The NASA Columbia Supercomputer. The National Aeronautics and Space Administration ( NASA, ˈnæsə is an agency of the United States government, responsible for the nation's public space program Columbia is a Supercomputer built by Silicon Graphics for NASA.

A computer is a machine that manipulates data according to a list of instructions. A machine is any device that uses Energy to perform some activity In Computer science, data is anything in a form suitable for use with a Computer. In Computer science, source code (commonly just source or code) is any sequence of statements or declarations written in some Human-readable

The first devices that resemble modern computers date to the mid-20th century (around 1940 - 1945), although the computer concept and various machines similar to computers existed earlier. Early electronic computers were the size of a large room, consuming as much power as several hundred modern personal computers. ^[1] Modern computers are based on tiny integrated circuits and are millions to billions of times more capable while occupying a fraction of the space. Microchipsjpg|right|thumb|200px|Microchips ( EPROM memory with a transparent window showing the integrated circuit inside ^[2] Today, simple computers may be made small enough to fit into a wristwatch and be powered from a watch battery. A watch is a timepiece that is made to be worn on a person The term now usually refers to a wristwatch, which is worn on the wrist with a strap or Bracelet. A watch battery, button cell, silver button cell, or coin cell is a small form-factor battery designed for use in wrist watches pocket Personal computers, in various forms, are icons of the Information Age and are what most people think of as "a computer"; however, the most common form of computer in use today is the embedded computer. A personal computer ( PC) is any Computer whose original sales price size and capabilities make it useful for individuals and which is intended to be operated Information Age is a term that has been used to refer to the present era An embedded system is a special-purpose Computer system designed to perform one or a few dedicated functions often with Real-time computing constraints Embedded computers are small, simple devices that are used to control other devices — for example, they may be found in machines ranging from fighter aircraft to industrial robots, digital cameras, and children's toys. A fighter aircraft is a Military aircraft designed primarily for air-to-air combat with other Aircraft, as opposed to a Bomber, which is designed An industrial robot is officially defined by ISO as an automatically controlled reprogrammable multipurpose manipulator programmable in three or more axes. Many compact digital still cameras can record Sound and moving Video as well as still Photograph. This article is about playthings For other uses of the term see Toy (disambiguation.

The ability to store and execute lists of instructions called programs makes computers extremely versatile and distinguishes them from calculators. Computer programs (also software programs, or just programs) are instructions for a Computer. A calculator is device for performing mathematical calculations distinguished from a Computer by having a limited problem solving ability and an interface optimized for interactive The Church–Turing thesis is a mathematical statement of this versatility: any computer with a certain minimum capability is, in principle, capable of performing the same tasks that any other computer can perform. Therefore, computers with capability and complexity ranging from that of a personal digital assistant to a supercomputer are all able to perform the same computational tasks given enough time and storage capacity. A supercomputer is a Computer that is at the frontline of processing capacity particularly speed of calculation (at the time of its introduction

History of computing

Main article: History of computer hardware

The Jacquard loom was one of the first programmable devices. The history of computer hardware encompasses the hardware, its architecture, and its impact on software. The Jacquard Loom is a mechanical Loom, invented by Joseph Marie Jacquard in 1801, that has holes punched in pasteboard each row of which corresponds to

It is difficult to identify any one device as the earliest computer, partly because the term "computer" has been subject to varying interpretations over time. Originally, the term "computer" referred to a person who performed numerical calculations (a human computer), often with the aid of a mechanical calculating device. Before electronic computers became commercially available the term " computer " in use from the mid 17th century literally meant "one who computes" A calculator is device for performing mathematical calculations distinguished from a Computer by having a limited problem solving ability and an interface optimized for interactive

The history of the modern computer begins with two separate technologies - that of automated calculation and that of programmability.

Examples of early mechanical calculating devices included the abacus, the slide rule and arguably the astrolabe and the Antikythera mechanism (which dates from about 150-100 BC). An abacus, also called a counting frame, is a calculating tool used primarily by Asians for performing arithmetic processes The slide rule, also known as a slipstick, is a mechanical Analog computer. The astrolabe is a historical Astronomical instrument used by classical astronomers, Navigators The Antikythera mechanism (ˌæntɪkɪˈθɪərə an-ti-ki- theer -uh is an ancient mechanical Calculator (also described as the first known " mechanical The end of the Middle Ages saw a re-invigoration of European mathematics and engineering, and Wilhelm Schickard's 1623 device was the first of a number of mechanical calculators constructed by European engineers. Wilhelm Schickard ( April 22 1592 &ndash October 24 1635) was a German Polymath who built one of the first Calculating machines However, none of those devices fit the modern definition of a computer because they could not be programmed.

Hero of Alexandria (c. Hero (or Heron) of Alexandria ( Ήρων ο Αλεξανδρεύς) (c 10 – 70 AD) built a mechanical theater which performed a play lasting 10 minutes and was operated by a complex system of ropes and drums that might be considered to be a means of deciding which parts of the mechanism performed which actions - and when. ^[3] This is the essence of programmability. In 1801, Joseph Marie Jacquard made an improvement to the textile loom that used a series of punched paper cards as a template to allow his loom to weave intricate patterns automatically. Joseph Marie Charles nicknamed Jacquard ( 7 July 1752 &ndash 7 August 1834) was a Straw hat maker before becoming A loom is a Machine or device for Weaving thread or Yarn into Textiles Looms can range from very small hand-held frames to large free-standing The resulting Jacquard loom was an important step in the development of computers because the use of punched cards to define woven patterns can be viewed as an early, albeit limited, form of programmability.

It was the fusion of automatic calculation with programmability that produced the first recognizable computers. In 1837, Charles Babbage was the first to conceptualize and design a fully programmable mechanical computer that he called "The Analytical Engine". The analytical engine, an important step in the History of computers, was the design of a mechanical general-purpose Computer by the British mathematician Charles ^[4] Due to limited finances, and an inability to resist tinkering with the design, Babbage never actually built his Analytical Engine.

Large-scale automated data processing of punched cards was performed for the U.S. Census in 1890 by tabulating machines designed by Herman Hollerith and manufactured by the Computing Tabulating Recording Corporation, which later became IBM. See also Unit record equipment The tabulating machine was a machine designed to assist in Tabulations. Herman Hollerith ( February 29, 1860 &ndash November 17, 1929) was a German-American statistician who developed a The Computing Tabulating Recording Corporation (CTR was incorporated on June 15 1911 in Endicott New York a few miles west of Binghamton International Business Machines Corporation abbreviated IBM and nicknamed "Big Blue", is a multinational Computer Technology By the end of the 19th century a number of technologies that would later prove useful in the realization of practical computers had begun to appear: the punched card, Boolean algebra, the vacuum tube (thermionic valve) and the teleprinter. Boolean algebra (or Boolean logic) is a logical calculus of truth values, developed by George Boole in the late 1830s This article is about the electronic device not an evacuated pipe used for experiments in Free-fall. A teleprinter (

During the first half of the 20th century, many scientific computing needs were met by increasingly sophisticated analog computers, which used a direct mechanical or electrical model of the problem as a basis for computation. An analog computer (spelt analogue in British English is a form of Computer that uses continuous physical phenomena such as electrical mechanical Computation is a general term for any type of Information processing. However, these were not programmable and generally lacked the versatility and accuracy of modern digital computers.

