flush

1. To delete something, usually superfluous, or to abort an

operation.

"Flush" was standard ITS terminology for aborting an output

operation. One spoke of the text that would have been

printed, but was not, as having been flushed. It is

speculated that this term arose from a vivid image of flushing

unwanted characters by hosing down the internal output buffer,

washing the characters away before they could be printed.

2. To force temporarily buffered data to be written to more

permanent memory. E.g. flushing buffered disk I/O to disk, as

with C's standard I/O library "fflush(3)" call. This

sense was in use among BLISS programmers at DEC and on

Honeywell and IBM machines as far back as 1965. Another

example of this usage is flushing a cache on a contextswitch where modified data stored in the cace which belongs

to one processes must be written out to main memory so that

the cache can be used by another process.

[Jargon File]