Black box

Black box is a technical term for a device or system or object when it is viewed primarily in terms of its input and output characteristics. Almost anything might occasionally be referred to as a black box: a transistor, an algorithm, humans, the Internet.

The opposite of a black box is a system where the inner components or logic are available for inspection (such as a free software/open source program), which is sometimes known as a white box, a glass box, or a clear box.

History

The modern term "black box" seems to have entered the English language around 1945.

The process of network synthesis from the transfer functions of black boxes can be traced to Wilhelm Cauer who published his ideas in their most developed form in 1941. [W. Cauer. "Theorie der linearen Wechselstromschaltungen", Vol.I. Akad. Verlags-Gesellschaft Becker und Erler, Leipzig, 1941.] Although Cauer did not himself use the term, others who followed him certainly did describe the method as black-box analysis. [E. Cauer, W. Mathis, and R. Pauli, "Life and Work of Wilhelm Cauer (1900 – 1945)", "Proceedings of the Fourteenth International Symposium of Mathematical Theory of Networks and Systems (MTNS2000)", p4, Perpignan, June, 2000. [http://www.cs.princeton.edu/courses/archive/fall03/cs323/links/cauer.pdf Retrieved online] 19th September 2008.] Belevitch [Belevitch, V, "Summary of the history of circuit theory", "Proceedings of the IRE", vol 50, Iss 5, pp848-855, May 1962.] puts the concept of black-boxes even earlier, attributing the explicit use of two-port networks as black boxes to Franz Breisig in 1921 and argues that 2-terminal components were implicitly treated as black-boxes before that.

Common usage

[
Cockpit voice recorder and flight data recorder]
* In aviation, the term "black box" refers to the flight data recorder and cockpit voice recorder responsible for recording all communications in the cockpit of an aircraft in flight. The phrase has become popularized by modern media while reporting aircraft crashes, despite the fact that the devices are usually not black.
* In electronics, a sealed piece of replaceable equipment; see "line-replaceable unit". (LRU)
* In computer programming and software engineering, "black box testing" is used to check that the output of a program is as expected, given certain inputs. [Black-Box Testing: Techniques for Functional Testing of Software and Systems, by Boris Beizer, 1995. ISBN 0471120944] The term "black box" is used because the actual program being executed is not examined.
* In computing in general, a "black box program" is one where the user cannot see its inner workings (perhaps because it is a closed source program) or one which has no side effects and the function of which need not be examined, a routine suitable for re-use.
* Also in computing, a Black Box refers to a piece of equipment provided by a vendor, for the purpose of using that vendor's product. It is often the case that the vendor maintains and supports this equipment, and the company receiving the Black Box typically are hands-off.
* In cybernetics a black box was described by Norbert Wiener as an unknown system that was to be identified using the techniques of system identification. [Cybernetics: Or the Control and Communication in the Animal and the Machine, by Norbert Wiener, page xi, MIT Press, 1961, ISBN 026273009X] He saw the first step in Self-organization as being to be able to copy the output behaviour of a black box.
* In neural networking or heuristic algorithms (computer terms generally used to describe 'learning' computers or 'AI simulations') a Black Box is used to describe the constantly changing section of the program environment which cannot easily be tested by the programmers. This is also called a White box (software engineering) in the context that the program code can be seen, but the code is so complex that it might as well be a Black box.
* In the stock market many people trade with "Black box" programs and algorithms designed by programmers. [Breaking the Black Box, by Martin J. Pring, McGraw-Hill, 2002, ISBN 0071384057] These programs automatically trade user's accounts when certain technical market conditions suddenly exist (such as a SMA crossover).
* In physics, a black box is a system whose internal structure is unknown, or need not be considered for a particular purpose. Sometimes black box is used as a synonym for black body.
* In mathematical modelling, a limiting case.
* In philosophy and psychology, the school of behaviorism sees the human mind as a black box; see "black box theory". ["Mind as a Black Box: The Behaviorist Approach", pp 85-88, in Cognitive Science: An Introduction to the Study of Mind, by Jay Friedenberg, Gordon Silverman, Sage Publications, 2006]
* In cryptography to capture the notion of knowledge obtained by an algorithm through the execution of a cryptographic protocol such as a zero-knowledge proof protocol. If the output of the algorithm when interacting with the protocol can be simulated by a simulator that interacts only the algorithm, this means that the algorithm 'cannot know' anything more than the input of the simulator. If the simulator can only interact with the algorithm in a black box way, we speak of a black box simulator.
* In pharmacology, a black box warning is a type of warning that appears on prescription drugs that may cause serious adverse effects. It is so named for the black border that usually surrounds the text of the warning. It means that medical studies indicate that the drug carries a significant risk of serious or even life-threatening adverse effects.

See also

* Black box theory
* Systems theory

References

External links

* [http://query.nytimes.com/gst/fullpage.html?res=9C05E0DC1F39F932A15757C0A960958260&sec=&spon=&pagewanted=all From an Airliner's Black Box, Next-to-Last Words] "The New York Times"