Computer:Computer is an electronic machine that

accepts information, process it according to specific instructions, and provide the result as new information.

An Abacus, also called a counting frame, is a calculating tool used primarily for performing arithmetic processes.

Pascaline invented a complicated set of gears which could only be used to perform addition.

Analytical engine

Difference engine Charles Babbage began

working on the Difference Engine, but it was not successful.

Babbage then began working on the Analytical Engine. This machine performed calculations by following a set of instructions, or "programs" entered into it using punched cards.

It to was not successful, however, its design was to serve as a model for the modern computer.

ENIAC: The First Electronic Computer

1943, John Mauchly and J. Proper Eckert began to work on the Electronic Numerical Integration and Calculator or ENIAC

ENIAC only occupied 1500 square feet, and weighs about 3tons. It was made up of 18000 vacuum tubes.

It runs single program which means it requires rewiring for every program, so they discovered another machine EDSAC that can store programs on punch cards that are much easier to manage.

The first Stored Program Computer:In the late 1940's, John von Neumann

considered the idea of storing computer instructions in a central processing unit, now known as the CPU.  Together with Mauchly and Eckert, von Neumann designed and built the EDVAC & EDSAC (Electronic Discrete Variable/Storage Automatic Computer).

Next was the UNIVAC Universal Automatic Computer (made by Mauchly and Eckert). It weighed 35 tons, did 1000 calculations per second,

Computers -present:Two inventions that change the way of computer

now built:

1. Transistors : The most significant invention of

modern era. It was invented by three scientists at At& T’s bell labs. It replace the vacuum tubes.

2.IC’s(integrated circuits): The IC revolutionized

entire electronic technology.Ex: pentium contains 3.1million transistors in 1.5

inch square.

Personal computerA personal computer (PC) is a computer

whose original sales price, size, and capabilities make it useful for individuals, and which is intended to be operated directly by an end user, with no intervening computer operator.

E.g: Desktop computer, Home computer, Laptop

computer, Portable computer, Tablet computer, Wearable computer

Personal computers:A Tablet PC is a slate-

shaped mobile computer, equipped with a touchscreen which allows the user to operate the computer with a stylus or digital pen, or a fingertip, instead of a keyboard or mouse.

Wearable computers are computers that are worn on the body.

Embedded computers:A specialized computer system

that is part of a larger system or machine. Typically, an embedded system is housed on a single microprocessor board with the programs stored in ROM.

The software written for embedded systems is often called firmware.

Embedded computers are small, simple devices that are used to control other devices — for example, they may be found in machines ranging from fighter aircraft to industrial robots, digital cameras, and children's toys.

Future Computers:

Quantum computer Chemical computer DNA computingOptical computer Spintronics based computer.

A chemical computer is an unconventional computer based on a semi-solid chemical "soup" where data is represented by varying concentrations of chemicals.

The computations are performed by naturally occurring chemical reactions.

A quantum computer is a device for computation that makes direct use of distinctively quantum mechanical phenomena, such as superposition and entanglement, to perform operations on data. In a classical (or conventional) computer, information is stored as bits; in a quantum computer, it is stored as qubits (quantum binary digits).

DNA computing is a form of computing which uses DNA, biochemistry and molecular biology, instead of the traditional silicon-based computer technologies.

An optical computer is a computer that uses light instead of electricity (i.e. photons rather than electrons) to manipulate, store and transmit data.