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Personal computer

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Personal computer and peripherals. From left to right: ink jet printer, an irrelevant TV, CRT monitor, broadband cable modem for the internet, flat bed scanner. The tower (CPU, hard drive, etc) can just be glimpsed at bottom right. The keyboard and mouse are wireless.
A Micron TransPort XPE laptop computer.

A personal computer or PC is generally a microcomputer intended to be used by one person at a time, and suitable for general purpose tasks such as word processing, programming, sending messages or digital documents (comprising text, images, audio or video) to other computers on the network (E-mail), multimedia editing or game play, usually used to run software not written by the user. Unlike minicomputers, a personal computer is often owned by the person using it, indicating a low cost of purchase and simplicity of operation. 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.

In modern usage PC nearly always refers to an IBM PC compatible and the term may even be used for machines that are in no way personal computers but still use the basic architecture of the IBM PC.

The first generation of microcomputers were called just that, and only sold in small numbers to those able to (build them from kits or) operate them: engineers and accomplished hobbyists (for example, the Altair 8800). The second generation micros were known as home computers, and are discussed in that section.

History

An early use of the term appeared in a 1962-11-03, New York Times article reporting John W. Mauchly's vision of future computing spoken to a meeting of the American Institute of Industrial Engineers that previous day. Mauchly told the gathering, "There is no reason to suppose the average boy or girl cannot be master of a personal computer." [1]

The first computers that can be called 'personal' were the first non-mainframe computers, the LINC and the PDP-8. By today's standards they were big (about the size of a refrigerator), expensive (around US$50,000), and had small magnetic core memories (about 4096 12-bit words for the LINC).

However, they were small enough and cheap enough for individual laboratories and research projects to use, freeing them from the batch processing and bureaucracy of the typical industrial or university computing center. In addition, they were moderately interactive and soon had their own operating systems. Eventually, this category became known as the mini-computer, usually with time-sharing and program development facilities. Eventually, the mini-computer grew up to encompass the VAX and larger mini-computers from Data General, Prime, and others. Deployment of mini-computer systems was a model for how personal computers would be used, but few of the mini-computer makers managed to profit from it.

Development of the single-chip microprocessor changed everything, since it dropped the cost of purchase of a computer by an order of magnitude or more.

The first generation of microcomputers that started to appear in the mid-1970s (see home computers) were less powerful and in some ways less versatile than business computers of the day (but in other ways more versatile, in terms of built-in sound and graphics capabilities), and were generally used by computer enthusiasts for learning to program, for running simple office/productivity applications, for electronics interfacing, and/or games, as well as for accessing BBS's and online services in general.

It was the launch of the VisiCalc spreadsheet, initially for the Apple II and later for the Atari 8-bit family, Commodore PET, and IBM PC that became the "killer app" that turned the microcomputer into a business tool. Later, Lotus 1-2-3, a combined spreadsheet (partly based on VisiCalc), presentation graphics, and simple database application, became the PC's own killer app. Good word processor programs also appeared for many home computers. The low cost of personal computers led to great popularity in the home and business markets during the 1980s. In 1982, Time magazine named the personal computer its Man of the Year.

During the 1990s, the power of personal computers increased radically, blurring the formerly sharp distinction between personal computers and multi-user computers such as mainframes. Today higher-end computers often distinguish themselves from personal computers by greater reliability or greater ability to multitask, rather than by brute CPU ability.

Architecture

Personal computers can be categorized by size and portability:

Many mass-market IBM PC compatible and Apple Macintosh personal computers are standardized to the point that purchased software is expected to run with little or no customization for the particular computer. Often memory and peripherals such as video boards and disk storage are easily upgradeable, even by the end user. Even the motherboard and central processing unit can be designed to be user-replacable. This upgradeability is, however, not indefinite due to rapid changes in the personal computer industry. A PC that was considered top-of-the-line five or six years prior may be impractical to upgrade due to changes in industry standards. Such a computer usually must be totally replaced once it is no longer suitable for its purpose. This upgrade and replacement cycle is partially related to new releases of the primary mass-market operating system, which tends to drive the acquisition of new hardware and tends to obsolete previously serviceable hardware (see planned obsolescence).

The hardware capabilities of personal computers can sometimes be extended by the addition of expansion cards connected via an expansion bus. Some standard peripheral buses often used for adding expansion cards in personal computers as of 2005 are PCI, AGP (a high-speed PCI bus dedicated to graphics adapters), and PCI Express. Most personal computers as of 2005 have multiple physical PCI expansion slots. Many also include an AGP bus and expansion slot or a PCI Express bus and one or more expansion slots, but few PCs contain both buses.

Motherboard

Main article: [[:PC motherboard]]

The motherboard (or mainboard) is the primary circuit board for a personal microcomputer. Many other components connect directly or indirectly to the motherboard. Motherboards usually contain one or more CPUs, supporting circuitry and ICs for CPU operation, main memory, and facilities for initial setup of the computer immediately after being powered on (often called boot firmware or a BIOS). 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 with the motherboard to provide further expandability or to satisfy space constraints.

Central processing unit

Main article: [[:Central processing unit]]

The central processing unit, or CPU, is the part of the computer that executes software programs, including the operating system. Nearly all PCs contain a type of CPU known as a microprocessor. The microprocessor often plugs into the motherboard using one of many different types of sockets. IBM PC compatible computers use an x86-compatible processor, usually made by Intel, AMD, VIA Technologies or Transmeta.

Main memory

Main article: [[:Primary storage]]

A PC's main memory (or primary storage) is fast storage space that is directly accessible to the CPU. It is generally used for storing relatively short-term data needed for software execution. Main memory is usually much faster than mass storage devices like hard disks or optical discs, but is also more expensive and therefore not generally suitable for long-term or archival data storage. As with the CPU, most PCs use some form of semiconductor random access memory such as DRAM or SRAM as their primary storage.

Hard disk drive

Main article: [[:Hard disk]]

The disk drives use a sealed head/disk assembly (HDA) which was first introduced by IBM's "Winchester" disk system. The use of a sealed assembly allowed the use of positive air pressure to drive out particles from the surface of the disk, which improves reliability. This technology is now industry standard, with costs, capacities and access speeds which conform to Moore's law.

If the mass storage controller provides for expandability, a PC may also be upgraded by the addition of extra hard disk or optical drives. For example, DVD-ROMs, CD-ROMs, and various optical disc recorders may all be added by the user to certain PCs. Standard internal storage device interfaces are ATA, Serial ATA, SCSI, and CF+ Type II in 2005.

Graphics - Video card

Main article: [[:Graphics card]]

The graphics card - otherwise called a graphics adapter, video adapter, or video card - processes and renders the graphics output from the computer to the VDU or computer monitor and is an essential part of the modern computer. On older and budget models graphics cards tended to be integrated with the motherboard but, more commonly, they are supplied in PCI, AGP, or PCI Express format. Graphic cards are also the most glamorised computer component as it is the component which creates all the visual effects on the computer which is essential for playing games

Non IBM-compatible personal computers

Though many personal computers are IBM PC compatible using either Microsoft Windows or closed and open-source Unixes such as Linux, a number of other personal computer types are also popular. The leading alternative is Apple Computer's Power Macintosh platform, based on the PowerPC microprocessor (although Apple has begun[2] a transition to Intel microprocessors as of January 2006.)

Further PC and PW (Personal Workstation) types through time:

The term "personal computer" is often avoided by advocates of the above computer systems, ostensibly because of the association it has to the "PC" in "IBM PC".

See also

Notes

  • ^ "Pocket Computer May Replace Shopping List", New York Times, 3 November 1962.
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