Every day, sitting down at his workplace in the office, a person takes a mouse in one hand and begins to perform his duties. He knows what he needs a keyboard, a printer, a scanner for, but he does not even imagine that they have their official name. All this - and information output.

How it works

All devices in a personal computer are controlled by a central processor. To ensure interaction with it, the output and input devices make requests to - a logical element of the motherboard. It serves to provide communication and processing requests from external devices to the north bridge or the central processor, if there is no bridge.

In general, computer science studies the structure of a personal computer. It defines input and output devices as components of a typical personal computer that provide the user with a computer. But before proceeding with the description of all devices, the basic I / O device deserves special mention. It is also a BIOS. This microcircuit on the motherboard of a personal computer provides an initial check of all connected devices and starts the operating system.

Classification

Information input and output devices of a personal computer can be classified in different ways. The determining factor for this will be their functional responsibilities.

The first point is the main input-output devices. In fact, there could be only one item here - the keyboard, since without it, no user computer will continue to boot. You can turn off your monitor and mouse completely, but your computer won't work without a keyboard. An exception is made by server computers that work without any external devices connected at all. So, the main I / O devices, without which a regular user cannot work, are:

• keyboard;
• monitor;
• mouse.

You can also highlight additional input-output devices:

• printers;
• scanners;
• joystick;
• projector;
• also I / O devices include audio devices.

This is not a complete list of possible devices that interact with the user; it can be very long to list them. Therefore, let's look at the input / output devices of the computer in more detail.

Monitors

Computer monitors have undergone many changes throughout their history. From the old ones using cathode ray tubes to modern LCDs.

The monitor or display itself is a device that is used for output to the end user. They can be divided according to several criteria.

1. By type of information.

• Alphanumeric. These displays are intended to display only text information.
• Graphic. We come across these monitors every day, sitting down at a personal computer. They are intended to represent information in a graphical form, including video.

2. By screen type.

• based on this you may have worked in 2000.
• LCD is a liquid crystal "flat" display, which is used everywhere today. Also this type of monitors is used in laptops.
• Plasma.
• Laser - has not yet entered mass production.

Keyboards

What about keyboards? The fantasy of manufacturers in this area has stepped far forward, and a sense of humor pushes for the most daring experiments.

Among keyboards, you can find minimalistic options - without an additional side panel with numbers, and huge gaming keyboards with built-in joysticks, additional buttons and speakers. There are keyboards with an additional USB-connector and pink keyboards with "incomprehensible buttons" for "blondes". There are also silicone, roll-up keyboards to make it easier to carry around, or simply fold up three times.

If you are going to get yourself a keyboard, just go to a computer store and choose the one that suits your taste.

Mouse

Computer mice are such computer input / output devices, without which the work of an ordinary user is impossible. If an advanced user can navigate through folders and files, as well as some programs and games, exclusively using the keyboard, then an ordinary person is simply not able to do this. For all the time of existence, computer mice have undergone not so strong changes.

The first mice worked on the basis of a ball at the base. By moving it in different directions, the ball rotated and controlled the controllers.

Then he was replaced by optical mice based on LEDs. The first generation of optical mice required the mandatory presence of a special mat, on which hatching was applied, contributing to the increased reflectivity of the surface. Moreover, the first mice had personal mats, they could not be replaced with others.

The second generation of optical mice has a more complex device. A mini-video camera is installed on the bottom of the mouse, which continuously takes micrographs of the surface and compares them with each other to determine the displacement of the device.

A newer device is mice. Among their advantages are low power consumption, reliability, lack of glow.

Another version of the mouse is found in the form of an add-on to a graphics tablet. Such induction mice are quite inconvenient to use, since they cannot be replaced with more comfortable ones for the hand, and the increased accuracy is discredited by the small opportunity to move away from the tablet with it.

Printers

These are devices for printing information. Throughout their existence, printers have not changed much. Technologies are developing, laser printers are replacing inkjet printers, however, previous generations continue to live. What is the reason for this? The point is that different types of printers are suitable for different types of printing. They all perform the same function and do not differ much in design. There are the following types of printers:

• matrix;
• inkjet;
• laser;
• thermal printers.

In the matter of choosing such a device, people usually adhere to personal preferences and habits. However, if you are going to print photographs on it, and not just text documents, then laser is more suitable for you due to the increased print quality.

Scanners

A device for entering information into a computer. The peculiarity lies in the fact that scanners enter information into a PC exclusively in graphical form. The development of scanners has stalled solely on resizing. At first they became smaller and more compact, and then they were replaced by huge "combine" - output and input devices that combine a copier, printer and scanner.

Sound

Each of us loves to watch movies, listen to music at home. Speakers, headphones, audio systems and home theaters, as well as headsets and microphones are all related to audio output and input devices.

There are many different microphones and speakers that differ in the quality of audio recording or playback, respectively. Probably, anyone can determine for themselves how good a particular speaker sounds. When choosing an audio system, it is also recommended to be guided by the design and power of your choice.

Video

To work with video graphics, special devices for output and input of information are distinguished - cameras and projectors.

A projector is a device designed to create an image of an object on a large screen. There are the following types of projectors:

• Diascopic... The image appears due to the passage of rays of light through a transparent film with a picture.
• Episcopal... Creates an image using the projection of reflected rays.
• Epidiascopic creates an image of both transparent and non-transparent objects on the screen.
• Multimedia the projector is directly related to the topic of the article. This is a device for displaying graphic information from a computer onto a large surface.

As for the cameras, you don't need to tell anyone. In most cases, the higher the resolution of the camera, the better the finished picture. With the advent of laptops, USB cameras began to be replaced with built-in laptop monitors.

After reading this article, you learned what output and input devices exist, what types they are divided into and what types are relevant today. If you are going to independently equip your work and play space, as well as independently choose the devices that you want to have at home at hand, then this article should help you with the choice of gadgets.

Remember the main rule of the buyer: more expensive does not mean better. In a computer store, purchasing a printer or headset, you may well overpay for a brand, and then regret your purchase for a long time.

HP printers are an example. Yes, they are considered one of the best, but replacing an exhausted cartridge or just a small malfunction will cost you a pretty penny solely because of the manufacturer's fame.

When purchasing a sound system, do not hesitate to test the sound and performance of your speakers. And if you are going to buy a webcam, then test its image, since the resolution stated in the documentation may not always correspond to the available one.

And the main rule. When purchasing any product, check with the seller for warranty information. For example, for some devices, services require the box in which the unit was delivered. A striking example is Asus laptops. In most cases, nowhere on the store's website is information that manufacturers require a branded box when contacting a service center.

Be attentive and have a good shopping!

Monitor

The monitor is a device for visual display of all types of information, which is connected to the PC video card.

A distinction is made between monochrome and color monitors, alphanumeric and graphic monitors, cathode-ray tube monitors and liquid crystal monitors.

Cathode ray monitors ($ CRT $)

The image is created using a beam of electrons, which are released by an electron gun. A high electrical voltage accelerates the electron beam, which falls on the inner surface of the screen, covered with a phosphor (a substance that glows under the influence of an electron beam). The beam control system runs it line by line across the entire screen (creates a raster) and adjusts its intensity (the brightness of the phosphor dot).

$ CRT $ -monitor emits electromagnetic and X-ray waves, high static electric potential, which have an adverse effect on human health.

Figure 1. Cathode-ray monitor

Liquid crystal monitors ($ LCD $) based on liquid crystals

Liquid crystal monitors (LCDs) are made from a liquid substance that has some of the properties of crystalline bodies. When exposed to an electrical voltage, liquid crystal molecules can change their orientation and change the properties of the light beam that passes through them.

The advantage of liquid crystal monitors over $ CRT $ -monitors is the absence of harmful electromagnetic radiation and compactness.

The digital image is stored in video memory, which is located on the video card. The image on the monitor screen is displayed after reading the contents of the video memory and displaying it on the screen.

The stability of the image on the monitor screen depends on the frequency of the image reading. The refresh rate of modern monitors is $ 75 or more times per second, which makes the image flicker invisible.

Figure 2. Liquid crystal monitor

a printer

Definition 2

a printer - a peripheral device designed to output numerical, textual and graphic information on paper. According to the principle of operation, a distinction is made between laser, inkjet and dot matrix printers.

Provides virtually silent printing, which is formed by xerographic effects. The entire page is printed at once, which provides high print speed (up to $ 30 pages per minute). High quality printing of laser printers is ensured by the high resolution of the printer.

Figure 3. Laser printer

Provides virtually silent printing at a fairly high speed (up to several pages per minute). In inkjet printers, printing is performed by an ink print head, which ejects ink under pressure from tiny holes onto the paper. The print head moves along the paper and leaves a line of characters or a strip of image. The print quality of an inkjet printer depends on the resolution that can achieve photographic quality.

Figure 4. Inkjet printer

It is an impact printer that forms characters using several needles located in the printer head. The paper is pulled in by a spinning roller and an ink ribbon passes between the paper and the printer head.

