Computer

A human computer, with microscope and calculator, 1952
The Ishango bone, a bone tool dating back to prehistoric Africa.
The Chinese suanpan (算盘). The number represented on this abacus is 6,302,715,408.
The Antikythera mechanism, dating back to ancient Greece circa 150–100 BC, is an early analog computing device.
A slide rule.
A portion of Babbage's Difference engine.
Sir William Thomson's third tide-predicting machine design, 1879–81
Replica of Konrad Zuse's Z3, the first fully automatic, digital (electromechanical) computer.
Colossus, the first electronic digital programmable computing device, was used to break German ciphers during World War II. It is seen here in use at Bletchley Park in 1943.
ENIAC was the first electronic, Turing-complete device, and performed ballistics trajectory calculations for the United States Army.
A section of the Manchester Baby, the first electronic stored-program computer
Bipolar junction transistor (BJT)
MOSFET (MOS transistor), showing gate (G), body (B), source (S) and drain (D) terminals. The gate is separated from the body by an insulating layer (pink).
Diagram showing how a particular MIPS architecture instruction would be decoded by the control system
Magnetic-core memory (using magnetic cores) was the computer memory of choice in the 1960s, until it was replaced by semiconductor memory (using MOS memory cells).
Hard disk drives are common storage devices used with computers.
Cray designed many supercomputers that used multiprocessing heavily.
Replica of the Manchester Baby, the world's first electronic stored-program computer, at the Museum of Science and Industry in Manchester, England
A 1970s punched card containing one line from a Fortran program. The card reads: "Z(1) = Y + W(1)" and is labeled "PROJ039" for identification purposes.
The actual first computer bug, a moth found trapped on a relay of the Harvard Mark II computer
Visualization of a portion of the routes on the Internet

Digital electronic machine that can be programmed to carry out sequences of arithmetic or logical operations automatically.

- Computer
A human computer, with microscope and calculator, 1952

500 related topics

Relevance

Example: 2D CAD drawing

Computer-aided design

Example: 2D CAD drawing
Example: 3D CAD model
A simple procedure of recreating a solid model out of 2D sketches.
A CAD model of a computer mouse

Computer-aided design (CAD) is the use of computers (or workstations) to aid in the creation, modification, analysis, or optimization of a design.

An iPhone smartphone and iPad tablet—two examples of mobile devices.

Mobile device

An iPhone smartphone and iPad tablet—two examples of mobile devices.
Smartphones, handheld mobile devices
Smartwatches, handheld mobile devices

A mobile device (or handheld computer) is a computer small enough to hold and operate in the hand.

The Internet Messenger by Buky Schwartz, located in Holon, Israel

Internet

Global system of interconnected computer networks that uses the Internet protocol suite (TCP/IP) to communicate between networks and devices.

Global system of interconnected computer networks that uses the Internet protocol suite (TCP/IP) to communicate between networks and devices.

The Internet Messenger by Buky Schwartz, located in Holon, Israel
T3 NSFNET Backbone, c. 1992.
ICANN headquarters in the Playa Vista neighborhood of Los Angeles, California, United States.
2007 map showing submarine fiberoptic telecommunication cables around the world.
Packet routing across the Internet involves several tiers of Internet service providers.
Number of mobile cellular subscriptions 2012–2016
As user data is processed through the protocol stack, each abstraction layer adds encapsulation information at the sending host. Data is transmitted over the wire at the link level between hosts and routers. Encapsulation is removed by the receiving host. Intermediate relays update link encapsulation at each hop, and inspect the IP layer for routing purposes.
Conceptual data flow in a simple network topology of two hosts (A and B) connected by a link between their respective routers. The application on each host executes read and write operations as if the processes were directly connected to each other by some kind of data pipe. After the establishment of this pipe, most details of the communication are hidden from each process, as the underlying principles of communication are implemented in the lower protocol layers. In analogy, at the transport layer the communication appears as host-to-host, without knowledge of the application data structures and the connecting routers, while at the internetworking layer, individual network boundaries are traversed at each router.
A DNS resolver consults three name servers to resolve the domain name user-visible "www.wikipedia.org" to determine the IPV4 Address 207.142.131.234
Creating a subnet by dividing the host identifier
This NeXT Computer was used by Tim Berners-Lee at CERN and became the world's first Web server.
Share of population using the Internet. See or edit source data.
Internet users per 100 population members and GDP per capita for selected countries.
Internet users per 100 inhabitants Source: International Telecommunication Union.
Internet users in 2015 as a percentage of a country's population Source: International Telecommunication Union.
'''Fixed broadband Internet subscriptions in 2012
as a percentage of a country's population''' Source: International Telecommunication Union.
'''Mobile broadband Internet subscriptions in 2012
as a percentage of a country's population''' Source: International Telecommunication Union.
Banner in Bangkok during the 2014 Thai coup d'état, informing the Thai public that 'like' or 'share' activities on social media could result in imprisonment (observed 30 June 2014).
Internet users by language<ref name=NIUBL-IWS>{{cite web|url=http://www.internetworldstats.com/stats7.htm|title=Number of Internet Users by Language|archive-url=https://web.archive.org/web/20120426122721/http://www.internetworldstats.com/stats7.htm|archive-date=26 April 2012|website=Internet World Stats, Miniwatts Marketing Group|date=31 May 2011|access-date=22 April 2012}}</ref>
Website content languages<ref name=UofCLBWApril2013>{{cite web|title=Usage of content languages for websites|url=http://w3techs.com/technologies/overview/content_language/all|work=W3Techs.com|access-date=26 April 2013|archive-url=https://www.webcitation.org/66ZQzUXh6?url=http://w3techs.com/technologies/overview/content_language/all|archive-date=31 March 2012|url-status=live}}</ref>

