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A COMPUTER is a programmable machine designed to sequentially andautomatically carry out a sequence of arithmetic or logical operations. The particular sequence of

operations can be changed readily, allowing the computer to solve more than one kind of

problem.

Conventionally a computer consists of some form ofmemory for data storage, at least one

element that carries out arithmetic and logic operations, and a sequencing and control element

that can change the order of operations based on the information that is stored. Peripheral devices

allow information to be entered from an external source, and allow the results of operations to be

sent out.

A computer's processing unit executes series of instructions that make it read, manipulate and

then store data. Conditional instructions change the sequence of instructions as a function of the

current state of the machine or its environment.

The first electronic computers were developed in the mid-20th century (19401945). Originally,

they were the size of a large room, consuming as much power as several hundred

modern personal computers (PCs).[1]

Modern computers based on integrated circuits are millions to billions of times more capable

than the early machines, and occupy a fraction of the space.[2]

Simple computers are small

enough to fit into mobile devices, and mobile computers can be powered by small batteries.

Personal computers in their various forms are icons of the Information Age and are what most

people think of as "computers". However, the embedded computers found in many devices

from mp3 players to fighter aircraft and from toys to industrial robots are the most numerous.

HISTORY OF COMPUTING

The first use of the word "computer" was recorded in 1613, referring to a person who carried out

calculations, or computations, and the word continued with the same meaning until the middle of

the 20th century. From the end of the 19th century onwards, the word began to take on its more

familiar meaning, describing a machine that carries out computations.

First general-purpose computers

In 1801, Joseph Marie Jacquard made an improvement to the textile loom by introducing a series

ofpunched paper cards as a template which allowed his loom to weave intricate patterns

automatically. The resulting Jacquard loom was an important step in the development of

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computers because the use of punched cards to define woven patterns can be viewed as an early,

albeit limited, form of programmability.

The Most Famous Image in the Early History of

Computing

This portrait of Jacquard was woven in silk on a Jacquard

loom and required 24,000 punched cards to create (1839). It

was only produced to order. Charles Babbage owned one of

these portraits ; it inspired him in using perforated cards in

his analytical engine[21]

It was the fusion of automatic calculation with

programmability that produced the first recognizable

computers. In 1837, Charles Babbage was the first to

conceptualize and design a fully programmable mechanical

computer, his analytical engine.[22]Limited finances and

Babbage's inability to resist tinkering with the design meant

that the device was never completed ; nevertheless his son,

Henry Babbage, completed a simplified version of the analytical engine's computing unit

(the mill) in 1888. He gave a successful demonstration of its use in computing tables in 1906.

This machine was given to the Science museum in South Kensington in 1910.

In the late 1880s, Herman Hollerith invented the recording of data on a machine readable

medium. Prior uses of machine readable media, above, had been for control, not data. "After

some initial trials with paper tape, he settled on punched cards ..."[23]

To process these punched

cards he invented the tabulator, and the keypunch machines. These three inventions were the

foundation of the modern information processing industry. Large-scale automated data

processing of punched cards was performed for the 1890 United States Census by Hollerith's

company, which later became the core ofIBM. By the end of the 19th century a number of ideas

and technologies, that would later prove useful in the realization of practical computers, had

begun to appear: Boolean algebra, the vacuum tube (thermionic valve), punched cards and tape,

and the teleprinter.

During the first half of the 20th century, many scientific computing needs were met by

increasingly sophisticated analog computers, which used a direct mechanical or electrical model

of the problem as a basis for computation. However, these were not programmable and generally

lacked the versatility and accuracy of modern digital computers.

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