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Interacting with your computer
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Input devices are the pieces of hardware which allow you to enter information into the computer. The most common are the keyboard and the mouse. We can interact with a computer by using one of these: a lightpen, a scanner, a trackball, a graphics tablet, a joystick, or a voice recognition device.
About the keyboard
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.
1. Alphanumeric keys: arranged in the same order as a typewriter.
2. Function keys: used by various programs to instruct the PC to perform specifictasks, such as Save, Copy, Paste, Help, etc.
3. Numeric keypad: set of numeric or editing keys. The NumLock key is used toswitch from numbers to editing functions.
4. Editing keys: cursor and other keys usually used within word processors topage up and down in a long document or to edit text (using Insert or Delete keys).
5. Special keys: used to issue commands or to produce alternative characters inkey combinations, for example, the Alt key.
(E.C.U.)
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Упражнение 37.
a) Попытайтесь ответить на следующие вопросы:
1. How is the mouse connected to the computer?
2. What does the mouse pointer look like on the screen?
3. What are the functions of the mouse buttons?
4. What are advantages of a computer mouse over a keyboard?
b) Прочитайте текст и проверьте, правильно ли вы ответили:
Point and Click!
Typically a mouse is a plain sized device, slightly smaller than a pack of cards. On top of the mouse there are one or more buttons for communicating with the computer. A ‘tail’ or wire extends from the mouse to a connection on the back of the computer.
The mouse is designed to slide around on your desktop. As it moves, it moves an image on the screen called a pointer or mouse cursor. The pointer usually looks like an arrow or I-bar, and it mimics the movements of the mouse on your desktop.
What makes the mouse especially useful is that it is very quick way to move around on a screen. Move a desktop mouse half an inch and the screen cursor will leap four inches. Making the same movements with the arrow keys takes much longer. The mouse also issues instructions to the computer very quickly. Point to an available option with the cursor, click on the mouse, and the option has been chosen.
Mice are so widely used in graphics applications because they can do things that are difficult if not impossible to do with keyboard keys. For example, the way you move an image with a mouse is to put the pointer on the object you want to move, press the mouse button and drag the image from one place on the screen to another. When you have the image where you want it, you release the mouse button and the image stays there. Some actions are so much more difficult to perform with keyboard that most graphics programs require a mouse.
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The buttons on the mouse are used to select items at which the mouse points. You position the pointer on an object on the screen, for example, on a menu or tool bar in a paint program, and then you press the mouse button to select it. Mice are also used to load documents into a program: you put the pointer on
the file name and double-click on the name – that is, you press a mouse button twice in rapid succession.
(E.C.U.)
Упражнение 38. Основными действиями, связанными с мышью яв - ляются «щелчок», «двойной щелчок» и «перетаскивание». Прочитайте дан - ные ниже описания и определите, к какому из действий относится каждое из них:
click double-click drag
1. Position the pointer on something, then rapidly press and release the mouse button twice. (You do this to load a program, open a document or select text or graphics).
2. Position the pointer on something, hold down the mouse button and move an image to a new location on the screen.
3. Position the pointer on something, then press and release the mouse button. (You do this to place the insertion point, to choose an option, or to close a window).
Упражнение 39. Устройством, которое значительно облегчает ввод информации в виде текста или графического изображения, является ска - нер. Прочитайте текст и сравните два основных вида сканеров. В чем пре - имущества и недостатки каждого из них?
Scanners
It’s not so long ago that a scanner was such a costly piece of equipment that it was difficult to justify buying one for anything except an absolute need. But scanners are now so much more affordable that their usage has become more wide-spread, and PC owners everywhere are realising that adding a scanner to their existing setup can open up whole new worlds of performance.
Put a scanner with an image editing package for instance and you too can perform the tricks of the electronic photo retoucher. Use a scanner to scan original artwork and you can create the basis for your own designs. Position photos for the newsletter that you edit, or create images for printed documents to feed to your fax/modem card. Or why not organise your collection of magazines by scanning in the pages and using a document indexing and retrieval program. By
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using an OCR - Optical Character Recognition - package you can even convert printed text into editable word processor files.
There are two main types of scanners that will do the many of the above tasks - hand-held and flatbed. Put simply hand held scanners are cheaper, but flatbed scanners are more convenient. However it isn’t necessarily the case that you would always choose to use a flatbed scanner for the job, as for some tasks a handheld may be just as suitable. A flatbed scanner for instance, takes up a lot of space, whilst a hand-held scanner is better at scanning objects that aren’t 100% flat!
