What are the ultimately geeky, deep knowledge numbers, that aren't as obvious as 64K, 8, or 0's and 1's? (And bear in mind, I might need an explanation!)
Thanks in advance...
80. The number of columns in a standard punch card.
132 (?). The number of columns in an extended punch card.
16407. On a TRS80 Model 1, the address of... something. Video controller register, maybe? Poking values into this register would result in weird (and sometimes entertaining) behavior on the screen. It often took a reboot to recover from, though.
132 was the line length of IBM line printers, imitated by many other popular brands, including Printronix and DEC. They printed on that wide green-stripe, fan-fold paper, which came in a standard size that fit 132-column printers.
https://en.wikipedia.org/wiki/Punched_card#IBM_96-column_for... points out there was a seldom used IBM 96 card.
There's also Rand's 90 column card.
I liked printing things out to the 132-column printer. I still don't stick to 80 columns in my code. ;)
0xB8000 is the base address for the CGA video buffer on a 1980s era PC. 0xB0000 was for MDA (eg, a Hercules card).
MDA's memory range didn't overlap with CGA, EGA, or VGA, so dual-head systems were possible, eg, program display on the color display, debugger in the monochrome display.
My go-to book for the internals, with all sorts of numbers like the above, was "The Peter Norton Programmer's guide to the IBM PC", available at https://archive.org/details/peternortonprogr00nort .
For example, philipswood at https://news.ycombinator.com/item?id=28053235 pointed out the IBM PC timer interrupt was 18.2 ticks per second. Norton explains that at https://archive.org/details/peternortonprogr00nort/page/148/... - the main clock, the 8284A, oscillates at 1,193,180 times per second. The clock interrupt is every 65536 oscillations = 18.20648... ticks per second. And 1,193,180 * 4 = 4.77 MHz.
Decimal 27 = hex 1B is a number I associate both with writing ANSI escape codes (still useful today), and with writing printer commands to my Epson MX-80, like setting to quad density mode for higher quality output. With 9-pins it could make very nice graphical printouts.
300, 1200, and 2400 baud were important modem speeds in my era. The earlier Bell 101 era used 110 baud.
3583: BASIC bytes free on an unexpanded VIC-20. 38911: same idea for a C-64.
Those were both prominent numbers since they showed up on the screen right when you turned it on and sat there until you got cranking on something else.
4096, the number of words that can be addressed by 12 bits -- so, the size (in 12-bit words) of the PDP-8 memory. There was a whole culture of writing useful programs that fit in 4096 words -- not as a stunt or tour-de-force, that was just the order of the day.
3270: IBM terminal.