4 list the main pc peripherals. Computer components and peripherals - web programmer's blog

Hello dear readers of the site. In one of the lessons, we figured out that a computer can be divided into a system unit with all its contents and into peripheral devices. It is about peripheral devices that will be discussed in today's article. If you have not read the article about computer devices, then follow the link « » .

Peripheral devices of a personal computer are devices that connect to a computer using special connectors. Below are examples of the main devices that you can often find on home computers.

Monitor, display, screen. It is a device that is often referred to as a "TV" by users. It displays the image on the screen, which means it is a very important component in the computer.

Monitors by operating technology are divided into CRT (Cathode-ray tube) and LCD (liquid crystal). The first type is a device containing a kinescope, the same as in old televisions. The use of such a monitor is quite harmful to the user's health, fortunately, today they are not used much. The second type - a liquid crystal monitor - is a modern solution, its use is much less harmful to health.

The second important characteristic is the size of the screen in the monitor. It is customary to measure it diagonally and indicate it in inches. LCD monitors are widescreen, which means that the screen will be slightly elongated in width, the aspect ratio of such a screen is usually 16: 9 (for a regular square 4: 3).

Monitors can be connected via the following VGA, DVI, HDMI and DisplayPort interfaces. At this time, VGA and DVI interfaces are widely used on personal computers, there are also various adapters if these interfaces are not provided in the monitor or in the motherboard.

This is a device for entering information. All keys are divided into several groups:

• Alphanumeric;
• Controls (keys Enter, Backspace, Shift, Ctrl, Alt, Win, Caps Lock, Tab, Print Screen, Scroll Lock, Pause Break, Num Lock);
• Functional (keys F1 - F12);
• Cursor keys (Arrows, Insert, Delete, Home, End, Page Up, Page Down);
• Small numeric keypad.

In addition to those listed above, the keyboard may contain a set of multimedia keys for various purposes. Also, there are usually indicators of the Num Lock, Caps Lock, Scroll Lock mode.

The device can be connected via the Ps / 2, USB interface. There are also adapters that allow you to plug a USB keyboard into a PS / 2 port and vice versa.

Notebooks and netbooks may lack some key groups to save space. They may also be absent in conventional keyboards.

The advantage of the USB keyboard is that it can be connected with the computer turned on and after a while the operating system will automatically recognize the keyboard, thus you do not need to restart the computer to start working with it. If you connect a PS / 2 keyboard while the computer is on, the system will not be able to detect the device and will have to restart the computer to use the keyboard.

It is a manipulator device that converts the user's hand movements into cursor movements on the screen. The minimum set is two keys and a scroll wheel, some models may have an extended set: more than one wheel and additional keys on the left and right side of the mouse, which are very popular with "gamers".

Mouse buttons are usually called "left mouse button" (LMB, Mouse 1) and "right mouse button" (RMB, Mouse 2), there is usually also a third additional button under the wheel.

According to the principle of operation, mice are mechanical, optical and laser. Mechanical ones contain a rubberized ball inside, which, when moving, rotates small shafts, from which information about the direction and speed of movement of the manipulator is read (outdated model). Optical mice have a downward facing LED. The light reflected from the surface makes it possible to know the direction and speed of movement. Laser mice are a type of optical mice.

The difference is that the LED has been replaced with a miniature laser. This eliminated the mouse glow and improved positioning accuracy. Mechanical mice are outdated and almost never used; types of optical manipulators are usually used.

The connection methods for the mouse are the same as for the keyboard: USB and PS / 2. As with USB keyboards, mice are detected with the computer turned on.

This is a device for outputting (printing) information on paper.

First of all, they differ in printing technology. There are laser (LED printer), inkjet, dot matrix and other printers (solid ink, sublimation).

Laser printers are the most practical devices for work. They have the fastest print speeds, cartridge yields, and the lowest maintenance and refueling costs. They are usually black and white, although there are also colored ones. A special powder called toner is used for printing. It is applied to a sheet of paper in the right places, and then fixed to it by heating and melting. There is also an LED printer, which is a parallel branch of the development of laser printing technology.

