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 7 Layer model The Open Systems Interconnection Reference Model is an abstract description for layered communications and computer network protocol design. It was developed as part of the Open Systems Interconnection (OSI) initiative. In its most basic form, it divides network architecture into seven layers which, from top to bottom, are the Application, for computer network A computer network is a group of interconnected computers. Networks may be classified according to a wide variety of characteristics. This article provides a general overview of some types and categories and also presents the basic components of a network protocols In computing, a protocol is a set of rules which is used by computers to communicate with each other across a network. A protocol is a convention or standard that controls or enables the connection, communication, and data transfer between computing endpoints. In its simplest form, a protocol can be defined as the rules governing the syntax,, the OpenGL OpenGL is a standard specification defining a cross-language, cross-platform API for writing applications that produce 2D and 3D computer graphics. The interface consists of over 250 different function calls which can be used to draw complex three-dimensional scenes from simple primitives. OpenGL was developed by Silicon Graphics Inc. (SGI) in 1992 graphics drawing library, and the byte stream In computer science, a byte stream is a bit stream, in which data bits are grouped into units, called bytes input/output (I/O) model originated by Unix Unix is a computer operating system originally developed in 1969 by a group of AT&T employees at Bell Labs, including Ken Thompson, Dennis Ritchie, Douglas McIlroy, and Joe Ossanna. Today's Unix systems are split into various branches, developed over time by AT&T as well as various commercial vendors and non-profit organizations and adopted by MSDOS, Linux Linux is a generic term referring to Unix-like computer operating systems based on the Linux kernel. Their development is one of the most prominent examples of free and open source software collaboration; typically all the underlying source code can be used, freely modified, and redistributed by anyone under the terms of the GNU GPL and other free, and most other modern operating systems An operating system is an interface between hardware and user; an OS is responsible for the management and coordination of activities and the sharing of the resources of the computer. The operating system acts as a host for computing applications that are run on the machine. As a host, one of the purposes of an operating system is to handle the.

In the Unix operating system, most types of input and output operations are considered to be streams of bytes being read from a device A personal computer is made up of multiple physical components of computer hardware, upon which can be installed an operating system and a multitude of software to perform the operator's desired functions or being written to a device. This stream of bytes model is used for file I/O, socket I/O, and terminal I/O in order to provide device independence Device independence is the process of making the web accessible by any device under any circumstance and by all people. The World Wide Web Consortium has initiated the Device Independence Working Group, which aims to unify the web, making it accessible from many types of Internet appliances. Its mission is to avoid the breaking up of the web into. In order to read and write to a device at the application level, the program calls a function to open the device which may be a real device such as a terminal or a virtual device such as a network port A software port is a virtual/logical data connection that can be used by programs to exchange data directly, instead of going through a file or other temporary storage location. The most common of these are TCP and UDP ports which are used to exchange data between computers on the Internet or a file in a file system In computing, a file system is a method for storing and organizing computer files and the data they contain to make it easy to find and access them. File systems may use a data storage device such as a hard disk or CD-ROM and involve maintaining the physical location of the files, they might provide access to data on a file server by acting as. The device's physical characteristics are mediated by the operating system which in turn presents an abstract The concept originated by analogy with abstraction in mathematics. The mathematical technique of abstraction begins with mathematical definitions; this has the fortunate effect of finessing some of the vexing philosophical issues of abstraction. For example, in both computing and in mathematics, numbers are concepts in the programming languages, interface Interface generally refers to an abstraction that an entity provides of itself to the outside. This separates the methods of external communication from internal operation, and allows it to be internally modified without affecting the way outside entities interact with it, as well as provide multiple abstractions of itself. It may also provide a that allows the programmer A programmer is someone who writes computer software. The term computer programmer can refer to a specialist in one area of computer programming or to a generalist who writes code for many kinds of software. One who practices or professes a formal approach to programming may also be known as a programmer analyst. A programmer's primary computer to read and write bytes A byte is a basic unit of measurement of information storage in computer science. In many computer architectures it is a unit of memory addressing. There is no standard but a byte most often consists of eight bits from/to the device. The operating system then performs the actual transformation A program transformation is any operation that takes a program and generates another program. It is often important that the derived program be semantically equivalent to the original, relative to a particular formal semantics. Other program transformations may generate programs that semantically differ from the original in predictable ways needed to read and write the stream of bytes to the device.