The linking of commercial networks and enterprises by the early 1990s marked the beginning of the transition to the modern Internet, and generated a sustained exponential growth as generations of institutional, personal, and mobile computers were connected to the network.

Modern DDR4 SDRAM module, usually found in desktop computers.

Computer memory

Modern DDR4 SDRAM module, usually found in desktop computers.
Detail of the back of a section of ENIAC, showing vacuum tubes.
8GB microSDHC card on top of 8bytes of magnetic-core memory (1core is 1bit).
Various memory modules containing different types of DRAM (from top to bottom): DDR SDRAM, SDRAM, EDO DRAM, and FPM DRAM

In computing, memory is a device or system that is used to store information for immediate use in a computer or related computer hardware and digital electronic devices.

Calculating-Table by Gregor Reisch: Margarita Philosophica, 1503. The woodcut shows Arithmetica instructing an algorist and an abacist (inaccurately represented as Boethius and Pythagoras). There was keen competition between the two from the introduction of the Algebra into Europe in the 12th century until its triumph in the 16th.

Abacus

Calculating tool which has been used since ancient times.

Calculating tool which has been used since ancient times.

Calculating-Table by Gregor Reisch: Margarita Philosophica, 1503. The woodcut shows Arithmetica instructing an algorist and an abacist (inaccurately represented as Boethius and Pythagoras). There was keen competition between the two from the introduction of the Algebra into Europe in the 12th century until its triumph in the 16th.
An early photograph of the Salamis Tablet, 1899. The original is marble and is held by the National Museum of Epigraphy, in Athens.
A Chinese abacus (suanpan) (the number represented in the picture is 6,302,715,408)
Copy of a Roman abacus
Japanese soroban
Representation of an Inca quipu
A yupana as used by the Incas.
Russian schoty
Early 20th century abacus used in Danish elementary school.
A twenty bead rekenrek
Two binary abacuses constructed by Dr. Robert C. Good, Jr., made from two Chinese abacuses

Although calculators and computers are commonly used today instead of abacuses, abacuses remain in everyday use in some countries.

Erasable programmable read-only memory (EPROM) integrated circuits in dual in-line packages. These packages have a transparent window that shows the die inside. The window is used to erase the memory by exposing the chip to ultraviolet light.

Integrated circuit

Set of electronic circuits on one small flat piece (or "chip") of semiconductor material, usually silicon.

Set of electronic circuits on one small flat piece (or "chip") of semiconductor material, usually silicon.

Erasable programmable read-only memory (EPROM) integrated circuits in dual in-line packages. These packages have a transparent window that shows the die inside. The window is used to erase the memory by exposing the chip to ultraviolet light.
Integrated circuit from an EPROM memory microchip showing the memory blocks, the supporting circuitry and the fine silver wires which connect the integrated circuit die to the legs of the packaging
Virtual detail of an integrated circuit through four layers of planarized copper interconnect, down to the polysilicon (pink), wells (greyish), and substrate (green)
Jack Kilby's original hybrid integrated circuit from 1958. This was the first integrated circuit, and was made from germanium.
Robert Noyce invented the first monolithic integrated circuit in 1959. The chip was made from silicon.
A-to-D converter IC in a DIP
The die from an Intel 8742, an 8-bit NMOS microcontroller that includes a CPU running at 12 MHz, 128 bytes of RAM, 2048 bytes of EPROM, and I/O in the same chip
Rendering of a small standard cell with three metal layers (dielectric has been removed). The sand-colored structures are metal interconnect, with the vertical pillars being contacts, typically plugs of tungsten. The reddish structures are polysilicon gates, and the solid at the bottom is the crystalline silicon bulk.
Schematic structure of a CMOS chip, as built in the early 2000s. The graphic shows LDD-MISFET's on an SOI substrate with five metallization layers and solder bump for flip-chip bonding. It also shows the section for FEOL (front-end of line), BEOL (back-end of line) and first parts of back-end process.
A Soviet MSI nMOS chip made in 1977, part of a four-chip calculator set designed in 1970
Upper interconnect layers on an Intel 80486DX2 microprocessor die

Computers, mobile phones and other home appliances are now inextricable parts of the structure of modern societies, made possible by the small size and low cost of ICs such as modern computer processors and microcontrollers.