On the print head of a dot matrix printer, there is a vertical column of small rods (usually $ 9 or $ 24), which the magnetic field "pushes" out of the head and they hit the paper (through the ink ribbon). The print head moves and leaves a string of characters on the paper.

Dot matrix printers print speed is slow, produce a lot of noise and print quality is not high.

Figure 5. Dot matrix printer

Plotter (plotter)

Definition 3

A device designed for complex and large-format graphic objects (posters, drawings, electrical and electronic circuits, etc.) under PC control.

The image is applied with a pen. It is used to obtain complex design drawings, architectural plans, geographical and meteorological maps, business diagrams.

Figure 6. Plotter

Projector

Definition 4

Multimedia projector (multimedia projector) is a stand-alone device that provides information transmission (projection) to a large screen from an external source, which can be a computer (laptop), VCR, DVD-player, video camera, document camera, TV tuner, etc.

$ LCD $ -projectors. The image is formed using a transmissive liquid crystal matrix, of which there are three $ 3LCD $ models (one for each of the three primary colors). $ LCD $ -technology is relatively inexpensive, therefore it is often used in models of various classes and purposes.

Figure 7. LCD Projector

$ DLP $ -projectors. The image is formed by a reflective matrix and a color wheel, which allows one matrix to be used to consistently display all three primary colors.

Figure 8. DLP Projector

$ CRT $ -projectors. The image is formed using three basic color cathode-ray tubes. Now they are practically not used.

Figure 9. CRT Projector

$ LED $ -projectors. The image is formed using an LED light emitter. The advantages include a long service life, which is several times longer than the life of projectors with a lamp, the ability to create ultra-portable models that can even fit in a pocket.

Figure 10. LED projector

$ LDT $ -projectors. The models use several laser light generators. The technology makes it possible to create compact projectors with very high brightness.

Audio output devices

Built-in speaker

Definition 5

Built-in speaker - the simplest device designed to play sound in a PC. The built-in speaker was the primary audio reproduction device until inexpensive sound cards were introduced.

In modern PCs, the speaker is used to signal errors, in particular during the POST program. Some programs (for example, Skype) always duplicate the ringing signal on the speaker, but do not output the conversation sound through it.

64-bit Windows does not support the built-in speaker, which is due to a conflict between the rehabilitation and power management tools of the sound card.

Devices for outputting audio information that are connected to the output of the sound card.

Figure 11. Speakers and headphones

After the user has entered the initial data, the computer must process them in accordance with the available program and display the results obtained for their perception by the operator or for use by automatic devices. The information displayed can be displayed on a monitor screen, printed on paper (using a printer or plotter), reproduced as sounds (using speakers or headphones), recorded as tactile sensations (virtual reality technology), and distributed as control signals ( automation devices), transmitted as electrical signals over the network.

The most common output devices are monitors (displays)... The vast majority of monitors use cathode ray tubes (CRTs) or liquid crystal matrices to form an image. Moreover, at present, there is a gradual replacement of monitors with CRT monitors using liquid crystals.

There are monitors based on other physical principles: plasma, luminescent, etc.

For example, monitors manufactured using FED (Field Emission Display) technology are based on the effect of creating emission over the entire surface of the screen. Unlike a CRT, the source of electrons is not a single point (electron gun), but a whole emitting surface. Irradiation is performed through a mask in which the number of holes is equal to the number of pixels. Due to this design, it is possible to obtain the image brightness the same as for monitors with CRT, and the dimensions (thickness) - as for liquid crystal monitors.

A new technology for manufacturing monitors - OLED (Organic Light Emitting Diodes) - is considered promising. Their design is based on the use of organic light-emitting diodes.

Printers, depending on the order of formation of the image, are divided into sequential, line and page. The belonging of a printer to one or another group depends on whether it forms on paper character by character, or an entire line at once, or even a whole page.

According to the physical principle of operation, printers are divided into the following types: thermographic, petal (daisy), matrix (needle), inkjet and laser.

The design of the first two types of printers is obsolete, and they are practically no longer used.

IN dot matrix printers the image is formed from dots by striking the ink ribbon with needles. Under the influence of control signals supplied to the electromagnets, the needles "knock out" the paint from the tape, leaving traces on the paper. Depending on the design, the print head of the dot matrix printer can have 9, 18 or 24 needles. All symbols are formed from separate points.

Printheads inkjet printers instead of needles, they contain thin tubes - nozzles through which droplets of ink are thrown onto the paper. The print head of an inkjet printer contains from 12 to 64 nozzles that are thinner than a human hair.

There are several known operating principles for inkjet printheads.

In one design, a small ink reservoir is located at the inlet end of each nozzle. A heater (thin film resistor) is located behind the tank. When the resistor is heated by the current passing through it to a temperature of 500 ° C, the surrounding ink boils, forming a vapor bubble. This expanding bubble expels ink droplets with a diameter of 50 ... 85 microns from the nozzle at a speed of about 700 km / h.

In another design of the printhead, the pressure source is a membrane driven by a piezoelectric element. Applying electrical voltage to the piezoelectric element causes its deformation, which is used to spray ink.

In all printer designs, electromechanical devices move the printheads and paper to print in the right place.

IN laser printers the electrographic principle of image creation is used. The printing process includes the formation of an invisible relief of the electrostatic potential in the semiconductor layer with its subsequent visualization. Visualization (development) is carried out using dry powder particles - toner applied to paper. Toner is a piece of iron coated with plastic. The most important parts of a laser printer are the semiconductor drum, the laser, and the precision opto-mechanical system that moves the beam (Figure 10.5).

The laser generates a thin beam of light that bounces off a rotating mirror to form an electronic image on a light-sensitive semiconductor drum.

Some static charge is preliminarily imparted to the drum surface. A mesh or thin wire is used to create an electrostatic charge. When a high voltage is applied to the wire, a corona discharge occurs, as a result of which a luminous ionized area of \u200b\u200bspace appears around the wire. The corona discharge evenly charges the drum surface. To obtain an image on the drum, the laser must be turned on and off in accordance with the generated image, which is provided by the control circuit. The control signals are received from the computer in accordance with the image stored in the memory. The rotating mirror is used to turn the laser beam into a line formed on the surface of the drum.

When a laser beam hits a pre-charged drum, the charge "drains" from the illuminated surface. Thus, the areas of the drum illuminated and not illuminated by the laser have different charges. As a result of scanning the entire surface of the semiconductor drum, a latent (electronic, invisible to humans) image is created on it.

The drum turns to a new line by a precision stepping motor. This offset determines the printer's resolution and can be 1/300, 1/600, or 1/1200 inches, for example. The process of scanning an image on a drum is in many ways similar to building an image on a monitor screen (creating a raster).

Figure: 10.5. Laser printer printing process

At the next stage of the printer's operation, the image is developed, that is, the latent electronic image is transformed into a visible one. When developing an image, the following physical phenomenon is used: charged toner particles are attracted only to those parts of the drum that have an opposite charge to that of the toner.

When the visible image on the drum is built and covered with toner in accordance with the original, the fed sheet of paper is charged in such a way that the toner from the drum is attracted to the paper. Powder adhered to the paper is fixed to the paper by heating the toner particles to their melting point. As a result, a waterproof imprint is formed. Color laser printers create an image by sequentially applying cyan, magenta, yellow and black toners to the photosensitive drum.

In a four-pass color printer, the print speed is significantly slower than that of a black and white printer. In a single-pass color printer, four toner cartridges are installed in the same plane one behind the other, each next to its own ram. All colors are applied in one pass instead of four, so the imaging speed is increased.

In addition to laser printers, there are so-called LED-printers (Light Emitting Diode), which got their name from the fact that the semiconductor laser in them is replaced by a "comb" (line) of LEDs. In this case, a complex mechanical mirror rotation system is not needed. The image of one line on the semiconductor drum is formed simultaneously.

Table 10.1. the characteristics of printers of various designs are given.

Table 10.1. Printer specifications

Plotters (or plotters) are graphical information output devices that are used in the design of large posters, drawings, geographic maps, sketches of printed circuit boards, diagrams, histograms.

The plotter's work is based on mechanical and non-mechanical methods of displaying graphic information. With the mechanical method, pencils, pens with ink are used. Similar to printers, non-mechanical plotters use thermal, dot matrix, inkjet and laser printing methods.

As devices capable of performing the functions of input and output of information, can be used communication adapters... With their help, communication between computers is carried out via a telephone line. Since telephone networks still operate more often not with digital, but with analog electrical signals in the audio range, it is necessary to convert digital signals coming from a computer into analog signals and transmit them to the telephone network. The other end of the telephone line needs to be reversed. These transformations are performed by a special device - a modem (from the words MODULATOR - DEModulator).

The modem is implemented either as an external device, which is connected to a telephone line with one output, and to a standard computer port with the other, or as an ordinary card (card) that is installed on the system bus of the computer (internal modem).

The output of audio information is carried out using speakers and headphones (Fig. 10.6), which are connected through a special adapter (controller, sound card).

Figure: 10.6. Headphones

There are several ways to play sounds (in particular, music). The frequency method (FM synthesis) of sound reproduction is based on imitating the sound of real instruments, while the table method (wave-table synthesis) operates on the sounds of real instruments recorded in memory.

