Tag Archives: ZX81

An Ode to the Sinclair ZX81

Sinclair-ZX81What do the PDP-11, Commodore PET, APPLE II and Sinclair’s ZX81 have in common? And, more importantly, for anyone under the age of 35, what on earth are they?  Well, these are respectively, the first time-share mainframe, first personal computer, first Apple computer, and the first home-based computer programmed by theDiagonal’s friendly editor back in the pioneering days of computation.

The article below on technological nostalgia pushed the recall button, bringing back vivid memories of dot matrix printers, FORTRAN, large floppy diskettes (5 1/4 inch), reel-to-reel tape storage, and the 1Kb of programmable memory on the ZX81. In fact, despite the tremendous and now laughable limitations of the ZX81 — one had to save and load programs via a tape cassette — programming the device at home was a true revelation.

Some would go so far as to say that the first computer is very much like the first kiss or the first date. Well, not so. But fun nonetheless, and responsible for much in the way of future career paths.

From ars technica:

Being a bunch of technology journalists who make our living on the Web, we at Ars all have a fairly intimate relationship with computers dating back to our childhood—even if for some of us, that childhood is a bit more distant than others. And our technological careers and interests are at least partially shaped by the devices we started with.

So when Cyborgology’s David Banks recently offered up an autobiography of himself based on the computing devices he grew up with, it started a conversation among us about our first computing experiences. And being the most (chronologically) senior of Ars’ senior editors, the lot fell to me to pull these recollections together—since, in theory, I have the longest view of the bunch.

Considering the first computer I used was a Digital Equipment Corp. PDP-10, that theory is probably correct.

The DEC PDP-10 and DECWriter II Terminal

In 1979, I was a high school sophomore at Longwood High School in Middle Island, New York, just a short distance from the Department of Energy’s Brookhaven National Labs. And it was at Longwood that I got the first opportunity to learn how to code, thanks to a time-share connection we had to a DEC PDP-10 at the State University of New York at Stony Brook.

The computer lab at Longwood, which was run by the math department and overseen by my teacher Mr. Dennis Schultz, connected over a leased line to SUNY. It had, if I recall correctly, six LA36 DECWriter II terminals connected back to the mainframe—essentially dot-matrix printers with keyboards on them. Turn one on while the mainframe was down, and it would print over and over:


Time at the terminals was a precious resource, so we were encouraged to write out all of our code by hand first on graph paper and then take a stack of cards over to the keypunch. This process did wonders for my handwriting. I spent an inordinate amount of time just writing BASIC and FORTRAN code in block letters on graph-paper notebooks.

One of my first fully original programs was an aerial combat program that used three-dimensional arrays to track the movement of the player’s and the programmed opponent’s airplanes as each maneuvered to get the other in its sights. Since the program output to pin-fed paper, that could be a tedious process.

At a certain point, Mr. Shultz, who had been more than tolerant of my enthusiasm, had to crack down—my code was using up more than half the school’s allotted system storage. I can’t imagine how much worse it would have been if we had video terminals.

Actually, I can imagine, because in my senior year I was introduced to the Apple II, video, and sound. The vastness of 360 kilobytes of storage and the ability to code at the keyboard were such a huge luxury after the spartan world of punch cards that I couldn’t contain myself. I soon coded a student parking pass database for my school—while also coding a Dungeons & Dragons character tracking system, complete with combat resolution and hit point tracking.

—Sean Gallagher

A printer terminal and an acoustic coupler

I never saw the computer that gave me my first computing experience, and I have little idea what it actually was. In fact, if I ever knew where it was located, I’ve since forgotten. But I do distinctly recall the gateway to it: a locked door to the left of the teacher’s desk in my high school biology lab. Fortunately, the guardian—commonly known as Mr. Dobrow—was excited about introducing some of his students to computers, and he let a number of us spend our lunch hours experimenting with the system.

And what a system it was. Behind the physical door was another gateway, this one electronic. Since the computer was located in another town, you had to dial in by modem. The modems of the day were something different entirely from what you may recall from AOL’s dialup heyday. Rather than plugging straight in to your phone line, you dialed in manually—on a rotary phone, no less—then dropped the speaker and mic carefully into two rubber receptacles spaced to accept the standard-issue hardware of the day. (And it was standard issue; AT&T was still a monopoly at the time.)

That modem was hooked into a sort of combination of line printer and keyboard. When you were entering text, the setup acted just like a typewriter. But as soon as you hit the return key, it transmitted, and the mysterious machine at the other end responded, sending characters back that were dutifully printed out by the same machine. This meant that an infinite loop would unleash a spray of paper, and it had to be terminated by hanging up the phone.

It took us a while to get to infinite loops, though. Mr. Dobrow started us off on small simulations of things like stock markets and malaria control. Eventually, we found a way to list all the programs available and discovered a Star Trek game. Photon torpedoes were deadly, but the phasers never seemed to work, so before too long one guy had the bright idea of trying to hack the game (although that wasn’t the term that we used). We were off.

John Timmer

Read the entire article here.

Image: Sinclair ZX81. Courtesy of Wikipedia.