An inkjet printer is the most suitable option for printing color images, including photographs. Liquid ink of 4 or 6 colors is used as a printing agent. Mixing these colors in different combinations gives the entire palette when printing. The disadvantage is the danger of drying the ink in the cartridge in the event of prolonged downtime and the slow printing speed. However, such printers provide the highest quality color printing, as well as a low cost of refueling, provided that CISS is used - a continuous ink supply system. This is a system in which ink containers are located next to the printer and the cartridges are fed through special tubes.

Matrix printer. This is the oldest and least convenient option. It uses a dye-impregnated ribbon for printing. The tape is pressed against the paper with special corners in the right places and forms an image from the dots. The main disadvantages of such printers are: low print speed, quality and increased noise during printing. However, they are still used in many organizations because some older software products can only print to these printers.

Printers are connected to the computer via USB or LPT (older models).

... A device for transferring information from paper to a computer. By scanning the image, we get a picture. If text is scanned and needs to be edited, special programs for text recognition are used. One of the popular programs that recognizes text from a scanned document is ABBYY FineReader, which is distributed as a paid software product.

Scanners are connected via USB.

... The abbreviation stands for Multifunctional Device. This is a very practical solution, which is a complete set of printer and scanner. Modern MFPs also make it possible to make copies without turning on a computer (copier), and can also perform fax functions.

Connected via USB and Ethernet (over the network).

... These are devices for playing sound.

The speakers differ primarily in power. They must be connected in two places: to the signal source - the green round connector on the motherboard or discrete sound card; and also to a power source, usually a regular outlet, but there are versions powered by USB. Peripheral devices include many other devices: uninterruptible power supplies, webcams, external modems, and many other useful devices. It is not possible to consider all of them within the framework of one lesson, therefore, we will focus on the most popular representatives of this periphery group described above. Wireless peripherals are currently being developed: mice, keyboards, printers, etc.

PC peripherals enable information exchange between the PC and the user. Without all these devices, all the capabilities and all the power of any personal computer is useless.

All external devices connected to are called PC peripheral devices, they are distinguished from the components included in the box. system unit... The interaction of the computer with the "outside world" is carried out using the periphery. , and are integral peripheral devices of any personal computer, but besides them there are many other useful devices.

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 look at texts and pictures on the monitor of a gadget.

Dot matrix printers were the first to appear, but due to the slow speed and loud grinding noise during printing, they were quickly replaced, first by inkjet and then laser printers. Today's inkjet printers are notable for their low price and the ability to print in color; their "disadvantages" include a relatively low print speed and high cost of cartridges, which, however, does not interfere with using them at home. In offices, however, 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 refueling and the large volume of printing per filling, quickly justifies their cost. High printing speed and quietness add "pluses" 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 you can do everything with the image that the PC software allows us to do. The most common uses of a scanner are to digitize photographs, store paper documents in an electronic database, and scan texts for later editing.

Scanners existing today are: hand-held scanners, flatbed scanners (the most convenient in the office and at home) and broaching scanners. It is clear that the quality of the image depends on the static nature of the scanned image during its shooting, which is why flatbed scanners are most widespread, despite the fact that they are rather bulky devices.

Multifunctional devices (MFPs) that combine a printer, scanner and copier are becoming more and more popular. Thanks to their versatility, MFPs can save desktop space. But such devices also have their drawbacks, which lie in the average indicators of their functions and low reliability, and if any one component, for example, 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 peripheral devices for PC does not end there, these include all devices that we can connect to a computer, these are sound speakers, game joysticks, web cameras and microphones, etc. But the most important devices, in our opinion opinion especially for work are printers and scanners.

What's happened peripherals computer or just peripherals? Peripherals are devices that connect to a computer and extend its functionality. Unlike a computer (, ...), their presence is not required for the computer to work. For example, a printer is a peripheral device used to print information. A computer will work without a printer, but not without a processor. Because the processor belongs to the mandatory PC devices.

