A rollicking and surprisingly political blog post takes us through a fascinating history, connecting 1860-era US bank note presses to the 80×20 terminal standard, passing though the Civil War, the US census, mechanical computers, punch cards, IBM, early display technology, VT100, ANSI, CP/M, and DOS along the way.
Why terminals are 80×25 characters by default
Submitted by crystall 2019-10-25 Graphics 6 Comments
Not to start an insane conversation here, but there was nothing other than rational human thought on display there. I’d rather not have to pretend that insane conspiracy theories might have some validity. Please don’t. For the sake of science, math and all that is divisible by one.
This reminds me of the apocryphal story about how modern rail gauges are due to the Roman army’s use of chariots. Sounds reasonable, but not really true. I’m not saying that this is wrong, but it has that feel.
Geez, that was an awful lot of nothing. In summary: terminals were 80×25 because 1) the punched cards they were replacing used 80 columns, and 2) at the time the terminals were made, 2KB was all you could afford in a terminal, and 2048/80 is 25.6, which is rounded to 25. There. Done.
The blog post does not mention that the VT100 terminal only displayed 80×24. The “high resolution” terminals of that vintage were typically 640×240 pixels and used an 8×10 pixel font box, I had not seen an 80×25 terminal until the early 80’s when IBM displays on their first PCs displayed as 80×25 in terminal mode.
I remember being told back in the 70’s that the 80-column display was a hold-over from 80-column punched cards, but it seems just as likely it was a result of the available resolution on the CRTs. I know folks back then who built computer terminals using televisions and they could only legibly get 64×16. You needed a more expensive monitor to get 80×24.
I appreciate you posting something again, sometimes it feels a bit like Thom’s blog. 🙂
Someone else has posted a theory as to why the 80×25 display and, for me, I think it holds a bit more water.