Text 22. Video Terminals

Video terminals are most commonly used whenever a permanent record is not needed. Because the computer video terminal does not use paper and is usually faster and much quieter than a print­ing terminal, video terminals are used much more often for the day-to-day entry of computer transactions. Airline reservation clerks, telephone directory assistance operators, and bank tellers are people who commonly use video terminals. They need to see information for only a few seconds and usually do not need a per­manent paper copy. In the few cases where a paper record is need­ed (an airline ticket or a bank deposit slip), that record is usually printed on a printer.

Video terminals can display dark letters on a light background or light letters on a dark background. Some terminals even display grey on black or grey on white, or allow blinking letters to call attention to an important message.

In many cases, more than just written words can and must be output from a computer. Video terminals are used by engineers in designing structures and machines, by pilots who fly aircraft, and by doctors who must diagnose a patient’s illness. In all of these cases, getting the computer output in a pictorial form is more valu­able than obtaining only printed words.

The use of colour in video terminals is becoming increasingly popular. Colour is used to call attention to important messages and to reduce operator fatigue, which sometimes results from sit­ting at a computer terminal all day. Colour video displays are be­coming more common as the pictures and drawings coming from a computer become more complicated. Related parts of computer­generated drawings can be colour-coded to produce drawings that are easier to understand. A computer-generated blueprint of an office building can be displayed showing all of the plumbing in green, the electrical wiring in yellow, the structure in blue, and the ventilating system in orange.

Notes

terminal ['ta:mini]	- прилад; термінал
transaction [træn'zæk/n]	- вхідне повідомлення
airline reservation clerk [kla:k]	- службовець, який бронює місця на авіарейси
telephone directory assistance[a'sistns] operator	- чергова телефонистка довідкового бюро
deposit slip [di'pozit]	- депозитна картка

to diagnose ['daisgnouz] — ставити діагноз

In a pictorial form [pik'torrial] — у вигляд зображення

fatigue [fs'tig] — втома

blueprint ['blu:print] — калька

Text 23. Mechanical and Electronic Calculating Machines

A great step forward in the art of adding mechanically was made by Blaise Pascal in 1642. Pascal used wheels divided into parts in­stead of wires holding ten beads. The ten-part wheel can be compared to the wire with the ten beads bent so the two ends meet, the wheel representing a great improvement over the bead-holding wire.

Modern mechanical calculating machines also use wheels. Electric motors cause the wheels to turn at a rapid rate, yet the basic princi­ple behind modern calculators is the same as that used by Pascal in his machine. An important achievement has been made, namely, elec­tric power is substituted for hand power.

To speed up the counting process, electronic devices may be sub­stituted for mechanical wheels. By shifting electrons from one place to another for each unit of the digit, the same counting effect can be produced as by moving a bead at a time, or turning a wheel a division at a time.

Why should a machine using moving electrons be so much faster than one using mechanical wheels? The answer to this question is very simple. The speed with which anything can be made to move depends on its weight, and the weight of an electron is practically nonexistent when compared to any mechanical gadget. Thus, with very little ener­gy applied, electrons can be made to travel at tremendous speeds.

With machines of such lightning speed, it becomes ridiculous to have the operator feed it one problem at a time. Therefore, a logical control was built into the computer. This logical control enables the machine to accept a complete routine of instructions at one time, and then perform each instruction in the proper sequence. As a matter of fact, the logical control enables the machine to accept generalized instructions which can cause it to perform more operations than are actually fed into the machine.

In fact, the tremendous speeds at which these machines can work, and the flexibility built into them due to the logical control, make modern electronic digital computers a thousandfold more powerful than mechnical calculators.

Notes

to compare [kam'pea]	- порівнювати
to cause [ko:z]	- змушувати
rapid ['rapid]	- швидкий
rate	- темп
to substitute ['sAbstitju:t]	- заміняти
weight ['weit]	- вага
gadget ['gaedjit]	- пристрій
tremendous [tri'mendas]	- величезний
ridiculous [ri'dikjulas]	- безглуздий
routine [ru:'ti:n]	- шаблон
sequence ['si:kwans]	- послідовність
flexible ['fleksabl]	- гнучкий

МАНСІ Єлизавета Олександрівна ГОНЧАРОВА Тетяна Володимирівна

RADIO ENGINEERING and COMPUTING TECNIQUE (Радіотехніка і комп’ютерна техніка)

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Англійською та українською мовами Редактор В. II. Авдієнко

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