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, 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.

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.
The initials "PC" have become virtually synonymous with IBM PC compatible computers such that they are rarely used to refer to non-IBM PC compatible personal computers such as the Apple Macintosh.

Contents
1 History
2 Architecture
2.1 Motherboard
2.2 Central processing unit
2.3 RAM - memory
2.4 Hard disk drive
2.5 PSU - power supply unit
2.6 Graphics - video Card
3 Non IBM-compatible personal computers

History
An early use of the term appeared in a November 3, 1962, 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.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 $50,000 US), 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, general online services such as CompuServe, The Source, or Genie, or platform-specific services such as Quantum Link (US) or Compunet (UK).

Maybe the most important push to IBM compatibles over all other computers was because Albert Clark, an Air Force program manager who was faced with a growing government user base, sharing mainframe time, who were purchasing the various non-compatible home computers to replace their VT-100 dumb terminals. There were as many as 10 different brands that could all emulate a VT-100, but required different actions to boot up and run. Rather than have to justify a single brand of computer with proprietary software and hardware, he chose what, at that time, was arguably the most backward computer of its time. It had no sound card, only a keyboard interface, but it was inexpensive and multiple manufacturers could legally produce them. He wrote the specification for an “IBM compatible” computer for purchase across the US Department of Defense. Contracting officials did not take the compatibility issue seriously so Albert Clark had to approve the next 3 major specifications prior to release to industry for bidding. The eventual result was the purchase of several million IBM compatible personal computers all across the government which encouraged many of the government contractors to buy IBM compatibles “to be compatible with the government.” The result was that the “IBM compatible computers”, Intel processors, and Microsoft became the standard.

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 PCs 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 straight CPU power.

Architecture
Personal computers can be categorized by size and portability:

the desktop computer
the portable computer
the notebook or laptop
the tablet computer
the PDA
the wearable computer
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, and even the motherboard can in some cases be changed to upgrade the power of the central processor. Such upgradeability is not indefinite since major changes in the personal computer industry occur every three to five years; a machine that was considered top-of-the-line say five or six years ago may be impractical to upgrade due to changes in processors, memory, and peripherals. This upgrade cycle is in part linked 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. The standard expansion bays for personal computers as of 2005 are PCI, AGP, and PCI Express. All personal computers as of 2005 have multiple PCI slots, and all but the cheapest prebuilt PCs have either a single AGP or at least one PCI Express slot, but rarely both. A PC may also be upgraded by the addition of extra drives (DVD, CD-ROM, flash drive, Hard drive, etc). Standard internal storage device interfaces are ATA, Serial ATA, SCSI, and CF+ Type II in 2005.

Motherboard
Main article: PC motherboard
The motherboard is the primary circuit board for a computer. Most other computer components plug directly into the motherboard to allow them to exchange information. Motherboards usually hold a chipset, BIOS, nonvolatile BIOS memory, parallel port, PS/2 keyboard and mouse ports and expansion bays. Sometimes a secondary daughter board is plugged into the motherboard to provide more expansion bays and to cut down on its size.

Central processing unit
Main article: central processing unit
The Central processing unit or CPU is the part of the computer that performs most of the calculations that make programs or operating systems run. The CPU plugs directly into the motherboard by one of many different types of sockets. Most IBM PC compatible computers use an x86-compatible processor made by Intel, AMD, VIA Technologies or Transmeta.

RAM - memory
Main article: random access memory
The Random Access Memory of the computer is the "short-term-memory" of the PC, It is much faster than the mass storage devices like Harddisk or CD-ROM, but its contents are lost when the Power is turned off.

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.

PSU - power supply unit
Main article: power supply
Essential. Provides steady DC supply from a domestic AC source. Many problems with Old PCs can be traced to a faulty or overheating PSU. Newer power supplies often have voltage regulators that will shut down the computer if the power supply is under strain.

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 still popular. The leading alternative is Apple Computer's Power Macintosh platform, based on the PowerPC microprocessor (although Apple has announced[2] a transition to Intel microprocessors beginning in 2006).

Black and white reversal films - which capture images in gray scales instead of colour as in color reversal films - are less common than color reversal films. Agfa manufactures the Agfa SCALA 200x Professional black and white reversal film for photography and it could only be developed with special Agfa processing procedure from designated labs.

Black and white reversal films are more commonly used in production of motion pictures, i.e. footage of video shot in black and white. The Kodak TRI-X Reversal Film 7266 is a black and white reversal film for movie making.