Frequency synthesis is based on the fact that mathematical formulas (models) are used to obtain a sound, which describe the frequency spectrum of a particular musical instrument. The sounds produced by this technology are characterized by a metallic tint.

Wave synthesis is based on the use of digital recording of real instruments, the so-called samples. Samples are samples of the sounds of various real instruments stored in the sound card's memory. When playing sounds using wave synthesis technology, the user hears the sounds of real instruments, so the created sound picture is closer to the natural sound of instruments.

Samples can be stored in two ways: either permanently in ROM, or loaded into the sound card's RAM before using them. There is a wide variety of samples available, allowing you to create an almost endless variety of sounds.

Display (monitor) is the most popular output device. There are monochrome (black and white) and color displays. First, let's look at the principle of operation of black and white monitors.

Figure: 10.7. Cathode-ray tube

The main display unit is cathode ray tube (CRT)... Sometimes the abbreviation CRT is used to refer to CRT - Cathode Ray Tube. One of the possible designs of a CRT is shown in Fig. 10.7.

Let's list the main parts that make up a CRT: cathode, anode, modulator, horizontal deflecting plates, vertical deflecting plates, screen, bulb.

The cathode, anode, and modulator form an electron gun, sometimes called an electron gun. The horizontal and vertical deflection plates form a deflection system. Such a deflection system is called electrostatic. There are magnetic deflection systems in which coils are used instead of plates to change the trajectory of the electron flow.

A CRT uses a stream of electrons focused into a narrow beam, controlled in intensity and position in space and interacting with the tube screen. An electron beam is emitted by an electron projector (more precisely, a cathode), and the position of the beam on the screen is changed by a deflecting system.

The movement of the electron beam across the CRT screen in accordance with a certain law is called a sweep, and the pattern drawn by the trace of the electron beam on the screen is called a raster. The sweep is carried out by applying periodically varying voltages to the deflection system of the CRT. During scanning, the electron beam sequentially runs along the lines along the surface of the CRT screen.

In the process of forming a raster, the flow of electrons moves along a zigzag path from the upper left corner of the screen to the lower right corner. In fig. 10.8 solid lines show the raster, dashed lines - the trajectory of the electron beam, on which it is "extinguished" (made invisible).

Figure: 10.8. Raster and trajectory of the electron beam

The screen is covered with a phosphor, therefore, in the places where the electron beam falls, a glow appears, the brightness of which is proportional to the intensity of the beam. The intensity of the flow of electrons changes in accordance with the signals supplied to the control electrode - modulator. It is these signals that form the required image on the display screen.

Figure: 10.9. The image of the letter "I"

In fig. 10.9 shows on a large scale the image of the letter "I". In this case, it took eight raster lines to display it. In fig. 10.10. shows timing diagrams for control signals supplied to the modulator. High potential corresponds to white areas of the screen, low potential to black. With the help of a deflecting system, the modulated electron beam is scanned into a raster, flashing line by line on the screen, thus reproducing the image frame by frame. Due to the inertia of vision, a person sees on the screen a continuous, often dynamic, image.

Figure: 10.10. Timing diagrams for control signals

Any image on a monitor screen consists of many discrete points called pixels (pixel - picture element).

The display interacts with its adapter, which may also be called a video card, video adapter, or controller. The display and the adapter are very closely related to each other and jointly determine the image quality - resolution, number of reproducible colors, refresh rate (number of frames per unit of time).

The resolution depends on the size of the screen and the minimum image element (the so-called "grain", equal for the best monitors 0.24 ... 0.28 mm). For 14-inch monitors, the resolution is usually no more than 800 × 600 elementary dots (pixels), for 15-inch - 1024 × 768, for 21-inch - 1280 × 1024 dots.

The adapter's ability to display an image with a given resolution and color depth (that is, the number of color shades) on the monitor screen is determined by the amount of RAM installed on the adapter board. To display 16.7 million color shades (24 bits per pixel), you need to install at least 1.37 MB of memory in the adapter at a resolution of 800 × 600 elementary pixels, 3.75 MB at a resolution of 1280 × 1024 and 5.49 MB at a resolution of 1600 × 1200.

For a comfortable perception of the image, without flickering tired eyes, you need a sufficiently high frame rate (recommended at least 85 Hz).

The principle of operation of a color monitor is similar to that of a monochrome monitor, but the design of a color monitor is much more complex. The color display contains three electron guns with separate control circuits. The screen is made in the form of a mosaic structure (rectangular matrix), consisting of phosphor grains of three luminescence colors: red (Red), green (Green) and blue (Blue). The grains are arranged in threes (triads) so that the electrons of each of the three guns fall only on the grains of "their" color. To ensure this, masks are installed on the path of the electrons.

The principle of operation of a color display is based on the physiological features of human vision. So, with the same intensity of luminescence of three different-colored small neighboring grains, this area of \u200b\u200bthe screen is perceived as a white point. The glow of the neighboring red and green grains is perceived as a yellow point, and the glow of the blue and green grains gives a blue point, etc. By changing the intensity of the glow of the three primary colors (RGB), you can get any color or shade. This method of obtaining any color is one of the color rendering systems and is called the RGB system (after the first letters of the corresponding English words).

Liquid crystal monitors (LCD) have the following advantages: low power consumption (2-3 times less than that of a CRT), no X-rays, static electrification, geometric distortions. LCDs have low weight and dimensions: the thickness of the monitor does not exceed 5 ... 6 cm. The disadvantages of LCDs are limited viewing angle, less contrast and color depth than CRTs, significant unevenness of brightness in different parts of the screen. LCDs have a large percentage of defects in their production (the presence of "dead" pixels). This is currently considered to be the main reason for the higher cost of LCDs compared to CRT monitors.

In cathode ray tubes, the phosphor is placed at certain points on the screen, forming a matrix. The stream of electrons is directed to these points using continuous (analog) control signals to the deflection system. The electron beam sequentially "runs around" all the points (pixels) of the screen line by line and alternately changes the intensity of their glow.

The complete image on the CRT screen, obtained with the participation of all pixels, is called a frame. To get the illusion of a moving image, the next frames must quickly replace each other (not less than 25 ... 30 times in 1 s). In a CRT, during the movement of the electron beam from the beginning of the frame to its end, the glow of the first excited elements of the matrix (phosphor) has time to weaken somewhat. To reduce the flickering of the screen, you have to increase the frequency of changing (refreshing) the next frames (they say: increase the frame rate). The vertical scan frequency of the CRT must be at least 85 Hz.

The principle of operation of a liquid crystal monitor is significantly different from the principle of operation of a monitor with a CRT. LCM uses the physical effect of changing the spatial position of crystal molecules under the action of an electric field. Just like in a CRT, an LCD image is formed from a large number of dots (pixels) that form a rectangular matrix. However, in a liquid crystal matrix, the imaging process is controlled digitally. In the LCD, the glow of all elements of the whole row of the matrix (screen) changes simultaneously. LCD flicker is fundamentally less than that of CRT displays, since only the changing pixels are updated during image formation. The image of static images does not require updating, so in these cases there is no LCD screen flickering at all. LCD matrix (Liquid Crystal Display, LCD) is made of a substance that is in a liquid state of aggregation, but has the properties of crystals. Under the action of an electric field, liquid crystals change their spatial orientation (turn) and thus vary the intensity of the transmitted light.

Figure: 10.11. Multi-layer monitor design

The monitor is a multilayer structure (Fig. 10.11), which contains polarizers, a matrix of control transistors, color filters, glass plates, between which liquid crystals are placed.

The principle of operation of the LCM (Fig. 10.12) is based on the effect of polarization. First, the light passes through the first polarizing filter (Polarizer 1), which is characterized by a certain polarization angle. Another polarizer is installed in the LCD (Polarizer 2). Depending on the polarization angle of the second filter, the light will either be completely absorbed by it (if the polarization angle of the second filter is perpendicular to the polarization angle of the first filter), or pass unhindered (if the angles coincide). A smooth change in the angle of polarization of the transmitted light allows you to adjust the intensity of the visible (transmitted) light. The angle of polarization of the transmitted light is changed using liquid crystals. Their orientation in space depends on the magnitude of the control voltage applied to the matrix of transistors.

Figure: 10.12. The principle of operation of the LCD

Thus, by changing the control voltage on each transistor of the matrix, it is possible to vary the spatial position of the liquid crystals at a given point. A change in the spatial position of the crystals leads to a change in the angle of polarization of light at a given point on the screen (and, hence, to a change in the intensity of the glow of a given point on the screen).

The discrete design of the LCD allows, in principle, to do without analog-to-digital conversion, i.e. to work directly with digital signals. Obviously, this design is more promising compared to devices working with analog signals. Recall that a CRT is an analog device. The signals on the deflection plates and the modulator are continuous. To control the operation of the CRT, it is necessary to transform the digital signal generated by the computer into an analog signal. However, any digital-to-analog conversion is associated with the appearance of distortion and interference, the complication of the design of controllers.

