# Personal Computers

An illustration of a contemporary personal desktop computer
A personal computer is a general-purpose computer whose size, capabilities and original sale price make it useful for individuals, and is intended to be operated directly by an end-user with no intervening computer operator. This contrasts with the batch processing or time-sharing models that allowed larger, more expensive minicomputer and mainframe systems to be used by many people, usually at the same time. A related term is "PC" that was initially an acronym for "personal computer," but later became used primarily to refer to the ubiquitous Wintel platform.Software applications for most personal computers include, but are not limited to, word processing, spreadsheets, databases, web browsers and e-mail clients, digital media playback, games and myriad personal productivity and special-purpose software applications. Modern personal computers often have connections to the Internet, allowing access to the World Wide Web and a wide range of other resources. Personal computers may be connected to a local area network (LAN), either by a cable or a wireless connection. A personal computer may be a desktop computer or a laptop,netbook, tablet or a handheld PC.Early computer owners usually had to write their own programs to do anything useful with the machines, which even did not include an operating system. The very earliest microcomputers, equipped with a front panel, required hand-loading of a bootstrap program to load programs from external storage (paper tape, cassettes, or eventually diskettes). Before very long, automatic booting from permanent read-only memory became universal. Today's users have access to a wide range of commercial software, freeware and free and open-source software, which are provided in ready-to-run or ready-to-compile form. Software for personal computers, such as applications and video games, are typically developed and distributed independently from the hardware or OS manufacturers, whereas software for many mobile phones and other portable systems is approved and distributed through a centralized online store.[81][82]Since the early 1990s, Microsoft operating systems and Intel hardware have dominated much of the personal computer market, first with MS-DOS and then with Windows. Popular alternatives to Microsoft's Windows operating systems include Apple's OS X and free open-source Unix-like operating systems such as Linux and BSD. AMD provides the major alternative to Intel's processors.

