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Computer A computer is a machine that can be Computer programming, programmed to automatically Execution (computing), carry out sequences of arithmetic or logical operations (''computation''). Modern digital electronic computers can perform generic set ...
s can be classified, or typed, in many ways. Some common classifications of computers are given below.


Classes by purpose

, - , style="text-align: left;", Notes:


Microcomputers (personal computers)

Microcomputer A microcomputer is a small, relatively inexpensive computer having a central processing unit (CPU) made out of a microprocessor. The computer also includes memory and input/output (I/O) circuitry together mounted on a printed circuit board (P ...
s became the most common type of computer in the late 20th century. The term "microcomputer" was introduced with the advent of systems based on single-chip
microprocessor A microprocessor is a computer processor (computing), processor for which the data processing logic and control is included on a single integrated circuit (IC), or a small number of ICs. The microprocessor contains the arithmetic, logic, a ...
s. The best-known early system was the Altair 8800, introduced in 1975. The term "microcomputer" has practically become an
anachronism An anachronism (from the Greek , 'against' and , 'time') is a chronological inconsistency in some arrangement, especially a juxtaposition of people, events, objects, language terms and customs from different time periods. The most common type ...
as it has fallen into disuse. These computers include: *
Desktop computer A desktop computer, often abbreviated as desktop, is a personal computer designed for regular use at a stationary location on or near a desk (as opposed to a portable computer) due to its size and power requirements. The most common configuratio ...
s – A case put under or on a desk. The display may be optional, depending on use. The case size may vary, depending on the required expansion slots. Very small computers of this kind may be integrated into the monitor. * Rackmount computers – The cases of these computers fit into
19-inch rack A 19-inch rack is a standardized frame or enclosure for mounting multiple electronic equipment modules. Each module has a front panel that is wide. The 19 inch dimension includes the edges or ''ears'' that protrude from each side of the ...
s, and may be space-optimized and very flat. A dedicated display, keyboard, and mouse may not exist, but a KVM switch or built-in remote control (via LAN or other means) can be used to gain console access. Many servers are rackmount computers and
data center A data center is a building, a dedicated space within a building, or a group of buildings used to house computer systems and associated components, such as telecommunications and storage systems. Since IT operations are crucial for busines ...
s may have dozens or hundreds of racks with hundreds or thousands of rackmount computers acting as servers. * In-car computers ( carputers) – Built into automobiles, for
entertainment Entertainment is a form of activity that holds the attention and Interest (emotion), interest of an audience or gives pleasure and delight. It can be an idea or a task, but it is more likely to be one of the activities or events that have deve ...
,
navigation Navigation is a field of study that focuses on the process of monitoring and controlling the motion, movement of a craft or vehicle from one place to another.Bowditch, 2003:799. The field of navigation includes four general categories: land navig ...
, etc. *
Laptop A laptop computer or notebook computer, also known as a laptop or notebook, is a small, portable personal computer (PC). Laptops typically have a Clamshell design, clamshell form factor (design), form factor with a flat-panel computer scree ...
s and
notebook computer A notebook computer or notebook is, historically, a laptop whose length and width approximate that of letter paper (). The term ''notebook'' was coined to describe slab-like portable computers that had a letter-paper footprint, such as Epson's ...
s – Portable and all in one case. *
Tablet computer A tablet computer, commonly shortened to tablet, is a mobile device, typically with a mobile operating system and touchscreen display processing circuitry, and a rechargeable battery in a single, thin and flat package. Tablets, being computers ...
– Like laptops, but with a
touch-screen A touchscreen (or touch screen) is a type of electronic visual display, display that can detect touch input from a user. It consists of both an input device (a touch panel) and an output device (a visual display). The touch panel is typically l ...
, entirely replacing the physical keyboard. *
Smartphone A smartphone is a mobile phone with advanced computing capabilities. It typically has a touchscreen interface, allowing users to access a wide range of applications and services, such as web browsing, email, and social media, as well as multi ...
s,
smartbook A smartbook was a class of mobile device that combined certain features of both a smartphone and netbook computer, produced between 2009 and 2010. Smartbooks were advertised with features such as wiktionary:always-on, always on, all-day battery lif ...
s, and palmtop computers – Small handheld personal computers with limited hardware specifications. *
Programmable calculator Programmable calculators are calculators that can automatically carry out a sequence of operations under the control of a stored computer programming, program. Most are Turing complete, and, as such, are theoretically general-purpose computers. ...
– Like small handhelds, but specialized in mathematical work. *
Video game console A video game console is an electronic device that Input/output, outputs a video signal or image to display a video game that can typically be played with a game controller. These may be home video game console, home consoles, which are generally ...
s – Fixed computers built specifically for entertainment purposes. *
Handheld game console A handheld game console, or simply handheld console, is a small, portable self-contained video game console with a built-in screen, game controls and speakers. Handheld game consoles are smaller than home video game consoles and contain the con ...
s – The same as game consoles, but small and portable.


