What is an information output device? Additional devices. Information. Unit of measurement of the amount of information

PC monitor is the most important device display text and graphic information. Monitors are available in color and monochrome. They can work in two modes: text or graphic.

Digital (TTL) monitors

The term TTL (Transistor Transistor Logic) refers to a standard series of digital chips used in electronic technology. And as always, when we're talking about about digital technology, it is read that signals have only two states: logical 1 and logical 0 (“yes” and “no”).

Monochrome monitors

When we talk about TTL monitors, we most often mean monochrome monitors, the control signals of which are generated by graphics cards of the MDA or Hercules standards. It is already clear from the very concept of monochrome that a point on the screen can only be light or dark. At best, the points can also differ in their brightness. The Hercules monitor is capable of displaying images only in the form of light and dark dots with a resolution of 728x348 and can work in conjunction with the entire system only with a video card. Other monitors produce images (similar to televisions) as a result of a high frame rate of the image with minimal flickering. This principle is not implemented in the Hercules type monitor. A TTL monitor can also be distinguished from an analog one by the number of connector pins for connecting to a PC. The Hercules monitor has a 9-pin D-type plug (male). However, be careful: the RGB monitor described below also has the same connector.

RGB-monitors

Digital RGB monitors (Red/Green/Blue - red/green/blue) are mainly designed to connect to an EGA card. Such devices also support monochrome mode with a resolution that allows you to display 16 colors. RGB monitors have a lower resolution compared to Hercules monitors. Such monitors can be recognized by the characteristic color markings on the front panel.

Analog monitors

In this case we'll talk about monitors that work with VGA and higher video cards. They are capable of supporting VGA standard resolutions of 640x480 pixels and higher.

The name "analog" does not mean resolution capabilities, but, unlike TTL monitors, the way information about the colors represented is transferred from the video card to the monitor. When working in True Color mode, there must be an appropriate number of lines to convey a color palette with 24 degrees of depth. Therefore, digital monitors do not transmit such information. This is the only small area of ​​PC where the analog principle of information processing has remained to this day. Analog signal transmission is carried out in the form of voltages of various levels. VGA monitors can operate not only in color, but also in monochrome mode. In the latter case, colors and their shades are replaced by shades of gray.

The principle of image formation in monitors based on a cathode ray tube (all of the above) is not much different from the principle of operation of a TV. A beam of electrons emitted by an electron gun (cathode) hits a screen coated with a phosphor, causing it to glow.

Liquid crystal displays (LCD)

At the end of the 80s, the first notebook (laptop) PC models were introduced. The main factor that led to the reduction in their weight was, first of all, the use of liquid crystal displays (Liquid Crystal Display, LCD) as information display devices. The screen of such a display consists of two glass plates, between which there is a mass containing liquid crystals, which can change their optical structure and properties depending on what is applied to them. electric charge. This means that the crystal, under the influence of an electric field, changes its orientation, thereby the crystals reflect light differently and make it possible to display information. Because the resistance is relatively high, the crystals can only move at a certain speed. This property was clearly manifested when moving the mouse cursor across the LCD screen of the first displays. When moving quickly, the cursor simply disappeared. The liquid crystals received an electrical impulse, but did not have time to react when the cursor had already moved to another place. To reduce blur and increase image contrast, liquid crystal displays were developed using DSTN (Dual-scan Super-Twisted Nematic) technology. Toshiba has developed a liquid crystal display with an active matrix using thin-film transistors, the so-called TFT (Thin Film Translator) technology. There is no slowdown in a TFT display, unlike a DSTN display. A variation of DSTN technology is MLA (Multiline Addressing) technology. One of the disadvantages of such displays may be familiar to you from wristwatches, calculators, etc., which work with LCD indicators. If you look at the screen at an angle, you can only see a silver surface. The image and sharpness of LCD screens depend on the viewing angle. Good image quality is achieved at an viewing angle of 90°. Liquid crystals themselves do not glow, so such monitors require backlighting or external lighting.

Gas plasma monitors

For gas plasma monitors there are no such restrictions as for LCD displays. They also have two glass plates, between which there are not crystals, but a gas mixture, which is illuminated in appropriate places under the influence of electrical impulses. The disadvantage of such monitors is that they cannot be used in laptop and battery-powered computers due to their high current consumption.

