The main types of peripheral devices. Computer Peripherals

PC peripherals provide the ability to exchange information between the computer and the user. Without all these devices, all the possibilities and all the power of any personal computer are useless.

PC peripherals are all external devices connected to, they are distinguished from the components contained in the box of the system unit. The interaction of a computer with the "outside world" is carried out with the help of peripherals. , and are integral peripherals of any personal computer, but there are many other useful devices besides them.

The information output devices, along with the monitor, include. The need for printing devices, even in the context of the transition to electronic document management, will never disappear, and in many cases it is more convenient to use material printed on paper than to view texts and pictures on a gadget monitor.

Dot-matrix printers were the first to appear, but due to their low speed and loud grinding sound during printing, they were quickly replaced first by inkjet and then by laser printers. Today's inkjet printers are notable for their low price and the possibility of color printing, their “minuses” include relatively low print speed and high cost of cartridges, which, however, does not prevent them from being used at home. In offices, an inkjet printer is used only when color printing is required.

For printing official documents, laser printers are more suitable, the price of which is higher than that of inkjet printers, but the low cost of printing, which is determined by the low cost of refilling and the high volume of printing per charge, quickly justifies their cost. High print speed and quietness add "pros" to these devices.

The next most important peripheral device of a personal computer, in our opinion, is a scanner. The scanner translates the images into computer memory, after which we can do everything that the PC software allows us to do with the image. The most common use of a scanner is to convert photographs into electronic form, save paper documents to an electronic database, and scan texts for subsequent editing.

Scanners that exist today are: hand-held scanners, flatbed scanners (the most convenient in the office and at home) and pull-through scanners. It is clear that the quality of the picture depends on the static nature of the scanned image during its capture, which is why flatbed scanners are most widely used, despite the fact that these are rather bulky devices.

Multifunction devices (MFPs) that combine a printer, scanner and copier are becoming more and more popular. Thanks to their versatility, MFPs save desktop space. But such devices also have their drawbacks, which lie in the average performance of their functions and low reliability, and even if any one component, such as a printing device, breaks down, both the scanner and the copier will have to be taken to the repair shop.

Of course, the list of PC peripherals does not end here, they include all devices that we can connect to a computer, these are speakers, game joysticks, webcams and microphones, etc. But the most important devices, in our opinion opinion especially for work are printers and scanners.

A peripheral device is a computer hardware that is structurally separate from the PC itself, but, at the same time, functions under its control. Such devices are intended to expand the functionality of a personal computer: organizing input-output, printing typed texts and images, exchanging data with other personal computers, to control a variety of external devices, including household appliances.

This peripheral device is designed to print various text and graphic information: photographs, drawings, typed texts, graphs, drawings, etc.

When possible, colors are divided into:

1. colored with the ability to print not only color pictures, but also full-fledged photographs (photo printers);
2. Black and white, which print plain text and graphics in grayscale but no color output.

Structurally, the currently existing printing devices can be divided into:

• Matrix, where the print head contains "needles" which strike through the ink ribbon on the paper and form characters and an image. The resolution of such printers can reach 300 dots per inch (dpi), and the number of needles in the head is 9 and 24 pieces. Flaw- low print speed and increased noise, but at the same time, such devices have the lowest cost per print and the ability to print through carbon paper;
• Inkjet, the very name of which speaks for itself - printing is carried out due to a controlled jet of ink using nozzles in the print head. Inkjet printers are available in both black and white and color, and color inkjet printers are excellent for printing photographs due to their high resolution (600-900 dpi) and excellent color reproduction characteristics. The print speed reaches 10-20 pages per minute.
  The main disadvantage such devices is the fact that if the printer is not used for a long time, then the print head quickly becomes unusable (the nozzles become clogged), and the cost of replacing it is comparable to the cost of the printer;
• Laser where the formation of the image on paper occurs by xerography. The image is transferred to paper using a laser beam and a special powder, which is poured into a special cartridge. Laser printers are characterized by high resolution (up to 1200 dpi for black and white and up to 2400 for color), high print speed (up to 60 pages per minute), low print cost, ease of maintenance and maintenance (they do not “dry out” like inkjet printers) , the possibility of color printing in color models of these devices. Due to the fact that in recent years the cost of these devices has decreased significantly, they are increasingly used by ordinary users at home.

The world's first dot matrix printer was released in 1964. But at first it was used not in computer systems, but for printing out the exact time ⌚ in the design of Seiko watches.
Cm. .

Although this device is practically not common among home PC users, it turns out to be very valuable for those who constantly work with drawings or drawings in large formats. Like a printer, a plotter is capable of printing on paper images made on a computer - drawings and drawings of very large formats (up to the A0 format). Design and architectural bureaus are supplied with such devices, they are indispensable for printing large, demonstration diagrams, diagrams and drawings for various presentations.

The first models of the plotter differed from the printer in that they did not mix colors - they constructively drew with "rapidographs" filled with each color. It was possible to select the thickness of the lines, but the color always remained one of the set installed in the plotter. Today, the latest models are completely devoid of this shortcoming.

Like a printer, a scanner is by far one of the most popular devices for almost all PC users, both office and industrial, and home. It is intended for scanning (making a visual copy) of any images and saving them in digital form on any storage medium. Today's scanners, having evolved from slow and primitive devices, are today a model of manufacturing technology and scientific achievements.