A succession of steadily more powerful and flexible computing devices were constructed in the 1930s and 1940s, gradually adding the key features that are seen in modern computers. The history of computer hardware encompasses the hardware, its architecture, and its impact on software. Computer programs (also software programs, or just programs) are instructions for a Computer. In computability theory, several closely-related terms are used to describe the "computational power" of a computational system (such as an Abstract machine or Konrad Zuse (ˈkɔnʁat ˈtsuːzə June 22, 1910 Berlin - December 18, 1995 Hünfeld) was a German Konrad Zuse 's Germany, officially the Federal Republic of Germany ( ˈbʊndəsʁepuˌbliːk ˈdɔʏtʃlant is a Country in Central Europe. In Engineering, electromechanics combines the Sciences of Electromagnetism of Electrical engineering and mechanics. This focuses on Motion picture film For Still photography film see Photographic film. Konrad Zuse 's The Atanasoff–Berry Computer ( ABC) was the first electronic Digital Computing device The United States of America —commonly referred to as the The Colossus machines were electronic Computing devices used by British codebreakers to read Encrypted German messages during The United Kingdom of Great Britain and Northern Ireland, commonly known as the United Kingdom, the UK or Britain,is a Sovereign state located The IBM Automatic Sequence Controlled Calculator ( ASCC) called the Mark I by Harvard University, was the first large-scale automatic digital The United States of America —commonly referred to as the The decimal ( base ten or occasionally denary) Numeral system has ten as its base. In Engineering, electromechanics combines the Sciences of Electromagnetism of Electrical engineering and mechanics. Punched tape or paper tape is a largely obsolete form of Data storage, consisting of a long strip of paper in which holes are punched to store data Konrad Zuse 's ENIAC, short for Electronic Numerical Integrator And Computer, was the first general-purpose electronic Computer. The United States of America —commonly referred to as the The decimal ( base ten or occasionally denary) Numeral system has ten as its base. The Manchester Small-Scale Experimental Machine (SSEM, nicknamed Baby, was the world's first stored-program Computer. The United Kingdom of Great Britain and Northern Ireland, commonly known as the United Kingdom, the UK or Britain,is a Sovereign state located The von Neumann architecture is a design model for a stored-program Digital computer that uses a processing unit and a single separate storage structure The Williams tube or the Williams-Kilburn tube (after inventors Freddie Williams and Tom Kilburn) developed about 1946 or 1947 ENIAC, short for Electronic Numerical Integrator And Computer, was the first general-purpose electronic Computer. The United States of America —commonly referred to as the The decimal ( base ten or occasionally denary) Numeral system has ten as its base. Electronic Delay Storage Automatic Calculator ( EDSAC) was an early British Computer. The United Kingdom of Great Britain and Northern Ireland, commonly known as the United Kingdom, the UK or Britain,is a Sovereign state located The von Neumann architecture is a design model for a stored-program Digital computer that uses a processing unit and a single separate storage structure Genesis in radar The basic concept of the delay line originated with World War II Radar research as a system to reduce clutter from reflections from the ground This article is about the early British computer. The term "Manchester Mark I" can also refer to the Avro Manchester heavy bomber in RAF service during The United Kingdom of Great Britain and Northern Ireland, commonly known as the United Kingdom, the UK or Britain,is a Sovereign state located The Williams tube or the Williams-Kilburn tube (after inventors Freddie Williams and Tom Kilburn) developed about 1946 or 1947 Drum memory is a magnetic Data storage device and was an early form of Computer memory widely used in the 1950s and into the 1960s invented by Gustav Tauschek CSIRAC ( C ouncil for S cientific and I ndustrial R esearch A utomatic C omputer, pronounced /'sаɪræk/ For a topic outline on this subject see List of basic Australia topics. The von Neumann architecture is a design model for a stored-program Digital computer that uses a processing unit and a single separate storage structure Genesis in radar The basic concept of the delay line originated with World War II Radar research as a system to reduce clutter from reflections from the ground The use of digital electronics (largely invented by Claude Shannon in 1937) and more flexible programmability were vitally important steps, but defining one point along this road as "the first digital electronic computer" is difficult (Shannon 1940). Claude Elwood Shannon (April 30 1916 – February 24 2001 an American Electronic engineer and Mathematician, is "the father of Information Notable achievements include:

EDSAC was one of the first computers to implement the stored program (von Neumann) architecture. Electronic Delay Storage Automatic Calculator ( EDSAC) was an early British Computer. The von Neumann architecture is a design model for a stored-program Digital computer that uses a processing unit and a single separate storage structure

• Konrad Zuse's electromechanical "Z machines". Konrad Zuse (ˈkɔnʁat ˈtsuːzə June 22, 1910 Berlin - December 18, 1995 Hünfeld) was a German In Engineering, electromechanics combines the Sciences of Electromagnetism of Electrical engineering and mechanics. The Z3 (1941) was the first working machine featuring binary arithmetic, including floating point arithmetic and a measure of programmability. Konrad Zuse 's The binary numeral system, or base-2 number system, is a Numeral system that represents numeric values using two symbols usually 0 and 1. In 1998 the Z3 was proved to be Turing complete, therefore being the world's first operational computer. In computability theory, several closely-related terms are used to describe the "computational power" of a computational system (such as an Abstract machine or
• The non-programmable Atanasoff–Berry Computer (1941) which used vacuum tube based computation, binary numbers, and regenerative capacitor memory. The Atanasoff–Berry Computer ( ABC) was the first electronic Digital Computing device Computation is a general term for any type of Information processing. Regenerative capacitor memory is a type of computer memory that uses the electrical property of Capacitance to store the Bits of data
• The secret British Colossus computers (1943)^[5], which had limited programmability but demonstrated that a device using thousands of tubes could be reasonably reliable and electronically reprogrammable. The Colossus machines were electronic Computing devices used by British codebreakers to read Encrypted German messages during It was used for breaking German wartime codes. Cryptanalysis (from the Greek kryptós, "hidden" and analýein, "to loosen" or "to untie" is the study of methods for
• The Harvard Mark I (1944), a large-scale electromechanical computer with limited programmability. The IBM Automatic Sequence Controlled Calculator ( ASCC) called the Mark I by Harvard University, was the first large-scale automatic digital
• The U. S. Army's Ballistics Research Laboratory ENIAC (1946), which used decimal arithmetic and is sometimes called the first general purpose electronic computer (since Konrad Zuse's Z3 of 1941 used electromagnets instead of electronics). The United States Army Ballistic Research Laboratory (BRL at Aberdeen Proving Ground, Maryland was the center for the army's research efforts in interior ENIAC, short for Electronic Numerical Integrator And Computer, was the first general-purpose electronic Computer. The decimal ( base ten or occasionally denary) Numeral system has ten as its base. Electronics refers to the flow of charge (moving Electrons through Nonmetal conductors (mainly Semiconductors, whereas electrical Konrad Zuse (ˈkɔnʁat ˈtsuːzə June 22, 1910 Berlin - December 18, 1995 Hünfeld) was a German Konrad Zuse 's An electromagnet is a type of Magnet in which the Magnetic field is produced by the flow of an electric current. Electronics refers to the flow of charge (moving Electrons through Nonmetal conductors (mainly Semiconductors, whereas electrical Initially, however, ENIAC had an inflexible architecture which essentially required rewiring to change its programming.

Several developers of ENIAC, recognizing its flaws, came up with a far more flexible and elegant design, which came to be known as the stored program architecture or von Neumann architecture. The von Neumann architecture is a design model for a stored-program Digital computer that uses a processing unit and a single separate storage structure This design was first formally described by John von Neumann in the paper "First Draft of a Report on the EDVAC", published in 1945. The First Draft of a Report on the EDVAC (commonly shortened to First Draft) was an incomplete 101-page document written by John A number of projects to develop computers based on the stored program architecture commenced around this time, the first of these being completed in Great Britain. See also Kingdom of Great Britain Great Britain (Breatainn Mhòr Prydain Fawr Breten Veur Graet Breetain is the larger of the two main islands The first to be demonstrated working was the Manchester Small-Scale Experimental Machine (SSEM) or "Baby". The Manchester Small-Scale Experimental Machine (SSEM, nicknamed Baby, was the world's first stored-program Computer. However, the EDSAC, completed a year after SSEM, was perhaps the first practical implementation of the stored program design. Electronic Delay Storage Automatic Calculator ( EDSAC) was an early British Computer. Shortly thereafter, the machine originally described by von Neumann's paper—EDVAC—was completed but did not see full-time use for an additional two years. EDVAC ( E lectronic D iscrete V ariable A utomatic C omputer) was one of the earliest electronic Computers

Nearly all modern computers implement some form of the stored program architecture, making it the single trait by which the word "computer" is now defined. By this standard, many earlier devices would no longer be called computers by today's definition, but are usually referred to as such in their historical context. While the technologies used in computers have changed dramatically since the first electronic, general-purpose computers of the 1940s, most still use the von Neumann architecture. The von Neumann architecture is a design model for a stored-program Digital computer that uses a processing unit and a single separate storage structure The design made the universal computer a practical reality.

Microprocessors are miniaturized devices that often implement stored program CPUs. A microprocessor incorporates most or all of the functions of a Central processing unit (CPU on a single Integrated

Vacuum tube-based computers were in use throughout the 1950s. This article is about the electronic device not an evacuated pipe used for experiments in Free-fall. Vacuum tubes were largely replaced in the 1960s by transistor-based computers. In Electronics, a transistor is a Semiconductor device commonly used to amplify or switch electronic signals When compared with tubes, transistors are smaller, faster, cheaper, use less power, and are more reliable. In the 1970s, integrated circuit technology and the subsequent creation of microprocessors, such as the Intel 4004, caused another generation of decreased size and cost, and another generation of increased speed and reliability. Microchipsjpg|right|thumb|200px|Microchips ( EPROM memory with a transparent window showing the integrated circuit inside A microprocessor incorporates most or all of the functions of a Central processing unit (CPU on a single Integrated The Intel 4004 is a 4-bit Central processing unit (CPU released by Intel Corporation in 1971 By the 1980s, computers became sufficiently small and cheap to replace simple mechanical controls in domestic appliances such as washing machines. A washing machine, or washer, is a machine designed to clean Laundry, such as Clothing, Towels and sheets The term is mostly applied The 1980s also witnessed home computers and the now ubiquitous personal computer. A home computer was a class of Personal computer entering the market in 1977 and becoming common during the 1980s A personal computer ( PC) is any Computer whose original sales price size and capabilities make it useful for individuals and which is intended to be operated With the evolution of the Internet, personal computers are becoming as common as the television and the telephone in the household. Television ( TV) is a widely used Telecommunication medium for sending ( Broadcasting) and receiving moving Images, either monochromatic Basic principle A traditional landline telephone system also known as "plain old telephone service" (POTS, commonly handles both signaling and audio information

Stored program architecture

Main articles: Computer program and Computer programming

The defining feature of modern computers which distinguishes them from all other machines is that they can be programmed. Computer programs (also software programs, or just programs) are instructions for a Computer. That is to say that a list of instructions (the program) can be given to the computer and it will store them and carry them out at some time in the future. In Computer science, an instruction is a single operation of a processor defined by an Instruction set architecture. Computer programs (also software programs, or just programs) are instructions for a Computer.