Light is electromagnetic radiation with a wavelength that is visible to the eye (visible light) or, in a technical or scientific setting, electromagnetic radiation of any wavelength. The three basic dimensions of light (i.e., all electromagnetic radiation) are:

intensity (or brilliance or amplitude, perceived by humans as the brightness of the light),
frequency (or wavelength, perceived by humans as the color of the light), and
polarization (or angle of vibration and not perceptible by humans under ordinary circumstances)
Due to wave-particle duality, light simultaneously exhibits properties of both waves and particles. The precise nature of light is one of the key questions of modern physics.

A piece of photographic film that has been exposed to light in a controlled manner must be developed before it can be used. Development does three things: it transforms the latent image into a visible image that can be seen, it makes the visible image permanent and resistant to deterioration with time, and it renders the film insensitive to light. Photographic paper is developed in a similar manner.

(This article does not apply to Polaroid film, which uses a self-contained developing process.)

The steps to black and white negative film developing are:

The film is removed from the camera and wound onto a reel in complete darkness (usually inside a darkroom or a lightproof bag with arm holes). The reel holds the film in a spiral shape, with space between each successive loop so the chemicals may flow freely across the film's surfaces. The reel is placed in a specially designed light-proof tank.
The film is then treated with a series of chemicals:
The first of these is developer, which makes the latent image visible.
The second chemical is a stop bath, which stops the action of developer. (Sometimes plain water is used for this step.) It also helps to clean the developer residue off of the film to prevent contaminating the fixer.
The third chemical is called fixer. It makes the image permanent and light-resistant.
Fixer itself is slightly corrosive, so the film must be washed. Sometimes, it is then placed in a bath of a hypo clearing agent (and sometimes another material, such as selenium). It is then treated with a solution to prevent the appearance of hard-water stains, dried, and cut into strips of a convenient length.
In color negative processes the silver halide crystals present in the emulsion need to be removed. This is called bleaching. Bleaching may be done as an additional step or the bleaching agent, usually potassium ferricyanide, may be formulated in with the fixer. Bleaching may be skipped intentionally to create an optical effect on the film called Bleach bypass.

A chicken (Gallus gallus) is a type of domesticated bird which is often raised as a type of poultry. It is believed to be descended from the wild Asian Red Junglefowl.

Chickens are the most common bird in the world. The population in 2003 was 24 billion, according to the Firefly Encyclopedia of Birds.

Chickens in agriculture
In the United States, chickens were once raised primarily on the family farm. Prior to about 1930, chicken was served for primarily on special occasions or on Sunday as the birds were typically more valued for their eggs than meat. Excess roosters or non-productive hens would be culled from the flock first for butchering. As cities developed and markets sprung up across the nation, live chickens from local farms could often be seen for sale in crates outside the market, to be butchered and cleaned onsite by the butcher.

With the advent of refrigeration, poultry production changed dramatically. Large farms and packing plants emerged that could grow birds by the thousands. Adult chickens could be sent to factories for butchering and processing into pre-packaged commercial products to be frozen or shipped fresh to markets or wholesalers. Large farms or factories could be established devoted solely to egg production and packaging. Once a meat consumed only occasionally, the common availability has made chicken a common and significant meat product within developed nations. Growing concerns over cholesterol in the 1980s and 1990s further resulted in increased consumption.

Similarly, egg production also changed with the development of automation and refrigeration. Today, eggs are grown on factory farms in highly controlled settings. Special varieties of chickens are fed special diets high in calcium and protein to stimulate maximum egg production. Chickens are exposed to artificial light cycles to stimulate egg production year-round. In addition, it is a common practice to force chickens to molt through the careful manipulation of light and the amount of food they receive in order to further increase egg production.

Birds are bipedal, warm-blooded, egg-laying vertebrates characterized primarily by feathers, forelimbs modified as wings, and hollow bones.

Birds range in size from the tiny hummingbirds to the huge Ostrich and Emu. Depending on taxonomic viewpoint, there are about 8,800–10,200 living bird species (plus about 120–130 that have become extinct in the span of human history) in the world, making them the most diverse class of terrestrial vertebrates.

Birds are a very differentiated class, with some feeding on nectar, plants, seeds, insects, rodents, fish, carrion, or other birds. Most birds are diurnal, or active during the day. Some birds, such as the owls and nightjars, are nocturnal or crepuscular (active during twilight hours). Many birds migrate long distances to utilise optimum habitats (e.g., Arctic Tern) while others spend almost all their time at sea (e.g. the Wandering Albatross). Some, such as frigatebirds, stay aloft for days at a time, even sleeping on the wing.

