Since an IBM Electric was used as genuine terminal for the very first DEC machine ( PDP-1), it could be argued that DEC's 80 column orientation is originated here :)) Still, without 80 column support they were less than desirable for any serious usage (aka mainframe related) beside specialized data entry. A general purpose terminal needs to support at least the most common data structure at once. Memory for holding the text in a glass terminal like the 3300 was generally constructed using shift registers. These tended to be small, so the memory for a "screen of text" required many chips. Using fewer chips was better than more, but there was no strong requirement to use a particular number of them unless you were going for the lowest possible cost. Multiples of 18: 18, 36, 54, 72, 90, 108, 126, 144, 162, 180, 198, 216, 234, 252, 270, 288, 306, 324, 342, 360

Multiples of 10: 10, 20, 30, 40, 50, 60, 70, 80, 90, 100, 110, 120, 130, 140, 150, 160, 170, 180, 190, 200 Multiples of 17: 17, 34, 51, 68, 85, 102, 119, 136, 153, 170, 187, 204, 221, 238, 255, 272, 289, 306, 323, 340With 5 pixels to play with things become a bit better, but a major improvement in legibility happens at 6 pixels; along with spacing this means you can fit about 91 characters in a display. That manufacturers of typewriters for simple home/office usage did go for design decision with a shorter carriage so only letter size paper (and thus less characters) can be used is unrelated here. The 80 character came from IBM's extended punch card design of ~1930. The 'original' Hollerith card of 1890 had already evolved from 24 columns (characters) to 45 while keeping the basic structure. Still customers continued to ask for ever more storage capacity (*5). So one of the engineers Mr. Watson assigned the task came up with the idea of rectangular holes instead of the round one used up until then. Rectangular holes allowed (almost) doubling the density (*6) form 45 to 80 symbols while keeping the size of the card constant. This happened to be an important decision, as it only required modification on parts of the existing designs, while most of the production chain from paper manufacturing over card storage up to the mechanical parts of processing could be kept the same. Just punch thorn size and timing had to be modified (*7). Also around 1930 Remington doubled the capacity by keeping the round Hollerith holes, but storing two characters per column (90 characters per card). There were other formats as well. At the end of the 1940s (partly due the war) IBM's 80 column card was the industry wide accepted standard. Many early manufacturers did first ship with terminals with less then 80 characters and 24 lines. Sometimes even in large numbers.

Technically the gold standard of all CRT based terminals, the 3270, did not display 24 but 25 lines. Just this 25th line was (usually) not accessible to user programs, as it held status information about the connection, session status or terminal/keyboard mode. So on a user level every competitor had to offer (at least) 80x24, which most did. The IBM PC text adapters were designed with terminal emulation in mind. Thus the hardware had to provide a 25th line. A line general available for any program. But there was little demand for this width; 132 characters is useful because along with reasonable margins and standard fixed-width fonts, it's about the most characters you can fit on common paper size (e.g. A4 landscape or A3 portrait with 0.4" margins and a 12CPI font, or 8"x11" with 0.5" margins and the same font), so was useful because (1) you could use it for word-processing and see an approximation of what you'd see on paper and (2) you could have a printer that would print the same thing you saw on screen. But there was no such threshold in the region of 91 characters. The multiples of numbers calculator will find 100 multiples of a positive integer. For example, the multiples of 3 are calculated 3x1, 3x2, 3x3, 3x4, 3x5, etc., which equal 3, 6, 9, 12, 15, etc. You can designate a minimum value to generate multiples greater than a number. For example, to find 100 multiples of 36 that are greater than 1000 you will get: 1008, 1044, 1080, 1116, 1152, 1188, 1224, 1260, 1296, 1332, 1368, 1404, etc. Multiples of 8: 8, 16, 24, 32, 40, 48, 56, 64, 72, 80, 88, 96, 104, 112, 120, 128, 136, 144, 152, 160

That's why Tectronix introduced storage tube based terminals. First the 600 series devices which later evolved into the 4000 terminal series and further into the well known 4010 family. No dedicated memory needed for screen refresh - but also no real way to do things like scrolling. Conclusion: 80/132 character come from the age of punch cards, 24/25 lines due the 4:3 dimensions of common CRTs The next iteration as the VT50 of 1974 with 80x12 already reached the 80 characters goal, but mostly due memory constraints, only 12 lines were displayed. Since a 4:3 CRT was used, the resulting picture looked a bit like having every other line blanked out.