magic cookie

1. Something passed between routines or programs that enables

the receiver to perform some operation; a capability ticket

or opaque identifier. Especially used of small data objects

that contain data encoded in a strange or intrinsically

machine-dependent way. E.g. on non-Unix operating systems

with a non-byte-stream model of files, the result of "ftell"

may be a magic cookie rather than a byte offset; it can be

passed to "fseek", but not operated on in any meaningful

way. The phrase "it hands you a magic cookie" means it

returns a result whose contents are not defined but which can

be passed back to the same or some other program later.

2. An in-band code for changing graphic rendition (e.g. inverse

video or underlining) or performing other control functions.

Some older terminals would leave a blank on the screen

corresponding to mode-change magic cookies; this was also

called a glitch (or occasionally a "turd"; compare mousedroppings).

See also cookie.

[Jargon File]

(1995-01-25)