The most popular computer peripherals are and. It seemed that the keyboard and mouse belong to the indispensable devices, without which it is impossible to work on a computer, but this is not so. The work will be impossible for the user, while the computer without these devices will turn on, load and wait for commands entered using the keyboard or mouse. Let's take a look at some of the popular devices.

Headphones and speakers are the next most popular peripherals. In itself there is only a small speaker, used mainly for signaling errors at boot time. To fully listen to the sound, you need speakers or headphones.

- one more peripheral devices. Serve for long-term storage of information.

Printer and scanner - peripheral devices designed to print information (printer) and obtain a digital copy of an object (scanner). In home computers, the scanner is mainly used to digitize text and photos. Most often, these two devices are combined into one housing. Such a device is called an MFP - multifunctional device.

In addition to the above popular devices, there are quite a lot of computer peripherals for all sorts of tasks.

At first glance, laptops and PC monitors have some advantage over television equipment in terms of connectivity. However, modern TVs are equipped with a wide range of connectors, so connecting a computer to a TV is much easier than it seems. Variety of interfaces The reality is that the compatibility of a computer and a TV depends on the degree of deterioration (age) of the older device. If you leave home today [...]

The printer can rightfully be considered one of the most important office techniques in the everyday life of an ordinary user. Indeed, using a printer, you can print abstracts, term papers, scientific papers, family photos and much more. Depending on the cost of the device, the printer can perform various functions, for example, print on professional photo paper, use a wider color gamut, etc. [...]

Computer speakers are peripheral devices designed to output sound. For a home computer, the presence of speakers is a prerequisite, because without them, it is impossible to fully watch a movie, listen to music, play games. For an office PC, the lack of acoustics is somehow justified, but it is already impossible to imagine a home computer without them. What are the types of speakers for a computer Almost all computer speakers [...]

After turning on the scanner, you must install the driver for this device to enable data transfer between the computer and the scanner. Start by connecting the scanner to a USB port on your computer. (Check your scanner's instructions for use and find out how to connect it to your computer.) Turn on the scanner. Many scanners use Plug and Play technology, which allows Windows to recognize hardware and install [...]

The scanner is used to transfer text and images from paper to a computer in the form of a file, that is, it performs the opposite of printing on a printer. Previously, hand-held scanners were common, which needed to be smoothly moved along the scanned sheet. In addition to the inconvenience in use, their big drawback was that due to the uneven speed of movement, the resulting image was elongated or, conversely, [...]

What is computer hardware? What are the different types of it? For examples of computer hardware and peripherals, read this article.

By definition, different parts of a computer go into its hardware. Computer hardware includes the central processing unit, motherboard, microcircuits, and computer peripherals such as input / output and storage devices that have been added to the computer to enhance its capabilities. Here is an overview of various types of computer technology with photographs.

Computer components

Here is a list of the main components of a computer along with a list of multimedia devices, networking hardware components, and computer peripherals. Together they form a set of hardware components in a computer.

Main components

System bus: It is a subsystem that transfers data inside a computer. A computer bus provides a logical connection between various peripheral devices on a computer. Processors use a control bus to communicate with other devices in the computer. The address bus is used to indicate the physical address. The processor reads or writes to the address bus when determining the memory location. The values ​​that it should read or write are sent to the data bus. Thus, the data bus carries out the delivery of the processed data. A parallel bus is capable of carrying multiple data in parallel, while a serial bus carries data in bit form. The internal bus connects the internal components of the computer to the motherboard, the external bus connects the external peripherals to the motherboard.