## History

The Programma 101 was the first commercial "desktop personal computer", produced by the Italian company Olivetti and invented by the Italian engineer Pier Giorgio Perotto, inventor of the magnetic card system. The project started in 1962. It was launched at the 1964 New York World's Fair, and volume production began in 1965, the computer retailing for $3,200.[83]NASA bought at least ten Programma 101s and used them for the calculations for the 1969 Apollo 11 Moon landing. Then ABC used the Programma 101 to predict the presidential election of 1969, and the U.S. military used the machine to plan their operations in the Vietnam War. The Programma 101 was also used in schools, hospitals, government offices. This marked the beginning of the era of the personal computer.In 1968, Hewlett-Packard was ordered to pay about$900,000 in royalties to Olivetti after their Hewlett-Packard 9100A was ruled to have copied some of the solutions adopted in the Programma 101, including the magnetic card, the architecture and other similar components.[84]The Soviet MIR series of computers was developed from 1965 to 1969 in a group headed by Victor Glushkov. It was designed as a relatively small-scale computer for use in engineering and scientific applications and contained a hardware implementation of a high-level programming language. Another innovative feature for that time was the user interface combining a keyboard with a monitor and light pen for correcting texts and drawing on screen.[85]In what was later to be called the Mother of All Demos, SRI researcher Douglas Engelbart in 1968 gave a preview of what would become the staples of daily working life in the 21st century: e-mail, hypertext, word processing, video conferencing and the mouse. The demonstration required technical support staff and a mainframe time-sharing computer that were far too costly for individual business use at the time.
Commodore PET in 1983 (at American Museum of Science and Energy)
By the early 1970s, people in academic or research institutions had the opportunity for single-person use of a computer system in interactive mode for extended durations, although these systems would still have been too expensive to be owned by a single person.In 1973 the IBM Los Gatos Scientific Center developed a portable computer prototype called SCAMP (Special Computer APL Machine Portable) based on the IBM PALM processor with a Philips compact cassette drive, small CRT and full function keyboard. SCAMP emulated an IBM 1130 minicomputer in order to run APL\1130.[86] In 1973 APL was generally available only on mainframe computers, and most desktop sized microcomputers such as the Wang 2200 or HP 9800 offered only BASIC. Because SCAMP was the first to emulate APL\1130 performance on a portable, single user computer, PC Magazine in 1983 designated SCAMP a "revolutionary concept" and "the world's first personal computer."[87][88] This seminal, single user portable computer now resides in the Smithsonian Institution, Washington, D.C. Successful demonstrations of the 1973 SCAMP prototype led to the IBM 5100 portable microcomputer launched in 1975 with the ability to be programmed in both APL and BASIC for engineers, analysts, statisticians and other business problem-solvers. In the late 1960s such a machine would have been nearly as large as two desks and would have weighed about half a ton.[89]Another seminal product in 1973 was the Xerox Alto, developed at Xerox's Palo Alto Research Center (PARC), it had a graphical user interface (GUI) whch later served as inspiration for Apple Computer's Macintosh, and Microsoft's Windows operating system. Also in 1973 Hewlett Packard introduced fully BASIC programmable microcomputers that fit entirely on top of a desk, including a keyboard, a small one-line display and printer. The Wang 2200 microcomputer of 1973 had a full-size cathode ray tube (CRT) and cassette tape storage.[90] These were generally expensive specialized computers sold for business or scientific uses. The introduction of the microprocessor, a single chip with all the circuitry that formerly occupied large cabinets, led to the proliferation of personal computers after 1975.
IBM Personal Computer XT in 1988
Early personal computers—​generally called microcomputers—​were often sold in a kit form and in limited volumes, and were of interest mostly to hobbyists and technicians. Minimal programming was done with toggle switches to enter instructions, and output was provided by front panel lamps. Practical use required adding peripherals such as keyboards, computer displays, disk drives, and printers. Micral N was the earliest commercial, non-kit microcomputer based on a microprocessor, the Intel 8008. It was built starting in 1972 and about 90,000 units were sold.In 1976 Steve Jobs and Steve Wozniak sold the Apple I computer circuit board, which was fully prepared and contained about 30 chips. The Apple I computer differed from the other hobby computers of the time at the beckoning of Paul Terrell owner of the Byte Shop who gave Steve Jobs his first purchase order for 50 Apple I computers only if the computers were assembled and tested and not a kit computer so he would have computers to sell to everyone, not just people that could assemble a computer kit. The Apple I as delivered was still a kit computer as it did not have a power supply, case, or keyboard as delivered to the Byte Shop.The first successfully mass marketed personal computer was the Commodore PET introduced in January 1977, but back-ordered and not available until later in the year. At the same time, the Apple II (usually referred to as the "Apple") was introduced[91] (June 1977), and the TRS-80 from Tandy Corporation/Tandy Radio Shack in summer 1977, delivered in September in a small number. Mass-market ready-assembled computers allowed a wider range of people to use computers, focusing more on software applications and less on development of the processor hardware.
The 8-bit PMD 85 personal computer produced in 1985-1990 by the Tesla company in the former socialist Czechoslovakia. This computer was produced locally (in Piešťany) due to a lack of foreign currency with which to buy systems from the West.
During the early 1980s, home computers were further developed for household use, with software for personal productivity, programming and games. They typically could be used with a television already in the home as the computer display, with low-detail blocky graphics and a limited color range, and text about 40 characters wide by 25 characters tall. Sinclair Research,[92] a UK company, produced the ZX Series: the ZX80 (1980), ZX81 (1981), and the ZX Spectrum; the latter was introduced in 1982, and totaled 8 million unit sold. Following came the Commodore 64, totaled 17 million units sold.[93]In the same year, the NEC PC-98 was introduced, which was a very popular personal computer that sold in more than 18 million units.[94] Another famous personal computer, the revolutionary Amiga 1000, was unveiled by Commodore on July 23, 1985 at the Vivian Beaumont Theater in the Lincoln Center in New York. The Amiga 1000 featured a multitasking, windowing operating system, color graphics with a 4096-color palette, stereo sound, Motorola 68000 CPU, 256 kB RAM, and 880 kB 3.5-inch disk drive, for US$1,295.[95] IBM 5150, released in 1981. Somewhat larger and more expensive systems (for example, running CP/M), or sometimes a home computer with additional interfaces and devices, although still low-cost compared with minicomputers and mainframes, were aimed at office and small business use, typically using "high resolution" monitors capable of at least 80 column text display, and often no graphical or color drawing capability.Workstations were characterized by high-performance processors and graphics displays, with large-capacity local disk storage, networking capability, and running under a multitasking operating system.Eventually, due to the influence of the IBM PC on the personal computer market, personal computers and home computers lost any technical distinction. Business computers acquired color graphics capability and sound, and home computers and game systems users used the same processors and operating systems as office workers. Mass-market computers had graphics capabilities and memory comparable to dedicated workstations of a few years before. Even local area networking, originally a way to allow business computers to share expensive mass storage and peripherals, became a standard feature of personal computers used at home.In 1982 "The Computer" was named Machine of the Year by Time Magazine.In the 2010s, several companies such as Hewlett-Packard and Sony sold off their PC and laptop divisions. As a result, the personal computer was declared dead several times during this time.[96] ### Market and Sales Personal computers worldwide in million distinguished by developed and developing world In 2001, 125 million personal computers were shipped in comparison to 48,000 in 1977.[97] More than 500 million personal computers were in use in 2002 and one billion personal computers had been sold worldwide from the mid-1970s up to this time. Of the latter figure, 75% were professional or work related, while the rest were sold for personal or home use. About 81.5% of personal computers shipped had been desktop computers, 16.4% laptops and 2.1% servers. The United States had received 38.8% (394 million) of the computers shipped, Europe 25% and 11.7% had gone to the Asia-Pacific region, the fastest-growing market as of 2002. The second billion was expected to be sold by 2008.[98] Almost half of all households in Western Europe had a personal computer and a computer could be found in 40% of homes in United Kingdom, compared with only 13% in 1985.[99]The global personal computer shipments were 350.9 million units in 2010,[100] 308.3 million units in 2009[101] and 302.2 million units in 2008.[102][103] The shipments were 264 million units in the year 2007, according to iSuppli,[104] up 11.2% from 239 million in 2006.[105] In 2004, the global shipments were 183 million units, an 11.6% increase over 2003.[106] In 2003, 152.6 million computers were shipped, at an estimated value of$175 billion.[107] In 2002, 136.7 million PCs were shipped, at an estimated value of $175 billion.[108] In 2000, 140.2 million personal computers were shipped, at an estimated value of$226 billion.[109] Worldwide shipments of personal computers surpassed the 100-million mark in 1999, growing to 113.5 million units from 93.3 million units in 1998.[110] In 1999, Asia had 14.1 million units shipped.[111]As of June 2008, the number of personal computers in use worldwide hit one billion,[112] while another billion is expected to be reached by 2014. Mature markets like the United States, Western Europe and Japan accounted for 58% of the worldwide installed PCs. The emerging markets were expected to double their installed PCs by 2012 and to take 70% of the second billion PCs. About 180 million computers (16% of the existing installed base) were expected to be replaced and 35 million to be dumped into landfill in 2008. The whole installed base grew 12% annually.[113][114]Based on International Data Corporation (IDC) data for Q2 2011, for the first time China surpassed US in PC shipments by 18.5 million and 17.7 million respectively. This trend reflects the rising of emerging markets as well as the relative stagnation of mature regions.[115]In the developed world, there has been a vendor tradition to keep adding functions to maintain high prices of personal computers. However, since the introduction of the One Laptop per Child foundation and its low-cost XO-1 laptop, the computing industry started to pursue the price too. Although introduced only one year earlier, there were 14 million netbooks sold in 2008.[116] Besides the regular computer manufacturers, companies making especially rugged versions of computers have sprung up, offering alternatives for people operating their machines in extreme weather or environments.[117]
2014 Worldwide PC Vendor Unit Shipment Estimates
Source Date Lenovo HP Dell Acer Inc. Asus Others
IDC[118] Q2 2014 19.6% 18.3% 14.0% 8.2% 6.2% 33.6%
Gartner[119] Q2 2014 19.2% 17.7% 13.3% 7.9% 6.9% 35.0%
Deloitte consulting firm predicted that in 2011, smartphones and tablet computers as computing devices would surpass the PCs sales.[120] As of 2013, worldwide sales of PCs had begun to fall as many consumers moved to tablets and smartphones for gifts and personal use. Sales of 90.3 million units in the 4th quarter of 2012 represented a 4.9% decline from sales in the 4th quarter of 2011.[121] Global PC sales fell sharply in the first quarter of 2013, according to IDC data. The 14% year-over-year decline was the largest on record since the firm began tracking in 1994, and double what analysts had been expecting.[122][123] The decline of Q2 2013 PC shipments marked the fifth straight quarter of falling sales.[124] "This is horrific news for PCs," remarked an analyst. "It’s all about mobile computing now. We have definitely reached the tipping point."[125] Data from Gartner Inc. showed a similar decline for the same time period.[126] China's Lenovo Group bucked the general trend as strong sales to first time buyers in the developing world allowed the company's sales to stay flat overall.[127] Windows 8, which was designed to look similar to tablet/smartphone software, was cited as a contributing factor in the decline of new PC sales. "Unfortunately, it seems clear that the Windows 8 launch not only didn’t provide a positive boost to the PC market, but appears to have slowed the market," said IDC Vice President Bob O’Donnell.[128]In August 2013, Credit Suisse published research findings that attributed around 75% of the operating profit share of the PC industry to Microsoft (operating system) and Intel (semiconductors).[129]According to IDC, in 2013 PC shipments dropped by 9.8% as the greatest drop-ever in line with consumers trends to use mobile devices.[130]

