Abstraction layer: Difference between revisions
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:''This is about the concept in computer science, for the concept in grouping, see [[Principle of abstraction]].'' |
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An '''abstraction layer''' (or abstraction level) is a way of hiding the implementation details of a particular set of functionality. Software models that use layers of abstraction include the [[OSI model|OSI 7 Layer model]] for [[computer network]] [[Protocol (computing)|protocols]], the [[OpenGL]] graphics drawing library, and the [[byte stream]] input/output (I/O) model originated by [[Unix]] and adopted by [[MSDOS]], [[Linux]], and most other modern [[operating system]]s. |
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In the Unix operating system, most types of input and output operations are considered to be streams of bytes being read from a |
In the Unix operating system, most types of input and output operations are considered to be streams of bytes being read from a by the operating system which presents an [[abstraction (computer science)|abstract]] [[Interface (computer science)|interface]] which allows the [[programmer]] to read and write [[byte]]s from/to the device. The operating system then performs the actual [[Program transformation|transformation]] needed to read and write the stream of bytes to the device. |
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Most graphics [[library (computer science)|libraries]] such as OpenGL provide an abstract graphical device model as an interface. The library is responsible for translating the commands provided by the programmer into the specific device commands needed to draw the graphical elements and objects. The specific device commands for a [[plotter]] are different from the device commands for a [[Cathode ray tube|CRT]] [[computer display|monitor]] but the graphics library hides the implementation and device dependent details by providing an abstract interface which provides a set of [[primitive (computer science)|primitives]] that are generally useful for drawing graphical objects. |
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Most graphics [[library (computer science)|libraries]] such as OpenGL provide an abstract graphical device model as an interface. The library is responsible for translating the commands provided by the programmer |
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In [[computer science]], an abstraction level is a generalization of a model or [[algorithm]], away from any specific implementation. These generalizations arise from broad similarities that are best encapsulated by models that express similarities present in various specific implementations. The simplification provided by a good abstraction layer allows for easy reuse by distilling a useful concept or metaphor so that situations where it may be accurately applied can be quickly recognized. |
In [[computer science]], an abstraction level is a generalization of a model or [[algorithm]], away from any specific implementation. These generalizations arise from broad similarities that are best encapsulated by models that express similarities present in various specific implementations. The simplification provided by a good abstraction layer allows for easy reuse by distilling a useful concept or metaphor so that situations where it may be accurately applied can be quickly recognized. |
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*{{cite book |last= Tanenbaum |first=Andrew S. |authorlink=Andrew S. Tanenbaum |title=Structured Computer Organization |year=1979 |publisher=Prentice-Hall |location=[[Englewood Cliffs, New Jersey]] |language=english |id=ISBN 0-13-148521-0}} |
*{{cite book |last= Tanenbaum |first=Andrew S. |authorlink=Andrew S. Tanenbaum |title=Structured Computer Organization |year=1979 |publisher=Prentice-Hall |location=[[Englewood Cliffs, New Jersey]] |language=english |id=ISBN 0-13-148521-0}} |
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== See also == |
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*[[layer (object-oriented design)|Layer]] for object-oriented meaning |
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*[[Information hiding]] |
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*[[Abstraction (computer science)]] |
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*[[Transparency (computing)]] |
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*[[Protection ring]] |
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*[[Computer software]] |
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*[[Application programming interface]] |
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*[[Software engineering]] |
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*[[Software]] |
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*[[Hardware]] |
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*[[Database]] |
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*[[Computer network|Network]] |
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[[Category:Computer architecture]] |
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[[af:Abstraksielaag]] |
[[af:Abstraksielaag]] |
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Revision as of 05:09, 27 June 2008
In the Unix operating system, most types of input and output operations are considered to be streams of bytes being read from a by the operating system which presents an abstract interface which allows the programmer to read and write bytes from/to the device. The operating system then performs the actual transformation needed to read and write the stream of bytes to the device.
Most graphics libraries such as OpenGL provide an abstract graphical device model as an interface. The library is responsible for translating the commands provided by the programmer In computer science, an abstraction level is a generalization of a model or algorithm, away from any specific implementation. These generalizations arise from broad similarities that are best encapsulated by models that express similarities present in various specific implementations. The simplification provided by a good abstraction layer allows for easy reuse by distilling a useful concept or metaphor so that situations where it may be accurately applied can be quickly recognized.
A good abstraction will generalize that which can be made abstract; while allowing specificity where the abstraction breaks down and its successful application requires customization to each unique requirement or problem.
Frequently abstraction layers can be composed into a hierarchy of abstraction levels. The ISO-OSI networking model comprises seven abstraction layers. Each layer of the OSI ISO networking model encapsulates and addresses a different part of the needs of much digital communications thereby reducing the complexity of the associated engineering solutions.
A famous aphorism of Butler Lampson goes: All problems in computer science can be solved by another level of indirection; this is often deliberately mis-quoted with "abstraction" substituted for "indirection". Kevlin Henney's corollary to this is, "...except for the problem of too many layers of indirection."
Computer architecture
In computer architecture, a computer system is usually represented as consisting of five abstraction levels: hardware, firmware, assembler, operating system and processes (Tanenbaum 79).
Bibliography
- Tanenbaum, Andrew S. (1979). Structured Computer Organization. Englewood Cliffs, New Jersey: Prentice-Hall. ISBN 0-13-148521-0.