MS-DOS

MS-DOS: /M-S-dos/ n.  [MicroSoft Disk Operating System] A
   {clone} of {{CP/M}} for the 8088 crufted together in 6 weeks by
   hacker Tim Paterson, who is said to have regretted it ever since.
   Numerous features, including vaguely UNIX-like but rather broken
   support for subdirectories, I/O redirection, and pipelines, were
   hacked into 2.0 and subsequent versions; as a result, there are two
   or more incompatible versions of many system calls, and MS-DOS
   programmers can never agree on basic things like what character to
   use as an option switch or whether to be case-sensitive.  The
   resulting mess is now the highest-unit-volume OS in history.  Often
   known simply as DOS, which annoys people familiar with other
   similarly abbreviated operating systems (the name goes back to the
   mid-1960s, when it was attached to IBM's first disk operating
   system for the 360).  The name further annoys those who know what
   the term {operating system} does (or ought to) connote; DOS is
   more properly a set of relatively simple interrupt services.  Some
   people like to pronounce DOS like "dose", as in "I don't work on
   dose, man!", or to compare it to a dose of brain-damaging drugs
   (a slogan button in wide circulation among hackers exhorts:
   "MS-DOS: Just say No!").  See {mess-dos}, {ill-behaved}.