Or graphics tablet, -a device for digitizing graphic images, which allows converting an image resulting from the movement of an operator's hand into a vector format.

Digitizers are used in computer-aided design (CAD) systems for entering graphic information into a computer in the form of drawings and drawings: the designer moves the cursor over the tablet with the stylus, and the image is captured as a graphic file.

The digitizer consists of two elements: the base (tablet) and a pointing device (pen or cursor) that you move across the surface of the base. When you press the cursor button, its position on the tablet surface is fixed and the coordinates are transferred to the computer.

Digitizers are classified as electrostatic or electromagnetic, depending on the mechanism for locating the pointing device.

Graphic tablets of digitizers are made on hard surfaces (tablet digitizers) and flexible bases (flexible digitizers). Flexible digitizers are lighter, more compact, easier to transport and cheaper.

Pointing devicesin digitizers they are made in the form of a cursory or a feather.

The pen is a pointerequipped with one, two or three buttons. There are nibs that determine the force with which the pen tip is pressed against the tablet, and have 256 degrees of pressure. The thickness of the line, the color in the palette and its shade depend on the degree of pressure. To realize artistic possibilities, software such as Adobe Photoshop , CorelDRAWand etc.

Cursors are used primarily by CAD designers. They are performed by 4-, 8-12-, 16-keys. Usually, two to four keys are used, the rest are programmed in application programs, for example, in Autocad. One of the best is the CalComp 4-button cursor.

Lesson topic. Information output devices.

About 10 years ago, one could only dream of working on a computer like a typewriter or organizing a mini-typography with it, watching television programs, listening to CDs.

But time flies quickly, and today everyone knows those peripheral hardware that help bring the possibilities of personal computers to almost unlimited.

Of course, we are talking about all kinds of information output devices, the main purpose of which is to convert information contained in binary digital form in the memory of the machine into a form that is understandable for human perception.

Information output devices arecomputer hardware designed to output digital information from it by converting it into an analog form and presenting it in a form understandable to humans.

The hardware of any output device, just like the input device, includes the device itself, the control unit - a controller (or adapter), interface cords with connectors corresponding to the ports on the motherboard, and the driver for this specific device.

We know that thanks to his senses, a person can perceive visual, sign-symbolic, audio information, tactile (tactile) information, smells and tastes.

Of these forms today's personal computer, perhaps, can not satisfy only our olfactory organs and taste buds - the conclusion of "smelling" and "tasty" information is the prospect of the future. But the computer displays all the other forms that we understand in a completely real form.

According to this, we can divide all output devices into several classes:

Monitors - video information output;

Printers - output of symbolic written information;

- plotters(plotters) - output of graphic information;

Speakers, headphones, speakers - output of audio information;

Virtual reality devices - display of tactile information.

Lesson topic. Monitors: classification, characteristics and principle of operation.

1. Monitors: classification, characteristics and principle of operation.

Monitor— this a device for displaying symbolic and graphic information on the screen, by converting its computer (machine) representation into a form understandable to humans.

We can say a monitor is a device for displaying visual (visual) information.

Otherwise, monitors are called displays, less often - video terminals (this is usually called a monitor remote from other parts of the computer). The monitor is one of the main parts of the PC, and the convenience of using the computer largely depends on its characteristics.

The monitor is connected to the motherboard through a video adapter board (video card), and its normal operation is provided by a set of drivers - a special program supplied with the monitor.

The combination of a monitor, a video card and their drivers forms the video system of a personal computer.

Today you can meet a huge number of monitors of various brands and models. In order to somehow understand their diversity, you need to clearly imagine the signs by which they are classified.

We will consider their classification by:

1) the size, which is determined, like for TVs, by the diagonal of the screen;

2) functional features - alphanumeric or graphic;

3) the number of reproducible colors - monochrome or color;

4) physical principles of image formation - based on a cathode ray tube (CRT), liquid crystal, plasma and electroluminescent.

A smart choice in terms of "screen size" among monitors may be a display with a diagonal of 17 inches or more.

Alphanumeric Monitor (today, by the way, you will not find it anywhere) can only play a limited set of symbols. It can be compared to the display of a conventional wrist electronic watch, on which you can see only numbers and letters. Complex pictures cannot be reproduced on it.

Graphic monitors adapted for reproducing any information: both digital and graphic.

Monochrome monitor can reproduce an image in any one color with different gradations of brightness. A color monitor displays an image in several colors at once. Their number can be from 16 to 16 800 000.

Plasma Displays are a set of gas-discharge cells - they are expensive and their power consumption is quite high.

Fluorescent Displays consist of a matrix of active indicators that give a high-quality image, but they are also very energy-intensive and expensive.

Monitors based cathode ray tube (CRT) they work according to the same "principle as conventional televisions: a beam of electrons emitted by an electron gun is modeled by special electrodes and hits a screen covered with a phosphor." The screen image is made up of many individual dots called pixels.

Pixel- the minimum size of the image on the screen.

Under the action of scanning, the electron beam slides across the screen line by line and forms an image.

Colors on the monitor (as well as on a television screen) are obtained by an additive (total) mixing of three basic colors: RGB, i.e. red (Red), green (Green) and blue (Blu). This triad, mixed with the same intensity, gives a white color, and in order to achieve color shades, the intensity of each of these colors is dosed in the required proportion.

Electromagnetic radiation from CRT monitors is generated by a gun that accelerates electrons and is located at the back of the monitor, and X-rays are generated when electrons collide with the inner surface of the screen. Of course, modern CRT monitors have anti-radiation protection, however, it is not possible to completely suppress the resulting radiation.

LCD monitor does not have these drawbacks: its electromagnetic fields are at the background level from the power supply, and the image it creates does not flicker at all. This very circumstance alone makes those who are professionally connected with computer technology to seriously think about purchasing an LCD panel. The disadvantages of the LCD monitor include not yet sufficiently accurate color reproduction, as well as uneven image brightness. Ergonomics speaks in favor of purchasing an LCD monitor. This applies to those who spend a lot of time in front of the TV screen. The fact is that some models of LCD monitors, in addition to the standard VGA-input for connection to a computer, also have a video input to which you can send a signal from a TV, TV-tuner or VCR. This makes it possible to get rid of the harmful effects of a television CRT, which is much stronger than that of a CRT monitor.

TFT technology is used in modern thin-film semiconductor liquid crystal monitors. The liquid crystal material is sandwiched between two layers of glass.

The high efficiency of LCD monitors is due to the low consumption of materials and energy.

Traditional CRT monitors update the image on the screen one pixel at a time, so the frame rate is extremely important for them, which determines the image refresh time. Its value determines the visual flicker of the image on the screen. LCD monitors refresh the image progressively, so it doesn't jitter at almost any reasonable frame rate.

With the same size and high contrast, LCD panels have an indisputable advantage over traditional CRT monitors: they are much lighter and take up very little space, and some models can be hung on the wall, which completely eliminates the need to allocate space for the monitor at the workstation. table.

Attention should be paid another convenient feature that some models of LCD monitors have is the ability to rotate the display by 90 ° and thus change the screen orientation to portrait. This is very useful when working with Web pages or large documents, where the extra height of the portrait image is extremely useful.

The main characteristics of monitors include permissiveability, the size screen coverage points and frame rate.

Resolution Is the maximum number of dots (pixels) that this type of monitor can reproduce horizontally and vertically.

It is clear that the more these points fit horizontally and vertically, the better the picture on the monitor will be.

The resolution depends both on the characteristics of the monitor itself and, even more so, on the characteristics of the video controller, which provides for two modes of operation of monitors: text and graphic.

The clarity of the image on the monitor screen depends on the magnitude of the resolution, and it is generally accepted that in the text mode monitors do not differ much from each other in terms of the clarity of the picture, and in the graphic mode, the image quality also grows with increasing resolution.

The image quality is significantly influenced by such a physical parameter of the display as screen coverage dot size, or, as computer scientists say, "phosphor grains". This parameter determines the distance between points.

For modern monitorscurrently on sale, this parameter ranges from 0.32 mm to 0.25 mm. The concepts of "grain" and "pixel" should not be confused. The grain size cannot be changed, and the pixel size depends on the mode of the video adapter. A good monitor should be considered a display with a dot size of no more than 0.28 mm.

Another important characteristic monitors include the maximum to frequency sweep. Good image stability and the absence of flickering on the screen depend on it. The higher the frame rate, the less ripple on your monitor screen.

It is recommended to use monitors with a refresh rate of at least 85 Hz, which means that the image on the screen is refreshed 85 times per second. A lower frequency is harmful to the eyes - flickering is fatiguing and can lead to premature loss of vision.

notethat all the most important characteristics of the monitor are directly related to each other. Changing one of the parameters will entail a change in the operation of the other, for example, by decreasing the resolution, the number of supported colors will increase (as well as the maximum scan rate).