In most cases, computer instructions are simple: add one number to another, move some data from one location to another, send a message to some external device, etc. These instructions are read from the computer's memory and are generally carried out (executed) in the order they were given. Computer data storage, often called storage or memory, refers to Computer components devices and recording media that retain digital Execution in computer and Software engineering is the process by which a Computer or Virtual computer carries out the instructions However, there are usually specialized instructions to tell the computer to jump ahead or backwards to some other place in the program and to carry on executing from there. These are called "jump" instructions (or branches). A branch (or jump on some Computer architectures, such as the PDP-8 and Intel x86) is a point in a Computer program where the Furthermore, jump instructions may be made to happen conditionally so that different sequences of instructions may be used depending on the result of some previous calculation or some external event. In Computer science, conditional statements, conditional expressions and conditional constructs are features of a Programming language which Many computers directly support subroutines by providing a type of jump that "remembers" the location it jumped from and another instruction to return to the instruction following that jump instruction. In Computer science, a subroutine ( function, method, procedure, or subprogram) is a portion of code within a larger

Program execution might be likened to reading a book. While a person will normally read each word and line in sequence, they may at times jump back to an earlier place in the text or skip sections that are not of interest. Similarly, a computer may sometimes go back and repeat the instructions in some section of the program over and over again until some internal condition is met. This is called the flow of control within the program and it is what allows the computer to perform tasks repeatedly without human intervention. In Computer science control flow (or alternatively flow of control refers to the order in which the individual statements, instructions or Function

Comparatively, a person using a pocket calculator can perform a basic arithmetic operation such as adding two numbers with just a few button presses. A calculator is device for performing mathematical calculations distinguished from a Computer by having a limited problem solving ability and an interface optimized for interactive But to add together all of the numbers from 1 to 1,000 would take thousands of button presses and a lot of time—with a near certainty of making a mistake. On the other hand, a computer may be programmed to do this with just a few simple instructions. For example:

        mov      #0,sum     ; set sum to 0        mov      #1,num     ; set num to 1loop:   add      num,sum    ; add num to sum        add      #1,num     ; add 1 to num        cmp      num,#1000  ; compare num to 1000        ble      loop       ; if num <= 1000, go back to 'loop'        halt                ; end of program.  stop running

Once told to run this program, the computer will perform the repetitive addition task without further human intervention. It will almost never make a mistake and a modern PC can complete the task in about a millionth of a second. ^[6]

However, computers cannot "think" for themselves in the sense that they only solve problems in exactly the way they are programmed to. An intelligent human faced with the above addition task might soon realize that instead of actually adding up all the numbers one can simply use the equation

and arrive at the correct answer (500,500) with little work. ^[7] In other words, a computer programmed to add up the numbers one by one as in the example above would do exactly that without regard to efficiency or alternative solutions.

Programs

A 1970s punched card containing one line from a FORTRAN program. Fortran (previously FORTRAN) is a general-purpose, procedural, imperative Programming language that is especially suited to The card reads: "Z(1) = Y + W(1)" and is labelled "PROJ039" for identification purposes.

In practical terms, a computer program might include anywhere from a dozen instructions to many millions of instructions for something like a word processor or a web browser. Computer programs (also software programs, or just programs) are instructions for a Computer. A web browser is a software application which enables a user to display and interact with text images videos music games and other information typically located on a A typical modern computer can execute billions of instructions every second and nearly never make a mistake over years of operation.

Large computer programs may take teams of computer programmers years to write and the probability of the entire program having been written completely in the manner intended is unlikely. 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 Errors in computer programs are called bugs. A software bug (or just “bug” is an error flaw mistake Failure, fault or “undocumented feature” in a Computer program that prevents it Sometimes bugs are benign and do not affect the usefulness of the program, in other cases they might cause the program to completely fail (crash), in yet other cases there may be subtle problems. A crash in Computing is a condition where a program (either an application or part of the Operating system) stops performing its expected function and also Sometimes otherwise benign bugs may be used for malicious intent, creating a security exploit. An exploit (from the same word in the French language, meaning "achievement" or "accomplishment" is a piece of Software, a chunk of data or Bugs are usually not the fault of the computer. Since computers merely execute the instructions they are given, bugs are nearly always the result of programmer error or an oversight made in the program's design. ^[8]

In most computers, individual instructions are stored as machine code with each instruction being given a unique number (its operation code or opcode for short). Machine code or machine language is a system of instructions and data executed directly by a Computer 's Central processing unit. In computer technology an opcode ( op eration code) is the portion of a Machine language instruction that specifies the operation to be performed The command to add two numbers together would have one opcode, the command to multiply them would have a different opcode and so on. The simplest computers are able to perform any of a handful of different instructions; the more complex computers have several hundred to choose from—each with a unique numerical code. Since the computer's memory is able to store numbers, it can also store the instruction codes. This leads to the important fact that entire programs (which are just lists of instructions) can be represented as lists of numbers and can themselves be manipulated inside the computer just as if they were numeric data. The fundamental concept of storing programs in the computer's memory alongside the data they operate on is the crux of the von Neumann, or stored program, architecture. In some cases, a computer might store some or all of its program in memory that is kept separate from the data it operates on. This is called the Harvard architecture after the Harvard Mark I computer. The Harvard architecture is a Computer architecture with physically separate storage and signal pathways for instructions and data The IBM Automatic Sequence Controlled Calculator ( ASCC) called the Mark I by Harvard University, was the first large-scale automatic digital Modern von Neumann computers display some traits of the Harvard architecture in their designs, such as in CPU caches.

While it is possible to write computer programs as long lists of numbers (machine language) and this technique was used with many early computers,^[9] it is extremely tedious to do so in practice, especially for complicated programs. Machine code or machine language is a system of instructions and data executed directly by a Computer 's Central processing unit. Instead, each basic instruction can be given a short name that is indicative of its function and easy to remember—a mnemonic such as ADD, SUB, MULT or JUMP. A mnemonic device (nəˈmɒnɪk is a Memory aid Commonly met mnemonics are often verbal something such as a very short poem or a special word used to help a person remember These mnemonics are collectively known as a computer's assembly language. See the terminology section below for information regarding inconsistent use of the terms assembly and assembler Converting programs written in assembly language into something the computer can actually understand (machine language) is usually done by a computer program called an assembler. Machine languages and the assembly languages that represent them (collectively termed low-level programming languages) tend to be unique to a particular type of computer. In Computer science, a low-level programming language is a language that provides little or no abstraction from a computer's microprocessor. For instance, an ARM architecture computer (such as may be found in a PDA or a hand-held videogame) cannot understand the machine language of an Intel Pentium or the AMD Athlon 64 computer that might be in a PC. The ARM architecture (previously the Advanced RISC Machine, and prior to that Acorn RISC Machine) is a 32-bit RISC processor architecture A handheld video game is a Video game designed for a handheld device The Pentium brand refers to Intel 's single-core x86 Microprocessor based on the P5 fifth-generation Microarchitecture. The Athlon 64 is an eighth-generation AMD64 architecture Microprocessor produced by AMD, released on A personal computer ( PC) is any Computer whose original sales price size and capabilities make it useful for individuals and which is intended to be operated ^[10]

Though considerably easier than in machine language, writing long programs in assembly language is often difficult and error prone. Therefore, most complicated programs are written in more abstract high-level programming languages that are able to express the needs of the computer programmer more conveniently (and thereby help reduce programmer error). In computing a high-level programming language is a Programming language with strong abstraction from the details of the computer 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 High level languages are usually "compiled" into machine language (or sometimes into assembly language and then into machine language) using another computer program called a compiler. A compiler is a Computer program (or set of programs that translates text written in a computer language (the source language) into another ^[11] Since high level languages are more abstract than assembly language, it is possible to use different compilers to translate the same high level language program into the machine language of many different types of computer. This is part of the means by which software like video games may be made available for different computer architectures such as personal computers and various video game consoles.

The task of developing large software systems is an immense intellectual effort. Producing software with an acceptably high reliability on a predictable schedule and budget has proved historically to be a great challenge; the academic and professional discipline of software engineering concentrates specifically on this problem. Software engineering is the application of a systematic disciplined quantifiable approach to the development operation and maintenance of Software.

Example

A traffic light showing red.

Suppose a computer is being employed to drive a traffic light. The traffic light, also known as traffic signal, stop light, traffic lamp, stop-and-go lights, robot or semaphore, A simple stored program might say:

1. Turn off all of the lights
2. Turn on the red light
3. Wait for sixty seconds
4. Turn off the red light
5. Turn on the green light
6. Wait for sixty seconds
7. Turn off the green light
8. Turn on the yellow light
9. Wait for two seconds
10. Turn off the yellow light
11. Jump to instruction number (2)

With this set of instructions, the computer would cycle the light continually through red, green, yellow and back to red again until told to stop running the program.