• AGP: Accelerated graphics port for short is the point where the graphics card is attached to the computer's motherboard.
• HyperTransport: It is a low latency computer bus that uses high bandwidth and operates in a bidirectional manner.
• PCI: Component Interconnect refers to the bus of a computer connecting peripheral devices to the motherboard.
• PCI Express: It is a computer card interface format.
• USB:(Universal Serial Bus - universal serial bus), acts as an interface to the computer. USB is the most popular device for connecting external devices.
• QuickPath: Also known as the common system interface, QuickPath is a point-to-point interconnect processor and is in close competition with HyperTransport.
• Serial ATA: It is a computer bus that allows data to be transferred between storage devices and the motherboard.
• Serial Attached SCSI: It is a point-to-point serial interface. Provides data transfer from storage devices such as hard drives.

It is a collection of logical machines that can execute computer programs. The fundamental function of a processor is to execute a sequence of stored instructions known as programs. During its first step of operation, the processor retrieves instructions from program memory. This stage is known as the "download" stage. In the “decode” stage, the processor splits instructions into parts and then executes them. During the fourth phase of writeback, the processor writes the results of the processed instructions into memory.

It is attached to the CPU and is used to lower its temperature. Fans in the computer case help maintain a constant flow of air, thereby cooling the computer components.

Firmware: It is a computer program that is embedded in a hardware device. It is somewhere between hardware and software. As a part of a computer program, it is similar to software, while at the same time closely related to hardware and makes it close to hardware components.

It is the central printed circuit board, or PCB for short, that forms the complex electronic system of a computer. The motherboard provides a computer system with all the electrical connections, basic circuitry, and components required for it to function.

This component is responsible for supplying power to the computer. It converts AC power from the electrical outlet into low-voltage DC power for internal computer components.

Random access memory, abbreviated as RAM, the physical memory of a computer. It is used to store running programs and is attached to the motherboard.

It is a computer expansion board that allows the input and output of audio signals to and from the computer. Sound cards provide multimedia applications with audio components.

A video adapter, also known as a video card, is a hardware component that generates and displays images on a display.

Storage controllers: They are located on the motherboard or on expansion cards. Storage controllers include controllers for hard drives, CD-ROM drives, and other devices.

Media devices

Devices such as CD, DVD, Blu-Ray, and flash drives are some of the most popular removable media that can store digital data. Tape drives and floppy disks are obsolete. Hard drives and solid state drives are used for internal storage.

CD: Known as CD, a device for storing digital data. Standard CDs can store about 80 minutes of audio. The CD-ROM contains data that is readable and cannot be changed. CD-ROMs are used to distribute computer programs and multimedia applications. To write CDs, an optical drive is used, which uses laser radiation or electromagnetic waves to read and write data to discs.

Digital Versatile Disc: commonly known as digital video disc and abbreviated as DVD The digital versatile disk is one of the very popular storage media. With physical dimensions similar to a CD, DVDs can store data six times more than CDs. DVD-ROM drive is used to read data from DVD. DVD RW is used to read and write data to DVD. DVD-RAM discs allow you to write information to them multiple times. HD DVD is a high density optical disc format.

Disc Array Controller: A disk array controller, it manages physical drives and presents them as logical units on a computer. It almost always implements hardware RAID, thus it is sometimes referred to as a RAID controller. It also provides additional disk cache.

This is a disc made of a thin magnetic data carrier covered with a plastic shell. With the advent of optical storage devices, floppy disks have become obsolete.

Tape drive: This storage device reads and writes data stored on magnetic tape. Tape drives have storage capacities ranging from a few megabytes to several gigabytes. They are mainly used for archival storage of data.

It is a nonvolatile memory device that stores digital data on a magnetic surface. It is used for medium-term data storage.

Solid-State Drive: Abbreviated SSD also known as solid state drive. This storage device uses solid state memory to store persistent data. It can replace a hard drive in many applications, but it costs significantly more.

It is an optical disc storage medium format. It gets its name from the blue laser that is used to read and write such discs. Due to its short wavelength, Blu-Ray discs can store large amounts of data. BD-ROM drive is used to read data from Blu-ray discs, BD-ROM can be used both for reading and writing.

Better known as flash drive... It is a small, removable and rewritable storage device with storage capacities ranging from 64MB to 64GB. Due to their high capacity, durability and compact design, they have gained immense popularity in modern times.