Common characteristics of birds include a bony beak with no teeth, the laying of hard-shelled eggs, high metabolic rate, and a light but strong skeleton. Most birds are characterised by flight, though the ratites are flightless, and several other species, particularly on islands, have also lost this ability. Flightless birds include the penguins, Ostrich, kiwi, and the extinct Dodo. Flightless species are vulnerable to extinction when humans or the mammals they introduce arrive in their habitat, for example the Great Auk, flightless rails, and the moa of New Zealand.

Respiration
Birds respire by means of crosscurrent flow: the air flows at a 90 degree angle to the flow of blood in the lungs capillaries. In addition to the lungs themselves, birds have posterior and anterior air sacs (typically nine) which control air flow through the lungs, but do not play a direct role in gas exchange. There are three parts involved in respiration:

the anterior air sacs (interclavicular, cervicals, and anterior thoracics),
the lungs, and
the posterior air sacs (posterior thoracics & abdominals).
It takes a bird two full breaths (inhaling and exhaling), to completely cycle the air from each inhalation through the lungs and out again. The air flows through air sacs and lungs as follows.

First inhalation: air flows through the trachea and bronchi into the posterior air sacs.
First exhalation: air flows from the posterior air sacs to the lungs.
Second inhalation: air flows from the lungs to the anterior air sacs.
Second exhalation: air flows from the anterior sacs back through the trachea and out of the body.
In birds, at each inhalation and each exhalation fresh air flows through the lungs in only one direction. Birds are therefore able to diffuse more oxygen into their blood. Unlike humans and other mammals, there is no mixing of oxygen rich air and carbon dioxide rich air. Thus, the partial pressure of oxygen in a bird's lungs is the same as the environment. This is also why you would more likely see a bird on Mount Everest than, say, a mouse.

Avian lungs do not have alveoli, as mammalian lungs do, but instead contain millions of tiny passages known as parabronchi, connected at either ends by the dorsobronchi and ventrobronchi. Air flows through the honeycombed walls of the parabronchi and into air capillaries, where oxygen and carbon-dioxide are traded with cross-flowing blood capillaries by diffusion.

Snakes are cold blooded legless reptiles closely related to lizards, which share the order Squamata. There are also several species of legless lizard which superficially resemble snakes, but are not otherwise related to them. A love of snakes is called ophiophilia, a fear of snakes is called ophidiophobia (or snakephobia), a specialist in snakes is an ophiologist.

An old synonym for snake is serpent; in modern usage this usually refers to a mythic or symbolic snake, and information about such creatures will be found under serpent. This article deals with the biology of snakes.

Snake charmers
In some parts of the world, especially in India, snake charming is a roadside show performed by a charmer. In this, the snake charmer carries a basket that contain a snake which he seemingly charms by playing tunes from his flute-like musical instrument, to which the snake responds. However, snakes are deaf, so they cannot hear the music of the charmer's instrument. Researchers have pointed out that many of these snake charmers are good sleight-of-hand artists. The snake moves corresponding to the flute movement and the vibrations from the tapping of the charmer's foot which is not noticed by the public. They rarely catch their snakes and the snakes are either nonvenomous or defanged cobras. Sometimes these people exploit the fear of snakes by released snakes into the neigbourhood and claim to rid the residence of snakes. Other snake charmers also have a snake and mongoose show, where both the animals have a mock fight; however, this is not very common.

Snake trapping
Despite the existence of snake charmers, there have also been professional snake catchers. The tribals of "Irulas" from Andhra Pradesh and Tamil Nadu in India have been practicising this art for generations. They generally don't use gimmicks and with the help of a simple stick catch the snakes from the fields or houses. They are also known to eat some of the snakes they catch and are very useful in rat extermination in the villages. Their knowledge of snakes and their behaviour is uncanny. Modern day snake trapping involves an ornithologist using a long stick with a "V" shaped end. Some like Steve Irwin prefer to catch them using bare hands.

A board game is any game played with a premarked surface, with counters or pieces that are moved across the board. Simple board games are often seen as ideal "family entertainment" as they can provide entertainment for all ages. Some board games, such as chess or Go, have intense strategic value and have become lasting classics.

There are many different types and classifications of board games. Some games are simplified simulations of real life. These are popular for they can intermingle make-believe and role playing along with the game. Popular games of this type include Monopoly, which is a rough simulation of the real estate market, Cluedo, which is based upon a murder mystery, and Risk which is one of the most well known of thousands of games attempting to simulate warfare and geo-politics.

Other games only loosely, or do not at all, attempt to imitate reality. These include abstract strategy games like chess and checkers, word games, such as Scrabble, and trivia games, such as Trivial Pursuit.