Almost all modern monitors are equipped with a special digital control that allows you to manually adjust many parameters:

· Proportional compression / stretching of the image horizontally and vertically;

· Shift of the image horizontally or vertically;

· Correction of "barrel-shaped distortions" (ie, such when the edges of the image on the screen are too convex or, conversely, concave);

· Trapezoidal and parallelogram distortions, also associated with the "geometry" of the image;

· Color "temperature", ie, the ratio of the main screen colors - red, green and blue.

In professional monitors high-class, you can find several dozen of all kinds of settings and adjustments, many of which are carried out directly from the computer.

The back side of such monitors is decorated with many unusual connectors, through which you can fine-tune the colors and image parameters. In particular, the so-called “calibration” is the exact adjustment of the colors on the monitor to the specified standards.

Lesson topic. Video adapters.

Video card (video adapter). The main purpose of a video card is to control the process of displaying information on the monitor screen; its characteristics must correspond to the parameters of the monitor. The higher the resolution of the monitor screen and its size, the higher the requirements for the video card. Structurally, a video card is usually made in the form of an expansion card, which is inserted into the corresponding slot on the motherboard. Older computers used ISA buses for this, then PCI. In modern computers, the video card uses a special slot - AGP.

The main components of a modern video adapter are a video controller, video BIOS, video memory, a special digital-to-analog converter RAMDAC and an interface chip with a system bus.

All modern video subsystems can operate in two main video modes: text or graphic. Text mode in modern operating systems is used only at the boot stage.

In graphical mode for each point of the image (pixel) 1 ... 32 bits (from monochrome to color) are allocated. The maximum resolution and the number of reproducible colors of a specific video subsystem primarily depend on the total amount of video memory and the number of bits per image element. There are several standards for video cards... The main parameters in these standards are resolution (the number of pixels horizontally and vertically), the number of colors displayed on the screen and the frame rate, which determines the frequency of redrawing (refreshing) the image on the monitor screen.

Currently, all video cards must comply with VESA SVGA standards, which defines the following main characteristics:

Resolution - the number of pixels horizontally x the number of pixels vertically:

640x480; 800x600; 1024x768; 1152x864; 1280x1024; 1600x1280; 1800x1350;

· Color depth - the number of bits per pixel (colors).

Vertical scan rates (56; 60; 72; 75; 85; 90; 120 Hz). Vertical scan rate is extremely important parameter from the point of view of ergonomics. The image on the monitor screen is drawn by an electron beam with a frame rate equal to the frame rate. If this frequency is below 75 Hz, then the eye has time to notice the flickering of the image, which has a tiring effect on it. Flickering is most noticeable on a white background.

In order to set the required color depth, open the Control Panel and select "Display" (or right-click on the desktop and select "Properties"). Go to the "Settings" tab. In the "Color palette" section, select the desired mode and click the "Apply" button.

Set to HighColor or TrueColor for normal operation.

Video memory size... This parameter depends on the ability of the card to support various parameters of displaying the image on the monitor screen.

Video memory size, necessary to support a particular mode, is determined as follows: you need to intelligently live the number of pixels in the image horizontally and vertically by the number of bits and divide the resulting value by 8 (the number of bits in a byte). This way you can get the maximum possible resolution value for different sizes of video memory. It is easy to determine that to support the maximum resolution of 1600x180 at a color depth of 32 bits, 8 MB of video memory is required. Working with graphics applications, 3D graphics and video imposes increased demands on all characteristics of a video card, especially its memory. Therefore, cards with a memory capacity of at least 128 MB are currently produced.

Safety standards. There are several standards that the leading manufacturers of monitors adhere to. We list only the most famous ones.

Standard DPMS defines the power management modes that can be used when the monitor is idle.

In mode Standby only the screen is blanked out (switching off the high voltage on the picture tube), in the Suspend - decrease in the heating temperature of the CRT cathodes.

Modern motherboards support one more mode - Hibernate("hibernation"). When you enter this mode, all the contents of the RAM are saved on the hard disk, the monitor and hard disks are turned off, and then the computer is turned off. The advantage of this mode is that when the computer is activated, which is usually done by pressing any key on the keyboard, the state of the desktop, open and minimized windows is restored, i.e. the computer completely reproduces its state at the moment of "falling asleep".

Swedish specification Nutek - The National Council for Industrial and Technical Development of Sweden, requires that the monitor switches to the first mode of saving energy (Standby) if the mouse or keyboard has not been used for more than 5 minutes (but less than 1 hour); in this case, the monitor can return to normal in 3 s. In this mode, the power value must necessarily be less than 30 W, and preferably less than 15 W. After 70 minutes, the power consumed by the monitor must be reduced to less than 8 W, and preferably to less than 5 W. The exit time from the second mode (Off) is undefined. The energy efficiency levels defined by Nutek have been included in the TCO 92 and TCO 95 certification systems.

TCO abbreviation stands for as the Swedish Federation of Trade Unions. Initially, environmental standards applied only to monitors as the most dangerous element of a computer. The developers were only interested in minimizing the level of various emissions. TCO "92 in this sense turned out to be very tough. Its successor TCO" 95 only expanded the scope of TCO, making an attempt to describe the requirements for other computer elements for the first time. In addition, special attention was paid to the protection of the environment during the production process and the harmless disposal after the service life of all certified products. The requirements of the TCO "99 standard are mainly focused on ergonomics, ecology and environmental protection. The standard now includes LCD monitors, computers, laptops and keyboards.

All requirements of the TCO "99 standard are combined into seven groups:

1.visual ergonomic requirements (requirements for image clarity);

2. visual ergonomic requirements (requirements for image stability);

3. factors of external influence;

4. requirements for radiation and energy saving;

5. requirements for electrical safety;

6. environmental requirements;

7. additional characteristics.

Lesson topic. Additional video signal processing devices.

To better understand what is going on, imagine a stereo movie. Remember, in the recent past, in our country, there were stereo cinemas, where before watching a movie, each viewer was given stereo glasses. And if a tree was falling on the screen, then, looking at it through the stereo glass, the whole hall deviated, as there was an illusion that the tree was falling on you. It was a "virtual reality" effect.

The virtual reality Is a process of modeling physical impacts using video technology.

PictureIs what a personal computer user is dealing with. This means that in order to achieve the "stereo" effect on the monitor screen, it is necessary to make "three-dimensional" from the two-dimensional "picture". To do this, you just need to divide the picture perceived by our eyes on the monitor into two pictures, but specifically for the right and left eyes, and these pictures will differ from one another only by the angle of rotation in relation to the user.

These pictures are necessary show simultaneously, on one screen, where they will be superimposed on one another. And in order for the viewer to perceive them as a whole and look at the same time "in two eyes", you need to put on special multi-colored glasses, in which each eye perceives only the picture that is intended for him.

This technology is theoretically quite simple. Apparatus for her, in addition to penny glasses, is not required. But whoever wants to create programs, games and films for such glasses should know: this is a very laborious and complicated process. Therefore, all over the world there are only a couple of dozen games and encyclopedias created for multi-colored "virtual" glasses.

Later another method appeared artificially dividing the picture using the hardware of the PC itself. A small "phase shift" is required when creating a copy of the picture on the screen. This copy, slightly rotated in relation to the original, along with the original is fed at the right moment to the screen, and the "three-dimensional" picture is ready, mind you, practically without the participation of a complex program. Thus, you can "measure" any toy, even one that knew absolutely nothing about "virtual reality"!

Then the cheap plastic glasses were replaced by two small LCD monitors - one for the right and the other for the left eye, and they were moved closer to the eyes, at a distance of several centimeters, which, mind you, is very tired of the eyes and causes a headache.

It is on this principle was created thundering about 5 years ago Virtual reality helmet, which is still sold in a number of computer companies at prices ranging from $ 500 to $ 700. There is one more, perhaps the most optimal in terms of price and quality technology of "virtual reality" - liquid crystal glasses. By themselves, such glasses do not show anything. And they can only alternately cover one or the other eye with special liquid crystal "shutters". This process occurs at a high speed - and in parallel to it, pictures for the left and right eyes are fed to the monitor screen. At the same time, a special device that is installed between the video card and the monitor is engaged in the "breakdown" of the usual image.

The only drawback of this method - the frequency of vertical scanning of the image you see is reduced by half due to the alternate display of the picture, from which it follows that only the best monitors will "pull" the frequency of 120 Hz in 800 x 600 mode. The latest "squeak" of spectacle fashion is the so-called "Virtual monitors". Behind this loud name hides the already familiar "glasses" with liquid crystal displays, into the ears of which are inserted solid headphones that imitate high-quality sound.

Lesson topic. Printers: classification, characteristics and principle of operation.

1. Printers - devices for outputting text and graphic information from a personal computer to paper.

In modern models of printers, it is possible to output information not only to paper, but also to a medium of another kind, for example, synthetic film.