A medium-capacity floppy disk drive for storage, developed by Iomega in 1994, had a capacity of about 100 MB, later versions increased the storage capacity to 250 MB, and then 750 MB. The format became the most popular product, filling the portable storage niche in the late 1990s. However, it was never popular enough to replace 3.5-inch floppy disks and could not match the storage size available on CD-rewritable and later DVD-rewritable discs. Flash drives ultimately proved to be the best rewritable media among the general public due to the almost ubiquitous use of USB ports on personal computers, and the large size of Zip drives soon fell out of favor for mass portable storage in the early 2000s.

Network hardware and components

Here is a quick overview of some of the pieces of hardware that make it possible for a computer to be part of a network.

LAN card: It is one of the most important pieces of hardware, as it allows the computer to communicate with other computers over the network. It serves as a network medium and provides the computer with a MAC address system. A network card is also known as a network adapter, LAN (Local area network) card, or NIC (Network Interface Card).

Modem: This device is used for dial-up connections. It demodulates analog signals to decode digital carrier information and modulates analog signals to encode transmitted information.

Routers are not really a piece of equipment. Rather, they are devices that are used to connect multiple wired and wireless computer networks together.

Computer peripherals

Apart from the hardware components of a computer, there are many external devices that are equally important to its functioning. The keyboard, mouse, and monitor are the primary input and output devices. Joysticks, game controllers, and other pointing devices are commonly used for gaming applications on a computer. Headphones, speakers, microphones, and webcams are widely used to launch multimedia applications. Let's take a look at some examples of these peripherals.

It is an input device that evolved from a typewriter design. The keyboard consists of several keys set in a certain way. Each key acts like an electronic switch, producing a letter, number, or symbol as you type into a word processor or perform a specific computer operation.

Display: Known as a monitor, this is an electrical device that displays images resulting from video output from a computer.

A computer mouse is a pointing device that detects two-dimensional movement. The movement of the mouse translates into movement of the pointer on the computer display, which allows the user to graphically control the user interface.

It is a pointing device that contains a cursor along with a ball with rotational motion sensors. Trackballs have found use in special-purpose workstations and video games.

They consist of a pair of small speakers that can be held close to your ears. They can be connected to an audio source such as an amplifier or CD player.

It is an acoustic transducer that converts sound signals into electrical signals. Typically, microphones consist of a membrane that vibrates in response to sound. The vibrations are converted into electrical signals.

This peripheral device produces paper copies of electronic documents. It is attached to the computer using a peripheral cable or USB cable. A printer is often produced in conjunction with a scanner that doubles as a copier.

It is a peripheral device that can scan images, handwriting, or objects and convert them into digital images.

It is an input device that is used in video games or entertainment systems to provide input to video games, typically to control an object or character in a game.

Speaker: External computer speakers that allow computer users to listen to audio files.

A webcam is a small camera that is widely used during video conferencing and instant messaging. They are digital cameras that can upload images to a web server.

It was an introduction to various types of computer hardware. With the advancement of computer technology, we can count on the development of many other hardware components that translate technology into action!

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

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

• The first includes those peripheral devices that are absolutely necessary for the functioning of a computer system. These are commonly referred to as system peripherals. This group includes a video monitor, a keyboard, a floppy disk drive (floppy disk drive), 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 the professional computer with additional capabilities. However, their presence in its configuration is determined by a specific field of activity. In this regard, this group is called additional peripheral devices.

Many peripheral devices are connected to the computer through special slots (connectors), which are usually located on the back 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 handle with a button fixed on a hinge, 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's system unit, which controls the operation of the device, and the device itself is connected to this board with a cable.

More and more new and improved peripherals are currently being developed.

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

External devices (in relation to the system unit) by their functional purpose can be represented in the form of several groups: devices for input and output of information, 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 (camcorders and cameras), a microphone.

