1. Scheme Object System. 2. An infamously losing text editOR. Once, back in the 1960s, when a text editOR was needed fOR the PDP-6, a hacker crufted together a quick-and-dirty "stopgap editOR" to be used until a better one was written. UnfORtunately, the old one was never really discarded when new ones (in particular, TECO) came along. SOS is a descendant ("Son of Stopgap") of that editOR, and many PDP-10 users gained the dubious pleasure of its acquaintance. Since then other programs similar in style to SOS have been written, notably the early font editOR BILOS /bye' lohs/, the Brother-In-Law Of Stopgap (the alternate expansion "Bastard Issue, Loins of Stopgap" has been proposed). 3. The PDP-10 instruction to decrease a value. Oppose AOS. [Jargon File]