High Bit

Definitions

1. The most significant bit of a byte or word, also called the meta bit or the eighth bit in an octet. Because seven bits sufficed for ASCII, the high bit was historically free, and systems repurposed it for parity, for terminal meta-key encoding, or as an internal flag. That improvisation caused decades of interoperability pain when software stripped or set it unexpectedly, a class of failure the Jargon File records as 'dread high-bit disease', in which text passes through a system that silently clears the eighth bit and mangles any non-ASCII content. The advent of 8-bit-clean paths and Unicode largely ended the practice.