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

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

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

System peripherals

Video monitor

Video monitor (display or simply 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 graphic. In text mode, the monitor screen is conventionally divided into separate sections - familiarity, more often only 25 lines of 80 characters each (familiarity). Each familiarity can be output one of 256 predefined characters. These characters include large and small Latin letters, numbers, symbols:! @ # $% ^ & * () - + =? ():; ""< >/ | \. , ~ `, as well as pseudo-graphic symbols used to display tables and diagrams, and to draw frames around areas of the screen.

The number of characters displayed on the screen in text mode may 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, increased brightness of characters, underlining and image inversion (dark characters on a light background) are used to highlight certain parts of the text and areas of the screen.

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

In graphic mode, the monitor screen consists of dots, each of which can be dark or light on monochrome monitors or one of several colors on a color one. 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 horizontal dots and 200 vertical dots. It should be noted that the resolution does not depend on the size of the monitor screen, just as large and small TVs have 625 scan lines on the screen. Modern monitors have a resolution of up to 1024768 or 12481024 dots.

An important characteristic of the 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 point size ranges from 0.41 to 0.18 mm.

Other characteristics 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 a power-saving system.

Keyboard

Keyboard - one of the most important elements of human-computer communication. 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 work. 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 triggered by light pressing. The markings on it should be clear and not tiring for the eyes.

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

When working with a computer, it becomes necessary to enter certain commands or frequently perform certain functions. It would take a lot of time to enter them in printed form each time. Therefore, to enter these most commonly used commands and functions, computer keyboards are provided with a separate, so-called function keys. 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 can mean "position the cursor at the end of the line", while in another program, pressing it means "erase the text to the end of the line."

Computer keyboards also have keys that make it easier to operate them, the so-called control keys... So, for example, there are separate keys for moving the highlight cursor around the screen, for inserting characters, for deleting characters.

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

For computer keyboards, buttons of various types are used, 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 the printed circuit board that form the practically stationary electrodes of one variable capacitor. Each time you press the key, 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 press (or release). 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 can withstand up to 100 million or more press and release cycles.
• Contact buttons can be produced in different versions, but they are 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 when the button is pressed, one of the preloaded plates is released, which consequently comes into sharp contact with the other plate, creating contact. In this case, the force of contact of the two plates does not depend on the force of pressing the key, which significantly reduces the mechanical vibrations that occur at the time of contact. The service life of the contact buttons is characterized by a number of operations of the order of tens of millions of cycles. They are more immune to noise than capacitive ones.

a printer

Printer (or printing device) designed to display 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. Typically, 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 printers for the IBM PC. The principle of printing these printers is as follows: The printhead of the printer contains a vertical row of thin metal rods (needles). The head moves along the printed line, and the rods hit the paper through the ink ribbon at the right time. This ensures the formation of symbols and images on paper.

Cheap printers use a nine-rod printhead. The print quality of such printers is mediocre, but it can be slightly improved by printing in several passes (from two to four).

Better and faster printing is provided by printers with 24 printing pins (24-point printers). There are printers and 48 needles, they provide even better quality printing.

Dot matrix printers print speed from 60 to 10 seconds per page, drawings can be printed slower - up to 5 minutes per page. Special high-performance dot 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 micro-droplets of special ink blown onto the paper using nozzles. This printing method provides higher print quality and speed, and compared to dot matrix printers, it is very convenient for color printing. Modern inkjet printers can provide high resolution - up to 600 dots per inch, are close in quality to laser printers, and are not much more expensive, even dot 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 ranges from 15 to 100 seconds per page, and the time to print color pages can be up to ten minutes (usually 3-5 minutes).

• Laser printers currently provide the best (close to typographic) 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 ink particles 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 (typically $ 800 to $ 4000), are the most convenient devices for producing high-quality black and white high-quality printed documents. There are also color laser printers, but they cost significantly more - from $ 5000) 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 special image enhancement technology. The use of these technologies is equivalent to increasing the resolution of the printer by 1.5 times. The printing speed of laser printers is from 15 to 5 seconds per page when outputting texts. Picture pages can take significantly longer to render, and large pictures can take several minutes to render.

