meta bit

meta bit

The top bit of an 8-bit character, which is on in charactervalues 128--255. Also called high bit, alt bit, orhobbit. Some terminals and consoles (see space-cadet keyboard) have a META shift key. Others (including,*mirabile dictu*, keyboards on IBM PC-class machines) have anALT key. See also bucky bits.

Historical note: although in modern usage shaped by a universeof 8-bit bytes the meta bit is invariably hex 80 (octal0200), things were different on earlier machines with 36 bitwords and 9-bit bytes. The MIT and Stanford keyboards (seespace-cadet keyboard) generated hex 100 (octal 400) fromtheir meta keys.