Input Devices
Keyboard
The main input device for a computer is keyboard, which is a set of mechanical sensors that perceive pressure on the keys and close in one way or another a certain electrical circuit. Currently, two types of keyboards are common: with mechanical or with membrane switches. In the first case, the sensor is a traditional mechanism with special alloy contacts. In the second case, the switch consists of two membranes: the upper one is active, the lower one is passive, separated by a third membrane-gasket.
As a rule, inside the body of any keyboard, in addition to the key sensors, there are electronic decryption circuits and a microcontroller. The exchange of information between the keyboard and the motherboard is carried out via a special serial interface in 11-bit blocks. The basic principle of the keyboard is to scan the key switches. Closing and opening any of these switches corresponds to a unique digital code - a scan code. When the key is released, the IBM PC AT keyboard prefaces the scan code with code F016. When the keyboard controller detects a key being pressed or released, it will trigger a hardware interrupt IRQ1. If in keyboards of computers like IBM PC XT data transfer can be carried out only in one direction, then in keyboards like IBM PC AT such communication is already possible in two directions, i.e. the keyboard can receive special commands (setting auto-repeat delay parameters and auto-repeat frequency) . The keyboard is connected to the system board using electrically identical 5 DIN 5 connectors DIN (Deutsche Idustrie Norm) - German industrial standard. or 6 mini-DIN, the latter being first introduced in the IBM PS/2, from which it inherited its "slang" name. A single data line is used for bi-directional communication, but requires open-collector outputs.
Mouse
The first computer mouse was created by Douglas Engelbart in 1963 at the Stanford Research Center. The spread of the mouse was due to the growing popularity of software systems with a graphical user interface. The mouse makes it convenient to manipulate objects that are widely used in graphics packages, such as windows, menus, buttons, icons, etc.
The first mouse, when moving, rotated two wheels that were connected to the axes of variable resistors. Moving the cursor of such a mouse was caused by a change in the resistance of variable resistors. Most modern mice have an optical-mechanical design (Fig. 16.1). A heavy rubberized ball of a relatively large diameter is in contact with the surface along which the mouse is moved. When moving the mouse, this ball can rotate two perpendicular rollers pressed against it. The axis of rotation of one of the rollers is vertical, and the other is horizontal. Sensors are installed on the axis of the rollers, which are disks with slots, on opposite sides of which there are LED-photodiode optocouplers. The order in which the photosensitive elements of one axis are illuminated determines the direction of mouse movement, and the frequency of the pulses coming from them determines the speed.
Rice. 16.1.
Another popular mouse design is the all-optical design. With the help of an LED and a lens system that focuses its light, a surface area under the mouse is highlighted. The light reflected from this surface is in turn collected by another lens and hits the receiving sensor of the image processor chip. This chip takes pictures of the surface under the mouse at high frequency and processes them. Based on the analysis of a series of successive images, which is a square matrix of pixels of different brightness, the integrated DSP-processor calculates the resulting indicators indicating the direction of mouse movement along the X and Y axes, and transmits the results of its work to the peripheral interface. The main characteristics that ensure the reliability of the operation of optical mice are determined by the technical parameters of the sensors used (Table 16.1).
| Sensor brand | HDNS-2000 | ADNS-2620 | ADNS-2051 | ADNS-3060 |
| Resolution, cpi (dots per inch) | 400 | 400 | 400/800 | 400/800 |
| Image size, pix. | 18x18 | 16x16 | 30x30 | |
| Max. speed, cm/s | 30 | 30 | 35 | 100 |
| Max. acceleration (in a jerk), m/s 2 | 1,5 | 2,5 | 1,5 | 150 |
| Frame rate, frame/s | 1500 | 1500/2300 | 500-2300 | 500-6400 |
The first mice were connected to a PC through a special adapter board (the so-called bus mice - bus mouse). Then the method of connecting a mouse through a serial interface RS-232C became widespread. Mice with a serial interface for data transfer most often work with a protocol developed by Microsoft. Data is transmitted at 1200 bps, 7 data bits are used without parity check and one stop bit. One transmission contains three 7-bit numbers encoding 8-bit horizontal (dX) and 8-bit vertical movement (dY), as well as 2 bits (LB, RB) of button states (Table 16.2). The movement is specified as a signed number (-128:+127) in special units - counts, determined by the mouse resolution - counts per inch ( cpi ), which is usually 400 cpi . In addition to the Microsoft protocol, the Logitech protocol is also common (it differs from the Microsoft protocol in the way information about the middle button is transmitted) and the Mouse Systems protocol (5-byte, information about the "old" and "new" mouse position is transmitted).