Special high-performance (so-called "network") printers are available, such as HP Laser Jet 4Si, 4V and others, with a speed of 15 to 40 pages per minute. Typically, these printers are connected to a local network and shared by users of that network.

Storage devices

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

The drives communicate with the central processor of the computer 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 storage devices, and on the other hand, to control the operation of these storage devices. Communication between drives and CU 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 cyclical access to information. Magnetic tapes are sequential-access media. They read or write to the cells alternately from the beginning to the end of the tape. Principally differently functioning magnetic disk drives perform read or write operations in a time significantly less than is required for tape devices.

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

a) Floppy disk drives

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

There are different types of floatation systems. The most widely used devices are with media diameters of 133mm (5.25 ") and 89mm (3.5"). In professional computers, floppy disk drives with a 3.5-inch floppy disk are most often used.

When working with disk drives, one or two circular surfaces of the disk 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 indicated on its label. One-sided floppy disk drives have only one read-write head, that is, they are designed to use only one surface of a floppy disk. Double-sided floppy disk drives have two read-write heads and work simultaneously with two surfaces of a floppy disk. In cases where this is provided for by the design of the floppy disk drive and floppy disk, one-sided floppy disk drives can work alternately with two surfaces of the floppy disk. To do this, initially the floppy disk is set in the main position, in which writing or reading from the first surface occurs. After inserting the floppy disk in the opposite position, in which the two surfaces are swapped, 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 drive itself.

The floppy disk drive as an independent device unites 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 engine 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 surface of the medium. Tracks are concentric circles on the surface of the disc on which information is recorded. A stepper motor drives the read / write head from one track to another in two directions along the radius of the disc. The head is in constant contact with the surface of the floppy disk.
• Read-write system converts the information coming from the CU into electrical impulses that pass through the magnetic head and record on a 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 via the interface to the CU.

A characteristic feature of disk drives is the method of recording information on a medium. 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 associated with the reliability of the stored data, with the rate of exchange between the CU and the drive, with the complexity of the CU, and so on. In the floppy disk drive, two recording methods are mainly used - with frequency modulation FM (from the English FM - frequency modulation), and with modified In this way, the so-called data pulses are generated. In addition to them, synchronization pulses corresponding to the clock frequency of the binary series are also included in the FM coding sequence. These pulses are designed to synchronize the logic circuits of the floppy disk drive with the clock frequency of the control unit. To reduce the number of synchronizing pulses in the MFM method, the data pulses themselves are used for synchronization. Additional sync pulses are generated only in the case of multiple consecutive zeros when there are no data pulses. So, coding by the MFM method consists of the following operations: transmission of a data pulse for each unit of a binary recorded sequence; transmission of a sync pulse for every second and next zero in a group of consecutively written zeros in a binary row. The resulting sequence combines data and sync 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 obtain twice the amount of information stored on the disk than with the FM method. In this regard, in most of the floppy disk drives used in professional computers, coding using the MCHM method is used.

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

b) Hard disk drives

Non-removable media device Are hard disk drives (HDD). Unlike drives on floppy disks, 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's case, and the entire hard disk drive is usually mounted once when the computer is assembled. The winchester 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 Winchester, together with the magnetic heads, is hermetically sealed in a metal case, which isolates them from unwanted environmental influences. This significantly reduces the likelihood of recording errors due to dirty heads or damage to the hard disk surface. In HDD, magnetic heads read and write information without touching the surfaces of the carrier. These are the so-called floating heads, which, during the rotation of the disc, are held at a small distance from the surface by the lifting force generated by the air flow between the head and the surface of the disc. Contactless recording allows high media rotation speeds and prevents head wear. In turn, the high speed of the disk can significantly increase the speed of writing and reading the hard disk drive, which reduces the total access time to this type of memory.

