HP-UX is HewlettPackard's Unix operating system (see UnixOperatingSystems). Recent versions run on HP hardware with HP's PaRisc processors or Intel's ItaniumProcessorFamily (IPF) processors.
Resources
The HP-UX newsgroup: news:comp.sys.hp.hpux
The HP-UX (see HpuxOs) FAQ, maintained by IanPaulSpringer: http://faqs.org/faqs/hp/hpux-faq/
The legacy HP-UX FAQ (for releases 9.x and earlier): http://geocities.com/ian_springer/hpux/legacy_hpux_faq.html
Folklore
Version 9 of HP-UX changed the way the "heartbeat" light in the front blinks from mere blinking to a rhythm more similar to a real heartbeat
The man page for tunefs(1) says somewhere on the bottom "You can tune a file system but you can't tune a fish."
This operating system contains the best calculator program that I have come across: xhpcalc, which contains the original code from the HP-12C, 15C and 16C calculators. If you send the program a SIG_PWRFAIL, it will even turn on the low battery indicator.