Mike Schaeffer's Blog

Articles with tag: memories
January 20, 2023

As a child of the 80's, I had a front row seat to the beginning of what was then called personal computing. My elementary school got its first Apple around the time I entered kindergarten. That was also the time personal computers were starting to make inroads into offices (largely thanks to VisiCalc and Lotus 1-2-3). By modern standards these machines weren't very good. At the time they were transformative. They brought computing to places it hadn't been before, and gave access to entirely new sets of people. For someone with an early adopter's mindset, it an optimistic and exploratory time. It's for this reason (and the fact it was my childhood) that I like looking back on these old machines. That's something I hope to do here in an informal series of posts. If there happen to be a few lessons for modern computing along the way, so much the better.

If you're reading this, you're probably familar with retrocomputing. It's easy to go to eBay, buy some used equipment, and play around with a period machine from the early 80's. Emulators make it even easier. As much as I appreciate the movement, it doesn't quite provide the full experience of the time. To put it in perspective, an Apple //e was a $4,000 purchase in today's money. This is before adding disk drives, software, or a monitor. After bringing it home, and turning it on, all you had was a black screen and a blinking prompt from Applesoft basic. If you needed help, you were limited to the manual, a few books and magazines at the local bookstore, and whoever else you happened to know. The costs were high, the utility wasn't obvious, and there wasn't a huge network of people to fall back on for help. It was a different time in a way retrocomputing doesn't quite capture.

My goal here is to talk about my own experiences in that time. What it was like to grow up with these machines, both in school and at home. It's one person's perspective (from a position of privlidge) but hopefully it'll capture a little of the spirit of the day.

If you want a way to apply this to modern computing, I'd suggest thinking about the ways it was possible for these machines to be useful with such limited capabilities. I'm typing this on a laptop with a quarter million times the memory of an Apple //e. It's arguably suprising that the Apple was useful at all. But it was, and without much of the software and hardware we take for granted today. This suggests that we might have more ways to produce useful software systems than we think. Do you really need to take on the complexities of Kubernetes or React to meet your requirements? Maybe it's possible to bring a little of the minimalist spirit of 1983 forward, take advantage of the fact modern computers are as good as they are, and deliver more value for less cost.

Before I continue, I should start off by acknowledging just how privileged I am to be able to write these stories. I grew up in a stable family with enough extra resources to be able to devote a significant chunk of money to home computing. My dad is an engineer by training, with experience in computing dating back to the 60's. He was able to apply computing at his job in a number of capacities, and then had the desire and ability to bring it home. To support this, his employer offered financing programs to help employees buy their own home machines. For my mom's part, she taught third grade at my elementary school, which in 1983 (when I was in third grade) happened to be piloting a Logo programming course for third graders. Not only was I part of the course, my mom helped run the lab, and I often had free run after school to explore on my own. (At least one summer, when I was ten or eleven, I was responsible for setting up all the hardware in the lab for the upcoming school year.)

I didn't always see it at the time, but this was an amazingly uncommon set of circumstances. It literally set the direction of my intellectual and professional life, and is something I will always be thankful for. I am thankful to my parents, and also to the good fortune of the circumstances which enabled it to happen for us as a family. It could have been very different, and for most people, it was.

But before most of that, one of the first personal computers I was ever exposed to was my Uncle Herman's Timex Sinclair 1000. This was a Z80 machine, built in Clive Sinclair fashion - to the lowest possible price point. It was intended to be a machine for beginning hobbyists, and sold for $100. (In modern dollars, that's roughtly the same as a low end iPad.) Uncle Herman had his TS1000 connected to a black and white TV and sitting on his kitchen table. It's the first and only time I've ever computed on an embroidered tablecloth.

The machine itself, as you might guess from the price, was dominated by it's limitations. The first was memory. A stock 1000 had a total of 2KB of memory. KB. Not GB. Not MB. KB.

The second limitation of the machine was the keyboard. To save on cost, the keyboard was entirely membrane based. The keys were drawn on a sheet of flat plastic, didn't move when you pressed them, and offered no tactile feedback at all. The closest modern experience is the butterfly keyboard, for which Apple was recently sued and lost.

Fortunately for the machine, the software design had a trick up its sleeve that addressed both limitations at the same time. Like many other machines of the time, the 1000's only user interface was through a BASIC interpreter. When you plug the computer in (there was no power switch) you're immediately dropped into a REPL for a BASIC interpeter that serves as the command line interface. However, due to the memory limitations, the 1000 lacked space for a line editor. There wasn't enough memory in the machine to commit the bytes necessary to buffer a line of text character by character, before parsing it to a more memory efficient tokenized representation.

The solution to this problem was to allow users to enter BASIC code directly in tokenized form, without the need to parse text. Rather than typing the five characters PRINT and having the interpreter translate that to a one byte token code, the user directly pressed a button labeled PRINT. The code for the PRINT button then emitted the one byte code for that operation. This bypassed the need for both the string buffer and the parse/tokenize step.

Beyond the reduced memory consumption of this approach, it also meant you say PRINT with one keypress instead of five. This is good, given the lousy keyboard. There are also discoverability benefits. With each BASIC command labeled directly on the keyboard, it was easy for the beginner to see a list of the possible commands. The downside is that the number of possible operations is limited by the number of keys and shift states. (A problem shared by programmable pocket calculators of the time.)

Of course, the machine had other limitations too. Graphics were blocky and monochrome, and a lack of hardware forced a hard tradeoff between CPU and display refresh. It's easy to forget this now, but driving a display is a demanding task. Displays require continual refresh, with every pixel has to be driven every frame. If this doesn't happen the display goes blank. The 1000 was so down on hardware capacity that it forced a choice on the programmer. There were two modes for controlling the tradeoff between display refresh and execution speed. FAST mode gave faster execution of user code, at the expense of sacrificing display refresh. Run your code and the display goes blank. If you wanted simultaneous execution and display, you had to select SLOW mode and pay the performance price of multiplexing too little hardware to do too much work.

Despite these limitations, the machine did offer a few options for expansion. The motherboard exposed an edge connector on the back of the case. There were enough pins on this connector for a memory expansion module to hang off the back of the machine. 2K was easy to exhaust, so an extra 16K was a nice addition. The issue here is that the connection between the computer and the expansion module was unreliable. The module could rock back and forth as you typed and the machine would occasionlly totally fail when the CPU lost its electrical connection to the expansion memory.

The usual mitigation strategy for an unreliable machine is to save your work often. This is a good idea in general, and even more advisable when pressing any given key key might disconnect your CPU from its memory and totally crash the machine. The difficulty here is that the Timex only had an analog cassette tape interface for storage. I never did get this to work, but it provided at least theoretical persistant storage for your programs. The idea here is that the computer would encode a data stream as an analog signal that could be recorded on audio tape. Later, the signal could be played back from the tape to the computer to reconstruct the data in memory.

This is not the best example of an old computer with a lot of utilty. In fact, the closet analog to a Timex Sinclair 1000 might not have been a computer at all. Between the keystroke programming, limited memory, and flashing display, the 1000 was arguably closest in scope to a programmable pocket calculator. Even with those limitations, if you had a 1000, you had machine you could use to learn programming. It was possible to get a taste of what personal computing was about, and decide about taking the next step.