from
Jargon File (4.4.4, 14 Aug 2003)
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.
from
The Free On-line Dictionary of Computing (8 July 2008)
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-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.
[{Jargon File}]