This is a simple diagram illustrating the individual stages of the fetch-decode-execute cycle.

Execution (computing)

This is a simple diagram illustrating the individual stages of the fetch-decode-execute cycle.

Execution in computer and software engineering is the process by which a computer or virtual machine reads and acts on the instructions of a computer program.

A crowd of shoppers in the flatscreen TV section of the big box consumer electronics store Best Buy

Consumer electronics

Consumer electronics or home electronics are electronic (analog or digital) equipment intended for everyday use, typically in private homes.

Consumer electronics or home electronics are electronic (analog or digital) equipment intended for everyday use, typically in private homes.

A crowd of shoppers in the flatscreen TV section of the big box consumer electronics store Best Buy
A Radio Shack consumer electronics store in a mall
A radio and TV store in 1961
A typical CoCo 3 computer system, from the 1980s
A modern flat panel, HDTV television set
Gramophone factory in Hannover-Nordstadt
This picture illustrates how the mobile phone industry evolved to what we see today as modern smartphones
Guide to Greener Electronics 2017 findings
Electronic waste: discarded electronic equipment

They have essentially merged with the computer industry in what is increasingly referred to as the consumerization of information technology.

Size comparison of BJT transistor packages, from left to right: SOT-23, TO-92, TO-126, TO-3

Transistor

Semiconductor device used to amplify or switch electrical signals and power.

Semiconductor device used to amplify or switch electrical signals and power.

Size comparison of BJT transistor packages, from left to right: SOT-23, TO-92, TO-126, TO-3
Metal-oxide-semiconductor field-effect transistor (MOSFET), showing gate (G), body (B), source (S) and drain (D) terminals. The gate is separated from the body by an insulating layer (pink).
Julius Edgar Lilienfeld proposed the concept of a field-effect transistor in 1925.
John Bardeen, William Shockley and Walter Brattain at Bell Labs in 1948. Bardeen and Brattain invented the point-contact transistor in 1947 and Shockley the bipolar junction transistor in 1948.
A replica of the first working transistor, a point-contact transistor invented in 1947
Herbert Mataré in 1950. He independently invented a point-contact transistor in June 1948.
Philco surface-barrier transistor developed and produced in 1953
A Darlington transistor opened up so the actual transistor chip (the small square) can be seen inside. A Darlington transistor is effectively two transistors on the same chip. One transistor is much larger than the other, but both are large in comparison to transistors in large-scale integration because this particular example is intended for power applications.
A simple circuit diagram to show the labels of an n–p–n bipolar transistor
BJT used as an electronic switch, in grounded-emitter configuration
Amplifier circuit, common-emitter configuration with a voltage-divider bias circuit
Operation of a FET and its Id-Vg curve. At first, when no gate voltage is applied, there are no inversion electrons in the channel, so the device is turned off. As gate voltage increases, the inversion electron density in the channel increases, current increases, and thus the device turns on.
Transistor symbol created on Portuguese pavement in the University of Aveiro
Assorted discrete transistors
Soviet KT315b transistors

Transistors revolutionized the field of electronics, and paved the way for smaller and cheaper radios, calculators, and computers, among other things.

A physical Turing machine model. A true Turing machine would have unlimited tape on both sides, however, physical models can only have a finite amount of tape.

Turing machine

Mathematical model of computation describing an abstract machine that manipulates symbols on a strip of tape according to a table of rules.

Mathematical model of computation describing an abstract machine that manipulates symbols on a strip of tape according to a table of rules.

A physical Turing machine model. A true Turing machine would have unlimited tape on both sides, however, physical models can only have a finite amount of tape.
The head is always over a particular square of the tape; only a finite stretch of squares is shown. The instruction to be performed (q4) is shown over the scanned square. (Drawing after Kleene (1952) p. 375.)
Here, the internal state (q1) is shown inside the head, and the illustration describes the tape as being infinite and pre-filled with "0", the symbol serving as blank. The system's full state (its "complete configuration") consists of the internal state, any non-blank symbols on the tape (in this illustration "11B"), and the position of the head relative to those symbols including blanks, i.e. "011B". (Drawing after Minsky (1967) p. 121.)
The "3-state busy beaver" Turing machine in a finite-state representation. Each circle represents a "state" of the table—an "m-configuration" or "instruction". "Direction" of a state transition is shown by an arrow. The label (e.g. 0/P,R) near the outgoing state (at the "tail" of the arrow) specifies the scanned symbol that causes a particular transition (e.g. 0) followed by a slash /, followed by the subsequent "behaviors" of the machine, e.g. "P print" then move tape "R right". No general accepted format exists. The convention shown is after McClusky (1965), Booth (1967), Hill, and Peterson (1974).
The evolution of the busy beaver's computation starts at the top and proceeds to the bottom.
An implementation of a Turing machine
A Turing machine realization using Lego pieces
Another Turing machine realization

While they can express arbitrary computations, their minimalist design makes them unsuitable for computation in practice: real-world computers are based on different designs that, unlike Turing machines, use random-access memory.