Most models have impressive technical characteristics that determine the quality of the resulting copies:

• Optical resolution. One of the most important characteristics that is directly responsible for the quality of the resulting image when scanning. For modern models, this value can reach 11,000 dpi. True, you should not chase after such parameters and lay out “extra money” if, for example, high-quality printing on a laser printer requires only 100-200 dpi and 96 dpi when outputting to a monitor;
• Scan speed. It is also an important value, which allows you to significantly save time when processing a large number of images. There are models in which this value reaches up to 80 pages per minute! Typically, this indicator ranges from 1 to 3;
• Scanner dynamic range. Has values ​​on a logarithmic scale from 0 to 4. In this case, the value "0" characterizes absolute transparency, and "4" - an absolutely black surface. To obtain a high-quality image of photographs and other flat drawings, a density equal to 2 is required. If it is necessary to obtain a professional result, this value should be at least 3.2;
• Optical density. A value that characterizes the ability of the scanner to distinguish gradations of brightness. From a theoretical point of view, a 12-bit scanner is able to distinguish more gradations of brightness, but in practice this is not always the case. You can focus on the indicator of professional devices, which is 3 or more units;
• Color depth. This is an indicator that indicates how many shades of colors this scanner model can distinguish. To date, there are devices that have this figure equal to - 24, 30 and 36 bits / pixel. For comparison, 24 bits is enough to distinguish 16.7 million colors. An interesting fact is that the human eye is not able to distinguish between 24 and 32 bit images.

Structurally, all scanners are divided into:

1. Manual. The image is scanned by swiping across it;
2. Tablet. Great for home and office use when scanning photos or any other type of image;
3. Sheet-fed. Scanning is carried out by pulling the sheet through a special reader. The parameters are similar to flatbed scanners;
4. drums, are used exclusively for printing purposes, as they have highly professional parameters and are very expensive.

Today, these devices are very popular with office and home PC users, as this peripheral device is two (and in most cases) three devices "in one bottle" - printer, scanner and copier. Of course, this is very convenient - space is greatly saved on the table, and the cost of such a unit is much lower than the sum of these two or three devices.

The parameters of the MFP are identical to the parameters of the individual devices included in it, therefore, when choosing such a unit, you should consistently focus on them, that is, evaluate the technical characteristics of the printing device (printer) that is part of the MFP, and then the scanner, and after that make a decision. Sometimes such devices can have excellent data for the scanner, but at the same time, average print settings.

For many years, all motherboard manufacturers have included a sound card in their composition. That is, almost all PCs are capable of playing sound and music files, listening to music and watching videos with sound. In addition, as a rule, the motherboard also has audio inputs for connecting external devices - a microphone, tape recorder, external CD and DVD player, and other sound-reproducing devices.

In order to take full advantage of this technical possibility, it is necessary to have either an active speaker system or headphones for sound reproduction. An active speaker system is a pair of acoustic emitters (speakers) with a built-in or external sound amplifier.

Most modern models have a built-in amplifier right in the case of one of the speakers. which, on the one hand, is convenient - it saves working space, on the other hand, such a design, of course, has rather mediocre sound characteristics compared to high-quality models, in which the amplifier, as a rule, is always external. But it should be clearly understood that the "regular" audio codec built into the motherboard also does not shine with outstanding parameters, therefore, in most cases, the use of such acoustic systems is quite justified.

For more or less high-quality sound reproduction using a standard sound card, you should select acoustics that have two (or better three) frequency bands and a power of at least 15-20 watts. At the same time, we are not talking about loud listening to sound, although the greater the sound power of the speaker system, the louder your speakers will sound, of course, we are talking about the power reserve of your speakers for better sound reproduction even when listening at minimum volumes. Of course, you can also buy speakers that seem to have a “decent” output power, but at the same time, the sound quality leaves much to be desired.

If the acoustic system is supposed to be used in the most minimal way (for example, for holding conferences on the Internet via Skype, working with applications, etc.), then, of course, in order to save money, you can buy a small pair of speakers that have only one , wide band playback. In this case, you can also think about purchasing headphones, and complete with a microphone.

When choosing headphones, you should pay attention to at least three main parameters:

1. Frequency response, which should be no worse from 20 Hz to 20 kHz;
2. Active resistance, the value of which should be in the range from 16 to 32 ohms. With less resistance, the volume of the sound is higher, but it should be borne in mind that the amplifier must be designed for low resistance;
3. Sensitivity. This indicator directly determines the sound volume and should be no worse than 98-100 dB, otherwise, portable devices that do not have a powerful sound output simply cannot “shake” them and the sound will be quiet.

Always pay attention to the material of the ear pads - they are directly adjacent to the ears, and this will determine how comfortable you will be when listening, especially for a long time.

If the use of a microphone is intended only for conferences and conversations over the network, then it makes sense to purchase a webcam, which, in addition to the camera itself, also has a built-in microphone. In this case, you can save not only on the working space near the monitor, but also money.

One of the currently popular peripherals designed for inputting video data into a PC and their subsequent processing - saving, transferring, etc.

The main parameters that determine the quality of this device:

• Permission. Defined in pixels. The higher the resolution of the device, the better the picture will be when input into the PC. A good resolution can be considered the size of 640x480, expensive models have the value of this indicator - 1024x960 and higher;
• Matrix sensitivity. A very important parameter that characterizes the ability to produce a high-quality image at a low level of illumination. In fairness, it should be noted that even the most expensive models also have interference when shooting in poorly lit places;
• Number of frames per second (fps). The larger this setting, the sharper the image, especially when shooting fast-moving scenes. A good parameter is a value of 30 frames and above.

Most of the latest webcam models have a built-in microphone, autofocus, and backlight as additional features. At the same time, audio data is transmitted via the same interface as video data, which is very convenient - the number of connections to a PC is reduced, and the microphone input is freed up, which can be used to connect a professional microphone if necessary.

The webcam is connected to a PC via a USB port, while in order to obtain a high-quality image, the version of the USB port must be at least 2.0.

Modem

Modems have been used by personal computer users for many years to access the Internet. Previously, the connection went through Dial-Up modems, the speed of communication through which, as well as the quality, left much to be desired. The actual data transfer rate, as a rule, did not exceed 33.6 kbps, and constant gaps made it difficult to transfer or receive large files. The phone line was also busy.

The advent of xDSL technology has fundamentally changed the concept of data transmission over a copper pair, allowing users to make a reliable connection at speeds up to 24 Mbps. towards the subscriber and up to 1 Mbps from him. This is implemented using such a peripheral device - a typical ADSL modem.