Minicomputers (mid-range computers)

Minicomputer A minicomputer, or colloquially mini, is a type of general-purpose computer mostly developed from the mid-1960s, built significantly smaller and sold at a much lower price than mainframe computers . By 21st century-standards however, a mini is ...
s (colloquially, minis) are a class of multi-user
computer A computer is a machine that can be Computer programming, programmed to automatically Execution (computing), carry out sequences of arithmetic or logical operations (''computation''). Modern digital electronic computers can perform generic set ...
s that lie in the middle range of the computing spectrum, in between the smallest
mainframe computer A mainframe computer, informally called a mainframe or big iron, is a computer used primarily by large organizations for critical applications like bulk data processing for tasks such as censuses, industry and consumer statistics, enterprise ...
s and the largest single-user systems (
microcomputer A microcomputer is a small, relatively inexpensive computer having a central processing unit (CPU) made out of a microprocessor. The computer also includes memory and input/output (I/O) circuitry together mounted on a printed circuit board (P ...
s or
personal computers A personal computer, commonly referred to as PC or computer, is a computer designed for individual use. It is typically used for tasks such as Word processor, word processing, web browser, internet browsing, email, multimedia playback, and PC ...
). The term supermini computer or simply supermini was used to distinguish more powerful minicomputers that approached mainframes in capability. Superminis (such as the DEC VAX or Data General Eclipse MV/8000) were usually
32-bit In computer architecture, 32-bit computing refers to computer systems with a processor, memory, and other major system components that operate on data in a maximum of 32- bit units. Compared to smaller bit widths, 32-bit computers can perform la ...
at a time when most minicomputers (such as the
PDP-11 The PDP–11 is a series of 16-bit minicomputers originally sold by Digital Equipment Corporation (DEC) from 1970 into the late 1990s, one of a set of products in the Programmed Data Processor (PDP) series. In total, around 600,000 PDP-11s of a ...
or Data General Eclipse or
IBM Series/1 The IBM Series/1 is a 16-bit minicomputer, introduced in 1976, that in many respects competed with other minicomputers of the time, such as the PDP-11 from Digital Equipment Corporation and similar offerings from Data General and HP. The Ser ...
) were
16-bit 16-bit microcomputers are microcomputers that use 16-bit microprocessors. A 16-bit register can store 216 different values. The range of integer values that can be stored in 16 bits depends on the integer representation used. With the two ...
. These traditional minicomputers in the last few decades of the 20th century, found in small to medium-sized businesses, laboratories and embedded in (for example) hospital CAT scanners, often would be rack-mounted and connect to one or more terminals or tape/
card Card or The Card may refer to: Common uses * Plastic cards of various types: **Bank card **Credit card **Debit card **Payment card * Playing card, used in games * Printed circuit board, or card * Greeting card, given on special occasions Arts an ...
readers, like mainframes and unlike most personal computers, but require less space and electrical power than a typical mainframe. This term has fallen into disuse.


Mainframe computers

The term
mainframe computer A mainframe computer, informally called a mainframe or big iron, is a computer used primarily by large organizations for critical applications like bulk data processing for tasks such as censuses, industry and consumer statistics, enterprise ...
was created to distinguish the traditional, large, institutional computer intended to service multiple users from the smaller, single-user machines. These computers are capable of handling and processing very large amounts of data quickly. Mainframe computers are used in large institutions such as government, banks, and large corporations. They are measured in MIPS (million instructions per second) and can respond to hundreds of millions of users at a time.


