Методические указания и учебные задания по профессиональноориентированному чтению для студентов 2 курса технических специальностей
|Translate the text in writing.|
The mouse, developed by Douglas Englebart of Xerox in the 1960s, is perfectly suited for operations like pointing, drawing, and selecting. Programs that involve picking objects on the screen, choosing entries from menus, or manipulating graphic objects often make extensive use of the mouse.
A typical mouse translates the motion of its underside on a flat surface into cursor movement on the screen. The principle may be mechanical (a roller or ball whose rotation translates into cursor movement) or optical (involving reference to a special gridded pad on which the mouse must be used). A mouse may have one, two, or three buttons. A simple press and release (called a “click”) normally selects an item; a click and hold operation is used for dragging an object around the screen or sometimes for moving down to the next level of a menu structure. For a mouse with fewer buttons, double clicks or clicks combined with keystrokes are often used to extend the range of operations that can be performed.
A mouse may either be connected to the rest of the computer through a serial port (serial mouse) or else have its own interface card and connector, which hooks directly onto the system bus (bus mouse). It often requires a device driver that must be loaded at system start-up.
Lesson 4. Touch screen
Read and translate the text.
The touch screen is, in a sense, the ultimate in simplicity for the computer user: touch the screen with your finger and something happens. As with the bit pad, different regions of the screen are assigned to different actions and are visually indicated by shape, colour, and text. The visitor information systems at Epcot (Experimental Prototype Community of Tomorrow) theme park at Walt Disney World Resort use touch screens.
The principle of the touch screen is electrical; the screen is fabricated with conductive and insulating layers in such a way that when a human
finger presses on the screen (which is slightly deformable), an electrical connection is made. Making the screen sensitive to pressure rather than simply to touch improves its robustness under dirty conditions whether industrial grime or chocolate sauce on children’s hands. One problem with the touch screen is that the human finger is a rather imprecise pointing device compared to a light pen or mouse. This limits the number of choices that can be displayed on a normal-sized computer screen at one time and forces the programmer to deal with questions concerning what happens if someone presses partly inside and partly outside a region. These problems have limited touch screen applications in industry.
II .Answer these questions.
1. What is a touch screen? 2. What is the principle of a touch screen? 3. Why is the screen made sensitive to pressure and not to touch? 4. What is the problem with the screen touch? 5. Why are touch screen applications limited?
Speak on the principle of the touch screen.
Lesson 5. Scanner
Before reading the text discuss how many ways there are of capturing an image on a computer.
Read the text and see how many things from your list are
Read the text again and answer these questions.
Which device is used to input text and graphic images from a printed page?
How does a scanner send information to the computer?
Why is text scanning difficult?
In addition to flatbed (or desktop) scanners there are also handheld scanners, drum scanners, film (“slide” or negative) scanners and camera scanners. Do you know what they are used for?
A more recent and more widely applicable method of entering
graphical information into computers is the optical scanner. A scanner takes a black and white paper original and represents it as a set of ones and zeros that correspond to little black and white squares. This kind of image is often called bit-mapped, since the information in the drawing has been “mapped” into a sequence of black and white squares or binary bits. A
scanner “sees” images and converts the printed text or pictures into electronic codes that can be understood by the computer. With a flatbed colour scanner, the paper with the images is placed face down on a glass screen, as with a photocopier. Beneath the glass are the lighting and measurement devices. Once the scanner is activated, it reads the image as a series of dots and then generates the digitized image that is sent to the computer and stored as a file.
The scanner operates by using three rotating lamps, each of which has a different coloured filter: red, green and blue. The resulting three separate images are combined into one by appropriate software.
A difficulty with scanning technology is that the resulting image takes up a great deal of disk space if high resolution is desired. Text scanning is even more difficult, since the computer not only has to read in the image but must also decide whether the shape it is seeing is an A, a B, or whatever. Different types of fonts or poor quality printing sharply reduce the performance of text scanners, but the technology is developing.
Complete the following sentences.
The technology used in scanners is similar to that used in a .
The scanned image is sent to the , where you can manipulate it. 3.
To scan the text, you need special . 4. Flatbed scanners can scan
What other ways of capturing an image on a computer do you
What does a digital camera do?
What does the term “camcoder” stand for? What does a camcoder do?
What do you know about web cameras (webcams)?
Lesson 6. Output devices
I. Before reading the text try to answer these questions.
What types of displays do you know?
How can you change the picture using the controls?
Can you watch TV on your PC monitor?
Complete these definitions with words from the box. Then read the
text and check your answers.
Resolution pixel aspect ratio colour depth video adapter plasma screen
. - the smallest unit on a display screen or bitmapped image
(usually a coloured dot)
. - an expansion card that generates the video signal sent to
a computer display
. - the width of the screen in proportion to its height
. - also called gas discharge display
- the number of pixels contained in a display,
horizontally and vertically
- the number of bits used to hold a colour pixel; this
determines the maximum number of colours that can be displayed
Read the text again and answer these questions.
What do CRT and LCD stand for? 2. How is the screen size measured? 3. What technology is used in active-matrix LCDs? 4. What unit of frequency is used to measure the brightness of a display? 5. What substance produces light and colour when hit by electrons in a CRT monitor?
Displays, often called monitors or screens, are the most-used output device on a computer. They provide instant feedback by showing text and graphic images.
The monitor or screen is the computer’s usual means of
communicating with the user. The term “monitor” probably comes from the fact that the user monitors, or keeps track of, what the computer is doing by watching the display on the screen. Screens vary in size, resolution, colour and graphics capabilities, and the technology used to produce the screen image.