Main characteristics of monitors:

Vertical (frame) and horizontal (line) scanning frequency

Screen resolution, i.e. number of dots (pixels) reflected on the screen

Screen diagonal, i.e. distance between bottom right and top left corners

Monitor grain size, i.e. phosphor dot size on the inner surface of the screen

Type of cathode ray tube, on which the quality of the phosphor coating depends

Speed ​​of switching from text to graphic mode, i.e. change resolution

Availability and quality of anti-reflective coating (the screen acquires a blue tint)

Radiation level (it is advisable to purchase it together with the monitor) protective screen)

A monitor is a device for visually displaying information. The signals that the monitor receives (numbers, symbols, graphic information and synchronization signals) are generated by the video card. Thus, the monitor and video card are a kind of tandem, which must be configured accordingly for optimal performance. In order to ensure efficient work both components must fit together optimally. Currently there are more than 30 modifications various types video cards that differ in design, parameters and standards. Naturally, it is not possible to describe all the diversity of these types. In this regard, it was decided to classify video cards according to accepted standards. Perhaps, with such a division, standards will be considered that no longer play a significant role in the PC and are obsolete, but they are worth mentioning for the sake of completeness.

Designations:

MDA - Monochrome Display Adapter (monochrome display adapter)

CGA - Color Graphics Adapter

HGC - Hercules Graphics Card ( graphics card Hercules)

EGA - Enhanced Graphics Adapter (advanced graphics adapter)

VGA - Video Graphics Adapter (video graphics adapter)

SVGA - Super Video Graphics Adapter (super video graphics adapter)

Currently, MDA, CGA, Hercules and EGA standard monitors are not used, because they do not have adequate resolution, which leads to rapid eye fatigue. Moreover, they do not have the opportunity soft download Cyrillic fonts (Russian letters). Recently, SVGA monitors have become most widespread.

Printer

A printer (or printing device) is designed to output information onto paper. All printers can also output pictures and graphics, color or black and white images. There are several thousand printer models that can be used with the IBM PC. Let's look at the main types.

Matrix (needle) printers

The pin printer (Dot-matrix-Printer, also known as matrix) has long been the standard output device for PCs. In the recent past, when inkjet printers still performed unsatisfactorily and the price of laser printers was quite high, needle printers were widely used. They are still often used today. The advantages of these printers are determined primarily by the printing speed and their versatility, which consists in the ability to work with any paper, as well as the low cost of printing. When choosing a printer, you should always proceed from the tasks that will be assigned to it. If you need a printer that needs to print various forms all day without interruption, or printing speed is more important than quality, then it is cheaper to use a needle printer. If you want to get a high-quality image on paper, then use an inkjet or laser printer, but in this case, naturally, the cost of each sheet will increase significantly. Pin printers have a significant advantage - the ability to print several carbon copies of a document at once. The disadvantage of such printers is the noise they produce during operation. The principle by which a needle printer prints characters on paper is very simple. A pin printer produces characters using multiple pins located in the printer head. The mechanics of paper feeding are simple: the paper is pulled in using a shaft, and an ink ribbon is placed between the paper and the printer head. When a needle hits this tape, a painted mark remains on the paper. The needles located inside the head are usually activated electromagnetically. The head moves along a horizontal guide and is controlled by a stepper motor. There are heads: 9*9 needles, 9*18, 18*18, 24*37. The needles are arranged in one or two rows. Using a multi-color ink ribbon, color printing is possible.

Output devices

Monitor. Monitor is universal device output information and connects to the video card installed in the computer.

The image in computer format (in the form of sequences of zeros and ones) is stored in video memory located on the video card. The image on the monitor screen is formed by reading the contents of video memory and displaying it on the screen.

The frequency of image reading affects the stability of the image on the screen. In modern monitors, image updating usually occurs at a frequency of 75 or more times per second, which ensures comfortable perception of the image by the computer user (a person does not notice the flickering of the image). For comparison, we can recall that the frame rate in cinema is 24 frames per second.

IN desktop computers Cathode ray tube (CRT) monitors are usually used - fig. 4.14.

The image on the monitor screen is created by a beam of electrons emitted by an electron gun. This beam of electrons is accelerated by high electrical voltage (tens of kilovolts) and falls on the inner surface of the screen, coated with a phosphor (a substance that glows under the influence of an electron beam).

Rice. 4.14. CRT monitor

The beam control system forces it to run across the entire screen line by line (creates a raster), and also regulates its intensity (accordingly, the brightness of the phosphor dot). The user sees the image on the monitor screen, since the phosphor emits light rays in the visible part of the spectrum. The smaller the size of the image dot (phosphor dot), the higher the image quality; in high-quality monitors, the dot size is 0.22 mm.

However, the monitor is also a source of high static electrical potential, electromagnetic radiation and x-ray radiation, which may have adverse effects on human health. Modern monitors are practically safe, as they meet strict sanitary and hygienic requirements set out in the international safety standard TCO"99.

Laptop and pocket computers use flat-panel liquid crystal (LCD) monitors. Recently, such monitors have begun to be used in desktop computers.

