The history of microcomputers is often referred to by generations. Each generation has its own distinctive technological advantage resulting in cost efficiencies, smaller sizes, increased reliability and ease of use.

First Generation - 1940-1956: Vacuum Tubes
First generation computers used vacuum tubes for circuitry and magnetic drums for memory, and were often enormous, taking up entire rooms. They relied on machine language to perform operations, and they could only solve one problem at a time. Their Input was based on punched cards and paper tape.

Modern computing can probably be traced back to 1943 and the creation of the 'Harvard Mk I' and Colossus electronic computers. Colossus was built in Britain at the end of 1943 and was designed to crack German military codes. The 'Harvard Mk I' was a more general machine built at Harvard University with backing from a small company called IBM.

The 'ENIAC' (Electronic Numerical Integrator and Computer), which was completed in 1946, is an example of first generation computers from this time period. It weighed in at a staggering 30 tonnes contained 18,000 vacuum tubes, 1500 relays and consumed around 25,000 Watts of power. It was, however, capable of an amazing 100,000 calculations a second.

Second Generation - 1956-1963: The Transistor Revolution
Transistors replaced vacuum tubes and lead in an exciting new development of the computer. Even though the transistor was invented in 1947 it really 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 the first generation models. A great deal of heat was still generated and did subject systems to failures however it was a vast improvement over the tube. Second-generation computers still relied on punch cards for input and printouts for output. Some of the first computers of this generation were developed for the atomic energy industry.

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

Third Generation - 1964-1971: Here come the Integrated Circuits
The development of the IC (integrated circuit) was the hallmark of the third generation of computers. Transistors were miniaturized and embedded on silicon chips, called semiconductors, which drastically increased the speed and efficiency of computers.

Instead of punched cards and printouts, users interacted through peripherals such as keyboards and monitors and interfaced with an operating system, which allowed the device to run many different applications at one time. Computers for the first time became accessible to a larger audience because they were smaller and lower cost than their predecessors.

Fourth Generation - 1971-Present: Microprocessor based
The microprocessor is the king of fourth generation computers, as thousands of integrated circuits were built onto a single silicon chip. 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. It was this new microprocessor that led the way for modern-day computer technology. Thirty years on processing power and storage capacities have increased beyond all recognition and microchips appear in everything from telephones to toasters.

In 1981 IBM introduced its first personal computer for the home user, and in 1984 Apple introduced the Macintosh. As microprocessor based technology developed they became fully integrated into our lifestyles. 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 AI (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, molecular and nanotechnology will radically change the face of computers in years to come. The aspiration of fifth-generation computing is to develop devices that respond to natural language input and are capable of learning and self-organization. For the most part the fifth generation of computers is yet to be written. We are fortunate to live and experience a very exciting time in the midst of a technological revolution.