:green bytes: n. (also `green words') 1. Meta-information
embedded in a file, such as the length of the file or its name; as
opposed to keeping such information in a separate description file
or record. The term comes from an IBM user's group meeting
(ca. 1962) at which these two approaches were being debated and the
diagram of the file on the blackboard had the `green bytes' drawn
in green. 2. By extension, the non-data bits in any
self-describing format. "A GIF file contains, among other things,
green bytes describing the packing method for the image." Compare
{out-of-band}, {zigamorph}, {fence} (sense 1).
-- The AI Hackers Dictionary
magic number n.
[Unix/C; common] 1. In source code
some non-obvious constant whose value is significant to the
operation of a program and that is inserted inconspicuously in-line
(hardcoded), rather than expanded in by a symbol set by a
commented #define....