Radio Shack had a long history of buying things overseas, having their name slapped on them, and selling them in the United States. That was the case with the Tandy Pocket Computers, which were in that awkward space between calculators and full-blown computers. Like many computers of those days, if you wanted to do anything interesting, you needed to turn to assembly language. But as [Old Vintage Computing Research] recalls, the assembly for these little devices was very strange, even for an assembly language. He found out that there is a reason it is so strange and shares it in a deep dive into the device’s machine code history.
The story starts with the Japanese government. In 1969, the ministry in charge of such things decided that it wouldn’t be fair for people who knew a particular computer to have an advantage when taking the Information Technology Engineer exam. So, logically, they made up a fictitious instruction set and architecture for the test. Since no one used it, no one would have an unfair advantage.
However, eventually, Japanese manufacturers started making computers that used the architecture. The architecture was COMP-X, and the assembler was CAP-X. The post covers the history of machines either using the architecture or emulating it going back to the 1970s. It eventually winds up at the Sharp and Casio pocket computers that would wear Radio Shack livery in much of the world, especially the United States.
[Fred] has a Casio PB-700 pocket calculator / computer, complete with the companion docking station featuring a four-color pen plotter, model FA-10, and a microcassette tape recorder, model CM-1. He really wanted to see what this plotter could do, but there were no demos that he could find. So despite only having one working pen, [Fred] took matters into his own hands and proceeded to make his own.
What if I made a program where I type what I want to draw and the PB-700 just draws it?
[Fred] succeeds, shoehorning several sub-projects into a single convoluted work flow: request an image from the PB-700 and after a long pause the plot emerges. The cute microcassette recorder is too much of a hassle, so he emulates the audio interface on a PC using a utility called casutil that reads and writes .wav files in PB-700 format. Much of his effort is spent figuring out how to request an image from Midjourney without being banned, but eventually comes up with a workable but shaky solution. The last steps are to convert the image into a line drawing, and then wrap up all those X-Y coordinates into a Basic program and send it back down to the PB-700 for plotting.
You can read more details in the PloTTY GitHub repository. There were several of these pocket computers with plotters coming out of Japan in the 1980s. In addition to this Casio, the Radio Shack TRS-80 PC-1 and PC-2 come to mind, which were re-branded versions of the Sharp PC-1211 and PC-1500 models. We wrote about them last year. This author had a PC-2 in 1985 and used it to plot antenna patterns at his desk, bypassing the IT department’s red tape. Have you ever used any of these pocket plotters? If so, let us know in the comments below. Thanks to [Altomare] for send us the tip.
These days, having a little computer in your pocket is par for the course. But forty years ago, this was a new and high tech idea. [The 8-Bit Guy] has a great video covering the state of the art in pocket computers and personal digital assistants from the 1980s and 1990s. You can see the video below.
There are a lot of familiar faces on the video including the Radio Shack pocket computers, Palm Pilots, and some more obscure machines of varying quality.
It might impress you to know that the Radio Shack TRS-80 PC-1 pocket computer actually had two CPUs. Of course, each CPU was a 4-bit processor running at 256 kHz, so maybe not as impressive as it sounds. Still, what a marvel in its day, programming BASIC on a 24-character LCD.