However, suppose there is a simple on/off switch connected to the computer that is intended to be used to make the light flash red while some maintenance operation is being performed. A switch is a mechanical device used to connect and disconnect an electric Circuit at will The program might then instruct the computer to:

1. Turn off all of the lights
2. Turn on the red light
3. Wait for sixty seconds
4. Turn off the red light
5. Turn on the green light
6. Wait for sixty seconds
7. Turn off the green light
8. Turn on the yellow light
9. Wait for two seconds
10. Turn off the yellow light
11. If the maintenance switch is NOT turned on then jump to instruction number 2
12. Turn on the red light
13. Wait for one second
14. Turn off the red light
15. Wait for one second
16. Jump to instruction number 11

In this manner, the computer is either running the instructions from number (2) to (11) over and over or its running the instructions from (11) down to (16) over and over, depending on the position of the switch. ^[12]

How computers work

Main articles: Central processing unit and Microprocessor

A general purpose computer has four main sections: the arithmetic and logic unit (ALU), the control unit, the memory, and the input and output devices (collectively termed I/O). A microprocessor incorporates most or all of the functions of a Central processing unit (CPU on a single Integrated In Computing, an arithmetic logic unit ( ALU) is a Digital circuit that performs Arithmetic and Logical operations A control unit in general is a central (or sometimes distributed but clearly distinguishable part of whatsoever machinery that controls its operation provided that Computer data storage, often called storage or memory, refers to Computer components devices and recording media that retain digital These parts are interconnected by busses, often made of groups of wires. In Computer architecture, a bus is a subsystem that transfers data between computer components inside a Computer or between computers A wire is a single usually cylindrical, elongated string of drawn Metal.

The control unit, ALU, registers, and basic I/O (and often other hardware closely linked with these) are collectively known as a central processing unit (CPU). Early CPUs were composed of many separate components but since the mid-1970s CPUs have typically been constructed on a single integrated circuit called a microprocessor. Microchipsjpg|right|thumb|200px|Microchips ( EPROM memory with a transparent window showing the integrated circuit inside A microprocessor incorporates most or all of the functions of a Central processing unit (CPU on a single Integrated

Control unit

Main articles: CPU design and Control unit

The control unit (often called a control system or central controller) directs the various components of a computer. CPU design is the Design engineering task of creating a Central processing unit (CPU a component of Computer hardware. A control unit in general is a central (or sometimes distributed but clearly distinguishable part of whatsoever machinery that controls its operation provided that It reads and interprets (decodes) instructions in the program one by one. The control system decodes each instruction and turns it into a series of control signals that operate the other parts of the computer. ^[13] Control systems in advanced computers may change the order of some instructions so as to improve performance.

A key component common to all CPUs is the program counter, a special memory cell (a register) that keeps track of which location in memory the next instruction is to be read from. The program counter, or shorter PC (also called the instruction pointer, part of the instruction sequencer in some Computers is a register in In Computer architecture, a processor register is a small amount of storage available on the CPU whose contents can be accessed more quickly than storage ^[14]

Diagram showing how a particular MIPS architecture instruction would be decoded by the control system. MIPS (originally an acronym for Microprocessor without Interlocked Pipeline Stages) is a RISC microprocessor architecture developed by MIPS Technologies

The control system's function is as follows—note that this is a simplified description, and some of these steps may be performed concurrently or in a different order depending on the type of CPU:

1. Read the code for the next instruction from the cell indicated by the program counter.
2. Decode the numerical code for the instruction into a set of commands or signals for each of the other systems.
3. Increment the program counter so it points to the next instruction.
4. Read whatever data the instruction requires from cells in memory (or perhaps from an input device). The location of this required data is typically stored within the instruction code.
5. Provide the necessary data to an ALU or register.
6. If the instruction requires an ALU or specialized hardware to complete, instruct the hardware to perform the requested operation.
7. Write the result from the ALU back to a memory location or to a register or perhaps an output device.
8. Jump back to step (1).

Since the program counter is (conceptually) just another set of memory cells, it can be changed by calculations done in the ALU. Adding 100 to the program counter would cause the next instruction to be read from a place 100 locations further down the program. Instructions that modify the program counter are often known as "jumps" and allow for loops (instructions that are repeated by the computer) and often conditional instruction execution (both examples of control flow). In Computer science control flow (or alternatively flow of control refers to the order in which the individual statements, instructions or Function

It is noticeable that the sequence of operations that the control unit goes through to process an instruction is in itself like a short computer program - and indeed, in some more complex CPU designs, there is another yet smaller computer called a microsequencer that runs a microcode program that causes all of these events to happen. In Computer architecture and Engineering, a sequencer or microsequencer is a part of the Control unit of a CPU. Microprogramming (ie writing microcode) is a method that can be employed to implement Machine instructions in a CPU relatively easily often using less

Arithmetic/logic unit (ALU)

Main article: Arithmetic logic unit

The ALU is capable of performing two classes of operations: arithmetic and logic. In Computing, an arithmetic logic unit ( ALU) is a Digital circuit that performs Arithmetic and Logical operations

The set of arithmetic operations that a particular ALU supports may be limited to adding and subtracting or might include multiplying or dividing, trigonometry functions (sine, cosine, etc) and square roots. Circle-trig6svg|300px|thumb|right|All of the Trigonometric functions of an angle θ can be constructed geometrically in terms of a unit circle centered at O. In Mathematics, a square root of a number x is a number r such that r 2 = x, or in words a number r whose Some can only operate on whole numbers (integers) whilst others use floating point to represent real numbers—albeit with limited precision. The integers (from the Latin integer, literally "untouched" hence "whole" the word entire comes from the same origin but via French In Computing, floating point describes a system for numerical representation in which a string of digits (or Bits represents a Real number. In Mathematics, the real numbers may be described informally in several different ways However, any computer that is capable of performing just the simplest operations can be programmed to break down the more complex operations into simple steps that it can perform. Therefore, any computer can be programmed to perform any arithmetic operation—although it will take more time to do so if its ALU does not directly support the operation. An ALU may also compare numbers and return boolean truth values (true or false) depending on whether one is equal to, greater than or less than the other ("is 64 greater than 65?"). In Logic and Mathematics, a logical value, also called a truth value, is a value indicating the extent to which a Proposition is true

Logic operations involve Boolean logic: AND, OR, XOR and NOT. Boolean logic is a complete system for Logical operations It was named after George Boole, who first defined an algebraic system of In Logic and/or Mathematics, logical conjunction or and is a two-place Logical operation that results in a value of true if both of In Logic and Mathematics, negation or not is an operation on Logical values for example the logical value of a Proposition These can be useful both for creating complicated conditional statements and processing boolean logic. In Computer science, conditional statements, conditional expressions and conditional constructs are features of a Programming language which Boolean logic is a complete system for Logical operations It was named after George Boole, who first defined an algebraic system of

Superscalar computers contain multiple ALUs so that they can process several instructions at the same time. A superscalar CPU architecture implements a form of parallelism called Instruction-level parallelism within a single processor Graphics processors and computers with SIMD and MIMD features often provide ALUs that can perform arithmetic on vectors and matrices. In Computing, SIMD ( S ingle I nstruction M ultiple D ata is a technique employed to achieve data level parallelism as in a Vector In Computing, MIMD ( M ultiple I nstruction stream M ultiple D ata stream is a technique employed to achieve parallelism In Mathematics, a matrix (plural matrices) is a rectangular table of elements (or entries) which may be Numbers or more generally

Memory

Main article: Computer storage

Magnetic core memory was popular main memory for computers through the 1960s until it was completely replaced by semiconductor memory. Computer data storage, often called storage or memory, refers to Computer components devices and recording media that retain digital Magnetic core memory, or ferrite-core memory, is an early form of Random access Computer memory.

A computer's memory can be viewed as a list of cells into which numbers can be placed or read. Each cell has a numbered "address" and can store a single number. The computer can be instructed to "put the number 123 into the cell numbered 1357" or to "add the number that is in cell 1357 to the number that is in cell 2468 and put the answer into cell 1595". The information stored in memory may represent practically anything. Letters, numbers, even computer instructions can be placed into memory with equal ease. Since the CPU does not differentiate between different types of information, it is up to the software to give significance to what the memory sees as nothing but a series of numbers.

In almost all modern computers, each memory cell is set up to store binary numbers in groups of eight bits (called a byte). The binary numeral system, or base-2 number system, is a Numeral system that represents numeric values using two symbols usually 0 and 1. A bit is a binary digit, taking a value of either 0 or 1 Binary digits are a basic unit of Information storage and communication A byte (pronounced "bite" baɪt is the basic unit of measurement of information storage in Computer science. Each byte is able to represent 256 different numbers; either from 0 to 255 or -128 to +127. To store larger numbers, several consecutive bytes may be used (typically, two, four or eight). When negative numbers are required, they are usually stored in two's complement notation. The two's complement of a Binary number is defined as the value obtained by subtracting the number from a large power of two (specifically from 2 N for Other arrangements are possible, but are usually not seen outside of specialized applications or historical contexts. A computer can store any kind of information in memory as long as it can be somehow represented in numerical form. Modern computers have billions or even trillions of bytes of memory.