Supercomputers

A
supercomputer A supercomputer is a type of computer with a high level of performance as compared to a general-purpose computer. The performance of a supercomputer is commonly measured in floating-point operations per second (FLOPS) instead of million instruc ...
is focused on performing tasks involving intense numerical calculations such as weather forecasting, fluid dynamics, nuclear simulations, theoretical astrophysics, and complex scientific computations. A supercomputer is a computer that is at the front-line of current processing capacity, particularly speed of calculation. The term supercomputer itself is rather fluid, and the speed of today's supercomputers tends to become typical of tomorrow's ordinary computer. Supercomputer processing speeds are measured in floating-point operations per second, or
FLOPS Floating point operations per second (FLOPS, flops or flop/s) is a measure of computer performance in computing, useful in fields of scientific computations that require floating-point calculations. For such cases, it is a more accurate measu ...
. An example of a floating-point operation is the calculation of mathematical equations in real numbers. In terms of computational capability, memory size and speed, I/O technology, and topological issues such as bandwidth and latency, supercomputers are the most powerful, are very expensive, and not cost-effective just to perform batch or transaction processing.


Classes by function


Servers

Server usually refers to a computer that is dedicated to providing one or more services. A server is expected to be reliable (e.g. error-correction of RAM; redundant cooling; self-monitoring, RAID), fit for running for several years, and giving useful diagnosis in case of an error. For even increased security, the server may be mirrored. Many smaller servers are actually personal computers that have been dedicated to provide services for other computers. * A
database server A database server is a server which uses a database application that provides database services to other computer programs or to computers, as defined by the client–server model. Database management systems (DBMSs) frequently provide database- ...
is a server which uses a database application that provides
database In computing, a database is an organized collection of data or a type of data store based on the use of a database management system (DBMS), the software that interacts with end users, applications, and the database itself to capture and a ...
services to other computer programs or to
computer A computer is a machine that can be Computer programming, programmed to automatically Execution (computing), carry out sequences of arithmetic or logical operations (''computation''). Modern digital electronic computers can perform generic set ...
s.
Database management systems In computing, a database is an organized collection of data or a type of data store based on the use of a database management system (DBMS), the software that interacts with end users, applications, and the database itself to capture and ana ...
(DBMSs) frequently provide database-server functionality, and some database management systems (such as
MySQL MySQL () is an Open-source software, open-source relational database management system (RDBMS). Its name is a combination of "My", the name of co-founder Michael Widenius's daughter My, and "SQL", the acronym for Structured Query Language. A rel ...
) rely exclusively on the
client–server model The client–server model is a distributed application structure that partitions tasks or workloads between the providers of a resource or service, called servers, and service requesters, called clients. Often clients and servers communicate ov ...
for database access while others (such as SQLite) are meant for using as an embedded database. Users access a database server either through a " front end" running on the user's computer – which displays requested data – or through the " back end", which runs on the server and handles tasks such as data analysis and storage. * A
file server In computing, a file server (or fileserver) is a computer attached to a network that provides a location for shared disk access, i.e. storage of computer files (such as text, image, sound, video) that can be accessed by workstations within a co ...
does not normally perform computational tasks or run programs on behalf of its client workstations but manage and store a large collection of
computer file A computer file is a System resource, resource for recording Data (computing), data on a Computer data storage, computer storage device, primarily identified by its filename. Just as words can be written on paper, so too can data be written to a ...
s. The crucial function of a file server is storage. File servers are commonly found in schools and offices, where users use a
local area network A local area network (LAN) is a computer network that interconnects computers within a limited area such as a residence, campus, or building, and has its network equipment and interconnects locally managed. LANs facilitate the distribution of da ...
to connect their client computers and use Network-attached storage (NAS) systems to provide data access. * A
web server A web server is computer software and underlying Computer hardware, hardware that accepts requests via Hypertext Transfer Protocol, HTTP (the network protocol created to distribute web content) or its secure variant HTTPS. A user agent, co ...
is a server that can satisfy client requests on the
World Wide Web The World Wide Web (WWW or simply the Web) is an information system that enables Content (media), content sharing over the Internet through user-friendly ways meant to appeal to users beyond Information technology, IT specialists and hobbyis ...
. A web server can, in general, contain one or more
website A website (also written as a web site) is any web page whose content is identified by a common domain name and is published on at least one web server. Websites are typically dedicated to a particular topic or purpose, such as news, educatio ...