Printers - a fairly extensive class of devices, including up to 1000 different modifications. To somehow determine the characteristics, printers are classified by:

· Chromaticity (color and black and white);

· Print speed (this parameter is measured in the number of displayed characters per unit of time). For modern printers, this parameter can reach several thousand characters per second;

· By resolution (this parameter reflects the ability of the printer to display small lines and dots and is measured by the maximum number of lines, the length of which is equal to their width, per square centimeter or inch). For modern printers, this parameter can reach several
thousand dots per inch (dpi - inch per pixel);

· Along the width of the printer carriage (this parameter reflects the maximum possible document size);

· By printing methods (shock and non-shock);

· On the formation of output information when printing: sequential - the document is formed character by character, parallel (line) - the entire line is formed at once, and page - the image of the whole page is formed;

· For printing images on paper: letter, matrix, thermal, inkjet, laser.

All printers, as a rule, operate in two modes: text and graphic.

In text mode, character codes are sent from the computer to the printer, which must be printed. Printers support the most common fonts and their varieties.

When printing, it is possible to choose one of four modes of the quality of the resulting image:

Draft mode;

Print Mode Near Typographic (NLQ);

Typographic print quality (LQ) mode;

Super Quality Mode (SLQ).

Switching operating modes, depending on the type of printer, can be carried out both software and hardware, by pressing the buttons available on the printers.

In graphic mode, codes are sent to the printer that determine the sequence and location of the image dots. Modern printers in graphic mode, due to the pseudo-graphic symbols available in their memory, allow realizing service printing modes (dense, double-wide, two-pass printing, multicolor printing, etc.).

Introduction

The computer is a universal device for information processing. To allow the computer to process information, it must be entered there somehow. To carry out the input of information, special devices were created - first of all, a keyboard, a CD-ROM. Once in the computer, the information is processed and then the possibility of displaying this information is realized, i.e. the user has the ability to visually perceive the data. To display information, the main devices are used - a monitor, a video adapter and a printer. After entering and processing information, it can be saved, for which a hard disk, magnetic disks and optical data storage media were created. This test paper presents the topic "Input / Output Devices".

Information output devices are devices that translate information from machine language into human-readable forms. Information output devices include: monitor, video card, printer, plotter, projector, speakers.

Input devices are those devices through which information can be entered into a computer. Their main purpose is to implement the impact on the machine. The variety of input devices available has spawned entire technologies from tactile to voice. Although they work on different principles, they are intended to accomplish one task - to allow a person to communicate with a computer. Graphical information input devices are widely used due to the compactness and clarity of the way information is presented to humans. According to the degree of automation of the search and selection of image elements, graphic information input devices are divided into two large classes: automatic and semi-automatic. In semi-automatic devices for inputting graphic information, the functions of searching and highlighting image elements are assigned to a person, and the transformation of the coordinates of the read points is performed automatically. In semi-automatic devices, the process of searching and selecting image elements is carried out without human intervention. These devices are built either on the principle of scanning the entire image with its subsequent processing and conversion from raster to vector representation, or on the principle of tracking a line, which provides the reading of graphic information presented in the form of graphs, diagrams, contour images. The main areas of application of graphic input devices are computer-aided design, image processing, training, process control, animation and many others. These devices include scanners, encoding tablets (digitizers), light pen, touch screens, digital cameras, video cameras, computer keyboard, mouse and others.

Information input devices- devices for entering (entering) data into a computer during its operation. Input devices are those devices through which information can be entered into a computer. Their main purpose is to implement the impact on the machine. The variety of input devices available has spawned entire technologies from tactile to voice. Although they work on different principles, they are intended to accomplish one task - to allow a person to communicate with a computer. Graphic information input devices are widely used due to the compactness and clarity of the way information is presented to humans. According to the degree of automation of the search and selection of image elements, graphic information input devices are divided into two large classes: automatic and semi-automatic. In semi-automatic devices for inputting graphic information, the functions of searching and highlighting image elements are assigned to a person, and the transformation of the coordinates of the read points is performed automatically. In semi-automatic devices, the process of searching and selecting image elements is carried out without human intervention. These devices are built either on the principle of scanning the entire image with its subsequent processing and conversion from raster to vector form, or on the principle of tracking the line, which provides the reading of graphic information presented in the form of graphs, diagrams, contour images. The main areas of application of graphic information input devices are computer-aided design, image processing, training, process control, animation and many others. These devices include scanners, coding tablets (digitizers), light pens, touch screens, digital cameras, video cameras, computer keyboard, mouse and others.

Chapter 1. Devices of information output.

1.1 Monitor

The monitor provides information communication between the user and the computer. The first microcomputers were small units with practically no indication means. All the user had at his disposal was a set of blinking LEDs or the ability to print the results on a printer. Compared to modern standards, the first computer monitors were extremely primitive: text was displayed only in green, but in those years this was almost the most important technological breakthrough, since users were able to enter and output data in real time. With the advent of color monitors, the screen size increased and they moved from laptop computers to the user's desktop. There are two types of monitor: cathode ray and liquid crystal monitor.

Cathode ray monitor... In such a monitor, the image is transmitted using a cathode-ray tube (CRT). CRT is an electronic vacuum device in a glass flask, in the neck of which there is an electron gun, and at the bottom there is a screen covered with a phosphor. As the electron gun heats up, it emits a stream of electrons that move at high speed towards the screen. The stream of electrons passes through the focusing and deflecting coils, which direct it to a specific point on the phosphor-coated screen. Under the influence of electron impacts, the phosphor emits light visible to the user. EL monitors use three layers of phosphor: red, green and blue. To align the electron flows, a shadow mask is used - a metal plate that has slits or holes that divide the red, green and blue phosphors into groups of three points of each color. Image quality is determined by the type of shadow mask used; the sharpness of the image is affected by the distance between the groups of phosphors.

The chemical used as a phosphor has an afterglow time, which reflects the duration of the glow of the phosphor after exposure to an electron beam. The persistence time and the image refresh rate should be consistent with each other so that there is no noticeable image flickering and there is no blur and doubling of edges as a result of overlapping successive frames.

The electron beam moves very quickly, tracing the screen in lines from left to right and from top to bottom along a path called a raster. The horizontal scanning period is determined by the speed of the beam movement across the screen. In the process of scanning (moving across the screen), the beam affects those elementary areas of the phosphor coating of the screen, where the image should appear. The intensity of the beam is constantly changing, as a result of which the brightness of the glow of the corresponding areas of the screen changes. Since the glow disappears very quickly, the electron beam must run across the screen again and again, renewing it. This process is called image renewal (or regeneration).

Liquid crystal monitor... Borrowing technology from laptop display manufacturers, some companies have developed liquid crystal displays, also called Liquid-Crystal Display (LCD) displays. They are characterized by a non-glare screen and low power consumption (some models of such displays consume 5 W, while monitors with a cathode ray tube - about 100 W). In terms of color quality, active matrix LCD monitors currently outperform most EL monitors. LCD monitors use analog or digital active matrices. LCD monitors larger than 15 inches provide both the analog (VGA) and digital (DVI) connectors found on many mid to high cost video adapters. A polarizing filter creates two separate light waves and transmits only the one in which the polarization plane is parallel to its axis. By positioning the second filter in the LCD monitor so that its axis is perpendicular to the axis of the first, light can be completely prevented from passing through. By rotating the axis of polarization of the second filter, i.e. changing the angle between the axes of the filters, you can change the amount of transmitted light energy, and hence the brightness of the screen. The LCD color monitor has one more additional filter; which has three cells for each pixel in the image - one for displaying the red, green, and blue dots. The red, green, and blue cells that form a pixel are sometimes referred to as subpixels.

A dead pixel is a pixel whose red, green, or blue cell is always on or off. Permanently on cells are very clearly visible against a dark background as a bright red, green or blue dot. LCD monitors are available with an active and passive matrix.

Most LCD monitors use thin film transistors (TFT). Each pixel contains one monochrome or three color RGB transistors, packed in a flexible material that is exactly the same size and shape as the display itself. Therefore, the transistors of each pixel are located directly behind the LCD cells that they drive. Currently, two materials are used for the production of active matrix displays: hydrogenated amorphous silicon (a-Si) and low-temperature polycrystalline silicon (p-Si). The main difference between the two is the production price. In order to increase the visible horizontal viewing angle of LCD monitors, some manufacturers have modified the classic TFT technology. In-plane switching (IPS) technology, also known as STFT, involves aligning LCD cells in parallel with the screen glass, applying voltage to the planar sides of the cells, and rotating the pixels for crisp, even display across the entire LCD panel. Super-IPS technology - rearranges LCD molecules in a zig-zag pattern rather than row and column to reduce unwanted color mixing and improve color uniformity on the screen. In a similar technology, Multi-Domain Vertical Alignment (MVA), the monitor screen is divided into separate areas, for each of which the orientation angle is changed.

In passive matrix LCD monitors, the brightness of each cell is controlled by the voltage flowing through transistors whose numbers are equal to the row and column numbers of that cell in the screen matrix. The number of transistors (by rows and columns) determines the screen resolution. For example, a 1024x768 screen contains 1024 transistors horizontally and 768 vertically. The cell reacts to the incoming voltage pulse in such a way that the plane of polarization of the transmitted light wave rotates, and the angle of rotation is the greater, the higher the voltage.

