My Contribution to Computing Jargon

It's interesting how funny little ideas can spread much farther than originally expected. Sometime around 1980 I coined the word "plokta", an acronym for "press lots of keys to abort." The word was needed to describe a common act of desperation and/or frustration by a TRS-80 user such as myself at the time.

Many TRS-80 programs required the user to press an unusual combination of keys to exit the program. The TRS-80 keyboard had some unusual properties because of the way the keys were interfaced to the CPU. Rather than sending a stream of characters or key transition events as modern keyboards do, the instantaneous state of each key appeared as an independent bit in the memory address space. So the CPU could, in a single instruction, read the current state of 8 keys. This was especially useful in a real-time CPU-intensive program like most video games, which can't afford the overhead of a call to the operating system's keyboard scanning and character mapping routines in every loop, and don't have any sort of interrupt available to signal keyboard events asynchronously. So, many programs had checks for certain keyboard combinations in their main loops to allow for a user abort command without slowing down the program.

There were a few key combinations commonly used to mean "exit", like shift-break or clear-break, but no universal standard, so the user was often left guessing or struggling to remember how to exit an unfamiliar program.

Unlike the behavior of modern keyboards, there was no requirement to press the keys in a particular order. On modern computers, for example, the effect of pressing control, alt, and printscreen "simultaneously" might be very different depending on which key was actually pressed first. But not so for these TRS-80 programs - they could only observe the current state of the keys, and didn't attempt to keep any history of which one had been pressed first.

Because of the way the keyboard was wired (a wired-or 8 x 8 matrix) the hardware was incapable of providing N-key rollover - certain combinations of 3 or more keys would cause certain other keys to falsely appear depressed - ghost keys. For example, if you hold down D, A, and Y, the CPU sees D, A, Y, and 4. So programs were not free to define an arbitrary 3-key combination to have some meaning as a command (such as "exit") - only some such combinations were "safe" from ghosting.

So, it turned out that a fairly effective way to exit a TRS-80 program, was to press a large number of keys down at once. You didn't have to press all the keys - the ghost effect would probably ensure that all of the keys appeared depressed to the program even if you missed a few.

I named this technique "plokta" and advocated the term among my friends, and probably a few co-workers or other TRS-80 users I encountered in those days.

I believe that my friend Keith Gabryelski nominated the word for inclusion in the Jargon File some time around 1990. I was surprised that it was accepted; its use doesn't seem to have become widespread, except perhaps since then as a result of being in the Jargon File. I recently learned that the word has been adopted as the title of a science fiction fanzine, and although I haven't read it, I suppose the fact gives me a little satisfaction to think that a silly little meme I created 25 years ago is alive and well out there in the world.

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