### Average Selling Price

Selling prices of personal computers, unlike other consumer commodities, steadily declined due to lower costs of production and manufacture. Capabilities of the computers also increased. In 1975, an Altair kit sold for only around US $400, but required customers to solder components into circuit boards; peripherals required to interact with the system in alphanumeric form instead of blinking lights would add another$2,000, and the resultant system was only of use to hobbyists.[131]At their introduction in 1981, the US $1,795 price of the Osborne 1 and its competitor Kaypro was considered an attractive price point; these systems had text-only displays and only floppy disks for storage. By 1982, Michael Dell observed that a personal computer system selling at retail for about$3,000 US was made of components that cost the dealer about $600; typical gross margin on a computer unit was around$1,000.[132] The total value of personal computer purchases in the US in 1983 was about $4 billion, comparable to total sales of pet food. By late 1998, the average selling price of personal computer systems in the United States had dropped below$1,000.[133]For Microsoft Windows systems, the average selling price (ASP) showed a decline in 2008/2009, possibly due to low-cost netbooks, drawing $569 for desktop computers and$689 for laptops at U.S. retail in August 2008. In 2009, ASP had further fallen to $533 for desktops and to$602 for notebooks by January and to $540 and$560 in February.[134] According to research firm NPD, the average selling price of all Windows portable PCs has fallen from $659 in October 2008 to$519 in October 2009.[135]

## Terminology

"PC" is an initialism for "personal computer." However, it is used in a different sense: It means a personal computers with an Intel x86-compatible processor running Microsoft Windows (sometimes called Wintel). "PC" is used in contrast with "Mac", an Apple Macintosh computer.[136] This sense of the word is used in Get a Mac advertisement campaign that run between 2006 to 2009, as well as its rival, I'm a PC campaign, that appeared on 2008.

## Types

### Stationary

#### Workstation

Sun SPARCstation 1+ from the early 1990s, with a 25 MHz RISC processor
A workstation is a high-end personal computer designed for technical, mathematical, or scientific applications. Intended primarily to be used by one person at a time, they are commonly connected to a local area network and run multi-user operating systems. Workstations are used for tasks such as computer-aided design, drafting and modeling, computation-intensive scientific and engineering calculations, image processing, architectural modeling, and computer graphics for animation and motion picture visual effects.[137]

#### Desktop Computer

Prior to the widespread usage of PCs, a computer that could fit on a desk was remarkably small, leading to the "desktop" nomenclature. More recently, the phrase usually indicates a particular style of computer case. Desktop computers come in a variety of styles ranging from large vertical tower cases to small models which can be tucked behind an LCD monitor. In this sense, the term "desktop" refers specifically to a horizontally oriented case, usually intended to have the display screen placed on top to save desk space. Most modern desktop computers have separate screens and keyboards.
##### Gaming Computer
A Dell OptiPlex desktop computer
A gaming computer is a standard desktop computer that typically has high-performance hardware, such as a more powerful video card, processor and memory, in order to handle the requirements of demanding video games, which are often simply called "PC games." A number of companies, such as Alienware, manufacture prebuilt gaming computers, and companies such as Razer and Logitech market mice, keyboards and headsets geared toward gamers.
##### Single Unit
Single-unit PCs (also known as all-in-one PCs) are a subtype of desktop computers that combine the monitor and case of the computer within a single unit. The monitor often utilizes a touchscreen as an optional method of user input, but separate keyboards and mice are normally still included. The inner components of the PC are often located directly behind the monitor and many of such PCs are built similarly to laptops.