LCD (Liquid Crystal Display, LCD monitors- rice. 4.15) are made of a substance that is in a liquid state, but at the same time has some properties inherent in crystalline bodies. In fact, these are liquids that have anisotropy of properties (in particular, optical ones) associated with order in the orientation of molecules. Molecules of liquid crystals under the influence of electrical voltage can change their orientation and, as a result, change the properties of the light beam passing through them.

Rice. 4.15. LCD monitor

The advantage of LCD monitors over CRT monitors is the absence of harmful to humans electromagnetic radiation and compactness.

Monitors may have different screen sizes. Screen diagonal size is measured in inches (1 inch = 2.54 cm) and is usually 15, 17 or more inches.

Printers. Printers are intended for printing on paper (creating a “hard copy”) of numerical, text and graphic information. According to their operating principle, printers are divided into matrix, inkjet and laser.

Dot matrix printers(Fig. 4.16) are impact printers. The print head of a dot matrix printer consists of a vertical column of small rods (usually 9 or 24) that, under the influence of a magnetic field, are "popped" out of the head and strike the paper (through the ink ribbon). As the print head moves, it leaves a string of characters on the paper.

Rice. 4.16. Matrix printer

The disadvantages of dot matrix printers are that they print slowly, produce a lot of noise, and print quality is poor (about the quality of a typewriter).

In recent years, black-and-white and color inkjet printers have become widespread (Fig. 4.17). They use an ink print head that, under pressure, releases ink from a series of tiny holes onto the paper. As the print head moves along the paper, it leaves a line of characters or a strip of image.

Rice. 4.17. Jet printer

Inkjet printers can print quite quickly (up to several pages per minute) and produce little noise. The quality of printing (including color) is determined by the resolution of inkjet printers, which can reach photographic quality 2400 dpi. This means that a 1-inch horizontal stripe of image is formed from 2400 dots (ink drops).

Laser printers(Fig. 4.18) provide virtually silent printing. Laser printers achieve high printing speeds (up to 30 pages per minute) through page-by-page printing, in which the entire page is printed at once.

Acoustic speakers and headphones. Used to listen to sound acoustic speakers or headphones that connect to the sound card output.

Questions to Consider

1. What physical parameters affect the quality of the image on the monitor screen?

Practical tasks

4.6. Get acquainted with the computer structure and history computer technology by visiting virtual computer museums on the Internet.

Monitor

A monitor is a device for visually displaying all types of information that is connected to a PC video card.

There are 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 produced by an electron gun. High electrical voltage accelerates a beam of electrons, which falls on the inner surface of the screen, coated with a phosphor (a substance that glows when exposed to a beam of electrons). The beam control system drives it line by line across the entire screen (creates a raster) and regulates its intensity (the brightness of the phosphor dot).

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

Figure 1. CRT monitor

LCD monitors ($LCD$) based on liquid crystals

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

The advantage of LCD monitors over $CRT$ monitors is the absence of electromagnetic radiation harmful to humans and their compactness.

The image is digitally stored in video memory, which is located on the video card. The image is displayed on the monitor screen 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 image reading. The image refresh rate of modern monitors is $75$ or more per second, which makes image flickering invisible.

Figure 2. LCD monitor

Printer

Definition 2

Printer - peripheral device, designed to display numerical, text and graphic information on paper. Based on the principle of operation, laser, inkjet and matrix printers are distinguished.

Provides virtually silent printing, which is formed due to the effects of xerography. The entire page is printed at once, which ensures high printing speed (up to $30$ pages per minute). High print quality 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 releases ink under pressure from tiny holes onto the paper. The print head, moving along the paper, leaves a line of characters or a strip of image. The print quality of an inkjet printer depends on its resolution, which can reach photographic quality.

Figure 4. Inkjet printer

It is an impact printer that produces characters using several needles located in the printer head. The paper is pulled in by a rotating shaft, and an ink ribbon passes between the paper and the printer head.

On the print head of a dot matrix printer is a vertical column of small rods (usually $9 or $24) that are "pushed" out of the head by a magnetic field and hit the paper (through the ink ribbon). The print head, as it moves, leaves a string of characters on the paper.

Dot matrix printers print at low speed, produce a lot of noise, and have poor print quality.

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 drawn with a pen. Used to obtain complex design drawings, architectural plans, geographic and meteorological maps, and business diagrams.

Figure 6. Plotter

Projector

Definition 4

Multimedia projector (multimedia projector) is a stand-alone device that transmits (projects) information from external source, which can be a computer (laptop), VCR, DVD player, video camera, document camera, television tuner, etc.

$LCD$ projectors. The image is formed using a translucent liquid crystal matrix, of which $3LCD$ models have three (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 cathode ray tubes of basic colors. Now they are practically not used.