Most graphics libraries In computer science, a library is a collection of subroutines or classes used to develop software. Libraries contain code and data that provide services to independent programs. This allows the sharing and changing of code and data in a modular fashion. Some executables are both standalone programs and libraries, but most libraries are not 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 A plotter is a vector graphics printing device to print graphical plots, that connects to a computer. There are two types of main plotters. Those are pen plotters and electrostatic plotters are different from the device commands for a CRT The cathode ray tube is a vacuum tube containing an electron gun (a source of electrons) and a fluorescent screen, with internal or external means to accelerate and deflect the electron beam, used to create images in the form of light emitted from the fluorescent screen. The image may represent electrical waveforms (oscilloscope), pictures ( monitor but the graphics library hides the implementation and device dependent details by providing an abstract interface which provides a set of primitives In most programming languages, all basic data types are built-in. In addition, many languages also provide a set of composite data types. Opinions vary as to whether a built-in type that is not basic should be considered "primitive".[citation needed] that are generally useful for drawing graphical objects.

In computer science Computer science is the study of the theoretical foundations of information and computation, and of practical techniques for their implementation and application in computer systems. It is frequently described as the systematic study of algorithmic processes that describe and transform information; the fundamental question underlying computer, an abstraction level is a generalization of a model or algorithm In mathematics, computing, linguistics, and related subjects, an algorithm is a finite sequence of instructions, an explicit, step-by-step procedure for solving a problem, often used for calculation and data processing. It is formally a type of effective method in which a list of well-defined instructions for completing a task, will when given an, 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 The Open Systems Interconnection Reference Model is an abstract description for layered communications and computer network protocol design. It was developed as part of the Open Systems Interconnection (OSI) initiative. In its most basic form, it divides network architecture into seven layers which, from top to bottom, are the Application, 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 The name was first used in the Aphorisms of Hippocrates. The term came to be applied later to other sententious statements of physical science and later still to statements of all kinds of philosophical, moral or literary principles of David Wheeler goes: All problems in computer science can be solved by another level of indirection;[2] 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

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In computer architecture Computer architecture in computer engineering is the conceptual design and fundamental operational structure of a computer system. It is a blueprint and functional description of requirements and design implementations for the various parts of a computer, focusing largely on the way by which the central processing unit performs internally and, a computer system is usually represented as consisting of five abstraction levels: hardware A personal computer is made up of multiple physical components of computer hardware, upon which can be installed an operating system and a multitude of software to perform the operator's desired functions, firmware Firmware is a term sometimes used to denote the fixed, usually rather small, programs that internally control various electronic devices. Typical examples range from end-user products such as remote controls or calculators, through computer parts and devices like harddisks, keyboards, TFT screens or memory cards, all the way to scientific, assembler Assembly languages are a family of low-level languages for programming computers. They implement a symbolic representation of the numeric machine codes and other constants needed to program a particular CPU architecture. This representation is usually defined by the hardware manufacturer, and is based on abbreviations that help the programmer, operating system An operating system is an interface between hardware and user; an OS is responsible for the management and coordination of activities and the sharing of the resources of the computer. The operating system acts as a host for computing applications that are run on the machine. As a host, one of the purposes of an operating system is to handle the and processes In computing, a process is an instance of a computer program, consisting of one or more threads, that is being sequentially executed by a computer system that has the ability to run several computer programs concurrently [1].

References

  1. ^ a b Tanenbaum, Andrew S. Andrew Stuart "Andy" Tanenbaum (born March 16, 1944) is a professor of computer science at the Vrije Universiteit, Amsterdam in the Netherlands. He is best known as the author of MINIX, a free Unix-like operating system for teaching purposes, and for his computer science textbooks, regarded as standard texts in the field. He regards his (1979). Structured Computer Organization. Englewood Cliffs, New Jersey Englewood Cliffs is a borough in Bergen County, New Jersey, United States. As of the United States 2000 Census, the borough population was 5,322. The borough houses the world headquarters of CNBC and the American headquarters of Unilever. Until the early 1980s it had also been the home of Volkswagen of America. Today Englewood Cliffs is home to: Prentice-Hall. ISBN 0-13-148521-0.
  2. ^ Diomidis Spinellis. Another level of indirection. In Andy Oram and Greg Wilson, editors, Beautiful Code: Leading Programmers Explain How They Think, chapter 17, pages 279–291. O'Reilly and Associates, Sebastopol, CA, 2007.

See also

Categories: Computer architecture

 

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Figure 3 presents a class diagram for this abstraction layer Figure 3 Service definitions abstraction layer Putting it all together

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