Bit bucket
Encyclopedia
In computing
, the bit bucket is jargon
for where lost computer
ized 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 document
s go, as in:
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 system
s, this term is used to refer to /dev/null
. On HP OpenVMS
, this term refers to device "NLA0:" ("NL:" may also be used). The same Univac 90/60
operating systems such as VS/9
, it referred to "*DUMMY". On the DEC
PDP-11
, the bit bucket is "NL:". On DOS
and Windows
CMD, it is the "NUL" device, or simply "$null" in PowerShell
.
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". Some CPUs move the last bit shifted off the end of a number during a shift into the carry flag during some or all shift operations; since the bit bucket is usually considered the place where discarded (and therefore lost) bits go, the carry flag in this case would probably be excluded from the bit bucket—unless, perhaps, the speaker intended to ignore the bit saved in the carry flag and treat it as though it had been truly discarded.
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 C# it is the Stream.Null.
Computing
Computing is usually defined as the activity of using and improving computer hardware and software. It is the computer-specific part of information technology...
, the bit bucket is jargon
Jargon
Jargon is terminology which is especially defined in relationship to a specific activity, profession, group, or event. The philosophe Condillac observed in 1782 that "Every science requires a special language because every science has its own ideas." As a rationalist member of the Enlightenment he...
for where lost computer
Computer
A computer is a programmable machine designed to sequentially and automatically carry out a sequence of arithmetic or logical operations. The particular sequence of operations can be changed readily, allowing the computer to solve more than one kind of problem...
ized data has gone, by any means; any data
Data
The term data refers to qualitative or quantitative attributes of a variable or set of variables. Data are typically the results of measurements and can be the basis of graphs, images, or observations of a set of variables. Data are often viewed as the lowest level of abstraction from which...
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 document
Document
The term document has multiple meanings in ordinary language and in scholarship. WordNet 3.1. lists four meanings :* document, written document, papers...
s go, as in:
- "What happened to that important spreadsheetSpreadsheetA spreadsheet is a computer application that simulates a paper accounting worksheet. It displays multiple cells usually in a two-dimensional matrix or grid consisting of rows and columns. Each cell contains alphanumeric text, numeric values or formulas...
that I was just editing?"
- "Oh, it went into the bit bucket."
Teleprinter
A teleprinter is a electromechanical typewriter that can be used to communicate typed messages from point to point and point to multipoint over a variety of communication channels that range from a simple electrical connection, such as a pair of wires, to the use of radio and microwave as the...
machines or IBM
IBM
International Business Machines Corporation or IBM is an American multinational technology and consulting corporation headquartered in Armonk, New York, United States. IBM manufactures and sells computer hardware and software, and it offers infrastructure, hosting and consulting services in areas...
key punch
Key punch
A keypunch is a device for manually entering data into punched cards by precisely punching holes at locations designated by the keys struck by the operator. Early keypunches were manual devices. Later keypunches were mechanized, often resembled a small desk, with a keyboard similar to a...
machines into which chad
Chad (paper)
Chad refers to paper fragments created when holes are made in a paper, card or similar synthetic materials, typically computer punched tape or punched cards. Sometimes chad has been used as a mass noun or as a countable noun, and the plural is commonly either "chad" or "chads"...
from the paper tape punch or card
Punched card
A punched card, punch card, IBM card, or Hollerith card is a piece of stiff paper that contains digital information represented by the presence or absence of holes in predefined positions...
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
Unix
Unix is a multitasking, multi-user computer operating system originally developed in 1969 by a group of AT&T employees at Bell Labs, including Ken Thompson, Dennis Ritchie, Brian Kernighan, Douglas McIlroy, and Joe Ossanna...
and Unix-like
Unix-like
A Unix-like operating system is one that behaves in a manner similar to a Unix system, while not necessarily conforming to or being certified to any version of the Single UNIX Specification....
operating system
Operating system
An operating system is a set of programs that manage computer hardware resources and provide common services for application software. The operating system is the most important type of system software in a computer system...
s, this term is used to refer to /dev/null
/dev/null
In Unix-like operating systems, /dev/null or the null device is a special file that discards all data written to it and provides no data to any process that reads from it ....
. On HP OpenVMS
OpenVMS
OpenVMS , previously known as VAX-11/VMS, VAX/VMS or VMS, is a computer server operating system that runs on VAX, Alpha and Itanium-based families of computers. Contrary to what its name suggests, OpenVMS is not open source software; however, the source listings are available for purchase...
, this term refers to device "NLA0:" ("NL:" may also be used). The same Univac 90/60
UNIVAC 90/60
The Univac 90/60 series computer was a mainframe class computer manufactured by Sperry Corporation as a competitor to the IBM System 360 series of mainframe computers...
operating systems such as VS/9
VS/9
VS/9 was a computer operating system available for the Univac 90/60, 90/70 and 90/80 mainframe during the late 1960s through 1980s. The 90/60 and 90/70 were repackaged Univac 9700 computers...
