meta bit

The top bit of an 8-bit character, which is on in character

values 128--255. Also called high bit, alt bit, or

hobbit. Some terminals and consoles (see space-cadetkeyboard) have a META shift key. Others (including,

*mirabile dictu*, keyboards on IBM PC-class machines) have an

ALT key. See also bucky bits.

Historical note: although in modern usage shaped by a universe

of 8-bit bytes the meta bit is invariably hex 80 (octal

0200), things were different on earlier machines with 36 bit

words and 9-bit bytes. The MIT and Stanford keyboards (see

space-cadet keyboard) generated hex 100 (octal 400) from

their meta keys.

[Jargon File]