| 6 | 5 | 4 | 3 | 2 | 1 | 0 | |
|---|---|---|---|---|---|---|---|
| byte 1 | 1 | LB | R.B. | dY7 | dY6 | dX7 | dX6 |
| byte 2 | 0 | dX5 | dX4 | dX3 | dX2 | dX1 | dX0 |
| byte 3 | 0 | dY5 | dY4 | dY3 | dY2 | dY1 | dY0 |
In 1987, IBM released the PS/2 series of personal computers, which introduced a dedicated serial mouse interface with a 6 mini-DIN connector. One of the advantages of the new ports compared to serial was the low supply voltage - 5 V instead of 12 V, as well as independence from other devices, while serial mice often interfered with internal modems, since the PC's four COM ports shared only two IRQs. The disadvantages of this interface should also be noted. Most notably, there is a higher risk of port failure when a mouse is connected or disconnected while the computer is running. Although the PS/2 mouse and keyboard serial ports have a similar electrical interface and even the same connectors, the motherboard will not recognize the mouse and keyboard if they are not connected to the "own" port. data transfer protocols are different, and in addition, the data line in the keyboard port is bidirectional. The Microsoft PC 97 specification proposes a unified color coding for these ports: for the keyboard - purple, for the mouse - green. PS / 2 ports became widespread with the introduction of the ATX standard by Intel in 1997. And already in 2002, in the Microsoft PC 2002 specification, it was proposed to abandon these ports in favor of universal interface USB.
Other input devices - manipulators
The trackball is an "inverted" opto-mechanical mouse - not the body of the device itself is set in motion, but only its ball. This makes it possible to significantly improve the accuracy cursor control and, in addition, save space, which is why trackballs are often used in laptops.
A touchpad ( touchpad or trackpad ) is an input device used in laptops that moves the cursor depending on the movements of the user's finger. Used as a replacement for a computer mouse. Touch panels vary in size, but usually their area does not exceed 50 cm2. The operation of the touch panel is based on finger capacitance measurement or capacitance measurement between sensors. Capacitive sensors are located along the vertical and horizontal axes of the panel, which allows you to determine the position of the finger with the desired accuracy. Because the device is capacitance based, it will not work if you drive it with any non-conductive object such as the base of a pencil. If conductive objects are used, the touchpad will only work if there is sufficient contact area, so, for example, working with wet fingers is very difficult. The advantages of touch panels are:
- there is no need for a flat surface, as for a mouse;
- the location of the touchpad is generally fixed relative to the keyboard;
- to move the cursor to the entire screen, only a slight movement of the finger is enough;
- working with them does not require much getting used to, as, for example, in the case of a trackball.
The disadvantage of touch panels is the low resolution, which makes it difficult to work in graphic editors and 3D games.
A joystick is an analog coordinate input device, usually in the form of two rheostatic sensors with a +5 V supply. The joystick handle is connected to two variable resistors that change their resistance when it is moved. One resistor determines movement along the X coordinate, the other determines the Y direction. The joystick is usually connected to the game port adapter located on the multi-function input / output card (Multi I / O Card) or sound card (in the latter case, the game port connector is combined with the MIDI interface) . Obviously, the main element of the gaming adapter is the ADC. The adapter accepts up to four digital on/off signals (buttons) and up to four analog signals, allowing you to connect two 2-button joysticks.
The light pen works with a small optical detector at its tip. As the screen is scanned by the electron beam, an optical detector pulse is initiated when the beam reaches the screen point over which the pen is located. The time of occurrence of this pulse relative to the horizontal and vertical synchronization signals allows you to determine the position of the light pen. At its core, the light pen is an extension of the video system. Light pen connector was mandatory for video adapters
- hand-held scanners - the problem of smooth and uniform movement of the scanning head over the corresponding image (on which the quality of the scanned image depends) is assigned to the user;
- flatbed scanners - the scanning head moves relative to the paper using a stepper motor;
- roll scanners - individual sheets of documents are pulled through the device so that the scanning head remains in place (not applicable for scanning books and magazines);
- projection scanners - the input document is placed on the scanning surface with the image up, while the scanning unit is also on top, and only the scanning device moves (it is possible to scan projections of three-dimensional objects). In Microtek scanners, the scanned image is illuminated alternately in red, green, and blue, so that the page is scanned in three passes. A similar approach is used in Epson and Sharp scanners, however, there a color change occurs for each line, which avoids problems with "aligning" pixels in different passes. In Hewlett Packard and Ricoh scanners, the scanned image is illuminated by a white light source, and the reflected light through a reducing lens enters a three-line CCD line through a system of special filters that separate the light into three components: red, blue, green.
To communicate with a computer, scanners, as a rule, use one of the universal peripheral interfaces: SCSI, IEEE 1284 or USB.
For unification application programming interface scanner drivers (as well as digital cameras) in 1992, Aldus, Caere, Eastman Kodak, Hewlett Packard and Logitech developed the TWAIN 6 word specification. TWAIN was taken from "The Ballad of East and West" by R. Kipling: "...and never the twain shall meet ..." (and the two will never meet), reflecting the complexity of the interaction between a computer and a scanner at that time. After the frequent capitalization of the name of the specification, there was a prejudice that it was an abbreviation, and such options were proposed: Technology Without An Interesting Name (technology without an interesting name) or Toolkit Without Any Important Name (a tool without any important name). .
Periphery all external additional devices connected to the computer system unit through special connectors are called.
By purpose, peripheral devices can be divided into:
input devices;
data output devices;
data storage devices;
communication devices.
Input devices
Keyboard;
Mouse, trackball or touchpad;
Joystick;
Scanner;
Graphic tablet (digitizer).
Keyboard
Keyboard- keyboard control device for a personal computer.
Used to enter alphanumeric (character) data, as well as control commands.
The keyboard belongs to the standard means of a personal computer.
Its main functions do not need to be supported by special system programs (drivers).
The necessary software to get started with the computer is already in the ROM chip as part of the basic input/output system (BIOS), so the computer responds to keystrokes as soon as it is turned on.
The standard keyboard has more than 100 keys, functionally divided into several groups:
Group of alphanumeric keys is designed to enter character information and commands typed by letter.
Each key can work in several modes (registers) and, accordingly, can be used to enter several characters.
Switching between lower case (for entering lowercase characters) and upper case (for entering uppercase characters) is performed by holding down the SHIFT key (non-fixed switching).
If you need to hard-switch the case, use the CAPS LOCK key (fixed switching).
For different languages, there are different schemes for assigning symbols of national alphabets to specific alphanumeric keys. Such schemes are called keyboard layouts.
For IBM PC personal computers, QWERTY (English) and YTSUKENG (Russian) layouts are considered typical.
Layouts are usually named according to the symbols assigned to the first keys of the upper line of the alphabetic group.
Function key group includes twelve keys (from F1 to F12) located at the top of the keyboard.
The functions assigned to these keys depend on the properties of the particular program currently running, and in some cases, on the properties of the operating system.
It is a common convention in most programs that the key F1 calls the help system, where you can find help about the operation of other keys.
Service keys are located next to the keys of the alphanumeric group. Due to the fact that they have to be used especially often, they have an increased size. These include the SHIFT and ENTER keys discussed above, the ALT and CTRL register keys (they are used in combination with other keys to form commands), the TAB key (to enter tab stops when typing), the ESC key (from the English word Escape) to refuse from the execution of the last command entered and the BACKSPACE key to delete the characters just entered (it is located above the ENTER key and is often marked with an arrow pointing to the left).
The service keys PRINT SCREEN, SCROLL LOCK and PAUSE/BREAK are located to the right of the group of function keys and perform specific functions depending on the operating system.
Two groups of cursor keys are located to the right of the alphanumeric pad.
A cursor is a screen element that indicates the place where character information is entered.
The cursor is used when working with programs that perform data and command input from the keyboard.
Cursor keys allow you to control the input position.
The keyboard is the main input device.
Special keyboards are designed to increase the efficiency of the data entry process.
This is achieved by changing the shape of the keyboard, its key layout, or the method of connecting to the system unit.
Keyboards that have a special shape, designed to meet the requirements of ergonomics, are called ergonomic keyboards.
It is advisable to use them at workplaces intended for entering a large amount of sign information.
Ergonomic keyboards not only increase typing productivity and reduce overall fatigue during the working day, but also reduce the likelihood and severity of a number of diseases, such as carpal tunnel syndrome and osteochondrosis of the upper spine.
The key layout of standard keyboards is far from optimal. It has been preserved from the time of early examples of mechanical typewriters.
Currently, it is technically possible to manufacture keyboards with an optimized layout, and there are samples of such devices (in particular, the Dvorak keyboard belongs to them).
However, the practical implementation of keyboards with a non-standard layout is questionable due to the fact that you need to learn how to work with them specially.
In practice, only specialized workstations are equipped with such keyboards.
According to the method of connection to the system unit, they distinguish wired And wireless keyboards.
The transmission of information in wireless systems is carried out by an infrared beam.
The typical range of such keyboards is several meters. The signal source is the keyboard.
Mouse
Mouse- manipulator type control device.
Mouse movement on a flat surface is synchronized with the movement of a graphic object (mouse pointer) on the monitor screen.
Unlike the keyboard discussed earlier, the mouse is not a standard control, and the personal computer does not have a dedicated port for it. There is no persistent dedicated interrupt for the mouse, and the computer's basic input and output (BIOS) hosted in read-only memory (ROM) does not contain software to handle mouse interrupts.
In this regard, at the first moment after turning on the computer, the mouse does not work. It needs the support of a special system program - the mouse driver.
The driver is installed either when you connect the mouse for the first time or when you install the computer's operating system.
Although the mouse does not have a dedicated port on the motherboard, one of the standard ports is used to work with it, the means for working with which are included in the BIOS.
The mouse driver is designed to interpret the signals coming through the port. In addition, it provides a mechanism for communicating information about the position and state of the mouse to the operating system and running programs.
The computer is controlled by moving the mouse along the plane and briefly pressing the right and left buttons (These presses are called clicks.)
Unlike the keyboard, the mouse cannot be directly used to enter sign information - its control principle is event-driven.
Mouse movements and clicks of its buttons are events from the point of view of its driver program.
By analyzing these events, the driver determines when the event occurred and where the pointer was on the screen at that moment. This data is passed to the application that the user is currently working with. According to them, the program can determine the command that the user had in mind, and proceed to its execution.
A standard mouse has only two buttons, although there are non-standard mice with three buttons or two buttons and one rotary encoder.
Recently, more and more widespread mouse with scroll wheel, located between two buttons and allowing you to scroll in any Windows application.
In addition to the usual mouse, there are other types of manipulators, for example: trackballs, penmauses, infrared mice.
trackball Unlike a mouse, it is stationary, and its ball is driven by the palm of the hand.
The advantage of a trackball is that it does not require a smooth work surface, which is why trackballs are widely used in portable personal computers.
Penmaus is an analogue of a ballpoint pen, at the end of which, instead of a writing knot, a knot is installed that registers the amount of movement.
infrared mouse differs from the usual one by the presence of a wireless communication device with the system unit.
For computer games and in some specialized simulators, lever-push type manipulators are also used ( joysticks) and similar joypads, gamepads and steering-pedal devices. Devices of this type are connected to a special port on the sound card or to a USB port.
touchpad
touchpad(English touchpad - touch pad), touchpad - pointing input device, used most often in laptops.
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Like other pointing devices, the touchpad is typically used to control the "pointer", the movement of a finger across the surface of the device.
Touchpads are fairly low resolution devices. This allows you to use them in everyday work at the computer (office applications, web browsers, logic games), but makes it very difficult to work in graphic editors.
However, touchpads also have several advantages, compared to other manipulators:
do not require a flat surface (unlike a mouse);
do not require a lot of space (unlike a mouse or graphics tablet) the location of the touchpad is fixed relative to the keyboard (unlike a mouse);
to move the cursor to full screen, only a small movement of the finger is enough (unlike a mouse or a large graphics tablet);
working with them does not require much getting used to, as, for example, in the case of a trackball.
Joystick
Joystick(Eng. Joystick = Joy + Stick) - a control device in computer games.
It is a lever on a stand that can be deflected in two planes.
On the lever there can be various kinds of triggers and switches.
Also, the word "joystick" in everyday life is called the control lever, for example, in a mobile phone.
Scanner
Scanner- a device that, by analyzing an object (usually an image, text), creates a digital copy of the image of the object.
Depending on the method of scanning an object and the objects themselves, there are the following types of scanners:
Tablet- the most common type of scanners, because it provides maximum convenience for the user - high quality and acceptable scanning speed. It is a tablet, inside of which a scanning mechanism is located under a transparent glass.
Manual- they do not have an engine, therefore, the user has to scan the object manually, its only advantage is cheapness and mobility, while it has a lot of disadvantages - low resolution, low speed, narrow scanning bandwidth, image distortions are possible, since it will be difficult for the user to move the scanner at a constant speed.
Sheet-fed- a sheet of paper is inserted into the slot and pulled along the guide rollers inside the scanner past the lamp. It is smaller than a flatbed, but can only scan individual sheets, which limits its use mainly to company offices. Many models have an automatic feeder, which allows you to quickly scan a large number of documents.
Planetary Scanners- used to scan books or easily damaged documents. When scanning, there is no contact with the scanned object (as in flatbed scanners).
Book Scanners- Designed for scanning bound documents. Modern models of professional scanners can significantly increase the safety of documents in archives, thanks to the very delicate handling of originals. Modern technologies used in scanning books and bound documents allow you to achieve high results. Scanning is done face up - so your scanning action is indistinguishable from flipping pages during normal reading. This prevents their damage and allows the user to see the document during the scanning process. The software used in book scanners allows you to eliminate defects, smooth out distortions, and edit the scanned page pages. Book scanners have a unique book "de-kink" feature that ensures excellent quality of the scanned (or printed) image.
Drum Scanners- used in printing, have a high resolution (about 10 thousand dots per inch). The original is placed on the inner or outer wall of the transparent cylinder (drum).
slide scanners- as the name implies, they are used to scan film slides, they are produced both as independent devices and as additional modules for conventional scanners.
Barcode Scanners- small, compact models for scanning product barcodes in stores.
How flatbed scanners work:
The object to be scanned is placed on the glass of the tablet with the scanned surface down. Under the glass is a movable lamp, the movement of which is controlled by a stepper motor.
The light reflected from the object, through a system of mirrors, enters a sensitive matrix (CCD - Couple-Charged Device), then to an analog-to-digital converter and is transmitted to a computer. For each step of the engine, a strip of the object is scanned, which are then combined by the software into a common image.
Scanner Features:
Optical resolution- The scanner does not capture the entire image, but line by line. A strip of photosensitive elements moves along the vertical of the flatbed scanner and captures the image point by point line by line. The more photosensitive elements the scanner has, the more dots it can take from each horizontal strip of the image. This is called optical resolution. Usually it is considered by the number of dots per inch - dpi (dots per inch). Today, a resolution level of at least 600 dpi is considered the norm.
Work speed- Unlike printers, the speed of scanners is rarely indicated, since it depends on many factors. Sometimes they indicate the scanning speed of one line in milliseconds.
Color depth- Measured by the number of shades that the device can recognize. 24 bits corresponds to 16,777,216 shades. Modern scanners are produced with a color depth of 24, 30, 36, 48 bits.
G graphic tablets (digitizers)
These devices are designed to enter artistic graphic information.
There are several different ways in which graphics tablets work, but all of them are based on fixing the movement of a special pen relative to the tablet.
Such devices are convenient for artists and illustrators, as they allow them to create screen images with familiar techniques developed for traditional tools (pencil, pen, brush).
The technical characteristics of the tablets include: resolution (lines/mm), area of the working area and the number of levels of pen pressure sensitivity.
Hello. In today's issue, I will continue the topic of a computer device and talk about it peripherals. This is the second part of a large article, in the last publication we analyzed the first part of the computer device - the system unit.
If you have not read the first part of the article, then I recommend that you definitely get acquainted with it, in it I tell you about the device of the computer, namely.
Computer Peripherals
Well, the turn has come to talk about peripherals, let's consider the most basic ones.
Mouse
The mouse is needed in order to move the cursor to the required space on the desktop. There are three types of mice: mechanical, with a ball inside; optical and laser.
I remember once used a mechanical mouse. It was necessary to forcefully drive on the rug in order to move the mouse cursor to the desired location on the desktop. There are ordinary cheap mice and special heaped gaming ones. I have a large mat at home and a gaming laser mouse, which at that time I bought about $ 50.
Keyboard
The keyboard will play a supporting role in managing our computer.
With it, you can type text, chat with friends, play different games and much more. My keyboard played an important role in writing this article.
Monitor
Probably nowhere without a monitor. Without him, there probably wouldn't be a computer :). The display is needed to display information on the screen, which in turn passes through the video card. Monitors are divided into three groups: cathode ray tube (CRT), liquid crystal (LCD) and plasma. The latter are most often used for the manufacture of new TVs.
The average monitor starts at 15 inches and ends at 32 inches. If there are more inches, then this is already considered a TV.
Most PC users now have LCD monitors, but there are also CRTs. I use a regular LCD monitor with a diagonal of 19 inches, which is about 48 centimeters, almost half a meter, which suits me perfectly.
Speakers and headphones
Headphones and speakers are necessary to output sound from the computer to our ears. Every computer and laptop has a sound card. Basically, they are built into the motherboard.
If you have good speakers, high quality audio files and want to listen to them with pleasure, you can buy a separate sound card. Decent zvukovuhi cost about $ 100, of course there are cheaper ones, but why buy a cheap one if a similar one is already built into the mother.
There are times when the internal sound card is broken. Of course, you can try to solder the connector or the sound chip, but not everyone understands this. Therefore, to solve this problem, you can replace the entire motherboard or buy an inexpensive external sound card.
It is advisable to use speakers made of wood, they have a pretty good sound transmission capacity, but plastic ones are also not bad. The more watts your speakers can give you, the clearer and louder the sound will be.
Modem
A modem is a network device that was invented to access the Internet through it and communicate with other users.
Dialup (Dial Up) modems
There used to be simple slow 56k modems. The number 56 means a data transfer rate of 56 kbps. I remember a couple of years ago I worked in a company where we used just such modems.
For those who don't know, I'm posting an audio track Noise dialup modem when it goes online. And those who remember these times, just listen. When I heard it, for some reason, a smile crept onto my face.
Dial-Up Modem Connect
Some remote towns and villages still use such dial-up modems.
ADSL modems
At the moment, probably in all major cities they use high-speed Internet, using ADSL modems, dedicated VPN channels, wireless Wi-Fi and others.
Webcam
A webcam is needed to transmit pictures, video images, and sometimes sound, if there is a built-in microphone. Using a webcam, you can talk to a person both in the next room and in another country, using the Internet and third-party programs.
Microphone
A microphone is needed in order to record or transmit your voice. It is found in most webcams and headphones with a microphone.
USB drives
USB storage devices are small devices that store information on flash drives and hard drives. Such a device is universal, it can probably be connected to any computer via a USB port.
The volumes of flash drives are different, starting at 128 megabytes and ending at 1 terabyte. USB hard drives have a larger storage capacity of course.
a printer
A printer is needed in order to print any information, documents, photos, and so on.
They are matrix, inkjet and laser. I recently learned that there are such printers in which wax tubes are used instead of cartridges and toner.
Scanner
The scanner was invented to scan (read) information from printed and other media, then enter it on a computer.
If you often scan documents, then this tool is a must for you.
UPS or UPS
Uninterruptible power supplies or AC rectifiers are needed so that if a power surge occurs, they even out such surges.
Also, if you suddenly turn off the light, within 5 - 10 minutes your computer will be able to work.
Joysticks and Gamepads
With the help of joysticks and game pads, you can comfortably play various computer games. Children and teenagers love them.
Basically all the main peripherals, there are, of course, others, but they are less used than those listed above.
Conclusion
Today we talked in detail about the device of a computer and its peripheral components which include: mouse, keyboard, monitor, speakers and headphones, modem, webcam, microphone, USB drives, printer, scanner, UPS, joysticks, and gamepads.
Computer Peripherals | website
Perhaps you have or have questions related to the device of the computer and its peripherals. You can ask them below in the comments to this article, as well as use the form with me.
Thank you for reading me
The main purpose of the PU is to ensure that programs and data for processing enter the PC from the environment, as well as the output of the results of the PC in a form suitable for human perception or for transfer to another computer, or in another necessary form. PU to a large extent determine the possibility of using PC.
Peripheral devices can be divided into several groups according to their functional purpose:
1. I/O devices- designed to enter information into a PC, output in the format required for the operator or exchange information with other PCs. External drives, modems can be attributed to this type of PU.
2. Output devices- designed to display information in the required format for the operator. This type of peripherals includes: printer, monitor, audio system.
3. Input devices- Input devices are devices through which information can be entered into a computer. Their main purpose is to implement the impact on the machine. These types of peripherals include: keyboard, scanner, graphic tablet, etc.
4. Additional PU- such as the "mouse" manipulator, which only provides convenient control of the graphical interface of PC operating systems and does not carry pronounced functions of input or output of information; WEB-cameras that facilitate the transmission of video and audio information on the Internet, or between other PCs. The latter, however, can also be attributed to input devices, thanks to the ability to save photo, video and audio information on magnetic or magneto-optical media.
Each of the listed groups of devices perform certain functions limited by their capabilities and purpose.
Peripheral input-output information devices.
There are several types of I/O peripherals depending on the purpose.
Winchester
Winchesters or hard disk drives- this is a large-capacity external memory designed for long-term storage of information, combining the storage medium itself and the recording / reading device in one case. Compared to disk drives, hard drives have a number of very valuable advantages: the amount of stored data is immeasurably larger, and the access time of a hard drive is an order of magnitude less. The only drawback: they are not designed to share information.
The physical dimensions of hard drives are standardized by a parameter called the form factor.
A hard drive consists of several hard drives with a magnetic layer applied to the surface and located one under the other. Each disk has a pair of read/write heads. When the computer is turned on, the hard drive disks are constantly spinning, even when there is no access to the hard drive, thus saving time on overclocking it.
To date, the following types of hard drives have been developed: MFM, RLL, ESDI, IDE, SCSI.
External drives:
· Tape (magnetic) drives- streamers. Due to the relatively large volume and fairly high reliability, they are most often used as part of data backup devices in enterprises and large companies.
· Magneto-optical drives- drives CD-ROM, CD-R, CD-RW, DVD-R, DVD-RW. They can also be used as backup devices, but unlike tape drives, they have a much smaller data capacity.
Flash cards.
Fifteen years ago, Toshiba came up with a non-volatile semiconductor memory technology that it called flash memory. Flash memory allows you to write and erase data without such difficulties, thanks to which it has good speed and, moreover, is quite reliable.
Soon, flash memory chips began to be built into various devices, and on their basis flash cards were created, with which it was possible to transport various data.
Modems.
Currently, there are two types of modems: analog and digital.
Analog modems are more popular due to their low cost and are mainly used to access the Internet, and only occasionally to communicate with other PCs. Digital modems are quite expensive and are used for high-speed connections to the Internet, or to organize a local area network over long distances. Modems have several types of connections to a PC: COM, USB or via a network card. A modem connected via a COM port requires an additional power supply, and when connected via a USB port, there is no need for a power supply. xDSL modems also require an additional power supply.
Peripheral information output devices.
Peripheral output devices are designed to output information in the format required by the operator. Among them there are mandatory and optional devices.
Monitors
The monitor is a necessary information output device. The monitor allows you to display alphanumeric or graphical information in a form that is easy to read and control by the user. In accordance with this, there are two modes of operation: text and graphic. In text mode, the screen is presented in rows and columns. In graphical format, screen parameters are specified by the number of dots horizontally and the number of dotted lines vertically. The number of horizontal and vertical lines on the screen is called the resolution. The higher it is, the more information can be displayed per unit area of the screen.
· Digital monitors. The simplest - a monochrome monitor allows you to display only a black and white image. Digital RGB monitors support both monochrome and color modes.
· Analog monitors. Analog signal transmission takes place in the form of various voltage levels. This allows you to create a palette with shades of varying degrees of depth.
· Multi-frequency monitors. The video card generates clock signals that refer to the horizontal line rate and the vertical frame rate. The monitor must recognize these values and enter the appropriate mode.
CRT monitor
If possible, settings can be distinguished: single-frequency monitors that perceive signals of only one fixed frequency; multi-frequency, which perceive several fixed frequencies; multi-frequency, tuning to arbitrary values of the frequencies of synchronous signals in a certain range.
· Liquid crystal displays (LCD). The main disadvantage is the inability to quickly change pictures or quickly move the mouse cursor, etc. Such screens need additional illumination or external lighting. The advantages of these screens are in a significant reduction in the spectrum of harmful effects.
Liquid crystal display
· Gas plasma monitors. They do not have the limitations of LCD screens. Their disadvantage is the high consumption of electricity.
It is necessary to single out the group touch screens, since they allow not only to display data on the screen, but also to enter them, that is, they fall into the class of input / output devices. Such screens provide the easiest and shortest way to communicate with a computer: just point to what interests you. The input device is fully integrated into the monitor.
Gas plasma monitor
PC users spend many hours in close proximity to working monitors. In this regard, display manufacturers have increased their attention to equipping them with special means of protection against all types of influences that adversely affect the health of the user. Monitors with low radiation levels are currently being distributed. Other methods are used to increase the comfort of working with displays.
Printers
A printer is a widespread device for outputting information to paper, its name is derived from the English verb to print - to print. The printer is not included in the basic PC configuration. There are different types of printers:
· generic printer works like an electric typewriter. Advantages: a clear image of characters, the ability to change fonts when replacing a typical disk. Disadvantages: Printing noise, slow printing speed, graphics cannot be printed.
· Dot matrix (dot) printers- These are the cheapest devices that provide satisfactory print quality for a wide range of routine operations. Advantages: acceptable print quality, subject to a good ink ribbon, the possibility of carbon copy printing. Disadvantages: rather low print speed, especially for graphic images, significant noise level.
Matrix printer
· Inkjet printers provide better print quality. They are especially useful for color graphics output. The use of inks of different colors gives a relatively inexpensive image of acceptable quality.
Inkjet printers are much less noisy. The print speed depends on the quality. This type of printer occupies an intermediate accumulation between dot matrix and laser printers.
Jet printer
· Laser printers - have even higher print quality, close to photographic. They are much more expensive, but the print speed is 4-5 times faster than dot matrix and inkjet printers. The disadvantage of laser printers is rather stringent requirements for paper quality - it must be thick enough and not loose, printing on plastic-coated paper, etc. is unacceptable.
Laser printers are divided into two types: local and network. You can connect to network printers using an IP address.
Laser printer
· LED printers - alternative to laser.
Thermal printers are used to produce photographic quality color images. Requires special paper. Such printers are suitable for business graphics.
Much cheaper than laser and inkjet printers. Prints on any paper and cardboard. The printer operates at a low noise level.
Plotters (plotters ).
This device is used only in certain areas: drawings, diagrams, graphs, diagrams, etc. Plotters are indispensable in the development of architectural projects.
The plotting field of the plotter corresponds to A0-A4 formats, although there are devices that work with a roll that do not limit the length of the output drawing. That is, there are tablet and drum plotters.
· Tablet plotters, mainly for A2-A3 formats, fix the sheet and draw a drawing using a writing unit moving in two coordinates. They provide a higher accuracy of printing patterns and graphs compared to drum printing.
· Roll (drum) plotter - remains in fact the only developing type of plotter with a roller feed sheet and a writing unit that moves along one coordinate.
common cutting plotters to display the drawing on film, instead of a writing unit, they have a cutter.
Plotters usually communicate with a computer through a serial, parallel, or SCSI interface. Some models of plotters are equipped with a built-in buffer.
Plotters can use both special technologies and technologies familiar from printers. Currently, inkjet devices are becoming more common.
projection technology.
A multimedia projector allows you to play on a large screen information received from a wide variety of signal sources: a computer, a VCR, a camcorder, a camera, a game console. The modern projector is the most perfect link in the chain of evolution of projection equipment.
Multimedia projector
Multimedia projector is a modern and high-tech device. The reliability of most of the models produced is great, and the user is unlikely to have to contact a service center with a request for repairs. The only replaceable part of the projector is its lamp. Most projectors use high-brightness arc lamps with a smoother spectrum than incandescent lamps. Their average service life is 2000 hours of operation. Sometimes it is useful to use the lamp saver function, which doubles the lamp life.
Audio system
In personal computers, a wide variety of schemes for generating sound signals are used - from simple to complex.
