a b c d e f g h i j k l m n o p q r s t u v w x y zob-, obfuscated c contest, obi-wan error, objectionable-c, obscure, octal forty, off the trolley, off-by-one error, offline, ogg, old fart, old testament, on the gripping hand, one-banana problem, one-line fix, one-liner wars, ooblick, op, open, open source, open switch, operating system, operator headspace, optical diff, optical grep, optimism, oracle, the, orange book, oriental food, orphan, orphaned i-node, orthogonal, os, os/2, oss, ot, otoh, out-of-band, overclock, overflow bit, overrun, overrun screw, owned