computer

A computer is a machine that can be programmed to automatically carry out sequences of arithmetic or logical operations (computation). Modern digital electronic computers can perform generic sets of operations known as programs, which enable computers to perform a wide range of tasks. The term computer system may refer to a nominally complete computer that includes the hardware, operating system, software, and peripheral equipment needed and used for full operation, or to a group of computers that are linked and function together, such as a computer network or computer cluster.
Numbering only a few in the 1930s, today computers are ubiquitous over a broad range of industrial and consumer products that use computers as control systems. The price, size, and complexity of computers can range from simple single-purpose devices like key fobs, microwave ovens, and remote controls up to super computers and factories using industrial robots. Computers are at the core of general-purpose devices such as personal computers and mobile devices, such as smartphones. Computers power the Internet, which links billions of computers and users.
Early computers were meant to be used only for calculations. Simple manual instruments like the abacus have aided people in doing calculations since ancient times. Early in the Industrial Revolution, some mechanical devices were built to automate long, tedious tasks, such as guiding patterns for looms. More sophisticated electrical machines did specialized analog calculations in the early 20th century. Early digital electronic calculating machines were developed during World War II, beginning with electromechanicals (1930s), thermionic valves (1930s), semiconductor transistors (1940s), MOSFET (MOS transistors 1950s), and finally monolithic integrated circuits (1950s+). With each technology advancement resulting in smaller, more efficient circuit designs that lead to the microprocessor and the microcomputer revolution in the 1970s. Since then the speed, computing power, and versatility of computers have been increasing dramatically with transistor counts increasing at a rapid pace (Moore's law noted that counts doubled every two years), leading to the Digital Revolution during the late 20th and early 21st centuries.
Conventionally, a modern computer consists of at least one processing element, typically a central processing unit (CPU) in the form of a microprocessor, together with some type of computer memory, typically semiconductor memory chips. The processing element carries out arithmetic and logical operations, and a sequencing and control unit can change the order of operations in response to stored information. Peripheral devices include input devices (keyboards, mice, joysticks, etc.), output devices (monitors, printers, etc.), and input/output devices that perform both functions (e.g. touchscreens). Peripheral devices allow information to be retrieved from an external source, and they enable the results of operations to be saved and retrieved.

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