s. A web server processes incoming network requests over
HTTP HTTP (Hypertext Transfer Protocol) is an application layer protocol in the Internet protocol suite model for distributed, collaborative, hypermedia information systems. HTTP is the foundation of data communication for the World Wide Web, wher ...
and several other related
protocols Protocol may refer to: Sociology and politics * Protocol (politics), a formal agreement between nation states * Protocol (diplomacy), the etiquette of diplomacy and affairs of state * Etiquette, a code of personal behavior Science and technology ...
. The primary function of a web server is to store, process and deliver
web page A web page (or webpage) is a World Wide Web, Web document that is accessed in a web browser. A website typically consists of many web pages hyperlink, linked together under a common domain name. The term "web page" is therefore a metaphor of pap ...
s to clients. The communication between client and server takes place using the Hypertext Transfer Protocol (HTTP). Pages delivered are most frequently HTML documents, which may include
image An image or picture is a visual representation. An image can be Two-dimensional space, two-dimensional, such as a drawing, painting, or photograph, or Three-dimensional space, three-dimensional, such as a carving or sculpture. Images may be di ...
s, style sheets and scripts in addition to the text content. * A
terminal server A terminal server connects devices with a serial port to a local area network (LAN). Products marketed as terminal servers can be very simple devices that do not offer any security functionality, such as data encryption and user authentication. ...
enables organizations to connect devices with an
RS-232 In telecommunications, RS-232 or Recommended Standard 232 is a standard introduced in 1960 for serial communication transmission of data. It formally defines signals connecting between a ''DTE'' (''data terminal equipment'') such as a compu ...
, RS-422 or
RS-485 RS-485, also known as TIA-485(-A) or EIA-485, is a standard, originally introduced in 1983, defining the electrical characteristics of drivers and receivers for use in serial communications systems. Electrical signaling is balanced, and Telecomm ...
serial interface to a
local area network A local area network (LAN) is a computer network that interconnects computers within a limited area such as a residence, campus, or building, and has its network equipment and interconnects locally managed. LANs facilitate the distribution of da ...
(LAN). Products marketed as terminal servers can be very simple devices that do not offer any security functionality, such as
data encryption In cryptography, encryption (more specifically, encoding) is the process of transforming information in a way that, ideally, only authorized parties can decode. This process converts the original representation of the information, known as plai ...
and user authentication. These provide GUI sessions that can be used by client PCs that work someway like a remote control. Only the screen (and audio) output is shown on the client. The GUI applications run on the server, data (like in files) would be stored in the same LAN, thus avoiding problems, should a client PC be damaged or stolen. A server may run several
virtual machine In computing, a virtual machine (VM) is the virtualization or emulator, emulation of a computer system. Virtual machines are based on computer architectures and provide the functionality of a physical computer. Their implementations may involve ...
s (VMs) for different activities, supplying the same environment to each VM as if it ran on dedicated hardware. Different operating systems (OS) can therefore be run at the same time. This technology approach needs special hardware support to be useful and was first the domain of mainframes and other large computers. Nowadays, most personal computers are equipped for this task, but for long-term operation or critical systems, specialized server hardware may be needed.
Another approach is to implement VMs on the operating system level, so all VMs run on the same OS instance (or incarnation), but are fundamentally separated to not interfere with each other.


Workstations

Workstation A workstation is a special computer designed for technical or computational science, scientific applications. Intended primarily to be used by a single user, they are commonly connected to a local area network and run multi-user operating syste ...
s are computers that are intended to serve one user and may contain special hardware enhancements not found on a personal computer. By the mid-1990s personal computers reached the processing capabilities of mini computers and workstations. Also, with the release of multi-tasking systems such as
OS/2 OS/2 is a Proprietary software, proprietary computer operating system for x86 and PowerPC based personal computers. It was created and initially developed jointly by IBM and Microsoft, under the leadership of IBM software designer Ed Iacobucci, ...
,
Windows NT Windows NT is a Proprietary software, proprietary Graphical user interface, graphical operating system produced by Microsoft as part of its Windows product line, the first version of which, Windows NT 3.1, was released on July 27, 1993. Original ...
and
Linux Linux ( ) is a family of open source Unix-like operating systems based on the Linux kernel, an kernel (operating system), operating system kernel first released on September 17, 1991, by Linus Torvalds. Linux is typically package manager, pac ...
, the operating systems of personal computers could do the job of this class of machines. Today, the term is used to describe desktop PCs with high-performance hardware. Such hardware is usually aimed at a professional, rather than enthusiast, market (e.g. dual-processor motherboards, error-correcting memory, professional graphics cards).


