Black box

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Black box is technical jargon 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, the Internet.

The opposite of a black box, a system where the innards are available for inspection (such as a free software/open source program) is sometimes known as a white box, a glass box, or a clear box. Points of view such as interactive computation may see a black box as a useful fiction.

[edit] Some common uses of black boxes:

• In electronics, a sealed piece of replaceable equipment; see line-replaceable unit.
• 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. The term "black box" is used because the actual program being executed is not examined.
• In transportation, the term "black box" refers to any of a number of systems designed to collect and preserve data for analysis after an accident:
  • In aerospace, the term "black box" refers to a flight data recorder, an instrument designed to survive a catastrophic event which records the last few minutes of audio and instrument data from a complex system, such as an aircraft. (The actual recorders are painted a bright orange, not black, in order that they can be located quickly in the event of a disaster.)
  • Also in aerospace, the cockpit voice recorder;
  • In trains, the event recorder;
  • In automobiles, an Event Data Recorder.
• 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.
• In the stock market many people trade with "Black box" programs and algorithms designed by programmers. These programs automatically trade user’s accounts when certain technical market conditions suddenly exist (such as a SMA crossover). Some businesses on the internet specialize in coding these algorithms for TradeStation users such as Knowful.
• 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 copyright law, a single-purpose device which decrypts satellite television signals without authorization, which removes Macrovision coding, or which otherwise serves to defeat a broadcaster's or copyright holder's policy is sometimes known as a black box; the purpose of the anti-circumvention provisions of the Digital Millennium Copyright Act was sometimes characterized as removing these black boxes from the market.
• 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.
• In Phreaking a Black box (phreaking) was a home-made device used to avoid paying for telephone calls, now largely obsolete.