In this case, the use of a telephone number can be carried out simultaneously with the operation of a PC via a modem. It became possible to receive and transmit large files, conduct video conferences in real time, and perform group video broadcasting to a wide range of users (digital television).

Such a device is connected to a personal computer via Ethernet or USB port.

Game controllers

Computer peripheral devices also include game manipulators - joysticks, game sets - "steering wheel-pedals", and other devices.

They are connected to the USB port of a PC and are designed to simulate real control devices in gaming applications.

The device is made in the form of a regular pencil or pen, which fits comfortably in the hand and is connected to the PC by wire or wireless. It exactly copies all the movements of the user on a special rug or monitor screen, thus allowing you to draw in the usual way - by drawing. Besides, "light pen" can successfully play the role of a manipulator like a computer "mouse".

In comparison, the mouse does not allow you to draw in the traditional way, as its movements are difficult to coordinate. The light pen is completely devoid of this shortcoming.

Today, this device has gradually lost its relevance, since the advent of touchpads - panels sensitive to touch, made it possible to do the same, but without special devices connected to a PC. Computer drawings, on the other hand, turned out to be more convenient to perform on another device - a “digitizer”.

It is a graphics tablet connected to a personal computer and designed to enter graphic data that the user writes or draws on its surface.

The convenience of the digitizer is that the image is visible not only on the large screen of the monitor, but also on the tablet itself, that is, it seems that the user is performing actions on a sheet of paper.

The high accuracy of modern models and ease of use, provided this device with great popularity among the creators of animation graphics - the creators of modern cartoons, computer games, architects and designers, computer artists.

Various types of peripherals connected to a computer system play an important role in its operation. They largely determine the possibilities of using computers and their technical characteristics. A wide range of manufactured peripherals allows you to choose those with which professional computers are used most efficiently in various fields of activity.

Depending on the functions performed by the computer system, peripheral devices may fall into two main groups.

• The first includes those peripheral devices, the presence of which is absolutely necessary for the functioning of a computer system. They are commonly referred to as system peripherals. This group includes a video monitor, a keyboard, a floppy disk drive (FDD), a hard disk drive (HDD) and a printing device (printer).
• The second group of peripheral devices includes magnetic tape drives, devices for inputting graphic information, devices for outputting graphic information (plotters), modem, scanner, audio card, mouse or trackball, communication adapters, and others. They provide a professional computer with additional features. However, their presence in its configuration is determined by a specific area of ​​activity. In this regard, this group is called additional peripheral devices.

Many peripheral devices are connected to the computer through special sockets (connectors), usually located on the back wall of the computer's system unit. In addition to the monitor and keyboard, such devices are:

• printer - a device for printing text and graphic information;
• mouse - a device that facilitates the input of information into a computer;
• joystick - a manipulator in the form of a hinged handle with a button, used mainly for computer games;
• as well as other devices.

Some devices, for example, many types of scanners (devices for entering pictures and text into a computer), use a mixed connection method: only an electronic board (controller) is inserted into the computer system unit that controls the operation of the device, and the device itself is connected to this board with a cable.

Currently, more and more new and advanced peripheral devices are being developed.

Thus, the main components that ensure the execution of computer programs at the hardware level are located in the system unit of a stationary personal computer.

External devices (in relation to the system unit) according to their functional purpose can be represented in the form of several groups: input and output devices, devices that simultaneously perform the functions of input and output of information, external storage devices.

Information input devices include a keyboard, coordinate input devices (manipulators such as a mouse, trackball, contact or touch panel, joystick), a scanner, digital cameras (video cameras and cameras), a microphone.

Output devices include a monitor, printing devices (PU, printer and plotter), speakers and headphones.

Devices that perform the functions of input and output of information include a network adapter, a modem (modulator - demodulator), and a sound card.

External storage devices include: external floppy and hard disk drives, external optical and magneto-optical drives, flash memory drives, etc.

System Peripherals

video monitor

Video monitor (display or just a monitor) - a device for displaying text and graphic information in stationary PCs - on the screen of a cathode ray tube, and in portable PCs - on a liquid crystal flat screen.

Monitors are color and monochrome, can work in one of two modes: text or graphics. In text mode, the monitor screen is conditionally divided into separate sections - familiarity, most often into 25 lines of 80 characters each (familiarity). One of the 256 predefined characters can be output to each familiarity. These characters include large and small Latin letters, numbers, symbols: ! @ # $ % ^ & * () - + = ? ( ) : ; " "< >/ | \ . , ~ `, as well as pseudo-graphic symbols used to display tables and diagrams on the screen, to build frames around screen sections.

The characters displayed on the screen in text mode may also include Cyrillic characters (letters of the Russian alphabet).

On color monitors, each familiarity can have its own symbol color and its own background color, which allows you to display beautiful colored inscriptions on the screen. On monochrome monitors, to highlight individual parts of text and screen areas, increased character brightness, underlining and image inversion (dark characters on a light background) are used.

The graphic mode of the monitor is intended for displaying graphs, drawings. Of course, in this mode, you can also display textual information in the form of various inscriptions, and these inscriptions can have an arbitrary font, letter size.

In graphics mode, the monitor screen consists of dots, each of which can be dark or light on monochrome monitors, or one of several colors on color monitors. The number of horizontal and vertical dots is called the resolution of the monitor in this mode. For example, the expression "resolution 640200" means that the monitor in this mode displays 640 dots horizontally and 200 dots vertically. It should be noted that the resolution does not depend on the screen size of the monitor, just as both large and small TVs have 625 scan lines of the image on the screen. Modern monitors have a resolution of up to 1024x768 or 1248x1024 pixels.

An important feature of a monitor, which determines the clarity of the image on the screen, is the size of the dot on the screen. The smaller it is, the higher the clarity. Typically, the dot size ranges from 0.41 to 0.18 mm.

Other features of the monitor include: the presence of a flat or convex screen, the level of high-frequency radio emission, the refresh rate of the image on the screen, the presence of an energy saving system.