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But let’s take a closer look at the two main types of scanner and how they work.
Using a hand-held
A hand-held scanner takes the form of a small scanning head that has to be moved across the original piece of artwork. A small roller under the scanning head rotates as you move the scanner and lets the PC know how fast you are scanning. You have to move at a nice steady rate in as straight a line as you can manage. If you wobble1 then the input image will contain wiggles2 and distortions. As you scan, image data is sent to your PC as fast as the hardware can cope with it. However the amount of data in an image is so large that it is possible to swamp3 the machine. In simple terms, if you move the scanner too fast then the data will be generated faster than it can be accepted and bits of the image will be missing. How do you know what is too fast? Most scanners either have a light on the scanning head or an on-screen display that provides feedback – slow, fast, too fast.
So using a hand scanner is something of a skill – like driving a toy car down the page while keeping your eye on how fast it should be going. It isn’t a difficult skill to master, however, and many users swear by the convenience of the hand scanner for occasional image input. Another factor that you have to keep in mind is that most hand scanners are only four inches wide. To input an original that is wider than this you have to scan more than once and use special software to ‘stitch’4 the separate strips together. This sounds like a big disadvantage, but in practice it isn’t so bad and can even be an advantage because you can run the small scanning head over surfaces that aren’t completely flat – e.g. a page in a very thick book.
1 качаться, дрожать, «вихлять».
2 покачивание, «виляние».
3 засыпать, заваливать, загружать.
4 сшивать, брошюровать.
To Sum Up hand scanners are
– low cost;
– slightly fiddly to use;
– only able to scan narrow strips which have to be stitched together;
– but able to scan slightly curved surfaces.
Using a flat bed
A flatbed scanner on the other and works much like a photocopier. You place the original artwork on a glass plate, close the cover, and the scanning head moves automatically down the page. All this happens under the control of your PC so there is no need to worry about keeping the scan straight or getting the right speed as in the case of a hand scanner. However the or original still has to be placed squarely on the scanning plate – more difficult than you might imagine – and it has to be as flat as possible. For example if you want to scan a thick book or magazine then it is often better to remove the page in question than to try to flatten it with heavy weights!
The advantage of a flatbed scanner is that once you have placed the original in it, everything happens automatically, you can go away and do something else while a scan is in progress – and a full colour A4 scan can take minutes to complete. You can even get sheet feeder attachments that will allow you to scan in a pile of A4 pages completely automatically. The scanning method is also accurate in the sense that it doesn’t rely on how well you move a hand scanner down the original. This allows flatbed scanners to offer a higher resolution than hand scanners – although it has to be admitted that there is a lot of overlap in specified performance.
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To Sum Up flatbed scanners are
– easy to use as long as the original can be placed flat on the scanning plate;
– able to scan large areas in one pass;
– can work at higher resolutions;
– expensive.
(PC R.)
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Упражнение 40. Подготовьте краткое описание каждого из извест - ных Вам устройств ввода, отметьте его преимущества и недостатки. Ког - да и почему целесообразно использовать то или иное устройство?
Output
Упражнение 41.
a) Прочитайте текст, обращая внимание на новые термины:
The Monitor
dot; pixel; display; resolution; cathode ray tube; hertz; refresh rate; flicker; bit-mapped; electron beam; visualize
The characters and pictures that we see on the screen are made up of dots, also called picture elements (pixels). The total number of pixels in whichthe display is divided both horizontally and vertically is known as the resolution. If the number of pixels is very large we obtain a high resolution display and therefore a sharp image. If the number of pixels is small, a low resolution is produced. A larger number of pixels gives a much clearer image.
The cathode ray tube of the monitor is very similar to that of a TV set. Inside the tube there is an electron beam which scans the screen and turns on or off the pixels that make up the image. The beam begins in the top left corner and scans the screen from left to right in a continuous sequence, similar to the movement of our eyes when we read but much faster. This sequence is repeated 50, 60 or 75 times per second depending on the system. If the rate of this repetition is low, we can perceive a flickering, unsteady screen, which can cause eye fatigue. However, a fast moving 75 Hz refresh rate eliminates this annoying flicker.
What we see on the screen is created and stored in an area of RAM, so that there is a memory cell allocated to each pixel. This type of display is called bit-mapped. On monochrome monitors, bits 0 are visualized as white dots, andbits 1 as black dots.
