.

------
watmough
I really wanted a ZX-81, and my dad ordered one not long after they came out.
But typical for Sinclair, the delivery lead time was on the order of months!
Not even weeks or days, and my dad gave up and brought home an assembled Acorn
ATOM that one of the techs at the university has soldered up from a kit.

Great little machine, and introduced me to programming in ATOM Basic and 6502
assembly, leading to a career in computing that's still going 30+ years later.

Oddly enough, I just ordered parts from Mouser to build David Johnson Davies'
Tiny Lisp Computer 2, ... DJD being the author of ATOMIC Theory and Practice
and Practical Programs for the BBC Computer and ACORN ATOM.

~~~
glangdale
I had a similar story with the Spectrum; they had industrial action and wound
up not shipping. My dad cancelled and bought a Commodore 64. I think I dodged
a bullet there (although I'm sure the Spectrum would have been interesting).

~~~
watmough
Haha, I remember that. My maths teacher DM had a mate in the factory who
eventually got me a speccy out the factory door, but it was a longgg wait.
Spectrum was a fun machine. Basic was ok for very simple games. I never did
learn z80 assembler.

------
rcarmo
This was my first computer, and I remember it fondly.

Sadly, my parents dumped it (and my two ZX Spectrums), but I still have one of
the manuals squirreled away.

Edit: JS emulator, for that extra touch of nostalgia

[http://www.zx81stuff.org.uk/zx81/jtyone.html](http://www.zx81stuff.org.uk/zx81/jtyone.html)

~~~
dpkirchner
The first computer I used at home was either this or the Timex Sinclair 1000.
Membrane keyboards are the worst.

I did learn a lot about modern day programming, though. Everything I wrote was
really just copy/"pasted" from a book or magazine.

------
rwmj
I wonder if anyone has managed to connect a ZX81 to a modern display?
Apparently the design cuts corners, omitting the "back porch" part of the
signal, so modern TVs cannot determine the correct black level, and display
everything black.

(More here: [https://www.vintage-
radio.net/forum/showthread.php?t=73664](https://www.vintage-
radio.net/forum/showthread.php?t=73664))

~~~
jdietrich
Modern TVs are pretty poor at displaying analogue video. All sorts of retro
computers and consoles have quirky video output. Most retro enthusiasts use an
old CRT TV, typically a late-model Sony Trinitron. They're as cheap as chips
these days. If you're really keen, you can't do better than a Sony BVM
broadcast monitor.

~~~
lisper
How hard could it be to design a circuit that would reshape the video signal
into something reasonable? Or to feed the video signal into an analog input
and reprocess it in software?

~~~
LeoPanthera
The canonical solution to this problem is the Framemeister XRGB-mini, which
can convert pretty much anything into a 1080p HDMI signal.

[https://solarisjapan.com/products/xrgb-mini-framemeister-
com...](https://solarisjapan.com/products/xrgb-mini-framemeister-compact-up-
scaler-unit)

~~~
rwmj
Lovely kit but also £450 in the UK :-(

~~~
lisper
Yeah, I see no reason why such a thing should cost as much as a smart phone.
You should be able to do it with a Raspberry Pi Zero plus the right software.

~~~
rwmj
Apparently there are alternatives, including an open source one. This video
talks about them:
[https://www.youtube.com/watch?v=lHoOKLWIMKU](https://www.youtube.com/watch?v=lHoOKLWIMKU)

------
VSpike
Also my first computer. Definitely a gateway drug. I was lucky enough to have
a 16k RAM pack (held on with blutac). Later we had a series ZX Spectrums, the
Acorn Archimedes A440, then an Acorn RISC PC. After that, boring x86 only :/

~~~
LeoPanthera
RISC OS today runs natively on the Raspberry Pi, if you want to revisit your
history.

[https://www.riscosopen.org/content/downloads/raspberry-
pi](https://www.riscosopen.org/content/downloads/raspberry-pi)

~~~
digi_owl
I do wonder how well it works with one of those Ceed Pi-Top products.

~~~
LeoPanthera
You can buy a Pi-Top with a custom version of RISC OS preloaded.

[http://www.cjemicros.co.uk/micros/products/pitop.shtml](http://www.cjemicros.co.uk/micros/products/pitop.shtml)

------
YZF
My first home computer. My other non-home computer being an IBM mainframe. ;)
Still sitting in my parents attic somewhere. I gotta get it up and running
again.

I really wanted an Atari video game console but my parents thought the ZX81
would be more educational. And I guess they were right.

Endless hours on the floor in front of the TV writing programs in Basic with
that spiral bound user's manual for reference. I got the 16KB expansion pack
since the 1KB grew old pretty fast.

I remember the user's manual had the pins for the expansion port and a list of
all the Z80A assembly instructions. I spent hours looking at those having
absolutely no clue what that was. No Internet to look things up back...