Keyboard

Keyboard - one of the most important elements of communication between a person and a computer. The keyboard is the main device for entering information into a personal computer. The data to be processed and the commands to be executed are communicated to the computer via the keyboard. In addition, it controls the operation of the computer during the execution of the program.

The keyboard should be ergonomic, that is, comfortable and not tiring during operation. To do this, it can be installed at a slight slope (from 5 to 7) relative to the horizontal surface. The keys must be freely accessible, they must be activated by light pressing. The markings on it should be clear and not tiring for the eyes.

The arrangement of letters on the keyboard's typing field is similar to a conventional typewriter, which makes it possible to use the skills acquired while working with a typewriter in working with a computer, achieving high speed input of both text and digital data.

When working with a computer, it becomes necessary to enter certain commands or frequently perform certain functions. Entering them every time in printed form would take a lot of time. Therefore, to enter these most commonly used commands and functions in computer keyboards, a separate, so-called function key, is provided. When you press each of them, not a single letter or number is entered into the computer, but a whole sentence or command. So, for example, when entering text in one program, pressing this function key may mean "set the cursor at the end of the line", and in another program, pressing it means "erase the text to the end of the line."

The computer keyboard also has keys that make it easier to control them - the so-called control keys. So, for example, there are separate keys for moving the light cursor around the screen, for inserting characters, for deleting characters.

The controls also include keys that set the work with lowercase or uppercase letters, with the Russian or Latin alphabet.

Computer keyboards use buttons of various types, of which two are most widely used: capacitive and contact.

• Capacitive buttons have a fairly simple device. They consist of a movable metal plate attached to a button and two metal protrusions on a printed circuit board that form the virtually fixed electrodes of a single variable capacitor. Each time the key is pressed, the movable plate approaches the protrusions, which leads to a change in the capacitance of the capacitor. This change is an indication of a key being pressed (or released). In the electronic circuit of such a keyboard, there are components that distinguish the state of the button depending on its capacity. In addition to the simplicity of the device, capacitive buttons have a fairly high reliability. They withstand up to 100 or more million cycles of pressing and releasing.
• Contact buttons can be made in various versions, but always based on the principle of direct mechanical contact between two flexible metal plates. At the point of contact, the plates usually have a special coating that provides low contact resistance. Computer keyboards use contact buttons that are designed so that pressing the button releases one of the preloaded lamellae, which consequently makes violent contact with the other lamina. In this case, the force of contact between the two plates does not depend on the force of pressing the key, which greatly reduces the mechanical vibrations that occur at the time of contact. The service life of contact buttons is characterized by the number of operations, which is on the order of several tens of millions of cycles. They are more noise-resistant than capacitive ones.

Printer

Printer (or printing device) designed to print information on paper. All printers can output text information, many of them can also output pictures and graphics, and some printers can also output color images.

There are several thousand printer models that can be used with a PC. As a rule, the following types of printers are used: matrix, inkjet and laser, but there are others (LED, thermal printers, and so on).

• Dot matrix (or dot matrix) printers- until recently, the most common type of printer for the IBM PC. The principle of printing these printers is as follows: The print head of the printer contains a vertical row of thin metal rods (needles). The head moves along the printed line, and the rods at the right time hit the paper through the ink ribbon. This ensures the formation of symbols and images on paper.

Cheaper models of printers use a nine-bar print head. The print quality of these printers is mediocre, but it can be somewhat improved by printing in several passes (from two to four).

Higher quality and faster printing is provided by printers with 24 print pins (24 dot printers). There are printers and 48 needles, they provide even better printing.

Dot-matrix printers print at speeds of 60 to 10 seconds per page, while patterns may print slower, up to 5 minutes per page. Special high-performance matrix printers are also produced - they are used by banks, telephone companies and so on.

• Inkjet printers. In these printers, the image is formed by microdrops of special ink blown onto paper using nozzles. This printing method provides higher quality and speed of printing, and compared to dot matrix printers, it is very convenient for color printing. Modern inkjet printers can provide high resolution - up to 600 dpi, are close in quality to laser printers, and are not much more expensive than even matrix printers (2-3 times cheaper than laser printers).

It should be noted that inkjet printers require careful care and maintenance. The print speed of inkjet printers is from 15 to 100 seconds per page, and the print time for color pages can be up to ten minutes (typically 3-5 minutes).

• Laser printers currently provide the best (near print) print quality. In these printers for printing The principle of xerography is used: The image is transferred to paper from a special drum, to which particles of ink are electrically attracted. The difference from a conventional photocopier is that the print drum is electrified by a laser at the command of a computer.

Laser printers, although quite expensive (usually $800 to $4,000), are the most convenient devices for producing quality black and white quality printed documents. There are also color laser printers, but they are much more expensive - from $ 5,000) at a resolution of 300 dpi, from $ 10,000 at a resolution of 600 dpi.

The resolution of laser printers is usually at least 300 dpi, and modern laser printers (HP Laser Jet 4 series) usually have a resolution of 600 dpi or more. Some printers, such as the HP Laser Jet III and 4, use a special image enhancement technology. The use of these technologies is equivalent to increasing the resolution of the printer by 1.5 times. The print speed of laser printers is from 15 to 5 seconds per page when outputting texts. Pages with pictures may take much longer to render, and larger pictures may take several minutes to render.

Special high-performance (so-called "network") printers are produced, for example, HP Laser Jet 4Si, 4V and others, their speed is from 15 to 40 pages per minute. Typically, these printers are connected to a local network and shared between users on that network.

Drives

As an external memory of personal computers, drives on a magnetic disk and on a magnetic tape can be used. There are two types of storage media on a magnetic disk - with a floppy disk (floppy disk) and with a hard (non-removable) magnetic disk (HDD) . The presence of a floppy disk drive (FFMD) is mandatory.Tape drives are usually of the cassette type and are rarely used. They serve to rewrite a large amount of information from the HDD to a magnetic tape, after which this information can be written to the HDD of another personal computer or stored in an archive.