Figure 9. CRT projector

$LED$ projectors. The image is formed using an LED light emitter. The advantages include long term service life, which is several times longer than the service life of lamp-based projectors, the ability to create ultra-portable models that can even fit in your 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 on a PC. The built-in speaker was the main audio reproduction device until inexpensive sound cards became available.

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

64-bit Windows does not support the built-in speaker, which is due to a conflict between the recovery 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

Every day, sitting down at his workplace in the office, a person takes the mouse in one hand and begins to perform his duties. He knows why he needs a keyboard, a printer, a scanner, but he doesn’t even realize that they have their own official name. All this - and the output of information.

How it works

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

In general, computer science deals with the study of the structure of a personal computer. She defines input and output devices as components of a typical personal computer that provide interaction between the user and the computer. But before we begin to describe all the devices, the basic I/O device deserves special mention. It's also BIOS. This chip is motherboard personal computer provides an initial check of all connected devices and starts the operating system.

Classification

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

The first point will be the main input/output devices. In fact, only one item could be specified here - the keyboard, since without it not a single user's computer will continue to boot. You can completely turn off the monitor and mouse, but the computer will not work without the keyboard. The exception is server computers, which operate without any connected external devices at all. So, the main input/output devices, without which the average user cannot work, are:

• keyboard;
• monitor;
• mouse.

You can also select additional I/O devices:

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

This is not a complete list of possible devices that interact with the user; the list of them could take a very long time. So let's look at the computer's input/output devices in more detail.

Monitors

Computer monitors have undergone many changes throughout their history. Starting from old ones using a cathode ray tube to modern LCDs.

The monitor or display itself is a device that provides 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 text information only.
• Graphic. We come across these monitors every day when we sit down at Personal Computer. They are intended to present information in graphic form, including video.

2. By screen type.

• based on something you might have worked with in 2000.
• LCD is a liquid crystal "flat" display that is now used everywhere. This type of monitor is also used in laptops.
• Plasma.
• Laser - not yet in mass production.

Keyboards

What about keyboards? The imagination of manufacturers in this area has stepped far forward, and their sense of humor pushes them to the most daring experiments.

Among the keyboards you can find minimalistic options - without a side additional 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 “obscure buttons” for “blondes”. There are also silicone keyboards that roll up to make them easier to carry, or simply fold into three folds.

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

Mouse

Computer mice are computer input/output devices without which work is impossible regular user. If an advanced user can navigate through folders and files, as well as some programs and games, solely using the keyboard, then the average person is simply not able to do this. Throughout its existence computer mice have not undergone such significant 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 it was replaced by optical mice based on LEDs. The first generation of optical mice required the presence of a special mat, on which shading was applied to increase the light reflectivity of the surface. Moreover, the first mice had personal mouse pads; they could not be replaced with others.

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

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

Another version of the mouse is found as an addition to a graphics tablet. Such induction mice are quite inconvenient to use, since they cannot be replaced with more comfortable ones that fit your hand, and the increased accuracy is discredited by the small ability 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 to replace inkjet printers Laser ones are coming, but previous generations continue to live. What is the reason for this? The fact is that they are suitable for different types of printing different types printers. They all perform the same function and are not very different in design. The following types of printers exist:

• matrix;
• jet;
• laser;
• thermal printers.

When choosing such a device, people usually adhere to their 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 is that scanners enter information into the PC exclusively in graphic form. The development of scanners has stalled solely on changing their sizes. At first they became smaller and more compact, and then they were replaced by huge “combines” - output and input devices that combine a copier, printer and scanner.

Sound

Each of us likes to watch movies and listen to music at home. Speakers, headphones, audio systems and home theater systems, as well as headsets and microphones, all refer to audio output and input devices.

There are many different microphones and speakers, varying in the quality of audio recording or playback, respectively. Probably, any person can determine for himself how good the sound of a particular speaker is. When choosing an audio system, it is also recommended to be guided by the design and power to your taste.

Video

To work with video graphics, special output and input devices are used - cameras and projectors.

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

• Diascopic. The image appears due to the passage of light rays through a transparent film with a picture.
• Episcopic. Creates an image using the projection of reflected rays.
• Epidiascopic creates an image of both transparent and opaque 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 on a large surface.

As for cameras, there is no need to tell anyone. In most cases, the higher the camera resolution, the better. finished picture. With the advent of laptops, USB cameras began to be replaced by ones built into the laptop monitor.

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

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

An example is HP printers. Yes, they are considered one of the best, but replacing an exhausted cartridge or just a minor malfunction will cost you a pretty penny solely because of the manufacturer’s reputation.

When purchasing a sound system, do not hesitate to check the sound and performance of the 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 existing 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 supplied. A striking example is Asus laptops. In most cases, nowhere on the store’s website is there information that manufacturers require a branded box when contacting the service center.

Be careful and have a good shopping!