#### Nettop

A subtype of desktops, called nettops, was introduced by Intel in February 2008, characterized by low cost and lean functionality. A similar subtype of laptops (or notebooks) is the netbook, described below. The product line features the new Intel Atom processor, which specifically enables nettops to consume less power and fit into small enclosures.

#### Home Theater PC

An Antec Fusion V2 home theater PC, with a keyboard placed on top of it.
A home theater PC (HTPC) is a convergence device that combines the functions of a personal computer and a digital video recorder. It is connected to a TV set or an appropriately sized computer display, and is often used as a digital photo viewer, music and video player, TV receiver, and digital video recorder. HTPCs are also referred to as media center systems or media servers. The general goal in a HTPC is usually to combine many or all components of a home theater setup into one box. More recently, HTPCs gained the ability to connect to services providing on-demand movies and TV shows.HTPCs can be purchased pre-configured with the required hardware and software needed to add television programming to the PC, or can be cobbled together out of discrete components, what is commonly done with software support from MythTV, Windows Media Center, GB-PVR, SageTV, Famulent or LinuxMCE.

### Portable

#### Laptop

A modern laptop computer
A laptop computer or simply laptop, also called a notebook computer, is a small personal computer designed for portability. Usually, all of the hardware and interfaces needed to operate a laptop, such as the graphics card, audio devices or USB ports (previously parallel and serial ports), are built into a single unit. Laptops contain high-capacity batteries that can power the device for extensive periods of time, enhancing portability. Once the battery charge is depleted, it will have to be recharged through a power outlet. In the interests of saving power, weight and space, laptop graphics cards are in many cases integrated into the CPU or chipset and use system RAM, resulting in reduced graphics performance when compared to an equivalent desktop machine. For this reason, desktop or gaming computers are usually preferred to laptop PCs for gaming purposes.One of the drawbacks of laptops is that, due to the size and configuration of components, usually relatively little can be done to upgrade the overall computer from its original design. Internal upgrades are either not manufacturer-recommended, can damage the laptop if done with poor care or knowledge, or in some cases impossible, making the desktop PC more modular. Some internal upgrades, such as memory and hard disk drive upgrades are often easily performed, while a display or keyboard upgrade is usually impossible. Just as desktops, laptops also have the same possibilities for connecting to a wide variety of devices, including external displays, mice, cameras, storage devices and keyboards, which may be attached externally through USB ports and other less common ports such as external video.A subtype of notebooks, called subnotebook, has most of the features of a standard laptop computer, but with smaller physical dimensions. Subnotebooks are larger than hand-held computers, and usually run full versions of desktop or laptop operating systems. Ultra-Mobile PCs (UMPC) are usually considered subnotebooks, or more specifically, subnotebook tablet PCs, which are described below. Netbooks are sometimes considered to belong to this category, though they are sometimes separated into a category of their own (see below).
##### Desktop Replacement
An Acer Aspire desktop replacement laptop
A desktop replacement computer (DTR) is a personal computer that provides the full capabilities of a desktop computer while remaining mobile. Such computers are often actually larger, bulkier laptops. Because of their increased size, this class of computers usually includes more powerful components and a larger display than generally found in smaller portable computers, and can have a relatively limited battery capacity or none at all in some cases. Some use a limited range of desktop components to provide better performance at the expense of battery life. Desktop replacement computers are sometimes called desknotes, as a portmanteau of words "desktop" and "notebook," though the term is also applied to desktop replacement computers in general.[138]

#### Netbook

An HP netbook
Netbooks, also called mini notebooks or subnotebooks, are a subgroup of laptops[139] acting as a category of small, lightweight and inexpensive laptop computers suited for general computing tasks and accessing web-based applications. They are often marketed as "companion devices", with an intention to augment other ways in which a user can access computer resources.[140]Walt Mossberg called them a "relatively new category of small, light, minimalist and cheap laptops."[141] By August 2009, CNET called netbooks "nothing more than smaller, cheaper notebooks."[142]Initially, the primary defining characteristic of netbooks was the lack of an optical disc drive, requiring it to be a separate external device. This has become less important as flash memory devices have gradually increased in capacity, replacing the writable optical disc (e.g. CD-RW, DVD-RW) as a transportable storage medium.At their inception in late 2007—​as smaller notebooks optimized for low weight and low cost[143]—​netbooks omitted key features (e.g., the optical drive), featured smaller screens and keyboards, and offered reduced specifications and computing power. Over the course of their evolution, netbooks have ranged in their screen sizes from below five inches[144] to over 13 inches,[145] with weights around ~1 kg (2-3 pounds). Often significantly less expensive than other laptops,[146] by mid-2009 netbooks had been offered to users "free of charge", with an extended service contract purchase of a cellular data plan.[147]In the short period since their appearance, netbooks have grown in size and features, converging with new smaller and lighter notebooks. By mid-2009, CNET noted that "the specs are so similar that the average shopper would likely be confused as to why one is better than the other," noting "the only conclusion is that there really is no distinction between the devices."[148]