Drives communicate with the computer's central processing unit using the appropriate control devices (controllers). Control devices (CU) are designed to carry out, on the one hand, the exchange of information between the central processor and drives, and on the other hand, to control the operation of these drives. The connection of the drives with the control unit is usually carried out through a standard interface, which is a group of lines for transmitting electrical signals, each of which has a strictly defined purpose.

Magnetic disk drives are devices with so-called cyclic access to information. Magnetic tapes are sequential media. They read or write to cells alternately from the beginning to the end of the tape. In a fundamentally different way, magnetic disk drives perform read or write operations in much less time than required for magnetic tape devices.

The access time to information on the drive media is many times greater than the time to access the computer's RAM. When creating modern drives, they strive to minimize this difference. The access time to information in HDD is one order of magnitude less than the access time in HDD.

a) Floppy disk drives

The widespread use of floppy disk drives in personal computers is due to their relatively low cost, small size, and relatively fast access to information stored on a diskette. Another reason for the wide spread of floppy disk drives is the convenience of working with them and the ease of storing floppy disks.

There are different types of NGMD. The most widely used media diameters are 133mm (5.25 inches) and 89mm (3.5 inches). In professional computers, floppy drives with a floppy disk diameter of 3.5 inches are most often used.

When working with disk drives, one or two circular disk surfaces are used to store information. According to the number of information surfaces used, magnetic disks can be single-sided and double-sided, and drives, respectively, with one and two magnetic read-write heads. Professional computers use both single-sided and double-sided floppy disks. The ability to store information on one or two surfaces of a floppy disk is guaranteed by the manufacturer and is indicated on its label. Single-sided floppy disk drives have only one read-write head, that is, they are designed to use only one surface of the floppy disk. Double-sided floppy drives have two read-write heads and work simultaneously with two surfaces of the floppy disk. In cases where this is provided for by the design of the floppy disk and the floppy disk, one-sided floppy disk drives can work alternately with two surfaces of the floppy disk. To do this, the floppy disk is initially placed in the main position, in which writing or reading from the first surface takes place. After installing the floppy disk in the reverse position, in which the two surfaces are reversed, it is possible to write or read on its second surface.

The amount of information stored on a floppy disk depends both on the type of floppy disk and on the floppy disk itself.

NGMD as an independent device combines three main blocks:

• Drive system is designed to ensure the rotation of a floppy disk in a floppy disk at a strictly specified speed. The motor of the drive system is turned on and off by signals coming from the control unit through the interface.
• Positioning system serves to mount the read/write head on a precisely defined track on the media surface. Tracks are concentric circles on the surface of the disc, on which information is recorded. A stepper motor moves the read-write head from one track to another in two directions along the radius of the disk. The head is in constant contact with the surface of the diskette.
• Read-write system converts the information coming from the CU into electrical impulses that pass through the magnetic head and write to the floppy disk. When reading from a floppy disk, this system performs the inverse transformation - electrical impulses from the magnetic head are converted into binary information, presented in a form suitable for transmission over the interface to the control unit.

A characteristic feature of disk drives is the method of recording information on the media. This method determines the density of data arrangement on a magnetic disk and, therefore, has a significant impact on the maximum possible amount of stored information. In addition, the recording method is also associated with the reliability of the stored data, with the exchange rate between the CU and the drive, with the complexity of the CU, and so on. In NGMD, mainly two recording methods are used - with frequency modulation of the FM (from the English FM - frequency modulation), and with modified In this way, so-called data pulses are formed. In addition to them, the FM coding sequence also includes clock pulses corresponding to the clock frequency of the binary series. These pulses are designed to synchronize the NGMD logic circuits with the clock frequency of the CU. To reduce the number of clock pulses, the MFM method uses the data pulses themselves for synchronization. Generation of additional clock pulses is performed only in cases of several consecutive zeros, when there are no data pulses. So, MFM coding consists of the following operations: transmission of a data pulse for each unit of a binary recorded sequence; transmission of a clock pulse for each second and next zero in a group of zeros sequentially recorded in a binary series. The resulting sequence combines the data and clock pulses, but the total number of pulses is halved compared to the FM method. Consequently, with the same recording density, the MFM method allows you to get twice the amount of information stored on the disk than with the FM method. In this regard, in most floppy disk drives used in professional computers, coding according to the MFM method is used.

Another characteristic feature of NGMD is the recording density on a floppy disk. Depending on the direction in which the density is considered, a distinction is made between transverse and longitudinal recording density. The transverse density is measured by the number of tracks per unit length in the direction of the floppy disk radius, and the longitudinal density is measured by the number of bits of information per unit length along the circumference of the track. The recording density is determined mainly by the quality of the magnetic coating and the parameters of the read-write head.

b) Hard Disk Drives

Non-removable media device These are hard disk drives (HDDs). Unlike floppy disk drives, they usually do not provide for removing the media from the device and replacing it with a similar one - the hard drive is hermetically sealed in the device case, and the entire hard drive is usually mounted once when assembling the computer. The hard drive rotates continuously after the device is powered on. Since the amount of information stored by one device of this type is very significant (more than 300 MB), it is shared by all computer users.

The hard drive, together with the magnetic heads, is hermetically sealed in a metal case, which isolates them from undesirable environmental influences. This greatly reduces the possibility of recording errors due to dirty heads or damage to the surface of the hard disk. In a hard drive, magnetic heads read and write information without touching the surfaces of the media. These are the so-called floating heads, which during the rotation of the disk are held at a small distance from the surface by the lifting force formed by the air flow between the head and the surface of the disk. Non-contact recording allows you to achieve a high speed of rotation of the media and prevents wear of the heads. In turn, a high disk speed can significantly increase the speed of writing and reading HDD, which reduces the total access time to this type of memory.

Additional Peripherals

Plotter

Plotter (plotter) - a device for displaying graphic information on paper. To service the plotters, special software is used, with which you can draw graphic images of various formats at high speed.

Plotters - these are mechanical devices in which a special pen is fixed. To draw a graph or symbol, the pen moves across the paper. The pen (practically it is more like a pen) can be filled with colored paste or ink. Multi-pen plotters can change the drawing pen on command, allowing multi-color images to be drawn.

