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Personal computer

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A stylised illustration of a modern personal computer.

A university computer lab, containing many desktop PCs.

A personal computer (PC) is usually a microcomputer whose price, size, and capabilities make it suitable for personal usage. The term was popularized by Apple Computer with the Apple II in the late-1970s and early-1980s, and afterwards by IBM with the IBM PC.

1 History
2 Uses
3 Configuration
4 Laptop computers
5 Non IBM-compatible personal computers
6 See also
7 Notes
8 External links

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History

Time share "terminals" to central computers were sometimes used before the advent of the PC, such as the smart terminal — televideo ASCII character mode terminal pictured here.

Before their advent in the late-1970s to the early-1980s, the only computers possibly available, if the user was privileged, were "computer-terminal based" architectures owned by large institutions. In these, the technology was called "computer time share systems", and used minicomputers and main frame computers. These central computer systems frequently required large rooms — roughly, a handball-court-sized room could hold two to three small minicomputers and its associated peripherals, each housed in cabinets much the size of three refrigerators side by side (with blinking lights and tape drives). In that era, mainframe computers occupied whole floors; a big hard disk was a mere 10–20 Megabytes mounted on a cabinet the size of a small chest-type freezer. Earlier PCs were generally called desktop computers, and the slower Pentium-based personal computer of the late 1990s could easily outperform the advanced minicomputers of that era.

The first generations of personal microcomputers were usually sold as kits or merely instructions, and required a somewhat skilled person to assemble and operate them. These were usually called microcomputers, but the name "personal computer" was also used. Later generations were sometimes interchangeably called by the names "home computer" and "personal computer." By the mid-1980s, "home computer" was becoming a less common label in favor of "personal computer." These computers were pre-assembled and required little technical knowledge to operate. In today's common usage, personal computer and PC usually indicate an IBM PC compatible. Due to this association, some manufacturers of personal computers that are not IBM PCs avoid explicitly using the terms to describe their products. Mostly, the term PC is used to describe personal computers that use Microsoft Windows operating systems.

One early use of "personal computer" appeared in a November 3, 1962, New York Times article reporting John W. Mauchly's vision of future computing as detailed at a recent meeting of the American Institute of Industrial Engineers. Mauchly stated, "There is no reason to suppose the average boy or girl cannot be master of a personal computer.^[1]"

Some of the first computers that might be called "personal" were early minicomputers such as the LINC and PDP-8. By today's standards they were very large (about the size of a refrigerator) and cost prohibitive (typically tens of thousands of US dollars), and thus were rarely purchased by an individual. However, they were much smaller, less expensive, and generally simpler to operate than many of the mainframe computers of the time. Therefore, they were accessible for individual laboratories and research projects. Minicomputers largely freed these organizations from the batch processing and bureaucracy of a commercial or university computing center.

In addition, minicomputers were relatively interactive and soon had their own operating systems. Eventually, the minicomputer included VAX and larger minicomputers from Data General, Prime, and others. The minicomputer era largely was a precursor to personal computer usage and an intermediary step from mainframes.

Development of the single-chip microprocessor was an enormous catalyst to the popularization of cheap, easy to use, and truly personal computers. Arguably the first true "personal computer" was the Altair 8800, which brought affordable computing to an admittedly select market in the 1970s. However, it was arguably this computer that spawned the development of both Apple Computer as well as Microsoft, spawning the Altair BASIC programming language interpreter, Microsoft's first product. The first generation of microcomputers (computers based on a microprocessor) that appeared in the mid-1970s, due to the success of the Steve Wozniak-designed Apple Computer release, the Apple II, were usually known as home computers. These were less capable and in some ways less versatile than large business computers of the day. They were generally used by computer enthusiasts for learning to program, running simple office/productivity applications, electronics interfacing, and general hobbyist pursuits.

A release photo of the original IBM PC (ca. 1981).

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. This was followed by the August 1981 release of the IBM PC which would revolutionize the computer market. The Lotus 1-2-3, a combined spreadsheet (a clone of VisiCalc), presentation graphics, and simple database application, would become the PC's own killer app. Good word processor programs would also appear for many home computers, in particular the introduction of Microsoft Word for the Apple Macintosh in 1985 (While earlier versions of Word had been created for the PC, it became popular initially through the Macintosh.).

In the January 3, 1983 issue of Time magazine, the personal computer was named the "Machine of the Year" or its Person of the Year for 1982.

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.

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Uses

Personal computers are normally operated by one user at a time to perform such general purpose tasks as word processing, internet browsing, e-mail and other digital messaging, multimedia playback, video game play, computer programming, etc. Other more specific functions usually performed with the help of a PC include working, teleworking, learning, researching, printing, online banking, online shopping and dealing online with public sector institutions and services. 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 software written 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.

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Configuration

An exploded view of a modern personal computer:

Personal computers can be categorized by size and portability:

Most personal computers are standardized to the point that purchased software is expected to run with little or no customization for the particular computer. Many PCs are also user-upgradable, especially desktop and workstation class computers. Devices such as main memory, mass storage, even the motherboard and central processing unit may be easily replaced by an end user. 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).

A four-megabyte RAM card measuring about twenty-two by fifteen inches; made for the VAX 8600 minicomputer (circa 1986). Dual in-line package (DIP) Integrated circuits populate nearly the whole board; the RAM chips are in the majority located in the rectangular areas to the left and right.

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.

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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.

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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. Apple Macintosh processors were based on the Power PC (a RISC architecture) but as of 2005, Apple has used x86 compatible processors from Intel.

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Main memory

Main article: Primary storage

A PC's main memory place (or primary storage) is fast storage space that is directly accessible by 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 usually cannot retain data for more than a few fractions of a second without power and is more expensive. Therefore, it is 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.

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Mass storage

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.

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.

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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.

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Laptop computers

Main article: Laptop computer

A laptop computer or simply laptop (also notebook computer or notebook) is a small personal computer designed for mobility. Usually all of the peripherals needed to operate the laptop are built in to a single unit. Most laptops contain batteries to facilitate operation without a readily available electrical outlet.

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Non IBM-compatible personal computers

Though many personal computers are IBM PC compatible using either Microsoft Windows or closed and open-source Unix-likes such as Linux, a number of other personal computer types are also popular.

A leading alternative to the IBM PC is the Apple Macintosh, a combination of proprietary hardware and operating system. The Macintosh orignally used the Motorola 68000 series, then shifted to the IBM and Motorola PowerPC processors. In January, 2006, Apple shifted its architecture to the same Intel processor family found in IBM compatibles, the new Mac architecture is not strictly IBM-compatible—it does not employ the master boot record (MBR) technology used since the IBM PC, nor does it use BIOS, using instead the Extensible Firmware Interface (EFI) invented by Intel. Mainstream PC's are, however, slowly starting to follow Apple's lead in adopting these technologies—Windows Vista, for instance, will introduce compatibility with EFI.

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

Amiga (previously produced by Commodore, now under license from Amiga Inc.)
Acorn Archimedes & RiscPC
Atari ST
BeOS BeBox
Pegasos
NEC PC-9800 (At one time, in Japan.)
NeXT workstations
Sun SPARCstation
SGI workstations like the SGI Indigo and SGI Onyx

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".

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