Information appliances

Information appliances are computers specially designed to perform a specific "
user-friendly Usability can be described as the capacity of a system to provide a condition for its users to perform the tasks safely, effectively, and efficiently while enjoying the experience. In software engineering, usability is the degree to which a softw ...
" function—such as editing text, playing music,
photography Photography is the visual arts, art, application, and practice of creating images by recording light, either electronically by means of an image sensor, or chemically by means of a light-sensitive material such as photographic film. It is empl ...
,
videography Videography involves capturing moving images on electronic media (such as: videotape, direct to disk recording, or solid state storage), and can include streaming media. It encompasses both video production and post-production methods. Historic ...
etc. The term is most commonly applied to battery-operated
mobile device A mobile device or handheld device is a computer small enough to hold and operate in hand. Mobile devices are typically battery-powered and possess a flat-panel display and one or more built-in input devices, such as a touchscreen or keypad. ...
s, though there are also wearable devices.


Embedded computers

Embedded computers are computers that are a part of a machine or device. Embedded computers generally execute a program that is stored in
non-volatile memory Non-volatile memory (NVM) or non-volatile storage is a type of computer memory that can retain stored information even after power is removed. In contrast, volatile memory needs constant power in order to retain data. Non-volatile memory typ ...
and is only intended to operate a specific machine or device. Embedded computers are very common. The majority are
microcontroller A microcontroller (MC, uC, or μC) or microcontroller unit (MCU) is a small computer on a single integrated circuit. A microcontroller contains one or more CPUs (processor cores) along with memory and programmable input/output peripherals. Pro ...
s. Embedded computers are typically required to operate continuously without being reset or rebooted, and once employed in their task the software usually cannot be modified. An automobile may contain a number of embedded computers; however, a washing machine or
DVD player A DVD player is a machine that plays DVDs produced under both the DVD-Video and DVD-Audio technical standards, two different and incompatible standards. Some DVD players will also play audio CDs. DVD players are connected to a television to ...
would contain only one microcontroller. Embedded computers are chosen to meet the requirements of the specific application, and most are slower and cheaper than CPUs found in a personal computer.


Classes by usage


Public computer

Public computers are open for public uses, possibly as an
Interactive kiosk An interactive kiosk is a computer terminal featuring specialized hardware and software that provides access to information and applications for communication, commerce, entertainment, or education. By 2010, the largest bill pay kiosk network ...
. There are many places where one can use them, such as cybercafes, schools and libraries. They are normally fire-walled and restricted to run only their pre-installed software. The operating system is difficult to change and/or resides on a file server. For example, "
thin client In computer networking, a thin client, sometimes called slim client or lean client, is a simple (low-Computer performance, performance) computer that has been Program optimization, optimized for Remote desktop, establishing a remote connectio ...
" machines in educational establishments may be reset to their original state between classes. Public computers are generally not expected to keep an individual's data files.


Personal computer

A
personal computer A personal computer, commonly referred to as PC or computer, is a computer designed for individual use. It is typically used for tasks such as Word processor, word processing, web browser, internet browsing, email, multimedia playback, and PC ...
has one user who may also be the owner (although the term has also come also mean any computer hardware somewhat like the original
IBM PC The IBM Personal Computer (model 5150, commonly known as the IBM PC) is the first microcomputer released in the List of IBM Personal Computer models, IBM PC model line and the basis for the IBM PC compatible ''de facto'' standard. Released on ...
, irrespective of how it is used). This user often may use all hardware resources, has complete access to any part of the computer and has
rights Rights are law, legal, social, or ethics, ethical principles of freedom or Entitlement (fair division), entitlement; that is, rights are the fundamental normative rules about what is allowed of people or owed to people according to some legal sy ...
to install/remove software. Personal computers normally store personal files, and often the owner/user is responsible for routine maintenance such as removing unwanted files and virus-scanning. Some computers in a business setting are for one user but are also served by staff with protocols to ensure proper maintenance.