Passive matrix LCD cells are supplied with a ripple voltage, so they are inferior in image brightness to active matrix LCD monitors, each cell of which is supplied with a constant voltage. To increase the brightness of the image, some designs use a control method called double-scan, and the corresponding devices - double-scan LCD monitors. The screen is split into two halves (upper and lower) that operate independently, resulting in a shorter interval between pulses arriving at the cell. Dual scanning not only increases the brightness of the image, but also reduces the screen response time, as it reduces the time to create a new image. Therefore, dual-scan LCD monitors are more suitable for creating fast-moving images.

1.2 Printer

One of the purposes of a computer is to create a printed version of a document, or a so-called hard copy. That is why the printer is a necessary computer accessory. Printers (printing devices) - These are devices for outputting data from a computer that convert information ASCII codes into the corresponding graphic symbols and fix these symbols on paper. The printer expands the relationship of the computer with the material world, filling the paper with the results of its work. In terms of speed capabilities, printers form a range from sluggish to light. They rival plotters for the ability to draw graphics. Today there are three types of printers:

Laser. A laser printer works as follows: an electrostatic image of a page is created on a photosensitive drum using a laser beam. A specially colored powder, called toner, placed on the drum, "sticks" only to the area that is the letters or images on the page. The drum turns and presses against the sheet of paper, transferring the toner onto it. After fixing the toner on the paper, the finished image is obtained.

After downloading the data to the printer, the computer begins the process of interpreting the code. First, the interpreter extracts control commands and document content from the received data. The printer processor reads the code and executes commands that are part of the formatting process, and then performs other instructions to configure the printer (for example, selecting a paper tray, printing on one side or two sides, etc.).

The process of interpreting data includes a formatting phase, during which commands are executed that indicate how the content of the document should be positioned on the page. The formatting process also includes converting font outlines and vector graphics to bitmaps. These bitmap images of characters are placed in a temporary font cache, from where they are retrieved as needed for direct use in one place or another in the document.

The formatting process uses a detailed set of commands to determine the exact location of each character and graphic on each page of the document. At the end of the data interpretation process, the controller executes commands to create an array of points, which will then be transferred to the paper. This procedure is called rasterization. The created array of points is placed in the page buffer and remains there until transferring to paper. Printers using stripe buffers divide the page into multiple horizontal stripes. The controller rasterizes the data of one strip, sends it to print, clears the buffer and proceeds to process the next strip (the page is sent in parts to a photosensitive drum or other printing device).

Once rasterized, the image of the page is stored in memory and then transferred to the printing device, which physically performs the printing process. Printer is a general term for devices that directly transfer an image to paper in a printer and include the following items: laser scanning unit, photosensitive element, toner container, toner dispenser, corotrons, discharge lamp, fusing unit, and paper transport mechanism. Most often, these elements are structurally made in the form of a single module (a similar printing device is used in copying machines).

Jet... In inkjet printers, ionized ink droplets are sprayed onto the paper through nozzles. Spraying takes place in the places where it is necessary to form letters or images.

The data interpretation process for inkjet and laser printing is basically the same. The only difference is that inkjet printers have less memory and a less powerful computing system. Liquid ink is sprayed directly onto the paper - where the dots are formed in the laser printer. Currently, there are two main types of inkjet printing: thermal and piezoelectric. The cartridge consists of a reservoir of liquid ink and small (about one micron) holes through which the ink is pushed onto the paper. The number of holes depends on the printer resolution and can range from 21 to 256 per color. Color printers use four (or more) tanks of different color inks (cyan, magenta, yellow, and black). By mixing these four colors, almost any color can be reproduced.

1.3Plotter

The task of displaying information presented in graphical form arose simultaneously with the advent of computing, and its solution is one of the main goals of computing tools used for design automation. Devices that perform the functions of displaying graphic information on paper and some other media are called plotters or plotters (from the English plotter).

Pen plotters

Pen plotters are vector type electromechanical devices that traditionally display graphic images, various vector software systems such as AutoCAD. Pen plotters create an image using writing elements, collectively called pens, although there are several types of such elements that differ from each other in the type of liquid dye used. Writing elements are disposable and reusable (rechargeable). The nib is attached to the nib holder, which has one or two degrees of freedom of movement.

There are two types of pen plotters: tablet, in which the paper is stationary, and the pen moves across the entire plane of the image, and drum, in which the pen moves along one coordinate axis, and the paper moves along the other due to the capture by the transport shaft. The movements are performed using stepper or linear motors, which generate a fairly large noise. Although the output accuracy of drum plotters is slightly lower than that of flatbed plotters, it satisfies the requirements of most tasks. These plotters are more compact and can automatically cut a sheet of the required size from the roll (A3 pen plotters are usually flatbed).

A distinctive feature of pen plotters is the high quality of the resulting image and good color rendering when using colored writing elements. Unfortunately, the speed of information output in them is low, despite the faster mechanics and attempts to optimize the drawing procedure.

Inkjet plotters

Inkjet imaging technology has been around since the 1970s, but its true breakthrough was only possible with Canon's development of the Bubblejet, a targeted spray of ink onto paper using hundreds of tiny nozzles on a disposable printhead. Each nozzle has its own microscopic heating element (thermistor), which instantly (in 7-10 μs) heats up under the influence of an electric pulse. The ink boils and the vapor creates a bubble that pushes a drop of ink out of the nozzle. When the pulse ends, the thermistor cools down quickly and the bubble disappears.

Printheads can be "colored" and have an appropriate number of nozzle groups. To create a full-fledged image, the standard for printing CMYK color scheme is used, using four colors: Cyan - cyan, Magenta - magenta, Yellow - yellow and Black - black. Complex colors are formed by mixing the main ones, and shades of different colors are obtained by thickening or thinning the points of the corresponding color in a fragment of the image.

Inkjet technology has a number of advantages. These include ease of implementation, high resolution, low power consumption, and relatively fast print speeds. Reasonable price, high quality and great capabilities make inkjet plotters a serious competitor to pen devices, however, the low speed of outputting graphic information and fading over time of the resulting color image without taking special measures limits their use.

Electrostatic plotters

Electrostatic technology is based on the creation of a latent electrical image on the surface of the carrier - a special electrostatic paper, the working surface of which is covered with a thin layer of dielectric, and the base is impregnated with hydrophilic salts to provide the required moisture and electrical conductivity. The potential relief is formed when free charges are deposited on the dielectric surface, which are formed when the thinnest electrodes of the recording head are excited by high-voltage voltage pulses. When the paper passes through the developing unit with the liquid magnetized toner, the toner particles are deposited on the charged areas of the paper. The full color gamut is obtained in four cycles of latent image creation and the passage of the media through four developing units with the corresponding toners.

Electrostatic plotters could be considered ideal devices if it were not for the need to maintain stable temperature and humidity in the room, the need for careful maintenance and their high cost, in connection with which they are purchased by users who have justifiably high requirements for productivity and quality. For maximum efficiency, electrostatic plotters typically operate as network devices with network interface adapters. Also important are the high resistance of the image to the effects of ultraviolet rays and the low cost of electrostatic paper.

Direct output plotters

The image in such plotters is created on special thermal paper (paper impregnated with a heat-sensitive substance). Thermal paper, which is usually fed from a roll, moves along the "comb" and changes color in places of heating. The image is high quality (resolution up to 800 dpi (dots per inch)), but only in monochrome. Considering their high reliability, productivity and low operating costs, plotters of direct image output are used in large design organizations to output proof copies.

Thermal plotters

The difference between these plotters and plotters for direct image output is that a "donor color carrier" is placed in them between the thermal heaters and the paper - a thin, 5-10 micron thick ribbon facing the paper with a coloring layer made on a wax base with a low (less than 100 ° C) melting point.

On the donor tape, areas of each of the primary colors are sequentially applied with a size corresponding to the sheet of the used format. In the process of displaying information, a paper sheet with a donor tape superimposed on it passes under the print head, which consists of thousands of tiny heating elements. The wax melts in the hot spots, and the pigment remains on the sheet. One color is applied in one pass. Its image is obtained in four passes. Thus, each sheet of color image uses four times more ink ribbon than a sheet of monochrome.

Due to the high cost of each print, these plotters are used as part of computer-aided design tools for high-quality output of 3D modeling objects, in cartography systems, and advertising agencies for displaying color proofs of posters and banners for colorful presentations.

Laser (LED) plotters

These plotters are based on electrographic technology, which is based on the physical processes of the internal photoelectric effect in light-sensitive semiconductor layers of selenium-containing materials and the force effect of an electrostatic field. The intermediate imaging medium (rotating selenium drum) in the dark can be charged to a potential of hundreds of volts. A beam of light removes this charge, creating a latent electrostatic image that attracts magnetized fine toner, which is then mechanically transferred to the paper. The toner-coated paper then passes through a heater, causing the toner particles to bake to create an image.

Due to its high speed (an A1 sheet is displayed in less than half a minute), laser plotters are convenient to use as network devices, and they have a network interface adapter as standard. Equally important, these plotters can run on plain paper, which saves on operating costs.