Plotters are several types:

• In devices of the first type, the paper or film is fixedly fixed on a flat surface, and the pen can move in two dimensions.
• Plotters of the second type are designed so that the pen moves in one dimension, but the paper also moves.
• Plotters are drum type, that is, they work with a roll of paper.

Plotters receive a sequence of commands from the computer that controls the drawing process. Of course, this requires the appropriate software and hardware. The hardware includes an interface and a communication cable. The software must be able to generate a sequence of control codes that is passed to the plotter. Most plotters have a built-in encoding table, according to which these codes are converted into elementary pen movements. In other words, the computer gives commands to the plotter in a special language. There is no special standard for the command language of plotters.

Mouse

Mouse is a manipulator for entering information into a computer. The mouse is a small box with two or three keys that easily shrinks in the palm of your hand. Together with a cable for connecting to a computer, this device really resembles a mouse with a tail.

The mouse allows you to move the cursor to the desired location on the screen by moving the mouse on the table mouse on the table or other surface and fix the selection by pressing one of the buttons on its surface. As in other cases, the software must be able to recognize the presence of the hardware, i.e. the mouse, and perceive the control signals. Fortunately, most programs that "understand" keyboard cursor control can use the mouse after connecting a small additional program that presents the computer with information about mouse movement in the form of an equivalent sequence of codes generated when the cursor control key is pressed.

There are two main design options for a mouse: mechanical and optical.

The mechanical device uses a freely rotating ball, which is located on the "bottom" of the mouse. The ball rotates as a result of friction when the mouse is moved on a flat surface. The mouse circuitry senses this, counts the number of revolutions, and relays the information to the computer.

An optical mouse is moved along a special reflective panel. The beam of light emitted by the mouse reflects off evenly applied strokes on the panel. In this case, the sensor located inside the mouse determines the distance traveled and the direction of movement and sends this information to the computer.

There may be two or three buttons on the surface of the mouse. How they are used depends on the software.

Some application programs are designed to work only with the mouse, but most programs that use the mouse allow keyboard commands to be replaced by the mouse. However, often with such a replacement, working with the program is very difficult.

Modem

Modem - a device for exchanging information with other computers through the telephone network. By design, modems are built-in (inserted into the PC system unit) or external (connected through a communication port). Modems differ from each other in the maximum data transfer rate (1200, 2400, 9600 baud and so on, 1 baud = bits per second), as well as whether they support error correction tools (V42bis or MNP-5 standards). For stable operation on domestic telephone lines, imported modems must be adapted accordingly.

fax modem

fax modem - a device that combines the capabilities of a modem, and means for exchanging facsimile images with other fax modems and conventional telefax machines.

Scanner

Scanner - a device for reading graphic and textual information into a computer. Scanners can input drawings into the computer. With the help of special software, a computer can recognize characters in a picture entered through a scanner, this allows you to quickly enter printed (and sometimes handwritten) text into a computer. Scanners are desktop (they process the entire sheet of paper) and manual (they need to be held over the desired pictures or text), black and white and color (perceiving colors). Scanners differ from each other in resolution, the number of perceived colors or shades of gray. For regular use (for example, in publishing systems), a desktop scanner is necessary, although it is more expensive. Naturally, a color scanner is required for the preparation of color publications.

Audio board

The audio card allows you to play music and play sounds with your computer. Speakers are usually supplied with the audio card, and often a microphone. The audio card is a means of recording, playing and editing music and voice messages.

Many programs, especially gaming ones, use audio cards to output musical accompaniment, sound effects, including speech effects.

CD drive

The CD-ROM reader allows you to read data from special CD-ROMs (CD-ROMs). These CDs are more reliable and can store much more information than floppy disks, so at present in the West many large software systems, databases, multimedia programs are distributed on CDs.

trackball

trackball - a manipulator in the form of a ball on a stand. used to replace the mouse, especially common in portable computers.

Graphics tablet

Graphics tablet – a device for input of contour images (digitizer). It is used, as a rule, in automatic design systems (CAD) to enter drawings into a computer.

Link adapters

Communication channel adapters are designed to implement exchange of information between professional computers, both located in close proximity to each other, and those remote at a great distance. In addition, with their help, individual professional computers are connected to other small and large computers. A typical example in this case is the use of a professional computer as an "intelligent" terminal through which access to various types of computer networks is provided.

Two types of communication channel adapters are used - asynchronous and synchronous.

• The asynchronous adapter is connected to the system bus of the computer when the connector for connecting to the transmission medium is installed on it.

The asynchronous adapter performs all the functions of communicating, transmitting the desired character at the appropriate rate, generating the start and stop bits, monitoring, as well as detecting the start bit upon receipt, recognizing the received character and presenting it to the appropriate service program, and so on.

The asynchronous adapter can be used for both local and remote communication. With local communication through such an adapter, various peripheral devices that have the means to support asynchronous mode (for example, a printer or terminal) can be connected to a professional computer.

Direct communication via an interface in asynchronous mode is the simplest way to communicate between two PCs. When using modems in this mode, computers located at a distance of hundreds of kilometers from each other can also communicate. In this case, communication can be organized via a dedicated line (non-switched communication), and using the means of an existing telephone network (switched communication). The use of the telephone network makes it possible to interconnect a large number of computers, of which only two are interconnected at a time.

It should be noted that in the asynchronous mode of data transfer, the exchange rates are relatively low - up to several thousand bits per second, which is insufficient in most practical applications.

• The synchronous adapter is also connected to the system bus. It is characterized by a synchronous mode of operation, in which information is transmitted as a sequence of characters representing part of the message or the whole message. In this case, the beginning and end of each individual sequence are marked with service characters. In synchronous transmission, various rules of dialogue between computers are used, which make up the so-called exchange protocol. Depending on the protocol used, service characters are called "flags" or "sync characters". There are two types of synchronous communication protocols - bit-oriented and byte-oriented. Professional computers provide separate communication channel adapters to serve the most common representatives of the two types of protocols.