Shared computer

These are computers where different people might log on at different times; unlike public computers, they would have usernames and passwords assigned on a long-term basis, with the files they see and the computer's settings adjusted to their particular account. Often the important data files will reside on a central file server, so a person could log onto different computers yet still see the same files. The computer (or workstation) might be a "
thin client In computer networking, a thin client, sometimes called slim client or lean client, is a simple (low-Computer performance, performance) computer that has been Program optimization, optimized for Remote desktop, establishing a remote connectio ...
" or
X terminal X, or x, is the twenty-fourth letter of the Latin alphabet, used in the modern English alphabet, the alphabets of other western European languages and others worldwide. Its name in English is ''ex'' (pronounced ), plural ''exes''."X", ' ...
, otherwise it may have its own disk for some or all system files, but usually will need to be networked to the rest of the system for full functionality. Such systems normally require a system administrator to set up and maintain the hardware and software.


Display computer

Computers that are used just to display selected material (usually audio-visual, or simple slide shows) in a shop, meeting or trade show. These computers may have more capabilities than they are being used for; they are likely to have
WiFi Wi-Fi () is a family of wireless network protocols based on the IEEE 802.11 family of standards, which are commonly used for Wireless LAN, local area networking of devices and Internet access, allowing nearby digital devices to exchange data by ...
and so be capable of Internet access, but are rarely firewalled (but have restricted port access or monitored in some way). Such computers are used and maintained as appliances, and not normally used as the primary store for important files.


Classed by generation of computer technology

The history of computing hardware is often used to reference the different generations of computing devices: *First generation computers (1940-1955): It used
vacuum tube A vacuum tube, electron tube, thermionic valve (British usage), or tube (North America) is a device that controls electric current flow in a high vacuum between electrodes to which an electric voltage, potential difference has been applied. It ...
s such as the 6J6 or specially designed tubes - or even mechanical arrangements, and were relatively slow, energy-hungry and the earliest computers were less flexible in their programmability. *Second generation computers (1956-1963): It uses
discrete Discrete may refer to: *Discrete particle or quantum in physics, for example in quantum theory * Discrete device, an electronic component with just one circuit element, either passive or active, other than an integrated circuit * Discrete group, ...
transistors A transistor is a semiconductor device used to Electronic amplifier, amplify or electronic switch, switch electrical signals and electric power, power. It is one of the basic building blocks of modern electronics. It is composed of semicondu ...
, and thus smaller and consumes less power. *Third generation computers (1964-1970): It used Integrated Circuits (ICs), the main difference between hardware in computers of the 1960s and today being the density of transistors in each IC (beginning with Small Scale Integration chips like the Transistor-transistor logic (TTL) SN7400 gates with 20 transistors, through Medium Scale Integration and
Large Scale Integration An integrated circuit (IC), also known as a microchip or simply chip, is a set of electronic circuits, consisting of various electronic components (such as transistors, resistors, and capacitors) and their interconnections. These components ...
to Very-large-scale integration (VLSI) with over ten billion transistors in a single silicon-based IC "chip". *Fourth generation computers(1971–present): It uses
Microprocessor A microprocessor is a computer processor (computing), processor for which the data processing logic and control is included on a single integrated circuit (IC), or a small number of ICs. The microprocessor contains the arithmetic, logic, a ...
s, as millions of ICs were built onto a single silicon-based chip. Since then form factor of computers reduced, task processing & graphic rendering improved and it became more battery-powered with the advent of personal mobile devices such as laptops, tablets, smartphones etc.


See also

* Lisp machine * List of computer size categories * Bell's law of computer classes *
Analog computers An analog computer or analogue computer is a type of computation machine (computer) that uses physical phenomena such as Electrical network, electrical, Mechanics, mechanical, or Hydraulics, hydraulic quantities behaving according to the math ...
* Feng's classification *
Flynn's taxonomy Flynn's taxonomy is a classification of computer architectures, proposed by Michael J. Flynn in 1966 and extended in 1972. The classification system has stuck, and it has been used as a tool in the design of modern processors and their functionalit ...


References


External links

* {{Computer sizes