Simon TathamMay 13, 2025

The standard baud rate 38400, if you write it in hex, becomes 0x9600, which is confusing, because 9600 (decimal) is another of the standard baud rates.

(I first encountered this fact while reading a hex dump of an SSH session. The SSH terminal setup packet has a baud rate field, and I saw 00 00 96 00 in the hex dump, and thought "fine, yes, baud rate, move on … wait, *what*?")

A much more well known hex/decimal coincidence is that 100 decimal = 0x64 hex, which looks confusingly backwards because you expect numbers that look round in *hex* to look like familiar power-of-2 things in *decimal*.

But these aren't separate coincidences: they're two facets of the same one.

Because if 100 = 0x64 and 256 = 0x100, then multiplying both together gives you a number that ends in two zeroes in both bases: 25600 = 0x6400. And you can divide by 2 to get 12800 = 0x3200, and multiply by 3 to get 38400 = 0x9600, without any carries on the hex side spoiling the fun.

Show threadSimon TathamMay 13, 2025

I'm posting about numerical coincidences in the middle of the night, incidentally, because I woke up and couldn't get back to sleep.

Rolled over and looked at the clock. It read 4:04. Sinking feeling. "Oh hell, what's gone wrong *now*?"

Show threadMark Dominus

@simontatham The important east-west highway that runs through Philadelphia is Interstate 76. People assume that this is to commemorate Philadelphia's important role as the place where the 1776 Declaration of Independence was signed. But no, Interstate highways are numbered from south to north and I-76 is so-called because it is somewhat north of I-70 and a bit south of I-78, leaving room for I-72 should they ever want to build such a thing.

Also, the emergency services number in the entire US is 911, and young people assume this has something to do with the September 11 disaster, but the choice predates that by decades.

May 13, 2025 at 6:20amWeb
Show threadMark DominusMay 13, 2025
@simontatham My wife once remarked that the choice of 404 was clever, since it suggests "File not found", with 0 representing "not". I had to sadly explain to her that this was pure coincidence.
Show threadrelsquiMay 13, 2025
@mjd @simontatham great mnemonic though
Show threadSimon TathamMay 13, 2025
@mjd the 911 thing reminds me of hearing that these days people learning about the Watergate scandal for the first time get confused that it didn't involve water, because all the other "-gate" scandal names are related to the word that came first.
Show threadAlexandre MuñizMay 13, 2025
@mjd @simontatham The north-south highway on the west side of the Willamette River in Portland, OR is Macadam Ave. / Hwy 43. By the principle of Scottish Highway Symmetry, the north-south highway on the east side is McLoughlin Blvd. / Hwy 99E. (John McAdam developed a road surface while John McLoughlin was the first white person in charge of things around these parts. Neither of them knew about Scottish Highway Symmetry during their lifetimes.) Hwy 99W does exist, but it's a few miles to the west. It meets Hwy 99E farther south in Junction City, OR. Junction City's name has nothing to do with this fact; it was named for a railroad junction.
Show threadcameronMay 14, 2025
@mjd @simontatham I remember the 911 thing being described to me as a child (in the US) in the early 00s as "the terrorists picked September 11 because it looks like the emergency number." In retrospect, I should have understood that as a manifestation of the general insanity of the era.
Show threadSimon TathamMay 14, 2025

@ohdeargodwhy @mjd that was definitely a theory I remember hearing when it happened, though I'm pretty sure nobody ever proved whether or not it was really part of the terrorists' motivation!

Tangentially, I also remember a poster-style image circulating on the British parts of the Internet depicting our Houses of Parliament blowing up, as if the Gunpowder Plot of 1605 had succeeded, and in the corner of the image, the caption '5/11'. Struck me as an almost stereotypically British thing to do – refer to an American disaster in such a way that you get in a dig at them writing dates the wrong way round!

Show threadMark DominusMay 14, 2025

@simontatham @ohdeargodwhy The terrorists actually chose that day to draw attention to the unjust and centuries-old occupation of Catalonia by the Castillian imperialist aggressors. Sadly, that part of their message was ignored. https://en.wikipedia.org/wiki/National_Day_of_Catalonia

#itsTrue

National Day of Catalonia - Wikipedia