Bit bucket

An imaginary trash can. The phrase "it went into the bit bucket" means the data was lost.

Download Computer Desktop Encyclopedia to your iPhone/iTouch

[very common]

1. The universal data sink (originally, the mythical receptacle used to catch bits when they fall off the end of a register during a shift instruction). Discarded, lost, or destroyed data is said to have gone to the bit bucket. On Unix, often used for /dev/null. Sometimes amplified as the Great Bit Bucket in the Sky.

2. The place where all lost mail and news messages eventually go. The selection is performed according to Finagle's Law; important mail is much more likely to end up in the bit bucket than junk mail, which has an almost 100% probability of getting delivered. Routing to the bit bucket is automatically performed by mail-transfer agents, news systems, and the lower layers of the network.

3. The ideal location for all unwanted mail responses: “Flames about this article to the bit bucket.” Such a request is guaranteed to overflow one's mailbox with flames.

4. Excuse for all mail that has not been sent. “I mailed you those figures last week; they must have landed in the bit bucket.” Compare black hole.

This term is used purely in jest. It is based on the fanciful notion that bits are objects that are not destroyed but only misplaced. This appears to have been a mutation of an earlier term ‘bit box’, about which the same legend was current; old-time hackers also report that trainees used to be told that when the CPU stored bits into memory it was actually pulling them “out of the bit box”. See also chad box.

Another variant of this legend has it that, as a consequence of the “parity preservation law”, the number of 1 bits that go to the bit bucket must equal the number of 0 bits. Any imbalance results in bits filling up the bit bucket. A qualified computer technician can empty a full bit bucket as part of scheduled maintenance.

The source for all these meanings, is, historically, the fact that the chad box on a paper-tape punch was sometimes called a bit bucket.

Not to be confused with the Mercurial hosting service Bitbucket.

The bit bucket is jargon for where lost computerized data has gone, by any means; any data which does not end up where it is supposed to, being lost in transmission, a computer crash, or the like is said to have gone to the bit bucket — that mysterious place on a computer where lost documents go, as in:

"What happened to that important spreadsheet that I was just editing?"

"Oh, it went into the bit bucket."

The chip receiver (or "bit bucket") from a UNIVAC key punch.

Originally, the bit bucket was the container on teletype machines or IBM key punch machines into which chad from the paper tape punch or card punch was deposited; the formal name is "chad box" or (at IBM) "chip box".

The term was then generalized into any place where useless bits go including the trash can or rubbish bin. In Unix and Unix-like operating systems, this term is used to refer to /dev/null. In OpenVMS, this term refers to SYS$NULL:. On Univac 90/60 operating systems such as VS/9, it was referred to as "*DUMMY". On the DEC PDP-11, it was known as "NL:". On DOS and Windows, it is referred to as "NUL".

The bit bucket is also used in discussions of bit shift operations. When the width of a given binary number is fixed, one or more bits are lost when performing a simple shift. These bits are said to have "fallen off" or to have "fallen into the bit bucket".

Such a device is sometimes referred to as a "write once read never" or WORN device (named after the magneto-optical WORM devices used during the 80s), and was indeed implemented as such as an Easter egg in early versions of Atari BASIC.

The WORN is related to the FINO "First In Never Out" stack and the WOM "Write Only Memory", implemented by Signetics in 1972.

In programming languages the term is used to denote a bitstream which does not consume any computer resources such as CPU or memory. In java this is the Stream.null, and in C# it is the Stream.Null^[1].

See also

• Black hole (networking) (Unix jargon)
• Null route (Cisco jargon)
• /dev/null

References

1. ^ "Using null stream as bit bucket" - an article on C# at java2s.org.

External links

• Bit Bucket entry from The Jargon File (version 4.4.7)
• A "Write Once Read Never" device available on Atari 8-bit hardware

This entry is from Wikipedia, the leading user-contributed encyclopedia. It may not have been reviewed by professional editors (see full disclaimer)