#### Tablet

HP Compaq tablet PC with rotating/removable keyboard
A tablet is a type of portable PC that de-emphasizes the use of traditional input devices (such as a mouse or keyboard) by using a touchscreen display, which can be controlled using either a stylus pen or finger. Some tablets may use a "hybrid" or "convertible" design, offering a keyboard that can either be removed as an attachment, or a screen that can be rotated and folded directly over top the keyboard.Some tablets may run a traditional PC operating system such as Windows or Linux; Microsoft attempted to enter the tablet market in 2002 with its Microsoft Tablet PC specifications, for tablets and convertible laptops running Windows XP. However, Microsoft's early attempts were overshadowed by the release of Apple's iPad; following in its footsteps, most modern tablets use slate designs and run mobile operating systems such as Android and iOS, giving them functionality similar to smartphones. In response, Microsoft built its Windows 8 operating system to better accommodate these new touch-oriented devices.[149]

#### Ultra-Mobile PC

A Samsung Q1 ultra-mobile PC
The ultra-mobile PC (UMPC) is a specification for small-configuration tablet PCs. It was developed as a joint development exercise by Microsoft, Intel and Samsung, among others. Current UMPCs typically feature the Windows XP, Windows Vista, Windows 7, or Linux operating system, and low-voltage Intel Atom or VIA C7-M processors.

#### Pocket PC

An O2 pocket PC
A pocket PC is a hardware specification for a handheld-sized computer (personal digital assistant, PDA) that runs the Microsoft Windows Mobile operating system. It may have the capability to run an alternative operating system like NetBSD or Linux. Pocket PCs have many of the capabilities of modern desktop PCs.Numerous applications are available for handhelds adhering to the Microsoft Pocket PC specification, many of which are freeware. Some of these devices also include mobile phone features, actually representing a smartphone. Microsoft-compliant Pocket PCs can also be used with many other add-ons like GPS receivers, barcode readers, RFID readers and cameras. In 2007, with the release of Windows Mobile 6, Microsoft dropped the name Pocket PC in favor of a new naming scheme: devices without an integrated phone are called Windows Mobile Classic instead of Pocket PC, while devices with an integrated phone and a touch screen are called Windows Mobile Professional.[150]

## Hardware

Computer hardware is a comprehensive term for all physical parts of a computer, as distinguished from the data it contains or operates on, and the software that provides instructions for the hardware to accomplish tasks. The boundary between hardware and software might be slightly blurry, with the existence of firmware that is software "built into" the hardware.
An exploded view of a modern personal computer and peripherals: (1) Scanner; (2) CPU (Microprocessor); (3) Memory (RAM); (4) Expansion cards (graphics cards, etc.); (5) Power supply; (6) Optical disc drive; (7) Storage (Hard disk or SSD); (8) Motherboard; (9) Speakers; (10) Monitor; (11) System software; (12) Application software; (13) Keyboard; (14) Mouse; (15) External hard disk; (16) Printer
Mass-market consumer computers use highly standardized components and so are simple for an end user to assemble into a working system. A typical desktop computer consists of a computer case that holds the power supply, motherboard, hard disk drive, and often an optical disc drive. External devices such as a computer monitor or visual display unit, keyboard, and a pointing device are usually found in a personal computer.The motherboard connects all processor, memory and peripheral devices together. The RAM, graphics card and processor are in most cases mounted directly onto the motherboard. The central processing unit (microprocessor chip) plugs into a CPU socket, while the memory modules plug into corresponding memory sockets. Some motherboards have the video display adapter, sound and other peripherals integrated onto the motherboard, while others use expansion slots for graphics cards, network cards, or other I/O devices. The graphics card or sound card may employ a break out box to keep the analog parts away from the electromagnetic radiation inside the computer case. Disk drives, which provide mass storage, are connected to the motherboard with one cable, and to the power supply through another cable. Usually, disk drives are mounted in the same case as the motherboard; expansion chassis are also made for additional disk storage. For extended amounts of data, a tape drive can be used or extra hard disks can be put together in an external case.The keyboard and the mouse are external devices plugged into the computer through connectors on an I/O panel on the back of the computer case. The monitor is also connected to the I/O panel, either through an onboard port on the motherboard, or a port on the graphics card.Capabilities of the personal computers hardware can sometimes be extended by the addition of expansion cards connected via an expansion bus. Standard peripheral buses often used for adding expansion cards in personal computers include PCI, PCI Express (PCIe), and AGP (a high-speed PCI bus dedicated to graphics adapters, found in older computers). Most modern personal computers have multiple physical PCI Express expansion slots, with some of the having PCI slots as well.

### Computer Case

A stripped ATX case lying on its side.
A computer case is an enclosure that contains the main components of a computer. They are usually constructed from steel or aluminum combined with plastic, although other materials such as wood have been used. Cases are available in different sizes and shapes; the size and shape of a computer case is usually determined by the configuration of the motherboard that it is designed to accommodate, since this is the largest and most central component of most computers.The most popular style for desktop computers is ATX, although microATX and similar layouts became very popular for a variety of uses. Companies like Shuttle Inc. and AOpen have popularized small cases, for which FlexATX is the most common motherboard size.

