calcifer 
Computer
Lptputer
(For the 5 people who get this joke: psst we’re old)
mcSlibinas@calcifer imagine this: live so long to understand the joke and hearing the joke for the first time.
Oblomov@mcSlibinas @calcifer I wonder if there are greybeards who are old enough to get the joke, but don't get it because they never used DOS, only other operating systems.
M-A.Delsuc@oblomov @mcSlibinas @calcifer
I am !
never used DOS and barely Windows actually.
Even though, got my hand first on PDP-11 running RTX-11M (in 1978), got my personal ZX81 (in 1981!) were I wrote my first Fourier transform algo, Used RTX-11M, CP/M, Apple ][, Adakos (Bruker), VMS, CTSS (Cray), Unix (many flavors), Unice, Basic, Forth, Linux, MacOs 6 to 10, Android, e/os (in chronological order)... but no DOS ever.
@ma_delsuc @mcSlibinas @calcifer
oh wow. So, do you want the joke explained? 8-D
Arnout de Groot@ma_delsuc @mcSlibinas @calcifer
well, comp was a DOS command, but the joke is that COM[1-9] was the designator for the serial ports, and LPT[1-9] the one for parallel ports (the list of such reserved names also includes CON, AUX, PRN, NUL). They are basically the equivalent of the /dev/* stuff in Unix and similar systems, but they were first introduced in DOS when it didn't even have the concept of a directory so they're in the global namespace for files.
@ma_delsuc @mcSlibinas @calcifer
Fun fact: because of backwards compatibility the names are reserved in Windows too.
Tim ChaseBonus fun fact: because IIS can still use path-traversal for finding scripts you can encounter pages at microsoft-dot-com where swapping a directory in the path component for garbage will give you a 404, but swapping it for one of those reserved names will give you a 5xx error. So if
microsoft.com/path/to/location
has problems, using
microsoft.com/path/asdfasdf/location
will 404, but using
microsoft.com/path/lpt1/location
will give a 5xx error. 😆 (I usually use NUL when testing, but there are also CLOCK$, AUX, PRN as well)