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Химия Peripherals
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Major computer applications

Supplementary Texts

Appendix.

A student learns French by playing a computer game in which the

object is to successfully rent an apartment in Paris.

Instead of building a physical model, an aerospace engineer saves millions of dollars and thousands of hours by testing an airframe concept on a computer.

His electronics-industry counterpart, using powerful computer-aided-design (cad) tools, creates a computer that would have required the work of 40 engineers two decades ago.

A production manager uses an off-the-shelf expert system to help her troubleshoot a complex piece of machine-tool manufacturing equipment.

A marketing executive stores thousands of data points from a massive survey of consumer preferences and correlates them with a list of product characteristics.

A publishing executive has begun a survey of computer technology be­cause he senses a market for new kinds of information products.

Each of these people (and thousands more like them) has a vital interest in knowing what computers can (and cannot) do: if these managers and professionals are to succeed, they also need to know when the various rich promises of the technology will be realized in usable programs and devices. For the electronics and aerospace engineers improvements in computer speed are extremely important. The production manager would like to know when she will have a diagnostic system that can learn different malfunction patterns as they evolve. The publishing executive faces a question of when and how to get on the technology curve: he must decide whether to convince skeptical and traditionally minded colleagues to embark on the development of software products for hardware that has only just begun to reach the market.

The answers to these questions and many other challenges will unfold as computer science evolves. But that is too late for the men and women in business, government, the professions and academic life who must make plans now for how computers will be used. After all, these managers and professionals, although generally aware of the potential of computers, are not computer experts or even literate in the simplest computer lan­guages and uses.

Terms that are often used when people talk about computers are hardware, software and peripherals.

The computer hardware can best be described as the actual parts that go together to make up the computer such as wires, switches, electronic circuits, microprocessors and anything else that is involved in the working parts.

Software refers to the programs that are input into the computer. Disks and cassettes are often referred to as software once they have computer programs on them but they are really peripherals.

The peripherals of the computer are the devices for input, output or storage of data and include the keyboard, visual display unit, cassettes, disk drives and printers. The VDU is also known as the monitor and the program and the results of the processing can be seen on this, as well as the data entered. The printer will produce the print-out of the results of the processing. This is often referred to as hard copy.

The highest quality of printer available is the daisy wheel. This consists of a wheel with flexible stems radiating from the centre. The letters are well-defined and can be read clearly. The printer moves bi-directionally printing both ways from left to right and then right to left. Remember that what is to be printed already exists in the memory of the computer and the daisy wheel does not have to type in sequence as would be expected from a human brain. The carriage therefore need not waste time returning at the end of each line.

The dot matrix is usually faster than the daisy wheel. The printer has a print head consisting of a row of needles. This moves speedily over the place where a letter has to be printed using dots to make up the letter. The needles print on to a special typewriter ribbon. The quality of print-out is not of a very high standard and would not generally be used at high business levels. However, it is often used for the production of rough drafts. Characters of different sizes can be built up with dot-matrix printers and some may have two-colour ribbons.

An ink-jet printer forms dot matrix characters by applying ejected droplets of ink, vibrated at an appropriate frequency, towards a special absorbent paper. A charged electrode is placed near the jet, so that each droplet carries a charge. By a special electrostatic technique the ink drops can be directed to particular parts of the paper. The printers use information that is stored digitally.

Thermal printers require a heat sensitive paper which is marked by a heated needle-like writing implement known as a stylus.

Laser printers are very fast and can use different sizes of paper. Since they are non-impact printers they are very quiet and can produce good graphics. The laser printer works by beaming a laser on to an electrically charged drum which creates an invisible image on the drum, revealed when a special substance, called toner, is poured over it. When the paper is brought into contact with the drum, the image melts on to the paper as it is heated.

The keyboard is where the data, or information, is input into the computer. It is usually arranged like an ordinary typewriter keyboard with a number of other keys added which carry out special functions.

Some computer programs display what are called icons on the computer screen. The icons may represent items of furniture in an office for instance. The user is able to instruct the computer by the use of a tiny moveable device known as a mouse which is connected to the computer by a cable and can be moved about the top of a desk. The desk represents the VDU screen and as the mouse moves about, it moves with the short bright line, known as the cursor, on the screen.


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  • - Peripherals

    Major computer applications Supplementary Texts Appendix. A student learns French by playing a computer game in which the object is to successfully rent an apartment in Paris. Instead of building a physical model, an aerospace engineer saves millions of dollars and thousands of hours by testing an airframe concept on a computer. His electronics-industry counterpart, using powerful computer-aided-design (cad) tools, creates a computer that would have required the work of 40... [читать подробенее]