Synchronous adapters are primarily used to connect professional computers to mainframe computers or to computer networks.

Peripherals include all external additional devices connected to the computer system unit through special standard connectors.

This computer equipment, physically separated from the system unit of the computing system, has its own control and acts both on the commands of its central processor, and is equipped with its own processor and even an operating system. Designed for external preparation and modification of data, input, storage, protection, output, control and transmission of data via communication channels.

Computer peripherals are divided by purpose:

The main purpose of the PU is to ensure that programs and data for processing enter the PC from the environment, as well as the output of the results of the PC in a form suitable for human perception or for transfer to another computer, or in another necessary form. PU to a large extent determine the possibility of using PC.

Peripheral devices can be divided into several groups according to their functional purpose:

1. I/O devices- designed to enter information into a PC, output in the format required for the operator or exchange information with other PCs. External drives, modems can be attributed to this type of PU.

2. Output devices- designed to display information in the required format for the operator. This type of peripherals includes: printer, monitor, audio system.

3. Input devices- Input devices are devices through which information can be entered into a computer. Their main purpose is to implement the impact on the machine. These types of peripherals include: keyboard, scanner, graphic tablet, etc.

4. Additional PU- such as the "mouse" manipulator, which only provides convenient control of the graphical interface of PC operating systems and does not carry pronounced functions of input or output of information; WEB-cameras that facilitate the transmission of video and audio information on the Internet, or between other PCs. The latter, however, can also be attributed to input devices, thanks to the ability to save photo, video and audio information on magnetic or magneto-optical media.

Each of the listed groups of devices perform certain functions limited by their capabilities and purpose.

Peripheral input-output information devices.

There are several types of I/O peripherals depending on the purpose.

Winchester

Winchesters or hard disk drives- this is a large-capacity external memory designed for long-term storage of information, combining the storage medium itself and the recording / reading device in one case. Compared to disk drives, hard drives have a number of very valuable advantages: the amount of stored data is immeasurably larger, and the access time of a hard drive is an order of magnitude less. The only drawback: they are not designed to share information.

The physical dimensions of hard drives are standardized by a parameter called the form factor.

A hard drive consists of several hard drives with a magnetic layer applied to the surface and located one under the other. Each disk has a pair of read/write heads. When the computer is turned on, the hard drive disks are constantly spinning, even when there is no access to the hard drive, thus saving time on overclocking it.

To date, the following types of hard drives have been developed: MFM, RLL, ESDI, IDE, SCSI.

External drives:

· Tape (magnetic) drives- streamers. Due to the relatively large volume and fairly high reliability, they are most often used as part of data backup devices in enterprises and large companies.

· Magneto-optical drives- drives CD-ROM, CD-R, CD-RW, DVD-R, DVD-RW. They can also be used as backup devices, but unlike tape drives, they have a much smaller data capacity.

Flash cards.

Fifteen years ago, Toshiba came up with a non-volatile semiconductor memory technology that it called flash memory. Flash memory allows you to write and erase data without such difficulties, thanks to which it has good speed and, moreover, is quite reliable.

Soon, flash memory chips began to be built into various devices, and on their basis flash cards were created, with which it was possible to transport various data.

Modems.

Currently, there are two types of modems: analog and digital.

Analog modems are more popular due to their low cost and are mainly used to access the Internet, and only occasionally to communicate with other PCs. Digital modems are quite expensive and are used for high-speed connections to the Internet, or to organize a local area network over long distances. Modems have several types of connections to a PC: COM, USB or via a network card. A modem connected via a COM port requires an additional power supply, and when connected via a USB port, there is no need for a power supply. xDSL modems also require an additional power supply.

Peripheral information output devices.

Peripheral output devices are designed to output information in the format required by the operator. Among them there are mandatory and optional devices.

Monitors

The monitor is a necessary information output device. The monitor allows you to display alphanumeric or graphical information in a form that is easy to read and control by the user. In accordance with this, there are two modes of operation: text and graphic. In text mode, the screen is presented in rows and columns. In graphical format, screen parameters are specified by the number of dots horizontally and the number of dotted lines vertically. The number of horizontal and vertical lines on the screen is called the resolution. The higher it is, the more information can be displayed per unit area of ​​the screen.

· Digital monitors. The simplest - a monochrome monitor allows you to display only a black and white image. Digital RGB monitors support both monochrome and color modes.

· Analog monitors. Analog signal transmission takes place in the form of various voltage levels. This allows you to create a palette with shades of varying degrees of depth.

· Multi-frequency monitors. The video card generates clock signals that refer to the horizontal line rate and the vertical frame rate. The monitor must recognize these values ​​and enter the appropriate mode.

CRT monitor

If possible, settings can be distinguished: single-frequency monitors that perceive signals of only one fixed frequency; multi-frequency, which perceive several fixed frequencies; multi-frequency, tuning to arbitrary values ​​of the frequencies of synchronous signals in a certain range.

· Liquid crystal displays (LCD). The main disadvantage is the inability to quickly change pictures or quickly move the mouse cursor, etc. Such screens need additional illumination or external lighting. The advantages of these screens are in a significant reduction in the spectrum of harmful effects.

Liquid crystal display

· Gas plasma monitors. They do not have the limitations of LCD screens. Their disadvantage is the high consumption of electricity.

It is necessary to single out the group touch screens, since they allow not only to display data on the screen, but also to enter them, that is, they fall into the class of input / output devices. Such screens provide the easiest and shortest way to communicate with a computer: just point to what interests you. The input device is fully integrated into the monitor.

Gas plasma monitor

PC users spend many hours in close proximity to working monitors. In this regard, display manufacturers have increased their attention to equipping them with special means of protection against all types of influences that adversely affect the health of the user. Monitors with low radiation levels are currently being distributed. Other methods are used to increase the comfort of working with displays.

