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. 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.