Resolution refers to the number of dots of colour, known as pixels (picture elements), contained in a display. It is expressed by identifying the number of pixels on the horizontal and vertical axes.
The size of display is described by the aspect ration and the screen size. Historically, computer displays, like most televisions, have had an aspect ratio of 4:3 - the width of the screen to the height is four to three. For widescreen LCDs, the aspect ratio is 16:9.
Inside the computer there is a video adapter, or graphics card, which processes images and sends signals to the monitor. CTR monitors use VGA (video graphics adapter) cable, which converts digital signals into analogue signals. LCDs use a DVI (digital video interface) connection.
Colour depth refers to the number of colours a monitor can display. This depends on the number of bits used to describe the colour of a single pixel.
Most desktop displays use Cathode Ray Tube (CRT) or Liquid Crystal Display (LCD) technology, while portable computing devices incorporate LCDs.
The CRT is the oldest and most commonly used display technology in the computer world. The principle of operation is similar to a television set in that a tube similar to a picture tube projects dots of coloured light onto different parts of the screen to form letters and other images. However, the process by which information is transferred from computer memory to a screen image is different from the reconstruction of a television picture from a broadcast signal, as will be explained shortly.
Monochrome (one colour) monitors display either one colour (most commonly yellow, green, or white) on a black background, or else black on a white background. The colour is determined by the chemical makeup of the phosphor, a substance that coats the inner surface of the CRT and generates the display by glowing when excited by light.
Colour monitors have three phosphor dots for each point (or pixel, for a picture cell) on the screen that can be activated by the scanning beam. Each of these dots will glow red, blue, or green when excited by light. Since these are the three light primaries, other colours can be produced by exciting more than one of the dots for a given pixel. More shades of colour can be generated if the intensity of the dots can be varied.
As in a television set, the phosphor dots are activated by a light beam that scans the screen in horizontal lines, moving from top to bottom. Scan time or refresh rate is a measure of how long the beam takes to make a complete pass over the screen. Scan time is important because the excited phosphor dots stay bright for only a limited time (this time is called the “persistence” of the phosphor). Display quality therefore involves matching the scan time with the characteristics of the phosphor. If the scan is too slow for the phosphor, the display will flicker because some phosphor dots will have a chance to grow visibly dim before the beam comes back to recharge them. A high-persistence phosphor, however, will leave a “ghost” image on the screen for a noticeable time after the light stimulus is removed. The faster scanning needed with a low-persistence phosphor is
more expensive because the electronics and control circuitry for the beam must have a faster response time.
When a computer must be small or portable, CRT technology becomes difficult to implement. The tube cannot be compressed front to back beyond a certain point without compromising image quality (as the scanning beam must move through a wider angle, the dots near the edge become elliptical instead of circular). Moreover, CRTs are highly subject to impact damage or breakage. Therefore, many portable computers use LCD technology instead.
LCDs are widely used in calculators, digital watches, and instruments as well as in computers. The screen consists of a sheet of crystalline material sandwiched between two sheets of glass. The crystals can assume two shapes: one when excited by an energy input, the other when unexcited. In their unexcited state, the crystals reflect most of the incident light and appear pale grey; when excited, they absorb light and appear black.
One advantage of LCDs is that the amount of energy required to make the crystals change shape is much less than that needed to turn on a dot on a CRT phosphor display. The lesser energy input, however, plus the fact that the LCD is merely reflecting or absorbing the ambient light rather than itself emitting light, means that LCDs can suffer from poor contrast, especially in marginal lighting conditions or when viewed at an angle. More recent designs use improved crystals or backlighting to obtain more contrast.
Active-matrix LCDs use TFT (thin film transistor) technology, in which each pixel has its own switch. The amount of light the LCD monitor produces is called brightness or luminance, measured in cd/ m2 (candela per square meter).
UNIT 5. BASIC SOFTWARE Lesson 1. What is an operating system (OS)?
I. Before reading the text discuss these questions.
How many operating systems can you think of? Make a list.
What is the function of an operating system?
Read the text. Prepare a list of 8-10 questions to ask about the text. Get ready to interview the students in your group.
Not all computers have operating systems. The computer that controls the microwave oven in your kitchen, for example, doesn’t need an operating system. It has one set of tasks to perform, very straightforward input to expect (a numbered keypad and a few pre-set buttons) and simple, never-changing hardware to control. For a computer like this, an operating system would be unnecessary baggage, driving up the development and manufacturing costs significantly and adding complexity where none is required. Instead, the computer in a microwave oven simply runs a single hard-wired program all the time.
All desktop computers have operating systems. The most common are the Windows family of operating systems developed by Microsoft, the Macintosh operating systems developed by Apple and the UNIX family of operating systems (which have been developed by a whole history of individuals, corporations and collaborators). There are hundreds of other operating systems available for special-purpose applications, including specializations for mainframes, robotics, manufacturing, real-time control systems and so on.
In any device that has an operating system, there’s usually a way to make changes to how the device works. This is far from a happy accident; one of the reasons operating systems are made out of portable code rather than permanent physical circuits is so that they can be changed or modified without having to scrap the whole device.
For a desktop computer user, this means you can add a new security update, system patch, new application or even an entirely new operating system rather than junk your computer and start again with a new one when you need to make a change. As long as you understand how an operating system works and how to get at it, in many cases you can change some of the ways it behaves. The same thing goes for your phone, too.