What does DOS stand for?

What does DOS mean?

DOS	Degrees Of Separation Academic & Science » Astronomy
DOS	Di-Octyl Sebacate Academic & Science » Chemistry
DOS	Denial Of Service Computing » Drivers
DOS	Density Of States Academic & Science » Electronics
DOS	Department of State (U.S.) Governmental » FDA
DOS	DOS related file (Win95) Computing » File Extensions
DOS	External command file (1st Reader) Computing » File Extensions
DOS	Defunct Operating System Miscellaneous » Funnies
DOS	Difficult Operating System Miscellaneous » Funnies
DOS	Disk Opening System Miscellaneous » Funnies
DOS	Dense Operating System Miscellaneous » Funnies
DOS	Dumb Operating System Miscellaneous » Funnies
DOS	Dirty Operating System Miscellaneous » Funnies
DOS	Dinosaur Operating System Miscellaneous » Funnies
DOS	Dead Operating System Miscellaneous » Funnies
DOS	Declaration Of Support Computing » General
DOS	Disk Operating System Computing » General
DoS	Denial of Service Computing » General
DOS	Department of State Business » International Business
DOS	Denial Of Service Internet
DOS	Disk Operating System Community » Media
DOS	Department of State Academic & Science » Meteorology
DOS	Department of State Governmental » Military
DOS	Day Of Supply Governmental » Military
DOS	Disk Operating System Governmental » Military