The CPU contains a special set of memory cells called registers that can be read and written to much more rapidly than the main memory area. In Computer architecture, a processor register is a small amount of storage available on the CPU whose contents can be accessed more quickly than storage There are typically between two and one hundred registers depending on the type of CPU. Registers are used for the most frequently needed data items to avoid having to access main memory every time data is needed. Since data is constantly being worked on, reducing the need to access main memory (which is often slow compared to the ALU and control units) greatly increases the computer's speed.

Computer main memory comes in two principal varieties: random access memory or RAM and read-only memory or ROM. RAM can be read and written to anytime the CPU commands it, but ROM is pre-loaded with data and software that never changes, so the CPU can only read from it. ROM is typically used to store the computer's initial start-up instructions. In general, the contents of RAM is erased when the power to the computer is turned off while ROM retains its data indefinitely. In a PC, the ROM contains a specialized program called the BIOS that orchestrates loading the computer's operating system from the hard disk drive into RAM whenever the computer is turned on or reset. In Computing, the BIOS (ˈbaɪoʊs An operating system (commonly abbreviated OS and O/S) is the software component of a Computer system that is responsible for the management and coordination In embedded computers, which frequently do not have disk drives, all of the software required to perform the task may be stored in ROM. An embedded system is a special-purpose Computer system designed to perform one or a few dedicated functions often with Real-time computing constraints Software that is stored in ROM is often called firmware because it is notionally more like hardware than software. In Computing, firmware is a computer program that is Embedded in a hardware device for example a Microcontroller. Flash memory blurs the distinction between ROM and RAM by retaining data when turned off but being rewritable like RAM. Flash memory is non-volatile computer memory that can be electrically erased and reprogrammed However, flash memory is typically much slower than conventional ROM and RAM so its use is restricted to applications where high speeds are not required. ^[15]

In more sophisticated computers there may be one or more RAM cache memories which are slower than registers but faster than main memory. Generally computers with this sort of cache are designed to move frequently needed data into the cache automatically, often without the need for any intervention on the programmer's part.

Input/output (I/O)

Main article: Input/output

Hard disks are common I/O devices used with computers. In Computing, input/output, or I/O, refers to the communication between an Information processing system (such as a Computer) and the outside A hard disk drive ( HDD) commonly referred to as a hard drive, hard disk, or fixed disk drive, is a Non-volatile storage device

I/O is the means by which a computer receives information from the outside world and sends results back. Devices that provide input or output to the computer are called peripherals. For an account of the words periphery and peripheral as they are used in biology sociology politics computer hardware and other fields see the On a typical personal computer, peripherals include input devices like the keyboard and mouse, and output devices such as the display and printer. A personal computer ( PC) is any Computer whose original sales price size and capabilities make it useful for individuals and which is intended to be operated In Computing, a mouse (plural mice, mouse devices, or mouses) A visual display unit, often called simply a monitor or display, is a piece of Electrical equipment which displays images generated from the Video Hard disk drives, floppy disk drives and optical disc drives serve as both input and output devices. A hard disk drive ( HDD) commonly referred to as a hard drive, hard disk, or fixed disk drive, is a Non-volatile storage device A floppy disk is an increasingly Obsolete data storage medium that is composed of a disk of thin flexible ("floppy" Magnetic storage medium encased In Computing, an optical disc drive ( ODD) is a Disk drive that uses Laser light or electromagnetic waves near the Light spectrum Computer networking is another form of I/O. Computer networking is the Engineering Discipline concerned with communication between Computer systems or devices Networking routers

Often, I/O devices are complex computers in their own right with their own CPU and memory. A graphics processing unit might contain fifty or more tiny computers that perform the calculations necessary to display 3D graphics. 3D computer graphics (in contrast to 2D computer graphics) are graphics that use a three-dimensional representation of geometric data that is stored in the computer Modern desktop computers contain many smaller computers that assist the main CPU in performing I/O. A desktop computer is a Personal computer (PC in a form intended for regular use at a single location as opposed to a mobile Laptop or portable computer

Multitasking

Main article: Computer multitasking

While a computer may be viewed as running one gigantic program stored in its main memory, in some systems it is necessary to give the appearance of running several programs simultaneously. In computing Multitasking is a method by which multiple tasks also known as processes, share common processing resources such as a CPU. This is achieved by having the computer switch rapidly between running each program in turn. One means by which this is done is with a special signal called an interrupt which can periodically cause the computer to stop executing instructions where it was and do something else instead. In Computing, an interrupt is an asynchronous signal from hardware indicating the need for attention or a synchronous event in software indicating the need for a change By remembering where it was executing prior to the interrupt, the computer can return to that task later. If several programs are running "at the same time", then the interrupt generator might be causing several hundred interrupts per second, causing a program switch each time. Since modern computers typically execute instructions several orders of magnitude faster than human perception, it may appear that many programs are running at the same time even though only one is ever executing in any given instant. This method of multitasking is sometimes termed "time-sharing" since each program is allocated a "slice" of time in turn.

Before the era of cheap computers, the principle use for multitasking was to allow many people to share the same computer.

Seemingly, multitasking would cause a computer that is switching between several programs to run more slowly - in direct proportion to the number of programs it is running. However, most programs spend much of their time waiting for slow input/output devices to complete their tasks. If a program is waiting for the user to click on the mouse or press a key on the keyboard, then it will not take a "time slice" until the event it is waiting for has occurred. This frees up time for other programs to execute so that many programs may be run at the same time without unacceptable speed loss.

Multiprocessing

Main article: Multiprocessing

Cray designed many supercomputers that used multiprocessing heavily. Multiprocessing is the use of two or more central processing units (CPUs within a single computer system Cray Inc ( is a Supercomputer manufacturer based in Seattle Washington.

Some computers may divide their work between one or more separate CPUs, creating a multiprocessing configuration. Traditionally, this technique was utilized only in large and powerful computers such as supercomputers, mainframe computers and servers. A supercomputer is a Computer that is at the frontline of processing capacity particularly speed of calculation (at the time of its introduction Mainframes (often colloquially referred to as Big Iron) are Computers used mainly by large organizations for critical applications typically bulk data A server is a Computer dedicated to providing one or more services over a computer network typically through a request-response routine However, multiprocessor and multi-core (multiple CPUs on a single integrated circuit) personal and laptop computers have become widely available and are beginning to see increased usage in lower-end markets as a result. A multi-core processor (or chip-level multiprocessor, CMP) combines two or more independent cores into a single package composed of a single Integrated

Supercomputers in particular often have highly unique architectures that differ significantly from the basic stored-program architecture and from general purpose computers. ^[16] They often feature thousands of CPUs, customized high-speed interconnects, and specialized computing hardware. Such designs tend to be useful only for specialized tasks due to the large scale of program organization required to successfully utilize most of the available resources at once. Supercomputers usually see usage in large-scale simulation, graphics rendering, and cryptography applications, as well as with other so-called "embarrassingly parallel" tasks. A computer simulation, a computer model or a computational model is a Computer program, or network of computers that attempts to simulate an Rendering is the process of generating an image from a model, by means of computer programs Cryptography (or cryptology; from Greek grc κρυπτός kryptos, "hidden secret" and grc γράφω gráphō, "I write" In the jargon of Parallel computing, an embarrassingly parallel workload (or embarrassingly parallel problem is one for which no particular effort is needed to segment the problem

Networking and the Internet

Main articles: Computer networking and Internet

Visualization of a portion of the routes on the Internet. Computer networking is the Engineering Discipline concerned with communication between Computer systems or devices Networking routers The Internet is a global system of interconnected Computer networks Routing is the process of selecting paths in a network along which to send network traffic

Computers have been used to coordinate information between multiple locations since the 1950s. The U. S. military's SAGE system was the first large-scale example of such a system, which led to a number of special-purpose commercial systems like Sabre. The Semi-Automatic Ground Environment ( SAGE) was an automated control system for tracking and intercepting enemy Bomber aircraft used by NORAD from Sabre is a Computer reservations system /global distribution system (GDS used by Airlines Railways Hotels Travel agents and other

In the 1970s, computer engineers at research institutions throughout the United States began to link their computers together using telecommunications technology. This effort was funded by ARPA (now DARPA), and the computer network that it produced was called the ARPANET. The Defense Advanced Research Projects Agency (DARPA is an agency of the United States Department of Defense responsible for the development of new Technology A computer network is a group of interconnected Computers. Networks may be classified according to a wide variety of characteristics The ARPANET ( Advanced Research Projects Agency Network) developed by ARPA of the United States Department of Defense, was the world's first operational The technologies that made the Arpanet possible spread and evolved. In time, the network spread beyond academic and military institutions and became known as the Internet. The Internet is a global system of interconnected Computer networks The emergence of networking involved a redefinition of the nature and boundaries of the computer. Computer operating systems and applications were modified to include the ability to define and access the resources of other computers on the network, such as peripheral devices, stored information, and the like, as extensions of the resources of an individual computer. Initially these facilities were available primarily to people working in high-tech environments, but in the 1990s the spread of applications like e-mail and the World Wide Web, combined with the development of cheap, fast networking technologies like Ethernet and ADSL saw computer networking become almost ubiquitous. Electronic mail, often abbreviated to e-mail, email, or originally eMail, is a Store-and-forward method of writing sending receiving The World Wide Web (commonly shortened to the Web) is a system of interlinked Hypertext documents accessed via the Internet. Ethernet is a family of frame -based Computer networking technologies for Local area networks (LANs Asymmetric Digital Subscriber Line ( ADSL) is a form of DSL, a data communications technology that enables faster data transmission over Copper Telephone In fact, the number of computers that are networked is growing phenomenally. A very large proportion of personal computers regularly connect to the Internet to communicate and receive information. A personal computer ( PC) is any Computer whose original sales price size and capabilities make it useful for individuals and which is intended to be operated The Internet is a global system of interconnected Computer networks "Wireless" networking, often utilizing mobile phone networks, has meant networking is becoming increasingly ubiquitous even in mobile computing environments.