I also upgraded to the Spectrum. An then surprisingly enough to an Atari 512ST
after the next Sinclair, the "QL", turned up to be a bit of a fail. Really
should have gotten an Amiga in retrospects ;)

------
FabHK
Anyone remember the tricks to save a few bytes when you didn't have the 16KB
extension pack?

A number (in source code) used a lot of memory, 6 bytes or so, while a command
used only 2 bytes, so you would replace numbers by VAL("1") or ORD("A") or
something along those lines, saving a full 3 bytes... :-)

------
owurkan
My first computer as well. As there was no hard drive included, I had to save
on audio tape the programs I was inventing or typing from UK 'Your Computer'
weekly magazine. Also, graphical definition was 64 by 44 if I remember well,
meaning that imagination was welcome when playing 'games'!

~~~
Someone
IIRC, graphics used 2x2 block characters. With 24 lines of 32 characters, that
would give you 64x48.

However, video memory ate into your 1k RAM. At 24 lines of 32 characters, a
conventional video memory would need 75% of that 1k bytes, so they did things
differently; video memory was laid out as you would do in a text editor, with
each line ending in a line separator character.

That way, an empty screen took just 24 bytes, a full one (32x24) + 24 = 792
bytes, leaving 232 bytes for a program.

=> few programs for the 1k version could use the full screen.

~~~
pascal_cuoq
You are correct, but the screen's last two lines of text required some tricks
to take advantage of (search for “reserved” in
[http://www.tebbo.com/archive/pw810601.htm](http://www.tebbo.com/archive/pw810601.htm)
), so “64x44” is also a correct description from the programmer's point of
view.

The particular trick that enabled the program to use the last two lines was
easy to come by (I was in the countryside, hundreds of kilometers from the
nearest user group, and I only had a few books as source of information). The
existence of such tricks, including the pure software “hi-res” more that I
read about at the time but didn't get to see until the Internet made it
possible 12 years later, is one of my fond memories of that era.

------
bane
For people interested, there's a small community of Spectrum fans on reddit at
/r/zxspectrum and one just for the zx81 /r/zx81

------
awful
Still have mine but dead, for now; infamous for ribbon keyboard decay, and the
Ferranti chip may have died, also an infamous component. But both the earlier
kit and the assembled computer made us start thinking about what to do, what
can be done.

------
nchristiny
Chiming in to say, this model was my dad's first home computer in the 80s in
Scotland. As such me and my brother did not fiddle with it much; however later
on we upgraded to the Spectrum ZX 16K with 48K removable daughterboard, a much
more amenable model to children. I learned BASIC on that machine and played
all kinds of amazing graphic and text games - I wrote about my experiences
with this machine on my blog
[http://nchristiny.com/history/#fnref:fn-2](http://nchristiny.com/history/#fnref:fn-2)

~~~
nchristiny
Correction: 32K removable daughterboard for a whopping 48K RAM

------
analog31
My first computer. I had already taken a programming course at school. I was
working on a project that required some repetitive calculations (designing a
loudspeaker using textbook formulas). The ZX81 went on sale at K-Mart for 40
bucks, and I rode my bike out there and got one.

I couldn't get the cassette storage to work, so for several days, I begged my
family to not unplug it. I remember one amusing thing about its architecture,
which was that it used the CPU for video generation, and did all of its
execution of BASIC programs during the vertical blanking interval.

~~~
FabHK
Yes, and it had the "FAST" mode, where the CPU would not do video, screen
would go black, and it would race through your program 4x faster :-)

------
protomyth
And a generation of programmers whose parents couldn't afford an Apple II
continued. I am so grateful for Sinclair, Atari, Commodore, and TI for making
computers for the rest of us.

~~~
cannam
The idea that an Apple II could have been "the computer you used when you were
growing up" was a rather late and surprising discovery to me. Nobody I knew
could afford an Apple II, and to this day I don't think I've ever seen one
running except under emulation. (Of course the Apple came out a good few years
before the Sinclairs as well, but I gather it was still sold throughout the
80s.)

My own first computer was a Spectrum, which I loved, but I didn't have access
to a colour TV at the time. I got to know all the fancy colour games in black
and white.

~~~
protomyth
Schools bought them because that was what schools bought in the late 70's and
it did carry over even into the IBM era (1981+). To Apple's credit, they did
get how to do educational sales.

I didn't know anyone who owned one personally, but that was probably an
income-based observation.

~~~
cannam
Here in the UK, I think schools in the 70s often had the Research Machines
380Z
([https://www.theregister.co.uk/2013/11/13/archaeologic_the_re...](https://www.theregister.co.uk/2013/11/13/archaeologic_the_research_machines_380z_story/))
which was a marvellously chunky Z80-powered machine running CP/M.

I used those at school and liked them a lot but, I guess like the Apple II,
nobody would have bought one for their home because they were expensive and
sold mostly through education channels.

In the 80s they generally switched to BBC Micros, which were affordable enough
that some better-off families had their own.

So I can see it being a regional thing that I never used an Apple II -- they
didn't appear in schools in the UK -- but I wonder about other countries
besides the US. Was the Apple all that widespread anywhere else?