### Power Supply Unit

Computer power supply unit with top cover removed.
The power supply unit (PSU) converts general-purpose mains AC electricity to direct current (DC) for the other components of the computer.The rated output capacity of a PSU should usually be about 40% greater than the calculated system power consumption needs obtained by adding up all the system components. This protects against overloading the supply, and guards against performance degradation.

### Processor

The central processing unit, or CPU, is a part of a computer that executes instructions of a software program. In newer PCs, the CPU contains over a million transistors in one integrated circuit chip called the microprocessor. In most cases, the microprocessor plugs directly into the motherboard. The chip generates so much heat that the PC builder is required to attach a special cooling device to its surface; thus, modern CPUs are equipped with a fanattached via heat sink.
AMD Athlon 64 X2 CPU.
IBM PC compatible computers use an x86-compatible microprocessor, manufactured by Intel, AMD, VIA Technologies or Transmeta. Apple Macintosh computers were initially built with the Motorola 680x0 family of processors, then switched to the PowerPC series; in 2006, they switched to x86-compatible processors made by Intel.

### Motherboard

A motherboard without processor, memory and expansion cards, cables
The motherboard, also referred to as system board or main board, is the primary circuit board within a personal computer, and other major system components plug directly into it or via a cable. A motherboard contains a microprocessor, the CPU supporting circuitry (mostly integrated circuits) that provide the interface between memory and input/output peripheral circuits, main memory, and facilities for initial setup of the computer immediately after power-on (often called boot firmware or, in IBM PC compatible computers, a BIOS or UEFI).In many portable and embedded personal computers, the motherboard houses nearly all of the PC's core components. Often a motherboard will also contain one or more peripheral buses and physical connectors for expansion purposes. Sometimes a secondary daughter board is connected to the motherboard to provide further expandability or to satisfy space constraints.

### Main Memory

1GB DDR SDRAM PC-3200 module
A PC's main memory is a fast primary storage device that is directly accessible by the CPU, and is used to store the currently executing program and immediately needed data. PCs use semiconductor random access memory (RAM) of various kinds such as DRAM, SDRAM or SRAM as their primary storage. Which exact kind is used depends on cost/performance issues at any particular time.Main memory is much faster than mass storage devices like hard disk drives or optical discs, but is usually volatile, meaning that it does not retain its contents (instructions or data) in the absence of power, and is much more expensive for a given capacity than is most mass storage. As a result, main memory is generally not suitable for long-term or archival data storage.

### Hard Disk

A Western Digital 250 GB hard disk drive
Mass storage devices store programs and data even when the power is off; they do require power to perform read and write functions during usage. Although flash memory has dropped in cost, the prevailing form of mass storage in personal computers is still the hard disk drive.If the mass storage controller provides additional ports for expandability, a PC may also be upgraded by the addition of extra hard disk or optical disc drives. For example, BD-ROMs, DVD-RWs, and various optical disc recorders may all be added by the user to certain PCs. Standard internal storage device connection interfaces are PATA, Serial ATA and SCSI.Solid state drives (SSDs) are a much faster (but also a much more expensive) replacement for traditional mechanical hard disk drives.

### Visual Display Unit

A visual display unit, computer monitor or just display, is a piece of electrical equipment, usually separate from the computer case, which displays visual images without producing a permanent computer record. A display device is usually either a CRT or some form of flat panel such as a TFT LCD. Multi-monitor setups are also quite common.The display unit houses an electronic circuitry that generates its picture from signals received from the computer. Within the computer, either integral to the motherboard or plugged into it as an expansion card, there is pre-processing circuitry to convert the microprocessor's output data to a format compatible with the display unit's circuitry. The images from computer monitors originally contained only text, but as graphical user interfaces emerged and became common, they began to display more images and multimedia content.The term "monitor" is also used, particularly by technicians in broadcasting television, where a picture of the broadcast data is displayed to a highly standardized reference monitor for confidence checking purposes.

### Video Card

The video card—otherwise called a graphics card, graphics adapter or video adapter—processes the graphics output from the motherboard and transmits it to the display. It is an essential part of modern multimedia-enriched computing. On older models, and today on budget models, graphics circuitry may be integrated with the motherboard, but for modern and flexible machines, they are connected by the PCI, AGP, or PCI Express interface.When the IBM PC was introduced, most existing business-oriented personal computers used text-only display adapters and had no graphics capability. Home computers at that time had graphics compatible with television signals, but with low resolution by modern standards owing to the limited memory available to the eight-bit processors available at the time.

### Keyboard

A "Model M" IBM computer keyboard from the early 1980s. Commonly called the "Clicky Keyboard" due to its buckling spring key spring design, which gives the keyboard its iconic 'Click' sound with each keystroke.
A keyboard is an arrangement of buttons that each correspond to a function, letter, or number. They are the primary devices used for inputting text. In most cases, they contain an array of keys specifically organized with the corresponding letters, numbers, and functions printed or engraved on the button. They are generally designed around an operators language, and many different versions for different languages exist.In English, the most common layout is the QWERTY layout, which was originally used in typewriters. They have evolved over time, and have been modified for use in computers with the addition of function keys, number keys, arrow keys, and keys specific to an operating system. Often, specific functions can be achieved by pressing multiple keys at once or in succession, such as inputting characters with accents or opening a task manager. Programs use keyboard shortcuts very differently and all use different keyboard shortcuts for different program specific operations, such as refreshing a web page in a web browser or selecting all text in a word processor.