, it referred to "*DUMMY". On the DEC
Digital Equipment Corporation
Digital Equipment Corporation was a major American company in the computer industry and a leading vendor of computer systems, software and peripherals from the 1960s to the 1990s...
PDP-11
PDP-11
The PDP-11 was a series of 16-bit minicomputers sold by Digital Equipment Corporation from 1970 into the 1990s, one of a succession of products in the PDP series. The PDP-11 replaced the PDP-8 in many real-time applications, although both product lines lived in parallel for more than 10 years...
, the bit bucket is "NL:". On DOS
DOS
DOS, short for "Disk Operating System", is an acronym for several closely related operating systems that dominated the IBM PC compatible market between 1981 and 1995, or until about 2000 if one includes the partially DOS-based Microsoft Windows versions 95, 98, and Millennium Edition.Related...
and Windows
Microsoft Windows
Microsoft Windows is a series of operating systems produced by Microsoft.Microsoft introduced an operating environment named Windows on November 20, 1985 as an add-on to MS-DOS in response to the growing interest in graphical user interfaces . Microsoft Windows came to dominate the world's personal...
CMD, it is the "NUL" device, or simply "$null" in PowerShell
Windows PowerShell
Windows PowerShell is Microsoft's task automation framework, consisting of a command-line shell and associated scripting language built on top of, and integrated with the .NET Framework...
.
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". Some CPUs move the last bit shifted off the end of a number during a shift into the carry flag during some or all shift operations; since the bit bucket is usually considered the place where discarded (and therefore lost) bits go, the carry flag in this case would probably be excluded from the bit bucket—unless, perhaps, the speaker intended to ignore the bit saved in the carry flag and treat it as though it had been truly discarded.
Such a device is sometimes referred to as a "write once read never" or WORN device (named after the magneto-optical WORM
Write Once Read Many
A Write Once Read Many or WORM drive is a data storage device where information, once written, cannot be modified. On ordinary data storage devices, the number of times data can be modified is not limited, except by the rated lifespan of the device, as modification involves physical changes that...
devices used during the 80s), and was indeed implemented as such as an Easter egg in early versions of Atari BASIC
Atari BASIC
Atari BASIC is a BASIC interpreter for the Atari 8-bit family of 6502-based home computers. The interpreter originally shipped on an 8 KB cartridge; on later XL/XE model computers it was built in, with an option to disable it, and started when the machines were booted with no other cartridges...
.
The WORN is related to the FINO
FINO
In computer science, FINO is a humorous scheduling algorithm. It is an acronym for "First In Never Out" as opposed to traditional "first in first out" and "last in first out" algorithms....
"First In Never Out" stack and the WOM "Write Only Memory
Write Only Memory
Write-only memory is the antithesis of read-only memory . By definition, a WOM is a memory device which can be written but never read...
", implemented by Signetics
Signetics
Signetics, once a major player in semiconductor manufacturing, made a variety of devices which included integrated circuits, bipolar and MOS, the Dolby circuit, logic, memory and analog circuits. They developed microprocessors like the 2650, the bipolar 8X300 and had licensed Motorola 68000...
in 1972.
In programming languages
Programming language
A programming language is an artificial language designed to communicate instructions to a machine, particularly a computer. Programming languages can be used to create programs that control the behavior of a machine and/or to express algorithms precisely....
the term is used to denote a bitstream
Bitstream
A bitstream or bit stream is a time series of bits.A bytestream is a series of bytes, typically of 8 bits each, and can be regarded as a special case of a bitstream....
which does not consume any computer resources such as CPU or memory
Computer memory
In computing, memory refers to the physical devices used to store programs or data on a temporary or permanent basis for use in a computer or other digital electronic device. The term primary memory is used for the information in physical systems which are fast In computing, memory refers to the...
. In C# it is the Stream.Null.
See also
- Black holeBlack hole (networking)In networking, black holes refer to places in the network where incoming traffic is silently discarded , without informing the source that the data did not reach its intended recipient....
(Unix jargon) - /dev/null/dev/nullIn Unix-like operating systems, /dev/null or the null device is a special file that discards all data written to it and provides no data to any process that reads from it ....
- Null route (Cisco jargon)
External links
- Bit Bucket entry from The Jargon File (version 4.4.7)
- http://www.atarimagazines.com/compute/issue95/056_1_INSIGHT_ATARI_THAT_MONTH_AGAIN.phpA "Write Once Read Never" device available on AtariAtariAtari is a corporate and brand name owned by several entities since its inception in 1972. It is currently owned by Atari Interactive, a wholly owned subsidiary of the French publisher Atari, SA . The original Atari, Inc. was founded in 1972 by Nolan Bushnell and Ted Dabney. It was a pioneer in...
8-bit hardware]