1.4 Projector

A projector is a light device that redistributes the light of a lamp with a concentration of the luminous flux on a small surface or in a small volume. The main element of any projector is a lamp, the light of which, passing through certain elements, hits the screen and thus forms a picture. Depending on which elements the light from the lamp passes through, the projectors are divided into LCD and DLP (micromirror). The advantages of liquid crystal projectors include less negative impact on vision, as well as compactness. Their disadvantage is insufficiently saturated black color (owners of LCD monitors will understand what this is about). The advantage of micromirror projectors is a better picture, and their main disadvantage is considered to be fatigue of vision during very long viewing.

Like any technical device, projectors have characteristics that you should pay attention to first. At first, this is the so-called "base graphics resolution". It is indicated by two numbers representing the number of horizontal and vertical points. Like monitors, the resolution is 800x600, 1024x768, etc. up to 1600x1200. Of course, the higher the resolution, the better the picture quality will be. For a home projector, the main task of which is to watch movies, 800x600 resolution will be enough. This is due to the fact that films intended for viewing on a TV screen have an even lower resolution, so 800x600 is quite enough. Secondly - the brightness of the projector. The brighter the projector, the better. If the brightness is too low, it may be necessary to completely darken the room for comfortable viewing. And the brightness of 1000 lumens (lumen is a unit of brightness measurement) will be quite enough for home conditions, lower values \u200b\u200bare practically not found today. The operating conditions of the projector must be taken into account. If it is installed in a separate room with the possibility of complete dimming, then such a parameter as brightness is not too important. If the projector is planned to be used in a living room, where it is difficult to achieve complete darkness, then you should pay attention to such a parameter as brightness. Thirdly- the contrast of the projector. With a low contrast ratio, dark scenes in movies may simply not be visible. The contrast ratio of a home video projector should be between 1000: 1 and 2000: 1.

1.5 Columns

Speakers, or acoustic system, is another output device that connects to a computer (there is an input socket on the back of the motherboard) and serves to reproduce sound effects, music, films, etc. Currently, there are two principles of acoustic systems: active and passive.

It is believed that active acoustics used mostly by professionals, although it connects to computers too. The sound is sent from the dvd player through the amplifier (receiver) directly to the speakers of the speaker system. Amplification of the sound signal plays a key role in this process. How can sound be amplified? There are two ways. First this is when, before being fed to the speakers, the audio signal enters the amplifier, and second - using the speaker system itself, in the speakers of which the amplifier is built.

In addition, the design of active acoustics allows for feedback between the amplifier and the speaker. This allows the amplifier to change the load on the speaker during maximum load and prevent damage to the latter. Because the amplifiers and speakers in the powered speakers are directly connected, the speaker system achieves maximum performance. This provides a very good sound output with small speaker sizes. Active speaker systems for home use usually consist of a subwoofer and a set of 5 satellites. An amplifier is built into the subwoofer, which is distributed over six speakers.

But active speakers have a drawback - the impossibility of modernization. Such a speaker system will always sound the same. The significance of this fact is very significant. Having become interested in acoustic systems, the buyer turns into a lover of sound technology and from time to time tries to improve the sound quality of his home acoustics. Therefore, the owner of active acoustics will have to come to terms with the quality of the sound produced with its help once and for all. They try to make active speakers initially high.

At work passive speaker the built-in crossover heats up, because it takes on a fairly large output power. Manufacturers try to avoid this in various ways, but the main thing is to understand the essence of this process. The amplifier sufficiently loads the electronics of the speaker system, as a result of which the quality of the output sound, just like the characteristics of passive speakers, change. If the speakers are used in a home theater, then the amateur is unlikely to hear the difference. But for a professional, this difference will be quite critical. Passive loudspeakers need to be slightly more powerful than the amplifier in order to cope with the power supplied to them at critical moments. Otherwise, when the amplifier is more powerful than the acoustics, the speakers may simply fail. Passive loudspeakers cannot provide feedback to the amplifier to deliver less power, and it cannot monitor the load itself. Despite the drawbacks, a passive loudspeaker is not so bad. Most buyers of acoustic systems buy it for a home theater, computer, and at home, as you know, comfort and coziness are very much appreciated. Active acoustics require a separate power cord to be connected to each speaker. So connecting all the active speakers to the network can be very confusing. The next point is much more important. Since all speaker systems are divided into classes, when using passive acoustics, you can upgrade the system over time by purchasing a new amplifier and receiver. The sound quality of good passive speakers can improve dramatically. Therefore, when choosing passive acoustics, the speakers can be taken, as they say, "for growth."

Chapter 2 Input Devices

2.1 Keyboard

Now the main widespread input device

the computer is a keyboard (keyboard device). She implements

interactive communication between the user and the PC:

User commands input, providing access to PC resources;

Writing, correcting and debugging programs;

Entering data and commands into the process of solving a problem.

The MFII keyboard standard is now adopted. Conditionally in it

five groups of keys can be distinguished, carrying their functional shipment.

Other types of keyboards include special keys for

blind people with tactile dots on the keys; keyboards for shops and

warehouses equipped with devices for reading bar codes or for

reading magnetic cards; industrial keyboards - touch, having in

as protection against harmful influences (chips, ash, etc.)

additional covering of keys with special touch foil; keyboard

for medical institutions with devices for reading information from

insurance cards. Currently, there are keyboards with additional

keys for the convenience of working with a particular operating system (OS),

for example a keyboard for Windows 95.

Thus, the choice of keyboard depends on the OS with which

supposed to work.

2.2 Mouse

It serves for data entry or single commands selected from the menu

whether textograms of graphic shells displayed on the monitor screen.

The mouse is a small box with two or three

keys and a recessed ball, freely rotating in any direction

on the bottom surface. It connects to the computer using

special cord and requires special software support.

A flat surface is required to operate the mouse, for this purpose

use rubber mats.

Since you cannot enter a series of commands into the computer using the mouse,

therefore, the mouse and keyboard are not interchangeable devices. Appointment

graphic shells - in providing the initialization of many commands without

long typing them from the keyboard. This reduces the likelihood of typos and

saves time. On the object in the form of a tectogram, a menu item is selected or

symbol and is initialized by mouse click. Of course, when typing or

the use of a mouse may be irrational for some functions,

if, for example, these functions are performed by pressing the function keys.

Nowadays there is also an optical mouse where the signal

transmitted by the mouse beam to a special mat and analyzed

electronics. While tailless (cableless) is less common

infrared mouse (its principle of operation is similar to that of remote controls

remote control) and a radio mouse.

In portable PCs (Lapton, Notebook), the mouse is usually replaced with a special built-in

into the keyboard with a ball on a stand with two keys on the sides, called

Its principle of operation is the same as that of a mouse. Despite

the presence of a trackball, the user of a laptop can use the usual

2.3 Scanners

For direct reading of graphic information from paper or

other media in the PC uses optical scanners.

The scanned image is read and digitized

elements of a special device: CCD - chips.

There are many types and models of scanners. Which one to choose,

depends on the tasks for which the scanner is intended.

The simplest scanners only recognize two colors: black and white.

These scanners are used to read bar codes.

Hand-held scanners are the simplest and cheapest. The main disadvantage is

that the person himself moves the scanner over the object, and the quality of the received

the image depends on the skill and firmness of the hand. Another important disadvantage is

small scanning bandwidth, making it difficult to read wide

originals.

Drum scanners are used in professional typography

activities. The principle is that the original on the drum

illuminated by a light source, and photosensors convert the reflected radiation into

digital value.

Sheet scanners. Their main difference from the previous two is that

when scanning, the ruler with CCD elements is fixed, and the sheet

with the scanned image moves relative to it using special

Flatbed scanners. This is the most common type for

professional work. The scanned object is placed on a glass sheet,

the image is read line by line at a uniform speed by the reading head from

CCD - sensors located at the bottom. A flatbed scanner can be

equipped with a special device slide attachment for scanning

transparencies and negatives.

Slide scanners are used to scan microimages.

Projection scanners. A relatively new direction. Color projection

the scanner is a powerful multifunctional tool for entering into a computer

any color images, including three-dimensional. It may well replace

camera.

Nowadays, scanners have another application - reading

handwritten texts, which then special recognition programs

characters are converted to ASC II codes and can be further processed

text editors.

Conclusion

In this test and course work, sufficiently detailed information about the devices for output / input of information and the principles of their operation was provided. The work of a modern computer cannot be imagined without equipping it with the above devices, since they provide irreplaceable assistance when the user works with a computer, and knowledge of the principles of operation of these devices ensures their more efficient use.

Conclusions on the performed laboratory work. During ...

Computer device and organization input withdrawal information

Abstract \u003e\u003e Informatics

External and internal devices of the computer. Organization input withdrawal information in a computer ……………………………………………………………………. CHAPTER II. DEVELOPMENT ... c) internal devices. 3.Examine the organization input - withdrawal information in a computer; 4. Conduct a case study ...

Information... Quantity unit information

Abstract \u003e\u003e Informatics

Parts: devices input information processing devices information storage devices withdrawal information... Structurally, these ... Additionally, other devices can be connected input and withdrawal informatione.g. speakers, printer, ...