What is a Computer?

Computers are machines that can be used for performing calculations automatically. They can perform complex and repetitive procedures quickly, precisely and reliably and can quickly store and retrieve large amounts of data.

The physical components from which a computer is constructed (electronic circuits and input/output devices) are known as "hardware". Most computers have four types of hardware components: input, processor, storage (main memory, auxiliary storage) and output.

Input and output (I/O) devices allow the computer to communicate with the user and the outside world. The CPU (central processing unit) executes programs ("software") which tell the computer what to do.

The two principal characteristics of a computer are:
It responds to a specific set of instructions in a well-defined manner.
It can execute a prerecorded list of instructions (a program).

Classification of computers

Computers can be generally classified by size and power as follows:

Personal computer : A small, single-user computer based on a microprocessor. In addition to the microprocessor, a personal computer has a keyboard for entering data, a monitor for displaying information, and a storage device for saving data.
Workstation : A powerful, single-user computer. A workstation is like a personal computer, but it has a more powerful microprocessor and a higher-quality monitor.
Minicomputer : A multi-user computer capable of supporting from tens to hundreds of users simultaneously.
Mainframe : A powerful multi-user computer capable of supporting many hundreds to thousands of users simultaneously.
Supercomputer : An extremely fast computer that can perform millions of instructions per second.

Generations of Computers

The history of computer development is often referred to in reference to the different generations of computing devices. Each generation of computer is characterized by a major technological development that fundamentally changed the way computers operate. It resulted in smaller, cheaper, and more powerful, efficient and reliable devices.

First Generation- 1940-1956: Vacuum tubes were used and it relied on machine language to perform operations, and they could only solve one problem at a time.
Second Generation - 1956-1963: Transistors were used and computers moved from cryptic binary machine language to symbolic, or assembly, languages, which allowed programmers to specify instructions in words.
Third Generation - 1964-1971: Integrated circuits -Transistors were miniaturized and placed on silicon chips, called semiconductors. Users interacted through keyboards and monitors and interfaced with an operating system.
Fourth Generation - 1971-Present: Microprocessors -The microprocessor brought the fourth generation of computers, as thousands of integrated circuits were built onto a single silicon chip.
Fifth Generation - Present and Beyond: Artificial intelligence -Computing devices, based on artificial intelligence, are still in development, though there are some applications, such as voice recognition, that are being used today.