### Mouse

A selection of computer mice built between 1986 and 2007
A computer mouse is a small handheld device that users hold and slide across a flat surface, pointing at various elements of a graphical user interface with an on-screen cursor, and selecting and moving objects using the mouse buttons. Almost all modern personal computers include a mouse; it may be plugged into a computer's rear mouse socket, or as a USB device, or, more recently, may be connected wirelessly via an USB dongle or Bluetooth link.In the past, mice had a single button that users could press down on the device to "click" on whatever the pointer on the screen was hovering over. Modern mice have two, three or more buttons, providing a "right click" function button on the mouse, which performs a secondary action on a selected object, and a scroll wheel, which users can rotate using their fingers to "scroll" up or down. The scroll wheel can also be pressed down, and therefore be used as a third button. Some mouse wheels may be tilted from side to side to allow sideways scrolling. Different programs make use of these functions differently, and may scroll horizontally by default with the scroll wheel, open different menus with different buttons, etc. These functions may be also user-defined through software utilities.Mice traditionally detected movement and communicated with the computer with an internal "mouse ball", and used optical encoders to detect rotation of the ball and tell the computer where the mouse has moved. However, these systems were subject to low durability, accuracy and required internal cleaning. Modern mice use optical technology to directly trace movement of the surface under the mouse and are much more accurate, durable and almost maintenance free. They work on a wider variety of surfaces and can even operate on walls, ceilings or other non-horizontal surfaces.

### Other Components

A proper ergonomic design of a personal computer workplace is necessary to prevent repetitive strain injuries, which can develop over time and can lead to long-term disability.
All computers require either fixed or removable storage for their operating system, programs and user-generated material. Early home computers used compact audio cassettes for file storage; these were at the time a very low cost storage solution, but were displaced by floppy disk drives when manufacturing costs dropped, by the mid-1980s.Initially, the 5.25-inch and 3.5-inch floppy drives were the principal forms of removable storage for backup of user files and distribution of software. As memory sizes increased, the capacity of the floppy did not keep pace; the Zip drive and other higher-capacity removable media were introduced but never became as prevalent as the floppy drive.By the late 1990s, the optical drive, in CD and later DVD and Blu-ray Disc forms, became the main method for software distribution, and writeable media provided means for data backup and file interchange. As a result, floppy drives became uncommon in desktop personal computers since about 2000, and were dropped from many laptop systems even earlier. (The NeXT computer introduced in 1988 did not include a floppy drive, which at the time was unusual.)A second generation of tape recorders was provided when videocassette recorders were pressed into service as backup media for larger disk drives. All these systems were less reliable and slower than purpose-built magnetic tape drives. Such tape drives were uncommon in consumer-type personal computers but were a necessity in business or industrial use.Interchange of data such as photographs from digital cameras is greatly expedited by installation of a card reader, which is often compatible with several forms of flash memory devices. It is usually faster and more convenient to move large amounts of data by removing the card from the mobile device, instead of communicating with the mobile device through a USB interface.A USB flash drive performs much of the data transfer and backup functions formerly done with floppy drives, Zip disksand other devices. Mainstream operating systems for personal computers provide built-in support for USB flash drives, allowing interchange even between computers with different processors and operating systems. The compact size and lack of moving parts or dirt-sensitive media, combined with low cost and high capacity, have made USB flash drives a popular and useful accessory for any personal computer user.The operating system can be located on any storage, but is typically installed on a hard disk or solid-state drive. A Live CD represents the concept of running an operating system directly from a CD. While this is slow compared to storing the operating system on a hard disk drive, it is typically used for installation of operating systems, demonstrations, system recovery, or other special purposes. Large flash memory is currently more expensive than hard disk drives of similar size (as of mid-2014) but are starting to appear in laptop computers because of their low weight, small size and low power requirements.Computer communications involve internal modem cards, modems, network adapter cards, and routers. Common peripherals and adapter cards include headsets, joysticks, microphones, printers, scanners, sound adapter cards (as a separate card rather than located on the motherboard), speakers and webcams.

## Software

A screenshot of the OpenOffice.org Writer software
Computer software is any kind of computer program, procedure, or documentation that performs some task on a computer system.[151] The term includes application software such as word processors that perform productive tasks for users, system software such as operating systems that interface with computer hardware to provide the necessary services for application software, and middleware that controls and co-ordinates distributed systems.Software applications are common for word processing, Internet browsing, Internet faxing, e-mail and other digital messaging, multimedia playback, playing of computer game, and computer programming. The user of a modern personal computer may have significant knowledge of the operating environment and application programs, but is not necessarily interested in programming nor even able to write programs for the computer. Therefore, most softwarewritten primarily for personal computers tends to be designed with simplicity of use, or "user-friendliness" in mind. However, the software industry continuously provide a wide range of new products for use in personal computers, targeted at both the expert and the non-expert user.

### Operating System

An operating system (OS) manages computer resources and provides programmers with an interface used to access those resources. An operating system processes system data and user input, and responds by allocating and managing tasks and internal system resources as a service to users and programs of the system. An operating system performs basic tasks such as controlling and allocating memory, prioritizing system requests, controlling input and outputdevices, facilitating computer networking, and managing files.Common contemporary desktop operating systems are Microsoft Windows, OS X, Linux, Solaris and FreeBSD. Windows, OS X, and Linux all have server and personal variants. With the exception of Microsoft Windows, the designs of each of the them were inspired by or directly inherited from the Unix operating system, which was developed at Bell Labs beginning in the late 1960s and spawned the development of numerous free and proprietary operating systems.