Further topics

Hardware

Main article: Computer hardware

The term hardware covers all of those parts of a computer that are tangible objects. Typical PC hardware A typical Personal computer consists of a case or chassis in a tower shape (desktop and the following parts Motherboard Circuits, displays, power supplies, cables, keyboards, printers and mice are all hardware.

Software

Main article: Computer software

Software refers to parts of the computer which do not have a material form, such as programs, data, protocols, etc. The history of computer hardware encompasses the hardware, its architecture, and its impact on software. The Antikythera mechanism (ˌæntɪkɪˈθɪərə an-ti-ki- theer -uh is an ancient mechanical Calculator (also described as the first known " mechanical The Difference Engine was an automatic mechanical calculator designed to tabulate polynomial functions. The Norden bombsight was a Bombsight used by the United States Army Air Forces during World War II, and the United States Air Force in the The Jacquard Loom is a mechanical Loom, invented by Joseph Marie Jacquard in 1801, that has holes punched in pasteboard each row of which corresponds to The analytical engine, an important step in the History of computers, was the design of a mechanical general-purpose Computer by the British mathematician Charles The IBM Automatic Sequence Controlled Calculator ( ASCC) called the Mark I by Harvard University, was the first large-scale automatic digital Konrad Zuse 's The Atanasoff–Berry Computer ( ABC) was the first electronic Digital Computing device The IBM 604 was a control panel programmable Electronic Calculating Punch introduced in 1948, and The Remington Rand 409 Plug-board programmed Punch card calculator designed in 1949, was sold in two models the UNIVAC 60 ( The Remington Rand 409 Plug-board programmed Punch card calculator designed in 1949, was sold in two models the UNIVAC 60 ( This is a list of Vacuum tube computers, arranged by date put into service Atanasoff–Berry Computer (1942 - not Turing complete The Colossus machines were electronic Computing devices used by British codebreakers to read Encrypted German messages during ENIAC, short for Electronic Numerical Integrator And Computer, was the first general-purpose electronic Computer. The Manchester Small-Scale Experimental Machine (SSEM, nicknamed Baby, was the world's first stored-program Computer. Electronic Delay Storage Automatic Calculator ( EDSAC) was an early British Computer. This article is about the early British computer. The term "Manchester Mark I" can also refer to the Avro Manchester heavy bomber in RAF service during CSIRAC ( C ouncil for S cientific and I ndustrial R esearch A utomatic C omputer, pronounced /'sаɪræk/ EDVAC ( E lectronic D iscrete V ariable A utomatic C omputer) was one of the earliest electronic Computers The UNIVAC I ( U N I V ersal A utomatic C omputer I) was the first commercial computer made in the United States The IBM 701, known as the Defense Calculator while in development was announced to the public on April 29, The IBM 702 ( photos was announced September 25, 1953 and withdrawn October 1, 1954, but the first production model was not installed until The IBM 650 ( photo was one of IBM ’s early Computers and the world’s first mass-produced ( photo computer See Z22 (handheld for the Palm Handheld The Z22 was the seventh Computer model Konrad Zuse developed (the first Microchipsjpg|right|thumb|200px|Microchips ( EPROM memory with a transparent window showing the integrated circuit inside Mainframes (often colloquially referred to as Big Iron) are Computers used mainly by large organizations for critical applications typically bulk data The IBM 7090 was a second-generation Transistorized version of the earlier IBM 709 vacuum tube Mainframe computers and was designed for "large-scale The IBM 7080 was a Transistorized variable word length BCD computer in the IBM 700/7000 series commercial architecture line introduced in August 1961 that The IBM System/360 ( S/360) is a Mainframe computer system family announced by IBM on April 7, 1964. The group of Mainframe computer competitors to IBM in the 1970s became known as the BUNCH: Burroughs, UNIVAC, NCR, Control Data A minicomputer (colloquially mini) is a class of multi-user Computers that lies in the middle range of the computing spectrum in between the largest Multi-user The PDP-8 was the first successful commercial Minicomputer, produced by Digital Equipment Corporation (DEC in the 1960s The PDP-11 was a series of 16-bit Minicomputers sold by Digital Equipment Corp "System 32" redirects here For the arcade system board see Sega System 32. The IBM System/36 was a Minicomputer marketed by IBM from 1983 to 2000 Name "VAX" was originally an Acronym for V irtual A ddress e' X' tension, both because the VAX was seen as a 32-bit The IBM System i is IBM's previous generation of systems designed for IBM i users and was subsequently replaced by the IBM Power Systems in April 2008 The Intel 4004, the world's first commercially available single- chip Microprocessor, was a 4-bit CPU. The Intel 4004 is a 4-bit Central processing unit (CPU released by Intel Corporation in 1971 The Intel 4040 Microprocessor was the successor to the Intel 4004. Eight-bit CPUs normally use an 8-bit data bus and a 16-bit address bus which means that their Address space is limited to 64 KBs This is not a "natural The Intel 8008 was an early byte-oriented Microprocessor designed and manufactured by Intel and introduced in April 1972 The Intel 8080 was an early Microprocessor designed and manufactured by Intel. The 6800 is an 8-bit Microprocessor produced by Motorola and released shortly after the Intel 8080 in late 1974 The Motorola 6809 is an 8-bit (arguably an 8/ 16-bit) Microprocessor CPU from Motorola, introduced circa 1979 The MOS Technology 6502 is an 8-bit Microprocessor that was designed by Chuck Peddle for MOS Technology in 1975 The Zilog Z80 is an 8-bit Microprocessor designed and sold by Zilog from July 1976 onwards The Intel 8088 is an Intel X86 Microprocessor based on the 8086, with 16- Bit registers and an 8-bit external Data bus The Z8000 was a 16-bit Microprocessor introduced by ZiLOG in 1979 The WDC 65816 (also 65C816) a 16-bit Microprocessor CPU developed by the Western Design Center (WDC, is an expanded and compatible The range of Integer values that can be stored in 32 bits is 0 through 4294967295 or −2147483648 through 2147483647 using Two's complement encoding The Pentium brand refers to Intel 's single-core x86 Microprocessor based on the P5 fifth-generation Microarchitecture. The Motorola 68000 is a 16/32-bit CISC Microprocessor core designed and marketed by Freescale Semiconductor (formerly Motorola Semiconductor The ARM architecture (previously the Advanced RISC Machine, and prior to that Acorn RISC Machine) is a 32-bit RISC processor architecture '64-bit' CPUs have existed in Supercomputers since the 1960s and in RISC -based workstations and servers since the early 1990s. x86-64 is a Superset of the x86 instruction set architecture. PowerPC is a RISC Instruction set architecture created by the 1991 Apple – IBM – Motorola alliance known as AIM MIPS (originally an acronym for Microprocessor without Interlocked Pipeline Stages) is a RISC microprocessor architecture developed by MIPS Technologies SPARC (from Scalable Processor Architecture is a RISC Microprocessor Instruction set architecture originally An embedded system is a special-purpose Computer system designed to perform one or a few dedicated functions often with Real-time computing constraints The Intel 8048 Microcontroller (µC (MCS-48 Intel's first microcontroller was used in the Magnavox Odyssey² Video game console, the Roland Jupiter-4 The Intel 8051 is a Harvard architecture, single chip Microcontroller (µC which was developed by Intel in 1980 for use in Embedded systems A personal computer ( PC) is any Computer whose original sales price size and capabilities make it useful for individuals and which is intended to be operated A desktop computer is a Personal computer (PC in a form intended for regular use at a single location as opposed to a mobile Laptop or portable computer A home computer was a class of Personal computer entering the market in 1977 and becoming common during the 1980s A laptop computer, also known as a notebook computer, is a small Personal computer designed for mobile use. A portable computer is a Computer that is designed to be moved from one place to another A Tablet PC is a Notebook or slate-shaped Mobile computer, equipped with a Touchscreen or Graphics tablet/screen hybrid technology which allows Wearable computers are Computers that are worn on the body They have been applied to areas such as Behavioral modeling, Health monitoring systems information A quantum computer is a device for Computation that makes direct use of distinctively Quantum mechanical Phenomena, such as superposition A chemical computer, also called reaction-diffusion computer BZ compter or gooware computer is an unconventional computer based on a semi-solid chemical "soup" DNA computing is a form of Computing which uses DNA, Biochemistry and Molecular biology, instead of the traditional silicon-based Computer An optical computer is a computer that uses light instead of electricity (i Spintronics (a Neologism meaning "spin transport electronics" also known as magnetoelectronics is an Emerging technology which exploits the intrinsic For an account of the words periphery and peripheral as they are used in biology sociology politics computer hardware and other fields see the In Computing, input/output, or I/O, refers to the communication between an Information processing system (such as a Computer) and the outside In Computing, a mouse (plural mice, mouse devices, or mouses) In Computing, a keyboard is an Input device partially modelled after the typewriter keyboard which uses an arrangement of buttons or keys A joystick is an input device consisting of a stick that pivots on a base and reports its angle or direction to the device it is controlling Historical precedent Scanners can be considered the successors of early telephotography input devices consisting of a rotating drum with a single Photodetector at A visual display unit, often called simply a monitor or display, is a piece of Electrical equipment which displays images generated from the Video A floppy disk is an increasingly Obsolete data storage medium that is composed of a disk of thin flexible ("floppy" Magnetic storage medium encased A hard disk drive ( HDD) commonly referred to as a hard drive, hard disk, or fixed disk drive, is a Non-volatile storage device A teleprinter ( In Computer architecture, a bus is a subsystem that transfers data between computer components inside a Computer or between computers In Telecommunications, RS-232 (Recommended Standard 232 is a standard for serial binary data signals connecting between a DTE ( Data Terminal Equipment The Peripheral Component Interconnect, or PCI Standard (commonly PCI) specifies a Computer bus for attaching peripheral devices to a Computer Computer networking is the Engineering Discipline concerned with communication between Computer systems or devices Networking routers Ethernet is a family of frame -based Computer networking technologies for Local area networks (LANs In electronic digital data transmission systems the Network protocol Asynchronous Transfer Mode (ATM encodes data traffic into small fixed-sized cells Fiber distributed data interface ( FDDI) provides a standard for Data transmission in a Local area network When software is stored in hardware that cannot easily be modified (such as BIOS ROM in an IBM PC compatible), it is sometimes called "firmware" to indicate that it falls into an uncertain area somewhere between hardware and software. In Computing, the BIOS (ˈbaɪoʊs IBM PC compatible computers are those generally similar to the original IBM PC, XT, and AT.