Luck, strategy and diplomacy
One way of defining board games are between those based upon luck and strategy. Some games, such as chess, have no luck involved. Children's games tend to be very luck based with games such as Sorry! having virtually no decisions to be made. Most board games have both luck and strategy. A player may be hampered by a few poor rolls of the dice in Risk or Monopoly, but over many games a player with a superior strategy will win more often. While some purists consider luck to not be a desirable component of a game, others counter that elements of luck can make for far more complex and multi-faceted strategies as concepts such as expected value and risk management must be considered. Still most adult game players prefer to make some decisions during play, and find purely luck based games such as Top Trumps quite boring.

The third important factor in a game is diplomacy. This generally applies only to games played with three or more people. An important facet of Settlers of Catan, for example, is convincing people to trade with you rather than with other players. In Risk, one example of diplomacy's effectiveness is when two or more players team up against another. Easy diplomacy consists of convincing other players that someone else is winning and should therefore be teamed up against. Difficult diplomacy (such as in the aptly named game Diplomacy) consists of making elaborate plans together, with possibility of betrayal.

Luck is introduced to a game by a number of methods. The most popular is using dice, generally six sided. These can determine everything from how many steps a player moves their token, as in Monopoly, how their forces fare in battle, such as in Risk, or which resources a player gains, such as in Settlers of Catan. Other games such as Sorry! use a deck of special cards that when shuffled create randomness. Scrabble does something similar with randomly picked letters. Other games use spinners, timers of random length, or other sources of randomness. Trivia games have a great deal of randomness based on which question a person gets. German-style board games are notable for often having rather less luck factor than in many North American board games.

 Intensity: Measured in both lux and lumens. For any given luminaire (lighting instrument or fixture), this depends upon the power of the bulb, the design of the instrument (and its corresponding efficiency), the presence or absence of color gels or gobos, distance from the area to be lit, the color and subtance to be lit, and the neuro-optics of the total scene (that is, the relative contrasts to other regions of illumination).
Color: Color temperature is measured in kelvin, and gel colors are organized by several different systems maintained by the color manufacturing companies. The apparent color of a light is determined largely by the gel color given it, but also in part by the power level the lamp is being run at and the color of material is it to light. As the percentage of full power a lamp is being run at drops, the tungsten filament in the bulb glows orange instead of more nearly white. This is known as amber drift or amber shift. Thus a 1000-watt instrument at 50% will appear far more orange than a 500-watt instrument at full.
Pattern: Pattern refers to the shape, quality and evenness of a lamp's output. The pattern of light an instrument makes is largely determined by three factors. The first are the specifics of the bulb, reflector and lens assembly. Different mounting positions for the bulb (axial, base up, base down), different sizes and shapes of reflector and the nature of the lens (or lenses) being used can all affect the pattern of light. Secondly, the specifics of how the lamp is focused affect its pattern. In Ellipsoidal Reflector Spotlights (ERS) and their derivatives (see below), there are two beams of light emitted from the lamp. When the cones of both intersect at the throw distance (the distance to the stage), the lamp has a sharply defined 'hard' edge. When the two cones do not intersect at that distance, the edge is fuzzy and 'soft'. Depending on which beam (direct or reflected) is outside the other, the pattern may be 'thin and soft' or 'fat and soft.' Lastly, a gobo or break up pattern may be applied to ERS's and similar lamps. This is typically a strip of metal with a shape cut into it. It is inserted into the lamp near its aperture. Gobos come in many shapes, but often include leaves, waves, stars and similar patterns.
In addition to these, certain modern instruments are 'movable' (or 'intelligent'), referring to motorized movement of either the entire lamp or a mirror placed in front of its outermost lens. These lamps and the more traditional follow spots add Direction to the relevant characterists of light.

A hoax is an attempt to trick an audience into believing that something false is real. Generally there is some material object involved, which is actually a forgery. Unlike a fraud or con (which usually has an audience of one or a few), which are made for illicit financial or material gain, or a fraud which is perpetrated to support a false religion, a hoax is often perpetrated as a practical joke with a humorous intent, to cause embarrassment, for personal aggrandizement or to serve political purposes. Still, many confidence tricks and the like have also been labeled as hoaxes.

Many hoaxes are also motivated by a desire to satirize or educate by exposing the credulity of the public or the absurdity of the target: literary and artistic hoaxes are often of this sort, although political hoaxes are sometimes motivated in part or whole by the desire to ridicule or expose politicians or political institutions.

The status of a given factoid as reliable or hoax is often the subject of considerable controversy.

The word hoax came from the common pretend magic spell "hocus pocus". "Hocus pocus", in turn, is commonly believed to be a distortion of "hoc est corpus" (= "this is the body") from the Latin Mass. Many etymologists dispute this claim.