First Generation (1940-1956) Vacuum Tubes

The first computers used vacuum tubes for circuitry andmagnetic drums for memory, and were often enormous, taking up entire rooms. They were very expensive to operate and in addition to using a great deal of electricity, generated a lot of heat, which was often the cause of malfunctions.

First generation computers relied on machine language, the lowest-level programming language understood by computers, to perform operations, and they could only solve one problem at a time. Input was based on punched cards and paper tape, and output was displayed on printouts.

The UNIVAC and ENIAC computers are examples of first-generation computing devices. The UNIVAC was the first commercial computer delivered to a business client, the U.S. Census Bureau in 1951.

Second Generation (1956-1963) Transistors

Transistors replaced vacuum tubes and ushered in the second generation of computers. The transistor was invented in 1947 but did not see widespread use in computers until the late 1950s. The transistor was far superior to the vacuum tube, allowing computers to become smaller, faster, cheaper, more energy-efficient and more reliable than their first-generation predecessors. Though the transistor still generated a great deal of heat that subjected the computer to damage, it was a vast improvement over the vacuum tube. Second-generation computers still relied on punched cards for input and printouts for output.

Second-generation computers moved from cryptic binary machine language to symbolic, orassembly, languages, which allowed programmers to specify instructions in words. High-level programming languages were also being developed at this time, such as early versions ofCOBOL and FORTRAN. These were also the first computers that stored their instructions in their memory, which moved from a magnetic drum to magnetic core technology.

The first computers of this generation were developed for the atomic energy industry.

Third Generation (1964-1971) Integrated Circuits

The development of the integrated circuit was the hallmark of the third generation of computers. Transistors were miniaturized and placed on silicon chips, called semiconductors, which drastically increased the speed and efficiency of computers.

Instead of punched cards and printouts, users interacted with third generation computers through keyboards and monitors and interfaced with an operating system, which allowed the device to run many different applications at one time with a central program that monitored the memory. Computers for the first time became accessible to a mass audience because they were smaller and cheaper than their predecessors.

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. What in the first generation filled an entire room could now fit in the palm of the hand. The Intel 4004 chip, developed in 1971, located all the components of the computer—from the central processing unit and memory to input/output controls—on a single chip.

In 1981 IBM introduced its first computer for the home user, and in 1984 Apple introduced the Macintosh. Microprocessors also moved out of the realm of desktop computers and into many areas of life as more and more everyday products began to use microprocessors.

As these small computers became more powerful, they could be linked together to form networks, which eventually led to the development of the Internet. Fourth generation computers also saw the development of GUIs, the mouse and handheld devices.

Fifth Generation (Present and Beyond) Artificial Intelligence

Fifth generation computing devices, based on artificial intelligence, are still in development, though there are some applications, such as voice recognition, that are being used today. The use of parallel processing and superconductors is helping to make artificial intelligence a reality.Quantum computation and molecular and nanotechnology will radically change the face of computers in years to come. The goal of fifth-generation computing is to develop devices that respond to natural language input and are capable of learning and self-organization.

Advantages of using computer:

1 - Introduction :

A computer is an electronic device that store, process and display information and data in a form that is easily understood. The main characteristics of a computer are the very high speed with which calculations and processes are carried out and also the very large amount of information and data that may be stored in a relatively small spaces called memory.

2 - Speed of Computing:

One of the main advantages in using computers is the possibility that a task that may take longer to do by hand may be done in a shorter period of time using a computer. Computers are designed to do tasks much faster and more accurately than humans. Numerical computations, creation and editing of documents, data organization and presentation, graphics are examples of tasks that are done efficiently when computers are used.

2 - Efficiency and Productivity:

It is perhaps easy to explain the efficiency of computers in comparing documents produced using a typewriter and a word processor (on a computer). Using a word processing makes it easy to make changes to letters, words, chapters or entire documents. There are possibilities to spell check words and therefore make changes. Deleting and inserting letters, words and paragraphs is done without leaving a trace. When all necessary changes are made, files may be saved, printed, edited as many times as is necessary, sent by e-mail to someone else in another continent within minutes. When using a typewriter, a simple typing error would be time consuming to fix. 
Several recent studies have shown a substantial increase in productivity due to the use of computers.

3 - Data Storage.

Computer storage or memory is measured in bytes. A byte correspond to 8 bits (binary digit). For example it takes 1 byte (or 8 bits) to represent (store) a character of the alphabet. A page of a book with 80 characters per line and 40 lines per page would need 80 * 40 = 3200 bytes of storage or 3 Kilobytes (1 Kilobyte = 1024 bytes). 

A book of 400 pages would need 400 * 3 Kilobytes = 1.2 Megabytes (1 megabyte = 1000 Kilobytes) 

What does all this mean in practical terms? 

Example 1: A CD has a storage capacity of 600 Megabytes and therefore can hold the contents of 600 / 1.2 = 500. Yes 500 books in ond CD!. 

Example 2: A DVD has a storage capacity of 4.7 Gigabytes (1 Gigabyte = 1000 Megabytes) and can therefore hold 4700 / 1.2 = 4000 (approximately) books. 

Now think about how much space and how much does it cost to store 4000 books!

Computer components: