Peripheral devices of a personal computer. Peripheral equipment. Purpose and classification
11.1. Input devices
Keyboard – used to enter alphanumeric data, as well as control commands. It belongs to standard PC tools. Its main functions do not need to be supported by special system programs - drivers, since the necessary software is in the ROM as part of the BIOS.
The principle of operation of the keyboard is as follows.
1) When you press a key, a special chip built into the keyboard produces a key code (scan code).
2) The scan code enters the chip, which plays the role of a keyboard port (the port is located on the motherboard).
3) The keyboard port provides the processor with an interrupt number (9).
4) Having received an interrupt, the processor accesses the special OP memory, which contains the interrupt vector (a list of addresses of programs that service a specific interrupt).
5) The processor executes the program, which is located at the address taken from the interrupt vector. The simplest keyboard interrupt processing program is located in ROM, but you can replace it with your own program if you change the data in the interrupt vector.
6) The interrupt handler program finds the scan code, writes it to the processor registers and determines the symbol corresponding to this code.
7) The handler program writes the character to a special area of the operating system, which is called the keyboard buffer and stops working.
8) The processor finishes processing the interrupt and returns to pending work.
9) The entered character is stored in the buffer until it is retrieved from there by the program for which it was intended. If characters arrive more frequently than they are received, a buffer overflow occurs.
A mouse is a manipulator-type control device. Moving the mouse on a flat surface is synchronized with the movement of the mouse pointer on the monitor screen. The operating principle is as follows:
Unlike a keyboard, a mouse is not a standard device and the PC does not have a dedicated port for it. There is no permanent dedicated interrupt for it, and the BIOS does not contain software to handle mouse interrupts. Therefore, the mouse needs a special control program - a mouse driver. The driver is installed either when you first connect the mouse, or when installing the OS. Although the mouse does not have a dedicated port on the motherboard, to work with it, they use one of the standard ports, tools for working with which are included in the BIOS. A mouse driver is needed to interpret signals coming through the port. The computer is controlled by moving the mouse along the plane and pressing the left and right buttons. The control principle is event-based, i.e., moving the mouse and pressing buttons are events from the point of view of its driver program. By analyzing events, the driver determines where this event occurred, that is, where the pointer was on the screen. This data is transferred to the program with which the user works. Based on them, the program determines the user command that it must execute.
Special manipulators:
· Trackball - unlike a mouse, it is installed permanently, its ball is driven by the palm of the hand, it does not need a smooth surface, therefore it is widely used in laptop PCs.
· Joystick – a manipulator used in game programs and training equipment.
· Infrared mouse – differs from the usual one by the presence of a wireless communication device with the system unit.
Graphic data input devices: scanners, graphics tablets (digitizers), digital video cameras.
Scanners. Using a scanner, you can enter any information, including symbolic ones. In this case, the source data is entered graphically and then processed using pattern recognition programs.
Flatbed scanners are the most common. They are designed for entering graphic information from a sheet. The principle of operation of the scanner is that a beam of light reflected from the surface of a sheet is recorded by special elements (CCD - charge-coupled devices). Typically, these elements are structurally designed in the form of a ruler located along the width of the sheet. Then either the sheet moves while the ruler is stationary, or vice versa - the ruler moves while the sheet is stationary.
Main characteristics of flatbed scanners:
· Resolution – depends on the density of the CCD elements on the line. A typical figure is 600-1200 dpi (dots per inch).
· Productivity – the duration of scanning one sheet of paper.
· Dynamic range – the ratio of the brightness of the lightest areas of the image to the brightness of the darkest areas.
Graphic tablets – designed for entering artistic graphic information. There are several different principles of their operation, but they all rely on fixing a special pen relative to the tablet. Such devices can be used by artists because they allow them to create screen images in familiar ways.
Digital cameras - these devices perceive graphic data using CCDs combined into a rectangular matrix. The main parameter is resolution, which is related to the number of CCDs in the matrix. The best consumer models have up to 1 million CCD cells and provide image resolutions of up to 800x1200 pixels. For professional models, these parameters are even higher.
11.2. Output devices
A monitor is a device for visually presenting data. This is the main information output device. Its main consumer parameters are:
Maximum image refresh rate;
Monitor size - measured between the opposite corners of the kinescope tube diagonally. The unit of measurement is inches. Standard sizes: 14”, 15”, 17”, 19”, 20”, 21”. Currently, the most versatile monitors are 15” and 17”, and for graphics operations it is better to use 19”-21” monitors.
The image on the monitor screen is obtained as a result of irradiation of the phosphor coating with a highly directed beam of electrons accelerated in a vacuum flask. To obtain a color image, the phosphor coating has three types of dots that glow in red, blue and green. In order for all three rays to converge at one point on the screen, a mask is placed in front of the screen - a panel with holes. Some monitors are equipped with a mask made of vertical wires, which enhances the brightness and saturation of the image. The smaller the step between the holes of the mask, the clearer the resulting image. The pitch of the mask is measured in fractions of a millimeter. Currently, the most common monitors are with a mask pitch of 0.25–0.27 mm.
The image regeneration (update) frequency shows how many times within a second the monitor can completely change the image. This parameter depends not only on the properties of the monitor, but also on the settings of the video adapter. The regeneration frequency is measured in Hz. The higher it is, the more stable the image, the less eye fatigue. The minimum value is considered to be 75 Hz, the normative value is 85 Hz, and the comfortable value is 10 Hz or more.
Video card (video adapter). Together with the monitor, the video card forms the PC video system. Physically, the video adapter is made in the form of a separate board called a video card. Video memory and the GPU, which converts the contents of video memory into images on the screen, are the two main components of a graphics card.
Currently, SVGA video adapters are used, which provide reproduction of up to 16.7 million colors with the ability to randomly select screen resolution from a standard range of values: 640x480, 800x600, 1024x768, 1280x1024, etc.
Screen resolution is one of the most important characteristics of a video system. The higher it is, the more information can be displayed on the screen.
Another important characteristic is color expansion, which determines the number of shades that a screen point can take on. The maximum possible color expansion depends on the amount of video memory installed and on the installed expansion. With a high screen resolution, less space is allocated to each pixel in the image, i.e., color information is limited. The required amount of video memory can be determined by the formula:
P – required amount of video memory,
m – horizontal screen expansion (dots),
n - vertical screen extension (dots),
b – color coding depth (bits).
The minimum color depth requirement today is 256 colors, although most programs require at least 65 thousand colors (High Color mode).
Another property of a video adapter is video acceleration, which means that part of the image construction operations can occur without mathematical calculations in the main PC processor, but purely in hardware - by converting data in video accelerator chips. The video accelerator can be part of the video adapter, or can be connected to it as a separate board.
There are 2 types of video accelerators: flat (2D) and three-dimensional (3D) graphics accelerators. The former are most effective for working with application programs, while the latter are focused on multimedia, mainly gaming applications, as well as professional 3D graphics processing programs. There are accelerators that have both two-dimensional and three-dimensional acceleration functions.
The first video accelerators provided rapid construction of two-dimensional drawings lying in the plane of the screen. At the same time, the load on the main processor was reduced and operations such as opening, closing, moving and scaling windows, drawing simple geometric shapes, drawing raster images (including transparent and translucent), and drawing characters (text) were accelerated. All modern video cards are capable of defect-free generation of two-dimensional images at any resolution and frame rate. Producing an image of a three-dimensional scene is a much more difficult task than reproducing a flat image. The idea of a 3D graphics accelerator is to take some of the workload associated with calculating 3D pictures off the CPU. As a result, it is possible to significantly increase the frame rate in a 3D scene and improve image quality.
The first 3D accelerator was an independent expansion card that worked in conjunction with the main video adapter. Having a 3D accelerator for computer games quickly became a necessity, and soon after that, the integration of 3D graphics accelerators and video adapters occurred.
The Windows system includes a standard DirectX graphical interface, which enables the activation of graphics accelerator functions from the program.
The first stage of development of 3D graphics accelerators for personal computers was marked by competition from 3dfx and Vidia. Vidia became a market leader with the introduction of the GeForce2 GTS graphics processor. after GeForce2 came GeForce3 and GeForce4.
Today, nVidia's main competitor in the field of the most productive adapters with a 3D graphics accelerator is ATI. ATI enjoyed well-deserved respect in the days of 2D video accelerators, but entered the 3D accelerator market late. The latest series of Radeon GPUs are competitive with contemporaneous nVidia products.
Printers are printing devices that make copies of documents on paper. Based on the principle of operation, there are matrix, laser, LED, and inkjet printers.
Dot matrix printers are the simplest printing devices. Data is displayed on paper in the form of an imprint formed when special “needles” are struck through an ink ribbon. Print quality depends on the number of needles in the printer's print head. The most common are 9-pin and 24-pin matrix printers. Printer performance is measured by the number of characters printed per second. For dot matrix printers, there are the following operating modes: draft - draft printing mode, normal - normal printing and NLQ (Near Letter Quality) - provides print quality close to the quality of a typewriter.
Laser printers - provide high quality printing, not inferior to printing. They also feature high print speeds, measured in pages per minute. Like dot matrix printers, the final image is formed from dots.
The operating principle is as follows. In accordance with the incoming data, the laser head emits light pulses that are reflected from the mirror and hit the surface of the photosensitive drum. As a result, the areas of the drum that were hit by the light pulse acquire a photosensitive charge. The drum then passes through a container of coloring powder (toner) and the powder is fixed to areas that have a static charge. With further rotation, the drum comes into contact with the paper sheet and the powder is transferred to the paper, the heating element heats the powder, as a result of which the powder particles are sintered and fixed on the paper.
The main parameters of laser printers include:
1. resolution (measured in dots per inch) – middle-class models provide print resolution up to 600dpi, professional models up to 1200dpi;
2. performance (pages per minute):
3. format of paper used;
4. volume of own EP;
5. cost of the print, i.e. the cost of consumables to obtain one printed sheet of A4 format (from 2 to 6 cents).
Inkjet printers - the image is formed by microdrops of special ink. Print quality depends on the shape of the drop and its size, as well as on the properties of the dye and paper. The positive properties of inkjet printers include the simplicity and reliability of the mechanical parts of the printer and its relatively low cost. But despite the fact that the price of inkjet printers is much lower than laser ones, the cost of printing one print on them can be several times higher. The quality of color images is very high, but the possibility of application in black and white halftone printing is limited due to unstable resolution.
Sound system
Sound card. It connects to one of the slots on the motherboard and performs computing operations related to speech, music, and sound processing. The sound is reproduced using sound speakers that are connected to the output of the sound card. The main parameter of a sound card is the bit depth - the number of bits used when converting signals from analog to digital form and vice versa. The higher the bit depth, the higher the sound quality. The minimum requirement is 16 bits (preferably 32 or 64).
11.3. Communication devices
The task of reliable exchange of binary signals represented by corresponding electromagnetic signals in computer networks is solved by a certain class of equipment. In local networks, these are network adapters, and in global networks - data transmission equipment, which includes, for example, devices that perform modulation and demodulation of discrete signals - modems. This equipment encodes and decodes each information bit, synchronizes the transmission of electromagnetic signals over communication lines, verifies the correctness of transmission using a checksum, and can perform several other operations. Network adapters are designed, as a rule, to work with a specific transmission medium - coaxial cable, twisted pair, optical fiber, etc. Each type of transmission medium has certain electrical characteristics that affect the way this medium is used, and determines the speed of signal transmission, the way they are transmitted encoding and some other parameters.
Modem– a device intended for exchanging information between remote computers (MOdulator+DEModulator). Communication channels are the physical communication lines (wire, fiber, cable, radio frequency), the method of their use (switched or leased) and the method of transmission (digital or analog signals). Depending on the type of communication channel, modems are divided into radio modems, cable modems and others. The most widely used modems are those connected to telephone communication channels. The modem can be external
Digital data enters the modem from the computer, is converted there by modulation in accordance with the selected protocol (standard) and is sent to the telephone line. The receiver modem performs inverse conversion (demodulation) and sends the recovered digital data to its computer. The main characteristic of the modem is the data transfer speed. It depends on the quality of the telephone connection and the data transmission standards supported by the modems. All modems are connected to serial ports. Modems can be either external, i.e. connected through a connector in the case, or internally, i.e. installed as a board in a computer.
What's happened peripherals computer or just peripherals? Peripherals are devices that connect to a computer and expand its functionality. Unlike a computer (, ...), their presence is not necessary for the computer to work. For example, a printer is a peripheral device used to print information. The computer will work without a printer, but not without a processor. Because The processor is a mandatory PC device.
The most popular computer peripherals are and. It seemed that the keyboard and mouse were mandatory devices, without which it would be impossible to work on a computer, but this is not so. Operation will be impossible for the user, while a computer without these devices will turn on, boot and wait for commands entered using the keyboard or mouse. Let's look at some popular devices.
Headphones and speakers are the next most popular peripheral devices. In itself there is only a small speaker, used mainly to signal errors at boot time. To fully listen to sound, speakers or headphones are required.
– another peripheral devices. Serve for long-term storage of information.
Printer and scanner are peripheral devices designed to print information (printer) and obtain a digital copy of an object (scanner). In home computers, a 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 - a multifunctional device.
In addition to the popular devices listed above, there are quite a lot of computer peripherals for various types of tasks.
At first glance, laptops and PC monitors have some advantage over television equipment in matters of connection. 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 wear (age) of the older device. If you leave home today [...]
The printer can rightfully be considered one of the most important office equipment in the everyday life of the average user. Indeed, with the help of a printer you can print out abstracts, term papers, scientific papers, family photographs and much more. Depending on the cost of the device, the printer can perform various functions, for example, printing on professional photo paper, using a wider color palette, etc. […]
Computer speakers are a peripheral device and are 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, or play games. For an office PC, the lack of acoustics is still somehow justified, but it is already impossible to imagine a home computer without them. What kinds of computer speakers are there? Almost all computer speakers [...]
After turning on the scanner, you must install the driver for this device so that data can be transferred between the computer and the scanner. Start by connecting the scanner to a USB port on your computer. (Read your scanner's manual to 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 the hardware and install […]
A scanner is used to transfer text and images from paper to a computer in file form, which is the reverse of printing on a printer. Previously, hand-held scanners were common, which had to be smoothly moved along the sheet being scanned. In addition to being inconvenient to use, their big drawback was that due to the uneven speed of movement, the resulting image was elongated or, conversely, […]
PC peripherals provide the ability to exchange information between the computer and the user. Without all these devices, all the capabilities and all the power of any personal computer are useless.
PC peripherals are all external devices connected to the computer; they are distinguished from the components contained in the box of the system unit. The interaction of the computer with the “outside world” is carried out using peripherals. , and are integral peripheral devices of any personal computer, but besides them there are many other useful devices.
Along with the monitor, information output devices include: The need for printing devices, even with the transition to electronic document management, will never disappear, and in many cases using material printed on paper is more convenient than looking at texts and pictures on a gadget monitor.
Dot matrix printers were the first to appear, but due to their slow speed and loud grinding sound during printing, they were quickly replaced first by inkjet and then by laser printers. Today's inkjet printers are distinguished by their low price and the ability to print in color; their “disadvantages” include the relatively low printing 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 large volume of printing per refill, quickly justify their cost. High printing speed and noiselessness add advantages to these devices.
The next most important peripheral device of a personal computer, in our opinion, is the scanner. The scanner transfers the images into computer memory, after which we can do whatever the PC software allows us to do with the image. The most common uses of a scanner are converting photographs into electronic form, storing paper documents into an electronic database, and scanning texts for later editing.
The scanners that exist today are: hand-held scanners, flatbed scanners (the most convenient in the office and at home) and broach scanners. It is clear that the quality of the image depends on the static state 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 increasingly popular. Thanks to their multifunctionality, MFPs save desktop space. But such devices also have their drawbacks, which are the average performance of their functions and low reliability, and even if one component breaks down, for example a printing device, both the scanner and copier will have to be taken to the repair shop.
Of course, the list of peripheral devices for a 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 In my opinion, printers and scanners are especially useful for work.
The main purpose of the PU is to ensure that programs and data are supplied to the PC from the environment for processing, 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. PUs to a large extent determine the possibilities of using PCs.
Peripheral devices can be divided into several groups according to their functionality:
1. I/O devices- are intended for entering information into a PC, outputting it in the format required by the operator, or exchanging information with other PCs. This type of control unit includes external drives and modems.
2. Output devices- designed to display information in the format required by the operator. This type of peripheral devices 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 an impact on the machine. This type of peripheral devices includes: keyboard, scanner, graphics tablet, etc.
4. Additional PU- such as a “mouse” manipulator, which only provides convenient control of the graphical interface of PC operating systems and does not have pronounced functions for 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 classified as input devices, thanks to the ability to save photos, 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 information input/output devices.
I/O peripherals come in several types depending on their purpose.
Winchester
Winchesters or hard drives is a large-capacity external memory designed for long-term storage of information, combining the storage medium itself and the writing/reading device in one package. Compared to disk drives, hard drives have a number of very valuable advantages: the volume of stored data is immeasurably larger, and the access time of a hard drive is an order of magnitude shorter. The only drawback: they are not designed for information exchange.
The physical dimensions of hard drives are standardized by a parameter called form factor.
The hard drive consists of several hard drives, with a magnetic layer applied to the surface and located one below the other. Each disk has a pair of write/read 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 their fairly large volume and fairly high reliability, they are most often used as part of data backup devices in enterprises and large companies.
· Magneto-optical storage- CD-ROM, CD-R, CD-RW, DVD-R, DVD-RW drives. They can also be used as backup devices, but, unlike streamers, they have much less data capacity.
Flash cards.
Fifteen years ago, Toshiba came up with a non-volatile semiconductor memory technology it called flash memory. Flash memory allows you to write and erase data without such difficulties, due to which it has good performance and, moreover, is quite reliable.
Soon, flash memory chips began to be built into various devices, and based on them, flash cards were created, with which various data could be transported.
Modems.
Currently, there are two types of modems: analog and digital.
Analogue modems are more popular because they are cheap and are used mainly for accessing the Internet, and only sometimes for communicating with other PCs. Digital modems are quite expensive and are used for high-speed connections to the Internet, or for organizing a local 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 source, but when connected via a USB port, there is no need for a power supply. xDSL modems also require an additional power source.
Peripheral information output devices.
Peripheral output devices are designed to display 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 graphic information in a form that is easy for the user to read and control. In accordance with this, there are two operating modes: text and graphic. In text mode, the screen is presented in rows and columns. In a graphic format, screen parameters are specified by the number of dots horizontally and the number of dot lines vertically. The number of horizontal and vertical lines on the screen is called resolution. The higher it is, the more information can be displayed per unit of screen area.
· Digital monitors. The simplest - a monochrome monitor allows you to display only black and white images. Digital RGB monitors support both monochrome and color modes.
· Analog monitors. Analog signal transmission occurs in the form of different voltage levels. This allows you to create a palette with shades of varying degrees of depth.
· Multi-frequency monitors. The video card generates synchronization signals that relate to the horizontal line frequency and vertical frame repetition rate. The monitor must recognize these values and switch to the appropriate mode.
CRT monitor
If possible, settings can be distinguished: single-frequency monitors, which perceive signals of only one fixed frequency; multi-frequency, which perceive several fixed frequencies; multi-frequency, tuning to arbitrary 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 require additional backlighting or external lighting. The advantages of these screens are a significant reduction in the range of harmful effects.
Liquid crystal display
· Gas plasma monitors. They do not have the limitations of LCD screens. Their disadvantage is their high energy consumption.
A special group needs to be highlighted touch screens, since they allow not only to display data on the screen, but also to enter it, that is, they fall into the class of input/output devices. Such screens provide the easiest and shortest way to communicate with a computer: you just need to point to what interests you. The input device is completely integrated into the monitor.
Gas plasma monitor
PC users spend many hours in a row 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 negatively affect the user’s health. Low-emission monitors are now becoming common. Other methods are also used to improve the comfort of working with displays.
Printers
A printer is a widespread device for outputting information onto 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:
· Typical printer works similarly to an electric typewriter. Advantages: clear image of characters, ability to change fonts when replacing a standard disk. Disadvantages: printing noise, low printing speed, graphic images cannot be printed.
· Matrix (needle) printers- these are the cheapest devices that provide satisfactory print quality for a wide range of routine operations. Advantages: acceptable print quality, provided there is a good ink ribbon, and the ability to print as a carbon copy. Disadvantages: rather low printing speed, especially graphic images, significant noise level.
Matrix printer
· Inkjet printers provide higher print quality. They are especially useful for displaying color graphics. The use of inks of different colors produces a relatively inexpensive image of acceptable quality.
Inkjet printers are much less noisy. Print speed depends on quality. This type of printer occupies an intermediate position 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 printing speed is 4-5 times higher than that of dot matrix and inkjet printers. The disadvantage of laser printers is that they have rather strict requirements for the quality of the paper - it must be thick enough and should not be 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. They require special paper. These printers are suitable for business graphics.
Much cheaper than laser and inkjet printers. Prints on any paper and cardboard. The printer operates at low noise levels.
Plotters ).
This device is only used in certain areas: drawings, diagrams, graphs, diagrams, etc. Plotters are also indispensable when developing architectural projects.
The plotter's drawing field corresponds to A0-A4 formats, although there are devices that work with a roll and do not limit the length of the output drawing. That is, there are flatbed and drum plotters.
· Flatbed plotters, mainly for A2-A3 formats, fix the sheet and draw a drawing using a writing unit moving in two coordinates. They provide higher accuracy of printing of drawings and graphs compared to drum printing.
· Roll (drum) plotter - remains in fact the only developing type of plotter with a roller sheet feed and a writing unit moving along one coordinate.
Distributed cutting plotters to print the drawing on film, instead of a writing unit, they have a cutter.
Plotters usually communicate with a computer via a serial, parallel or SCSI interface. Some plotter models are equipped with a built-in buffer.
Plotters can use both special technologies and technologies that are familiar from printers. Currently, inkjet devices are becoming increasingly widespread.
Projection technology.
A multimedia projector allows you to reproduce on a large screen information received from a wide variety of signal sources: computer, VCR, video camera, photo camera, game console. A modern projector is the most advanced link in the chain of evolution of projection equipment.
Multimedia projector
A multimedia projector is a modern and high-tech device. The reliability of most manufactured models is high, and the user is unlikely to have to contact a service center to request repairs. The only replaceable part of the projector is its lamp. Most projectors use arc lamps, which have high brightness and a flatter spectrum than incandescent lamps. Their average service life is 2000 hours of operation. Sometimes it is useful to use the lamp's economical mode function, which doubles its life.
Audio system
Personal computers use a wide variety of sound signal generation schemes, from simple to complex.
These days there are a lot of speaker systems on the market that consist of two active speakers and are made using a 2.1 system. Such systems are popularly called “tweeters” because they are not capable of providing high quality sound even at low volume levels.
More recently, the ideal in the world of computer speaker systems was the 5.1 system, but recently acoustic manufacturers have been expanding the capabilities of their systems, which led first to the emergence of the 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 an impact on the PC. The variety of input devices produced has given rise to entire technologies: from touch 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 tried to develop the main information input device. This led to the creation of multimedia keyboards, which are becoming more and more popular these days.
Additional keys include groups of keys for controlling multimedia applications, keys for controlling 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 the computer via the PS/2 port, USB and via the IR port for wireless models. In the latter connection method, the keyboard requires an additional power source, such as a battery.
Scanner
To directly read graphic information from paper or other media in a PC, optical scanners. The scanned image is read and converted into digital form by elements of a special device: CCD chips. There are many types and models of scanners.
Handheld scanners- the simplest and cheapest. The main disadvantage is that the person himself moves the scanner around the object, and the quality of the resulting image depends on the skill and steadiness of the hand. Another important disadvantage is the small bandwidth
laser handheld scanner
· Drum scanners used in professional printing activities.
"home" drum scanner industrial drum scanner
· Sheet scanners. Their main difference from the previous two is that during scanning, a ruler with CCD elements is fixedly fixed, and the sheet with the scanned image moves relative to it using special rollers.
· Flatbed scanners. This is the most common type for professional work today. The object to be 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 at the bottom.
Flatbed scanner
· Projection scanners. A color projection scanner is a powerful multifunctional tool for inputting any color images, including three-dimensional ones, into a computer.
Handheld projection scanner
The interface may 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 card supplied, then easy compatibility is not always achieved.
· LPT- the scanner may need the port to support one of the high-speed protocols. While EPP is usually always available, 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 engineering and design work have been equipped with graphics tablets for more than ten years. This device greatly simplifies the entry of drawings, diagrams and drawings into a PC. At first, tablets were expensive devices and therefore were designed for purely professional use. But cheap home models have been produced for about five years now.
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 peripheral devices. It is peripheral devices that will be discussed in today’s article. If you have not read the article about computer devices, then follow the link « » .
Personal computer peripherals are devices that connect to the computer using special connectors. Below are examples of the main devices that can often be found on home computers.
Monitor, display, screen. This is a device that users often call a “TV.” It displays images on the screen, which means it is a very important component in a computer.
Based on operating technology, monitors 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. Using such a monitor is quite harmful to the user’s health; fortunately, they are rarely used today. The second type - liquid crystal monitor - is a modern solution, its use is much less harmful to health.
The second important characteristic is the screen size of the monitor. It is usually measured diagonally and indicated 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 (a regular square one is 4:3).
Monitors can be connected via the following interfaces: VGA, DVI, HDMI and DisplayPort. Currently, VGA and DVI interfaces are widely used on personal computers, and there are also various adapters if the monitor or motherboard does not provide these interfaces. This is a device for entering information. All keys are divided into several groups:
- Alphanumeric;
- Control keys (Enter, Backspace, Shift, Ctrl, Alt, Win, Caps Lock, Tab, Print Screen, Scroll Lock, Pause Break, Num Lock keys);
- 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. There are also usually Num Lock, Caps Lock, and Scroll Lock mode indicators.
The device can be connected via Ps/2,USB interface. There are also adapters that allow you to connect a USB keyboard to a PS/2 port and vice versa.
On laptops and netbooks, in order to save space, some groups of keys may be missing. They may also be missing from regular keyboards.
The advantage of a 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, so you do not need to restart the computer to start working with it. If you connect a PS/2 keyboard while the computer is turned on, the system will not be able to detect the device and you will have to restart the computer to start using the keyboard.
This 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 expanded set: more than one wheel and additional keys on the left and right sides of the mouse, which are very popular among “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.
Based on the principle of operation, mice can be 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 find out the direction and speed of movement. Laser mice are a type of optical mouse.
The difference is that the LED is replaced by a miniature laser. This made it possible to get rid of the mouse glow and increased 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 when the computer is turned on.
This is a device for outputting (printing) information onto paper.
First of all, they differ in printing technology. There are laser (LED printer), inkjet, matrix and other printers (solid ink, sublimation).
Laser printers are the most practical devices for operation. They have the highest printing speed, cartridge life and the lowest cost of maintenance and refilling. They are usually black and white, although they also exist in color. A special powder called toner is used for printing. It is applied to a sheet of paper in the desired places, and then fixed to it by heating and melting. There is also an LED printer, which is a parallel branch of 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 medium. Mixing these colors in different combinations gives the entire palette when printing. The disadvantage is the danger of the ink drying out in the cartridge in case of prolonged inactivity and the low printing speed. However, such printers provide the highest quality color printing, as well as a low cost of refilling, provided they use CISS - a continuous ink supply system. This is a system in which ink containers are located next to the printer and the cartridges are supplied through special tubes.
Matrix printer. This is the oldest and least convenient option. It uses a ribbon impregnated with a dye 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 when printing. However, they are still used in many organizations because some older software products can only print on such printers.
Printers are connected to a computer via a USB or LPT interface (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 text recognition programs 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.
The 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 the computer (copier), and can also perform fax functions.
Connect 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 - a green round connector on the motherboard or discrete sound card; as well as to a power source, usually a regular outlet, but there are versions powered by USB. 
Peripheral devices include many other devices: uninterruptible power supplies, web cameras, external modems and many other useful devices. It is not possible to consider them all in one lesson, so we will focus on the most popular representatives of this group of peripherals described above. Currently, wireless peripherals are being developed: mice, keyboards, printers, etc.