On colour displays, there are three electron guns at the back of the monitor’s tube. Each electron gun shoots out a beam of electrons to strike the inside of the screen which is coated with substances called phosphors that grow when struck by electrons. Three different phosphor materials are used – one each for red, green and blue. To create different colours, the intensity of each of the three electron beams is varied.
The monitor is controlled by a separate circuit board, known as the display adapter, which plugs into the motherboard of the computer. Different boards drive different types of displays. For example, the VGA (Video Graphics Array) card has become a standard for colour monitors.
Portable computers use flat Liquid-Crystal Display instead of a picture tube. A LCD uses a grid of crystals and polarizing filters to show the image. The crystals block the light in different amounts to generate the dots in the image.
(E.C.U.)
b) Прочитайте текст еще раз и ответьте на следующие вопросы:
1. According to the writer, what is the importance of the ‘pixel resolution’?
2. Which unit of frequency is used to measure the refresh rate of a monitor?
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3. In the writer’s opinion, why can a low refresh rate produce eye fatigue?
4. What substance is hit by electron in a monitor?
5. What is the standard display system for many PCs?
6. What does LCD stand for? What type of computers use LCD?
Упражнение 42. Как Вы знаете, существуют определенные реко - мендации для людей, работающих на компьютере, которые помогают из - бежать переутомления, снизить вероятность нарушения зрения и т. д. При - веденные ниже правила даны в форме инструкции, однако, как известно, иногда лучше выразить их в форме совета. Измените следующие предло - жения по образцу:
Position your keyboard at the same height as you elbows. – You should/ ought to position your keyboard at the same height as you elbows.
Don’t use a monitor that is fuzzy or distorts the image. – You shouldn’t/ oughtn’t to use a monitor that is fuzzy or distorts the image.
1. Do not stare at the screen for long periods of time.
2. Avoid placing the monitor so that it reflects a source of bright light, such as a window.
3. Keep the screen clean to prevent distorting shadows.
4. If you work in an office with a large number of computers don’t sit too close to the sides or backs of monitors.
5. Buy a protective filter that cuts down the ELF (Extremely Low Frequency) emissions.
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Упражнение 43.
a) Прослушайте лекцию о принтерах и заполните таблицу:
| Type of printer | Advantages | Disadvantages | Notes |
b) Прочитайте текст о принтерах и дополните таблицу предыдущего задания:
Choosing a Printer
Types of Printers
Printing is the final stage in creating a document. That is the purpose of the printers joined to your computing equipment. Since the results you can obtain with different types of printers will vary substantially, here is a guide to help you decide which one is the most suitable for your needs.
To begin with, it must be taken into account that printers vary in cost, speed, print quality and other factors such as noise or compatibility. In fact, printing technology is evolving so quickly that there is always a printer for every application or personal requirement.
Daisywheel printers were very common a few years ago. They used asort of wheel with solid characters which rotated and hammered against the ribbon, but they couldn’t print pictures or diagrams, and were very slow and noisy.
Dot-matrix printers use pins to print the dots required to shape acharacter. They print text and graphics and nowadays some of them can print up to 450 characters per second (cps), however, they produce relatively low resolution output – 72 or 144 dots per inch. The level of quality, while suitable for preliminary drafts, is not recommended for reports or books that have a wide audience. They are slower than laser printers but much cheaper.
One common type of non-impact printer is an ink-jet printer. It operates by projecting small ink droplets onto paper to form the required image. This type of printer is quite fast, silent and not so expensive as a laser printer. Nevertheless, you can expect high quality results because there are some ink-jet printers on the market with a very high resolution.
Laser printers produce output at great speed and with a very highresolution. They scan the image with a laser beam and transfer it to paper with a special ink powder. They are constantly being improved. In terms of speed and image quality they are preferred by experts for different reasons: they have a wider range of scalable fonts, they can emulate different language systems, they can produce graphics, and they have many other advantages. It goes without saying, that they are still expensive.
We must not forget to mention thermal printers. They use heat, a special kind of paper and electrosensitive methods. They are silent and are considered to be expensive. However, some colour models that emulate HP (Hewlett Packard) plotters cost too much to be included in the same category.
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Photosetters can be regarded as an attractive alternative. They do notprint on regular paper, but on photographic paper or microfilm. They can produce output with resolution of over 2000 dots per inch (dpi). In addition, they are extremely fast. Although they produce the highest quality output, they have one important drawback: they are the most expensive.