Programming languages

Programming languages provide various ways of specifying programs for computers to run. An operating system (commonly abbreviated OS and O/S) is the software component of a Computer system that is responsible for the management and coordination Unix (officially trademarked as UNIX, sometimes also written as Unix with Small caps) is a computer Unix System V, commonly abbreviated SysV (and usually pronounced though rarely written as System 5 was one of the versions of the Unix Operating system HP-UX (Hewlett Packard UniX is Hewlett-Packard 's proprietary implementation of the Unix Operating system, based on System V (initially Solaris is a Unix -based Operating system introduced by Sun Microsystems in 1992 as the successor to SunOS. SunOS is a version of the Unix Operating system developed by Sun Microsystems for their Workstation and server Computer IRIX is a computer Operating system developed by Silicon Graphics Inc There are a number of Unix-like Operating systems under active development descended from the Berkeley Software Distribution (BSD series of UNIX variants GNU ( pronounced) is a computer Operating system composed entirely of Free software. Linux (commonly pronounced ˈlɪnəks What do you mean by template here? Technical variations of Linux distributions include support for different hardware devices and systems or software package configurations Microsoft Windows is a series of Software Operating systems and Graphical user interfaces produced by Microsoft. Windows 95 is a consumer-oriented Graphical user interface -based Operating system. Windows 98 ( codenamed Memphis) is a graphical Operating system released on 25 June 1998 by Microsoft and the successor to Windows 95 Windows NT is a family of Operating systems produced by Microsoft, the first version of which was released in July 1993 Windows 2000 (also referred to as Win2K) is a preemptive, interruptible graphical and business-oriented Operating system designed to work with Windows XP is a family of 32-bit and 64-bit Operating systems produced by Microsoft for use on Personal computers including home and Windows Vista (ˈvɪstə is a line of Operating systems developed by Microsoft for use on Personal computers including home and business desktops Windows CE (also known officially as Windows Embedded Compact post version 6 DOS, short for "Disk Operating System" is a shorthand term for several closely related Operating systems that dominated the IBM PC compatible market 86-DOS was an operating system developed and marketed by Seattle Computer Products for its Intel 8086 -based computer kit IBM PC-DOS is a DOS operating system for the IBM Personal Computer, sold throughout the 1980s and 1990s MS-DOS (short for M icro' s' oft D isk O perating S ystem is an Operating system commercialized by Microsoft. FreeDOS (formerly Free-DOS and PD-DOS) is an Operating system for IBM PC compatible computers Mac OS is the trademarked name for a series of Graphical user interface -based Operating systems developed by Apple Inc Mac OS is the trademarked name for a series of Graphical user interface -based Operating systems developed by Apple Inc Mac OS X (mæk oʊ ɛs tɛn is a line of computer Operating systems developed marketed and sold by Apple Inc, the latest of which is pre-loaded on all currently An embedded operating system is an Operating system for embedded computer systems. A real-time operating system ( RTOS; generally pronounced as "are-toss" is a multitasking Operating system intended for real-time Operating systems can be categorized by technology ownership licensing working state usage and by many other characteristics Amoeba is an Opensource Microkernel -based distributed Operating system developed by Andrew S Oberon is an Operating system, originally developed as part of the NS32032 -based Ceres workstation project it is written entirely in the Oberon Bluebottle, (formerly known as AOS) is the name of the next generation Native Oberon, the Oberon operating system for bare PC hardware Plan 9 from Bell Labs is a Distributed operating system, primarily used for research In Computer science, a library is a collection of Subroutines used to develop Software. Multimedia is media and content that utilizes a combination of different content forms. Microsoft DirectX is a collection of Application programming interfaces (APIs for handling tasks related to Multimedia, especially Game programming and OpenGL ( Open G raphics L ibrary is a standard specification defining a cross-language Cross-platform API for writing applications that produce OpenAL ( Open A udio L ibrary is a Free software cross-platform audio API. The C standard library (also known as libc) is a now-standardized collection of Header files and library routines used to implement common operations such The Standard Template Library ( STL) is a software library partially included in the C++ Standard Library. In Computer science, data is anything in a form suitable for use with a Computer. In computing, a protocol is a convention or standard that controls or enables the connection Communication, and Data transfer between two computing The Internet Protocol Suite (commonly TCP/IP) is the set of Communications protocols used for the Internet and other similar networks Kermit is a Computer file transfer/management protocol and a set of communications software tools primarily used in the early years of personal computing in the 1980s Hypertext Transfer Protocol ( HTTP) is a Communications protocol for the transfer of information on the Internet. Simple Mail Transfer Protocol ( SMTP) is a De facto standard for electronic mail (e-mail transmissions across the Internet. A file format is a particular way to encode information for storage in a Computer file. HTML, an initialism of HyperText Markup Language, is the predominant Markup language for Web pages It provides a means to describe the structure Don't change "Extensible" The Moving Picture Experts Group, commonly referred to as simply MPEG, is a Working group of ISO / IEC charged with the development of video and Portable Network Graphics ( PNG) is a bitmapped image format that employs Lossless data compression. The user interface (or Human Computer Interface) is the aggregate of means by which people&mdash the users '&mdash interact with the System In Human–computer interaction, WIMP stands for " window, icon, menu, Pointing device " denoting a style of interaction Microsoft Windows is a series of Software Operating systems and Graphical user interfaces produced by Microsoft. A gnome is a Mythical creature characterized by its extremely small size and subterranean lifestyle KDE ( K Desktop Environment) (ˌkeɪdiːˈiː is a Free software project which aims to be a powerful system for an easy-to-use Desktop environment. QNX (pronounced either Q-N-X or Q-nix is a commercial Unix-like Real-time operating system, aimed primarily at the Embedded systems market The Common Desktop Environment ( CDE) a Graphical Desktop environment for Unix, leverages the Motif Widget toolkit GEM ( G raphical E nvironment M anager was a Windowing system created by Digital Research Inc TUI short for Text User Interface or Textual User Interface (and sometimes Terminal User Interface) is a Retronym that was coined sometime In computing a shell is a piece of software that provides an interface for users Application software is a subclass of Computer software that employs the capabilities of a computer directly and thoroughly to a task that the user wishes to perform In Computing, an office suite, sometimes called an office software suite or productivity suite is a Software suite intended to be used by typical Word processing is the creation of documents using a Word processor. Desktop publishing (also known as DTP) combines a Personal computer and WYSIWYG page layout Software to create Publication Documents A presentation program is a Computer software package used to display information normally in the form of a Slide show. A database management system ( DBMS) is Computer software designed for the purpose of managing Databases DBMSes may use any of a variety of Data models A spreadsheet is a Computer application that simulates a paper worksheet Accounting software is Application software that records and processes Accounting transactions within functional modules such as Accounts payable, The Internet is a global system of interconnected Computer networks A web browser is a software application which enables a user to display and interact with text images videos music games and other information typically located on a An e-mail client, aka Mail User Agent (MUA aka e-mail reader is a frontend Computer program used to manage E-mail. The term web server can mean one of two things A Computer program that is responsible for accepting HTTP requests from web clients which are A mail transfer agent (MTA (also called a mail transport agent, message transfer agent, or smtpd (short for SMTP daemon) is a Computer-aided manufacturing ( CAM) is the use of computer-based software tools that assist engineers and machinists in manufacturing or prototyping product components Computer graphics are Graphics created by Computers and more generally the Representation and Manipulation of Pictorial Data A raster graphics editor is a Computer program that allows users to paint and edit Pictures interactively on the computer screen and save them in one A vector graphics editor is a Computer program that allows users to compose and edit Vector graphics Images interactively on the computer screen (compare 3D computer graphics software refers to programs used to create 3D Computer-generated imagery. Computer-generated imagery Computer animation is the art of creating moving images with the use of Computers It is a subfield of Computer graphics 3D computer graphics (in contrast to 2D computer graphics) are graphics that use a three-dimensional representation of geometric data that is stored in the computer The term video editing can refer to Non-linear editing system, using computers with Video editing software Linear video editing Image processing is any form of Signal processing for which the input is an image such as photographs or frames of video the output of image processing can be either an image Digital audio uses Digital signals for Sound reproduction. This includes analog-to-digital conversion, digital-to-analog conversion, storage A digital audio editor is a computer application for Audio editing, i An audio player is a kind of media player for playing back Digital audio, including Optical discs such as CDs SACDs DVD-Audio A software synthesizer also known as a softsynth or virtual instrument is a Computer program for Digital audio generation Computer music is a term that was originally used within academia to describe a field of study relating to the applications of Computing technology in music composition Software engineering is the application of a systematic disciplined quantifiable approach to the development operation and maintenance of Software. A compiler is a Computer program (or set of programs that translates text written in a computer language (the source language) into another See the terminology section below for information regarding inconsistent use of the terms assembly and assembler In Computer science, an interpreter normally means a Computer program that executes, i A debugger is a Computer program that is used to test and Debug other programs A text editor is a type of program used for editing plain Text files Text editors are often provided with Operating systems or software development In Computing, an integrated development environment ( IDE) is a Software application that provides comprehensive facilities to Computer programmers In Software engineering, performance analysis, more commonly today known as profiling, is the investigation of a program's behavior using information gathered as the Revision control (also known as version control (system (VCS, source control or (source code management (SCM) is the management of multiple revisions In Software engineering, software configuration Edutainment (also educational entertainment or entertainment-education) is a form of Entertainment designed to educate as well as to amuse Educational games are Games that have been specifically designed to teach people about a certain subject expand concepts reinforce development understand an historical event A serious game is a term used to refer to a Software or Hardware application developed with game technology and Game design principles for A flight simulator is a system that tries to copy or simulate, the experience of flying an aircraft A video game is a Game that involves interaction with a User interface to generate visual feedback on a video device. A strategy game is a Game (eg computer, video or Board game) in which the players' decision-making skills have a high significance Puzzle video games are a genre of Video games that emphasize Puzzle solving A first-person shooter ( FPS) is an action Video game from the Shooter game The initial development of Maze War Platform game, or platformer, is a video game genre characterized by jumping to and from suspended platforms or over obstacles A malware scanner is a program akin to Virus scanners which detects Malicious software in a computer's RAM or Hard drive. Installation (or setup) of a program (including drivers is the act and the effect of putting the program in a computer system so that it can be A package management system is a collection of tools to automate the process of installing upgrading configuring and removing software packages from a Computer A file manager or file browser is a Computer program that provides a User interface to work with File systems The most common operations used Unlike natural languages, programming languages are designed to permit no ambiguity and to be concise. In the Philosophy of language, a natural language (or ordinary language) is a Language that is spoken or written in phonemic-alphabetic or phonemically-related They are purely written languages and are often difficult to read aloud. They are generally either translated into machine language by a compiler or an assembler before being run, or translated directly at run time by an interpreter. Machine code or machine language is a system of instructions and data executed directly by a Computer 's Central processing unit. A compiler is a Computer program (or set of programs that translates text written in a computer language (the source language) into another See the terminology section below for information regarding inconsistent use of the terms assembly and assembler In Computer science, an interpreter normally means a Computer program that executes, i Sometimes programs are executed by a hybrid method of the two techniques. There are thousands of different programming languages—some intended to be general purpose, others useful only for highly specialized applications.

