UNIT VII.

Date: 2015-10-07; view: 326.

Text

Pre-reading discussion

COMPUTER GENERATIONS

UNIT VI

1. If there were no computers they had to be thought out!

2. Is computer a God's gift or a Devil's toy?

3. What do you think determine different generations of computers?

Active words:

column of mercury - стовпчик ртуті

energy consuming - споживання енергії

generate - виробляти

large scale integrated circuits – великомасштабні

інтегральні схеми

intelligent computer - розумний комп'ютер

artificial intelligence - штучний розум

high-speed memory - швидкодіюча пам'ять

generation - покоління

іngenious - хитромудрий

latticework - решітка

From the 1940s to the present, the technology used to build computers has gone through several revolutions. People sometimes speak of different generations of computers, with each generation using a different technology.

The First Generation.First-generation computers prevailed in the 1940s and for much of the 1950s. They used vacuum tubes for calculation, control and sometimes for memory as well. First-generation machines used several other ingeniousdevices for memory. In one, for instance, information was stored as sound waves circulating in a column of mercury. Since all these first-generation memories are now obsolete, no further mention will be made of them.

Vacuum tubes are bulky, unreliable, energy consuming, and generate large amounts of heat. As long as computers were tied down to vacuum tube technology, they could only be bulky, cumbersome, and expensive.

The second Generation. In the late 1950s, the transistor became available to replace the vacuum tube. A transistor, which is only slightly larger than a kernel of corn, generates little heat and enjoys long life.

At about the same time, the magnetic-core memory was introduced. This consisted of a latticework of wires on which were strung tiny, doughnut-shaped beads called cores. Electric currents flowing in the wires stored information by magnetizing the cores. Information could be stored in the core memory or retrieved from it in about a millionth of a second. Core memory dominated the high-speed memory scene for much of the second and third generations. To programmers during this period, core and high-speed memory were synonymous.

The Third Generation.The early 1960a saw the introduction of integrated circuits, which incorporated hundreds of transistors on a single silicon chip. The chip itself was small enough to fit on the end of your finger; after being mounted in a protective package, it still would fit in the palm of your hand. With integrated circuits, computers could be made even smaller, less expensive, and more reliable.

Integrated circuits made possible minicomputers, tabletop computers small enough and inexpensive enough to find a place in the classroom and scientific laboratory.

The most recent jump in computer technology came with the introduction of large scale integrated circuits, often referred to simply as chips. Whereas the older integrated circuits contained hundred of transistors, the new ones contain thousands or tens of thousands.

It is the large-scale integrated circuits that make possible the microprocessors and microcomputers. They also make possible compact, inexpensive, high-speed, high-capacity integrated-circuit memory. All these recent developments have resulted in a microprocessor revolution, which began in the middle 1970s and for which there is no end in sight.

The Fourth Generation. In addition to the common applications of digital watches, pocket calculators and personal computers, you can find microprocessors – the general-purpose-on-a-chip – in virtually every machine in the home or business – microwave ovens, cars, copy machines, TV sets, and so on. Computers today are hundred times smaller than those of the first generation, and a single chip is far more powerful than Electronic Numerical Integrator and Computer.

The Fifth Generation. The term was coined by the Japanese to describe the powerful, intelligent computers they wanted to build by the mid-1990s. Since then it has become am umbrella term, encompassing many research fields in the computer industry. Key areas of ongoing research are artificial intelligence (AI), expert systems, and natural language.