Finally, plotters are a special kind of printer. Plotters use ink and fine pens held in a carriage to draw very detailed design on paper. They are used for construction plans, engineering drawings and other technical illustrations.
(E.C.U.)
Упражнение 44. Одним из устройств вывода является графопост - роитель. Прочитайте текст и выясните его принцип действия. Затем про - читайте вопросы после текста и ответьте на них. Переведите текст на русский язык. При необходимости обратитесь к словарю.
The X-Y Plotter
An X-Y plotter is a device that moves a pen (one or more) across a normal piece of paper placed in the appropriate position on a board. Assuming that you have a good mechanical system then the resolution of the device can be as small as the thickness of the pen you are using. The basic idea is similar in principle to a gantry crane. The gantry moves along in the X-direction under the control of a motor. The pen then moves in the Y-direction up and down the gantry under the control of a second motor. To prevent the pen drawing all the time there is a device that will lift the pen off the paper when required. In some X-Y plotters an arrangement is made to select automatically several different coloured pens which are located in the pen park at the side of the plotter.
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The principle of operation is quite simple. At switch-on it is usually arranged for the plotter to go into a park position. This will usually be some position off the drawing area so that a new piece of paper may be put onto the plotter if desired. The usual mode of operation is then to print out to the plotter whatever is appearing on the screen.
There will therefore be several major sections to the rest of this chapter: mechanical construction; electronic control; and software. Only the basic principles will be covered as the actual details will vary according to size of the plotter that you wish to make and materials and tools that are available to you. However, there are some sections, e. g. pen mechanism and software, that will be transferable for most sizes of plotter.
End-stop detection
It is vital that provision be made to stop the plotter going too far in any direction. This can easily happen in the event of a fault in the software and especially whilst testing the hardware. Basically, all that is necessary is a microswitch placed at each corner of the plotter.
We now concentrate on the way in which the stepper motors will be controlled.
The motor drive routine will have a pair of coordinates (x,y) passed to it from the calling routine. It is the job of the motor drive routine to activate the correct stepper motors so that the pen goes in a straight line to its new destination (i. e. x,y). If we call the current position of the plotter (xnow, ynow), then the job of the routine is to move the pen from (xnow, ynow) to (x, y).
Suppose that we have to move 200 steps in the X direction and 100 steps in the Y direction. It is not enough simply to put the correct number of pulses out to each motor driver chip because then the Y motor would arrive before the X motor (assuming they were being driven at the same rate). We therefore need a method whereby one motor controls the other. For example, in the above case it would be possible to make the Y motor step every time the X motor did two steps.
This method is fine until we have to draw a line which is greater than 45° to the horizontal, i. e. we can’t make the Y motor step every time the X motor does half a step. If the line is greater than 45° the Y motor takes over as the leader. If the line is exactly 45° then both motors step at the same time. In addition to this, if the line is horizontal then only the X motor need be moved, or if the line is vertical then only the Y motor need be moved.
1. Define an X-Y plotter.
2. If several coloured pens are to be used with this plotter, where are they to be situated?
3. Where is the usual parked position of the plotter?
4. One of the headings in this passage is ‘End-stop detection’. How would you explain this phrase in everyday English?
5. Explain the function of the motor drive routine.
6. When we are drawing a line:
a) at which angle do the motors step in unison?
b) when does the Y motor move alone?
c) when does the X motor move alone?
d) when does the Y motor take the lead? (C.S.)
Упражнение 45. Расскажите о любом устройстве вывода.
Упражнение 46.
1) Вам поручено написать рекламный текст для компании по прода - же компьютеров. Выберите один из продуктов компании и опишите его ха - рактеристики, стараясь убедить потенциального покупателя. Это может быть новая клавиатура, «мышь», монитор, сканер, принтер и т. д. Придер - живайтесь следующего плана:
a) The product we are going to advertise is …
b) It is used for …
c) It is aimed at …
d) Its advantages over rival products are …
e) The slogan for our product is …
2) Опишите компьютерную систему (все ее составляющие), кото - рую Вы считаете идеальной на сегодняшний день. Вам могут пригодиться следующие выражения:
It has got …
It’s very fast.
It runs at …
The standard RAM memory is … and it is expandable …
The hard disk can hold …
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As for the disk drive …
I need … monitor because …
I decided to choose … printer as it is …
There should be some more output devices in my ideal computer system. They are …
It is convenient to use … for inputting information.
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3) Сделайте сообщение в группе, постарайтесь обосновать свой вы - бор. Будьте готовы ответить на возможные вопросы.
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