What is Computer?

A computer is a device that automatically can be instructed to bring off an arbitrary set of arithmetic or logical operations.

A program  is called by the ability of computers to follow a sequence of operations, make computers very flexible and useful. Such computers are used as control systems for a very wide variety of industrial and consumer devices. This includes simple special purpose devices like microwave ovens and remote controls, factory devices such as industrial robots and computer assisted design, but also in general purpose devices like personal computers and mobile devices such as smartphones. The Internet is run on computers. It connects millions of other computers.

Since remote time, simple manual devices like the abacus aided people in doing calculations.shown in picture.

 In vintage, the Industrial Revolution, some mechanical devices were built to automate long pesky tasks, such as guiding patterns for looms. More sophisticated electrical machines did specialized analog calculations in the early 20th century.

The first digital electronic calculating machines were developed during World War II (shown in picture below)

 The speed, power, and versatility of computers has increased continuously and dramatically since then.

Conventionally, a modern computer consists of at least one processing element, typically a central processing unit (CPU) and some form of memory. 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, joystick, etc.), output devices (monitor screens, printers, etc.), and input/output devices that perform both functions (e.g., the 2000s-era touchscreen). Peripheral devices allow information to be retrieved from an external source and they enable the result of operations to be saved and retrieved.