meta bit
n. 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-cadet
keyboard}) 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.