~~~
protomyth
I think Canada, and something about Japan since their was a special model:
Apple II J-Plus.

------
linuxhansl
My first one too!

So many things came together back then. On TV I saw a documentary about kids
in Japan writing their own games. In our city's airport there was a
advertising installation for the IBM PC (forgot which model exactly) in form
of a lunar lander game. And my best friend in school had just signed up for a
BASIC course taught by students of the local university.

I remember I sat there next to the phone going back and forth, unsure about
whether I should do the BASIC course and get one of those strange computers
myself, or not. Almost didn't do it.

When I did finally decide it basically set me on the path for my entire career
continuing to today.

Of course the first thing I did was figuring out how to do the lunar lander
(today I know what I did was the Euler Method).

Edit: I also remember I had a hand-written Z80 op code table of 256 op codes.
Using that I would write machine code.

------
Razengan
My first ever computer, before the Spectrum and Commodore, when my parents
decided to let me touch it. Any combination of pure cyan, red and yellow
colors still reminds me of the ZX Spectrum's tape loading screen and its dial-
up modem-like sounds.

------
pienight
Also my first computer (though I also had the 8K? expansion). It was already
pretty old when I was given mine but it definitely started something. From
there to C64, Amiga and then onto PC/Mac where it all started to get a bit
boring.

~~~
rwmj
Most likely the 16K "rampack". It was pretty much essential to get anything
done with the machine[1]. The rampack infamously suffered from "rampack
wobble" where a slight movement of the machine would disconnect lines between
the motherboard and the rampack causing a crash. Eventually I got a larger
case/keyboard and mounted the rampack internally.

[1] Though there was 1K chess, a mostly complete chess game in 672 bytes
[https://en.wikipedia.org/wiki/1K_ZX_Chess](https://en.wikipedia.org/wiki/1K_ZX_Chess)

~~~
Chris_Newton
_The rampack infamously suffered from "rampack wobble" where a slight movement
of the machine would disconnect lines between the motherboard and the rampack
causing a crash._

Oh, that wobble! Definitely on my short list of the most annoying hardware
problems in computing history. You’d spend ages typing in the code for a game
from your book, and then just as you were ready to go…

~~~
FabHK
Did teach you to save frequently though, on cassette tape, which only took a
few minutes! :-)

~~~
Chris_Newton
Cassette tape? We didn’t have such luxuries until we got an Acorn Electron a
few years later! So jealous. :-)

------
faragon
1KiB of RAM (1024 bytes) is 8 times the RAM of the Atari VCS/2600 (1977).

~~~
hollander
Yeah but it's only 1/64 of the Intertec Superbrain, available for only $11.000
at the time.

~~~
faragon
1/33? [1]

[1]
[http://www.columbia.edu/cu/computinghistory/superbrain.html](http://www.columbia.edu/cu/computinghistory/superbrain.html)

~~~
hollander
Don't forget the 2K ROM. I have the 64K model here.

------
hyperpallium
A great progress point! Budget phones now have 1GB RAM, a million times more.

The GPUs of budget phones have 10's of GFLOPS... to make a comparison with the
ZX81, what's the fastest Z80 routine you could write to multiply 32-bit
floating point numbers? Or perhaps, how fast is the routine in the ZX81 ROM
BASIC (by Steve Vickers)?

Thw ZX81 had a 4MHz Z80, but in "slow" mode, about 3/4 of that was occupied in
rendering the screen, making it effectively 1MHz. In "fast" mode, the screen
went black...

------
gjkood
This was the computer on which I first learned to program. After that it was
the Spectrum. Then the MSX series.

Does anyone remember the MSX series of computers from various vendors?

------
toomanybeersies
My father still has his ZX-81. It was his first computer. I tried getting it
hooked up to a modern TV a few years back but had no luck. I didn't have an
oscilloscope handy, and there are no LEDs or status lights of any kind on the
thing, so I didn't get round to figuring out what was wrong.

It's a pretty cool piece of history though. How many people can say they still
have their first computer?

------
drumhead
My first computer. 1k of ram and the membrane keyboard, but it worked so well.
The inspiration for the raspberry PI.

------
digi_owl
Seems to have been heavily cloned as well. I think my dad owned one such clone
called a Lambda 8300 or some such.

------
jaclaz
JFYI it has been recently revived (actually more ZX80 like, since it uses only
discrete components), article on HN:

[https://news.ycombinator.com/item?id=13314741](https://news.ycombinator.com/item?id=13314741)

------
austinjp
I remember it heating up significantly in "fast mode". Amazing times.

~~~
jeennaa
and you could use alternate fast and slow modes to make sounds through the
TV!!

------
stesch
I was late to the home computer party. I sometimes wonder what would have been
if I had started with a Z80 instead of a MOS6510.

------
jeennaa
my first computer too. I was 10 and spend all of xmas at my grandparents
typing in hex. such a cool looking machine even today

~~~
FabHK
Good point, the design has held up surprisingly well!

