Another interesting question: Where does the traditional 25-line height of a default terminal window come from?
Obviously it came from the 80x25 character mode displays of old CRT monitors. The IBM PC had an 80x25 monochrome display, but it was just mimicking older CRTs from the '70s.
Where did those displays get their dimensions: usually 80x25, sometimes 80x24?
It can't be punched cards. There's nothing particularly special about a deck of 25 cards vs. 21 or 29 or whatever.
It isn't the Teletype machines we used back in the day. Those use a continuous roll of paper.
In fact the first time I saw someone using a "glass teletype" at Tymshare where we all coded on Teletypes, I wondered what you would do when something scrolled off the top of the 25 line screen. Teletypes were noisy, but the paper coming out the top gave you an infinite scrollback buffer!
So why 25 lines?
I think it came from the standard coding forms used for FORTRAN and other languages in the '50s:
My theory's more boring: By the time CRT-based terminals became popular, CRTs were basically square. And many of the characters of the Roman alphabet are typically rendered about twice as high as they are wide. Then add in a half-line or so of line spacing, and you are now at 26 or 27 lines.
I think the more compelling reason for 80x24 is that it works out reasonably well to do the arithmetic for it by bit-shifting. 64x16 displays used to be common because that works out even better. I think the IBM PC went to 80x25 because that's as many as you can fit in 2048 bytes without going over, and they were willing to spend a lot more chips on video than earlier microcomputers were.
Coding forms? No. Commonly available CRTs were designed for 525 line alternate frame TV, which really give about 262 lines of resolution. That gives a just-barely legible 10 dots for a text line on a 24 line display.
Obviously it came from the 80x25 character mode displays of old CRT monitors. The IBM PC had an 80x25 monochrome display, but it was just mimicking older CRTs from the '70s.
Where did those displays get their dimensions: usually 80x25, sometimes 80x24?
It can't be punched cards. There's nothing particularly special about a deck of 25 cards vs. 21 or 29 or whatever.
It isn't the Teletype machines we used back in the day. Those use a continuous roll of paper.
In fact the first time I saw someone using a "glass teletype" at Tymshare where we all coded on Teletypes, I wondered what you would do when something scrolled off the top of the 25 line screen. Teletypes were noisy, but the paper coming out the top gave you an infinite scrollback buffer!
So why 25 lines?
I think it came from the standard coding forms used for FORTRAN and other languages in the '50s:
http://www.atkielski.com/PDF/data/fortran.pdf
(BTW if you want an authentic FORTRAN Coding Form of your own, that PDF prints beautifully on 8.5 x 14 legal-size paper.)
There you have it: six groups of three lines each, 24 lines on your coding form. So an 80x24 display was a perfect match for a standard coding form.
Add a status line at the bottom of the CRT and you have your 80x25 terminal.