Printers

A printer is a widespread device for outputting information to paper, its name is derived from the English verb to print - to print. The printer is not included in the basic PC configuration. There are different types of printers:

· generic printer works like an electric typewriter. Advantages: a clear image of characters, the ability to change fonts when replacing a typical disk. Disadvantages: Printing noise, slow printing speed, graphics cannot be printed.

· Dot matrix (dot) printers- These are the cheapest devices that provide satisfactory print quality for a wide range of routine operations. Advantages: acceptable print quality, subject to a good ink ribbon, the possibility of carbon copy printing. Disadvantages: rather low print speed, especially for graphic images, significant noise level.

Matrix printer

· Inkjet printers provide better print quality. They are especially useful for color graphics output. The use of inks of different colors gives a relatively inexpensive image of acceptable quality.

Inkjet printers are much less noisy. The print speed depends on the quality. This type of printer occupies an intermediate accumulation between dot matrix and laser printers.

Jet printer

· Laser printers - have even higher print quality, close to photographic. They are much more expensive, but the print speed is 4-5 times faster than dot matrix and inkjet printers. The disadvantage of laser printers is rather stringent requirements for paper quality - it must be thick enough and not loose, printing on plastic-coated paper, etc. is unacceptable.

Laser printers are divided into two types: local and network. You can connect to network printers using an IP address.

Laser printer

· LED printers - alternative to laser.

Thermal printers are used to produce photographic quality color images. Requires special paper. Such printers are suitable for business graphics.

Much cheaper than laser and inkjet printers. Prints on any paper and cardboard. The printer operates at a low noise level.

Plotters (plotters ).

This device is used only in certain areas: drawings, diagrams, graphs, diagrams, etc. Plotters are indispensable in the development of architectural projects.

The plotting field of the plotter corresponds to A0-A4 formats, although there are devices that work with a roll that do not limit the length of the output drawing. That is, there are tablet and drum plotters.

· Tablet plotters, mainly for A2-A3 formats, fix the sheet and draw a drawing using a writing unit moving in two coordinates. They provide a higher accuracy of printing patterns and graphs compared to drum printing.

· Roll (drum) plotter - remains in fact the only developing type of plotter with a roller feed sheet and a writing unit that moves along one coordinate.

common cutting plotters to display the drawing on film, instead of a writing unit, they have a cutter.

Plotters usually communicate with a computer through a serial, parallel, or SCSI interface. Some models of plotters are equipped with a built-in buffer.

Plotters can use both special technologies and technologies familiar from printers. Currently, inkjet devices are becoming more common.

projection technology.

A multimedia projector allows you to play on a large screen information received from a wide variety of signal sources: a computer, a VCR, a camcorder, a camera, a game console. The modern projector is the most perfect link in the chain of evolution of projection equipment.

Multimedia projector

Multimedia projector is a modern and high-tech device. The reliability of most of the models produced is great, and the user is unlikely to have to contact a service center with a request for repairs. The only replaceable part of the projector is its lamp. Most projectors use high-brightness arc lamps with a smoother spectrum than incandescent lamps. Their average service life is 2000 hours of operation. Sometimes it is useful to use the lamp saver function, which doubles the lamp life.

Audio system

In personal computers, a wide variety of schemes for generating sound signals are used - from simple to complex.

These days there are a lot of acoustic systems on the market, consisting of two active speakers, and made according to the 2.1 system. Such systems are popularly called "tweeters" because they are not able to provide high quality sound even at a low volume level.

More recently, the 5.1 system was the ideal in the world of computer speaker systems, but recently speaker manufacturers have been expanding the capabilities of their systems, which led first to the appearance of a 6.1 system, and later 8.1

Peripheral input devices.

Input devices are those devices through which information can be entered into a computer. Their main purpose is to implement the impact on the PC. The variety of input devices produced has given rise to entire technologies: from tactile to voice.

Keyboard

The main input device of most computer systems is keyboard. Until recently, a standard keyboard was used, 101/102 keys, but with the development of personal computers, manufacturers also tried to develop the main input device. This led to the creation of multimedia keyboards, which are gaining more and more popularity these days.

Additional keys include groups of keys for controlling multimedia applications, keys for controlling the system volume, a group of keys for quickly launching office applications, a calculator, Internet Explorer, etc.

Keyboards differ in two ways: connection method and design. The keyboard can be connected to a computer via the PS/2 port, USB and via the infrared port for wireless models. In the last connection method, the keyboard requires an additional power source, such as batteries.

Scanner

For direct reading of graphic information from paper or other media in a PC, optical scanners. The scanned image is read and converted into digital form by the elements of a special device: CCD - chips. There are many types and models of scanners.

Hand scanners- the simplest and cheapest. The main disadvantage is that the person himself moves the scanner over the object, and the quality of the resulting image depends on the skill and hardness of the hand. Another major disadvantage is the small bandwidth

laser handheld scanner

· Drum Scanners used in professional typographical activities.

"home" drum scanner industrial drum scanner

· Sheet Scanners. Their main difference from the two previous ones is that during scanning, the ruler with CCD elements is fixed, and the sheet with the scanned image moves relative to it with the help of special rollers.

· Flatbed scanners. This is the most common type for professional work now. The object being scanned is placed on a glass sheet, the image is read line by line at a uniform speed by a reading head with CCD sensors located below.

Flatbed Scanner

· Projection scanners. The color projection scanner is a powerful multifunctional tool for entering any color images into a computer, including three-dimensional ones.

Handheld projection scanner

The interface can be different:

· Own interface - the scanner comes with its own unique card and only works with it.

· SCSI- if you use the scanner not with the supplied card, then easy compatibility is not always obtained.

· LPT- the scanner may need to support one of the high-speed protocols on the port. If EPP is usually always there, then the 8-bit Bi-Directional option required for Epson scanners is not implemented everywhere.

· USB- the most common connection option today.

· Graphics tablet.

Desktop computers for design and design work have been equipped with graphics tablets for more than a decade. This device greatly simplifies the input of drawings, diagrams and drawings into a PC. At first, tablets were expensive devices and therefore were designed for purely professional use. But for five years, cheap home models have been produced.