Professions and organizations

As the use of computers has spread throughout society, there are an increasing number of careers involving computers. A programming language is an Artificial language that can be used to write programs which control the behavior of a machine particularly a Computer. This is a Timeline of historically important Programming languages. This is a list of Programming languages grouped by category Array languages CategoryArray programming languages|l1=CategoryArray programming Here a genealogy of Programming languages is shown Languages are categorized under the ancestor language with the strongest influence Non-English-based programming languages are computer Programming languages that unlike most well-known programming languages do not use keywords taken from or inspired by See the terminology section below for information regarding inconsistent use of the terms assembly and assembler The ARM architecture (previously the Advanced RISC Machine, and prior to that Acorn RISC Machine) is a 32-bit RISC processor architecture MIPS (originally an acronym for Microprocessor without Interlocked Pipeline Stages) is a RISC microprocessor architecture developed by MIPS Technologies x86 assembly language is the Assembly language for the X86 class of processors which includes Intel 's Pentium series and AMD In computing a high-level programming language is a Programming language with strong abstraction from the details of the computer In Computer programming, BASIC (an Acronym for Beginner's All-purpose Symbolic Instruction Code) is a family of High-level programming languages tags please moot on the talk page first! --> In Computing, C is a general-purpose cross-platform block structured C++ (" C Plus Plus " ˌsiːˌplʌsˈplʌs is a general-purpose Programming language. C# (pronounced C Sharp is a Multi-paradigm COBOL (ˈkoʊbɒl is one of the oldest programming languages still in active use Fortran (previously FORTRAN) is a general-purpose, procedural, imperative Programming language that is especially suited to Lisp (or LISP) is a family of Computer Programming languages with a long history and a distinctive fully parenthesized syntax Pascal is an influential imperative and procedural Programming language, designed in 1968/9 and published in 1970 by Niklaus Wirth as a small "Scripting" redirects here For other uses see Script. The Bourne shell, or sh, was the default Unix shell of Unix Version 7, and replaced the Thompson shell, whose executable file had the same JavaScript is a Scripting language most often used for Client-side web development Python is a general-purpose High-level programming language. Its design philosophy emphasizes programmer productivity and code readability Ruby is a dynamic, reflective, general purpose Object-oriented programming language that combines syntax inspired by Perl with Smalltalk PHP is a computer Scripting language. Originally designed for producing Dynamic web pages it has evolved to include a Command line interface capability NOTES FOR EDITORS "Perl" is not an acronym (read the "Name" section below Following the theme of hardware, software and firmware, the brains of people who work in the industry are sometimes known irreverently as wetware or "meatware".

The need for computers to work well together and to be able to exchange information has spawned the need for many standards organizations, clubs and societies of both a formal and informal nature. Electrical engineering, sometimes referred to as electrical and electronic engineering, is a field of Engineering that deals with the study and application of Electronic engineering is a discipline dealing with the behavior and effects of Electrons (as in electron tubes and transistors and with electronic devices systems or equipment Computer engineering (or Computer Systems Engineering) encompasses broad areas of both Electrical engineering and Computer science. Optical engineering is the field of study that focuses on applications of Optics. Nanoengineering is the practice of Engineering on the Nanoscale. Computer science (or computing science) is the study and the Science of the theoretical foundations of Information and Computation and their Human–computer interaction or HCI is the study of interaction between people ( users and Computers It is often regarded as the intersection of Information technology ( IT) as defined by the Information Technology Association of America (ITAA is "the study design development implementation support Software engineering is the application of a systematic disciplined quantifiable approach to the development operation and maintenance of Software. Computational science (or scientific computing) is the field of study concerned with constructing Mathematical models and numerical solution techniques and using computers Web page design is a process of conceptualization planning modeling and execution of Electronic media content delivery via Internet in the form Desktop publishing (also known as DTP) combines a Personal computer and WYSIWYG page layout Software to create Publication Documents

See also

• Computability theory
• Computer science
• Computing
• Computers in fiction
• Computer security and Computer insecurity
• Electronic waste
• List of computer term etymologies
• Virtualization

Notes

References