#### Microsoft Windows

Microsoft Windows is the collective brand name of several operating systems made by Microsoft. Microsoft first introduced an operating environment named Windows in November 1985,[152] as an add-on to MS-DOS and in response to the growing interest in graphical user interfaces (GUIs)[153] generated by Apple's 1984 introduction of the Macintosh.[154] The most recent client and server version of Windows are Windows 8.1 and Windows Server 2012 R2, respectively.

#### OS X

OS X (formerly Mac OS X) is a line of operating systems developed, marketed, and sold by Apple Inc. OS X is the successor to the original Mac OS, which had been Apple's primary operating system since 1984. OS X is a Unix-based graphical operating system, and Snow Leopard, Leopard, Lion, Mountain Lion, and the new Mavericks are version titles. The most recent version of OS X is entitled OS X Yosemite.On iPhone, iPad and iPod, versions of iOS (which is an OS X derivative) are available from iOS 1.0 to the recent iOS 8.

#### Linux

A Linux distribution running KDE Plasma Desktop.
Linux is a family of Unix-like computer operating systems. Linux is one of the most prominent examples of free software and open source development: typically all underlying source code can be freely modified, used, and redistributed by anyone.[155] The name "Linux" refers to the Linux kernel, started in 1991 by Linus Torvalds. The system's utilities and libraries usually come from the GNU operating system, announced in 1983 by Richard Stallman. The GNU contribution is the basis for the alternative name GNU/Linux.[156]Known for its use in servers, with the LAMP application stack as one of prominent examples, Linux is supported by corporations such as Dell, Hewlett-Packard, IBM, Novell, Oracle Corporation, Red Hat, Canonical Ltd. and Sun Microsystems. It is used as an operating system for a wide variety of computer hardware, including desktop computers, netbooks, supercomputers,[157] video game systems, such as the PlayStation 3 (until this option was removed remotely by Sony in 2010[158]), several arcade games, and embedded devices such as mobile phones,portable media players, routers, and stage lighting systems.

### Applications

A screenshot of GIMP, which is a raster graphics editor
Generally, a computer user uses application software to carry out a specific task. System software supports applications and provides common services such as memory management, network connectivity and device drivers, all of which may be used by applications but are not directly of interest to the end user. A simplified analogy in the world of hardware would be the relationship of an electric light bulb (an application) to an electric power generation plant (a system): the power plant merely generates electricity, not itself of any real use until harnessed to an application like the electric light that performs a service that benefits the user.Typical examples of software applications are word processors, spreadsheets, and media players. Multiple applications bundled together as a package are sometimes referred to as an application suite. Microsoft Office and OpenOffice.org, which bundle together a word processor, a spreadsheet, and several other discrete applications, are typical examples. The separate applications in a suite usually have a user interface that has some commonality making it easier for the user to learn and use each application. Often, they may have some capability to interact with each other in ways beneficial to the user; for example, a spreadsheet might be able to be embedded in a word processor document even though it had been created in the separate spreadsheet application.End-user development tailors systems to meet the user's specific needs. User-written software include spreadsheet templates, word processor macros, scientific simulations, graphics and animation scripts; even email filters are a kind of user software. Users create this software themselves and often overlook how important it is.

### Gaming

PC gaming is popular among the high-end PC market. Gaming platforms like Steam (software) and GOG.com (as well as competitive e-sports titles like League of Legends) are largely responsible for PC systems overtaking console revenue in 2013.[159]

## Toxicity

Toxic chemicals found in computer hardware include lead, mercury, cadmium, chromium, plastic (PVC), and barium. In a raw materials breakdown, computer is about 17% lead, copper, zinc, mercury, and cadmium; 23% is plastic, 14% is aluminum, and 20% is iron.Lead is found in a cathode ray tube (CRT) display, and on all of the printed circuit boards and most expansion cards. Mercury is located in the screen'sfluorescent lamp, in the laser light generators in the optical disk drive, and in the round, silver-looking batteries on the motherboard. Plastic is found mostly in the housing of the computation and display circuitry.While daily end-users are not exposed to these toxic elements, the danger arises during the computer recycling process, which involves manually breaking down hardware and leads to the exposure of a measurable amount of lead or mercury. A measurable amount of lead or mercury can easily cause serious brain damage or ruin drinking water supplies. Computer recycling is best handled by the electronic waste (e-waste) industry, and kept segregated from the general community dump.

### Electronic Waste Regulation

Personal computers have become a large contributor to the 50 million tons of discarded electronic waste that is being generated annually, according to the United Nations Environment Programme. To address the electronic waste issue affecting developing countries and the environment, extended producer responsibility (EPR) acts have been implemented in various countries and states.[160]Organizations, such as the Silicon Valley Toxics Coalition, Basel Action Network, Toxics Link India, SCOPE, and Greenpeace have contributed to these efforts. In the absence of comprehensive national legislation or regulation on the export and import of electronic waste, the Silicon Valley Toxics Coalition and BAN (Basel Action Network) teamed up with 32 electronic recyclers in the US and Canada to create an e-steward program for the orderly disposal of manufacturers and customers electronic waste. The Silicon Valley Toxics Coalition founded the Electronics TakeBack Coalition, a coalition that advocates for the production of environmentally friendly products. The TakeBack Coalition works with policy makers, recyclers, and smart businesses to get manufacturers to take full responsibility of their products.There are organizations opposing EPR regulation, such as the Reason Foundation. They see flaws in two principal tenants of EPR: First EPR relies on the idea that if the manufacturers have to pay for environmental harm, they will adapt their practices. Second EPR assumes the current design practices are environmentally inefficient. The Reason Foundation claims that manufacturers naturally move toward reduced material and energy use.

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