A personal computer (PC) is any general-purpose computer whose size, capabilities, and original sales price make it useful for individuals, and which is intended to be operated directly by an end-user with no intervening computer operator. PCs include any type of computer that is used in a “personal” manner. This is in contrast to the batch processing or time-sharing models which allowed large expensive mainframe systems to be used by many people, usually at the same time, or large data processing systems which required a full-time staff to operate efficiently.
A personal computer may be a desktop computer or other mobile types, for example a laptop, tablet PC or a handheld PC (also called a palmtop) that is smaller than a laptop.
The most common microprocessors in personal computers are x86-compatible CPUs. Software applications for personal computers include 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.
A PC may be used at home or in an office. Personal computers may be connected to a local area network (LAN), either by a cable or a wireless connection.
While early PC owners usually had to write their own programs to do anything useful with the machines, today’s users have access to a wide range of commercial and non-commercial software, which is provided in ready-to-run or ready-to-compile form. Since the 1980s, Microsoft and Intel have dominated much of the personal computer market, first with MS-DOS and then with the Wintel platform. Alternatives include Apple’s Mac OS X and the open-source Linux OS. Applications and games for PCs 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.
A computer network, often simply referred to as a network, is a collection of computers and devices interconnected by communications channels that facilitate communications and allows sharing of resources and information among interconnected devices. Computer networking or Data communications (Datacom) is the engineering discipline concerned with the computer networks. Computer networking is sometimes considered a sub-discipline of electrical engineering, telecommunications, computer science, information technology and/or computer engineering since it relies heavily upon the theoretical and practical application of these scientific and engineering disciplines.
The three types of networks are: the Internet, the intranet, and the extranet. Examples of different network methods are:
* Local area network (LAN), which is usually a small network constrained to a small geographic area. An example of a LAN would be a computer network within a building.
* Metropolitan area network (MAN), which is used for medium size area. examples for a city or a state.
* Wide area network (WAN) that is usually a larger network that covers a large geographic area.
* Wireless LANs and WANs (WLAN & WWAN) are the wireless equivalent of the LAN and WAN.
Networks may be classified according to a wide variety of characteristics such as topology, connection method and scale.
All networks are interconnected to allow communication with a variety of different kinds of media, including twisted-pair copper wire cable, coaxial cable, optical fiber, power lines and various wireless technologies. The devices can be separated by a few meters (e.g. via Bluetooth) or nearly unlimited distances (e.g. via the interconnections of the Internet). Networking, routers, routing protocols, and networking over the public Internet have their specifications defined in documents called RFCs.