Additional peripherals

Plotter

Plotter (plotter) - a device for outputting graphic information on paper. To maintain 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 nib (in practice it is more of a pen) can be filled with colored paste or ink. Multi-pen plotters can swap the pen on command, allowing for multi-color graphics.

Plotters are several types:

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

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

Mouse

Mouse Is a manipulator for entering information into a computer. The mouse is a small box with two or three keys that shrinks easily in the palm of your hand. Together with a wire 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 across the mouse table 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, that is, the mouse, and accept control signals. Fortunately, most programs that "understand" keyboard cursor control can use the mouse by plugging in a small additional program that provides the computer with information about mouse movement in the equivalent sequence of codes generated when the cursor is pressed.

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

The mechanical device uses a freely rotating ball that sits 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 circuits sense this, count the number of revolutions, and transmit the information to the computer.

The optical mouse is moved over a special reflective panel. A ray of light emitted by the mouse reflects off the strokes that are evenly applied to 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 can be two or three buttons on the surface of the mouse. How they are used depends on software.

Some application programs are designed to work only with the mouse, but most programs using a mouse allow replacing the mouse with commands entered from the keyboard. However, it is often very difficult to work with the program with such a replacement.

Modem

Modem - a device for exchanging information with other computers via the telephone network. By design, modems are built-in (inserted into the PC system unit) or external (connected via 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 (V42bis or MNP-5 standards). For stable operation on domestic telephone lines, imported modems must be appropriately adapted.

Fax modem

Fax modem - a device combining the capabilities of a modem, and means for the exchange of fax images with other fax modems and ordinary fax machines.

Scanner

Scanner - a device for reading graphic and text information into a computer. Scanners can enter drawings into the computer. With the help of special software, the computer can recognize the characters in the picture entered through the scanner, this allows you to quickly enter typed (and sometimes handwritten) text into the computer. Scanners are desktop (they process the entire sheet of paper as a whole) and manual (they must be carried 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 systematic use (for example, in publishing systems) a desktop scanner is required, although it is more expensive. For the preparation of color publications, of course, a color scanner is required.

Audio payment

The audio card makes it possible to play music and reproduce sounds using a computer. Speakers are usually supplied with the audio card, and often a microphone. The audio board represents a means of recording, playing and editing music and voice messages.

Many programs, especially games, use audio cards to output music, sound, including speech, effects.

CD-ROM drive

A CD-ROM drive allows you to read data from special compact discs (CD-ROMs). These CDs are more reliable and can store much more information than floppy disks; therefore, 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 in laptop computers.

Graphics tablet

Graphics tablet - a device for inputting contour images (digitizer). It is used, as a rule, in computer-aided design systems (CAD) for entering drawings into a computer.

Link adapters

Link adapters are designed to implement exchange of information between professional computers, both located in close proximity to each other, and remote at a great distance. In addition, they are used to connect individual professional computers with 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 carried out.

Two types of link adapters are used - asynchronous and synchronous.

• An asynchronous adapter is connected to the system bus of the computer when a media connector is installed on it.

The asynchronous adapter performs all the functions of communicating, transmitting the desired character at the appropriate rate, generating 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.

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

Direct communication via an interface in asynchronous mode is the simplest way of communicating between two PCs. When using modems in this mode, computers that are at a distance of hundreds of kilometers from each other can communicate. In this case, communication can be organized via a dedicated line (non-commutated communication), and using the means of the existing telephone network (dial-up communication). The use of the telephone network makes it possible to interconnect a large number of computers, of which only two are connected 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 also connects to the system bus. It is characterized by a synchronous mode of operation, in which information is transmitted as a sequence of characters representing a part of a message or a whole message. In this case, the beginning and end of each separate sequence are marked with service symbols. With synchronous transmission, the transmission uses various rules for the dialogue between computers, which constitute the so-called exchange protocol. Depending on the protocol used, the service symbols are called "flags" or "sync symbols". There are two types of synchronous communication protocols - bit-oriented and byte-oriented. Professional computers have separate link adapters to accommodate the most common two types of protocols.

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