These days there are a lot of acoustic systems on the market, consisting of two active speakers, and made according to the 2.1 system. Such systems are popularly called "tweeters" because they are not able to provide high quality sound even at a low volume level.
More recently, the 5.1 system was the ideal in the world of computer speaker systems, but recently speaker manufacturers have been expanding the capabilities of their systems, which led first to the appearance of a 6.1 system, and later 8.1
Peripheral input devices.
Input devices are those devices through which information can be entered into a computer. Their main purpose is to implement the impact on the PC. The variety of input devices produced has given rise to entire technologies: from tactile to voice.
Keyboard
The main input device of most computer systems is keyboard. Until recently, a standard keyboard was used, 101/102 keys, but with the development of personal computers, manufacturers also tried to develop the main input device. This led to the creation of multimedia keyboards, which are gaining more and more popularity these days.
Additional keys include groups of keys for controlling multimedia applications, keys for controlling the system volume, a group of keys for quickly launching office applications, a calculator, Internet Explorer etc.
Keyboards differ in two ways: connection method and design. The keyboard can be connected to a computer via the PS/2 port, USB and via the infrared port for wireless models. In the last connection method, the keyboard requires an additional power source, such as batteries.
Scanner
For direct reading of graphic information from paper or other media in a PC, optical scanners. The scanned image is read and digitized by the elements of a special device: CCD - chips. There are many types and models of scanners.
Hand scanners- the simplest and cheapest. The main disadvantage is that the person himself moves the scanner over the object, and the quality of the resulting image depends on the skill and hardness of the hand. Another major disadvantage is the small bandwidth
laser handheld scanner
· Drum Scanners used in professional typographical activities.
"home" drum scanner industrial drum scanner
· Sheet Scanners. Their main difference from the two previous ones is that during scanning, the ruler with CCD elements is fixed, and the sheet with the scanned image moves relative to it with the help of special rollers.
· Flatbed scanners. This is the most common type for professional work now. The object being scanned is placed on a glass sheet, the image is read line by line at a uniform speed by a reading head with CCD sensors located below.
Flatbed Scanner
· Projection scanners. The color projection scanner is a powerful multifunctional tool for entering any color images into a computer, including three-dimensional ones.
Handheld projection scanner
The interface can be different:
· Own interface - the scanner comes with its own unique card and only works with it.
· SCSI- if you use the scanner not with the supplied card, then easy compatibility is not always obtained.
· LPT- the scanner may need to support one of the high-speed protocols on the port. If EPP is usually always there, then the 8-bit Bi-Directional option required for Epson scanners is not implemented everywhere.
· USB- the most common connection option today.
· Graphics tablet.
Desktop computers for construction and design work have been equipped with graphics tablets for more than a decade. This device greatly simplifies the input of drawings, diagrams and drawings into a PC. At first, tablets were expensive devices and therefore were designed for purely professional use. But for five years, cheap home models have been produced.
Personal computer peripherals are all equipment that simplifies the interaction between the user and the computer.
In fact, the only elements of a PC that cannot be called its "peripherals" are, and RAM.
First of all, because they represent the computer itself, and also due to the fact that it is impossible to use a computing device without a chipset and a motherboard.
While without the rest it is quite possible to do this - and without a monitor, and without a video card, and even without a hard drive (when it is replaced with another drive), the system will start, although it will not be able to interact with a person.
By location, all peripherals for a PC can be divided into two groups:
- Internal devices installed inside the system unit. These include built-in drives for reading disks, hard and solid state drives, video cards and even microphones, and when it comes to laptop elements;
- External hardware located outside the computer. Among such devices, you can also find disk drives and hard drives - but only connected from the outside. External peripherals are called and, and, and input devices such as a keyboard and mouse.
Another classification option is by purpose.
All peripheral devices can be divided into three categories - input peripherals (manipulators, keyboards and scanners), output (display and printer) and data storage (and other types of drives).
Input Devices
Input peripherals are equipment designed to enter data into an electronic computer. There are several types of such devices:
In addition, devices for entering graphic and sound information are separately distinguished.
As well as pointing (coordinate) and gaming - while, for example, joysticks are classified as both the first and second types.
Whereas gamepads and steering wheels are only for devices designed for games.
Rice. 2. The main devices for entering information into a computer.
Keyboards and manipulators
Computer mice are designed to control the cursor and issue commands to the computer using the keys and wheels located on the manipulators.
Keyboards allow you to do the same by mechanically entering characters.
Modern operating systems practically cannot work without these devices - except for monoblocks with touch screens.
And for their connection, three connector options can be used (outdated Com-port, more modern PS / 2 and universal USB).
Although some models can connect to a PC (primarily laptops).
Certain types of coordinate peripherals for input include gaming devices - steering wheels, joysticks.
And even special dance platforms and light guns. In the same list is the trackball, the principle of which resembles a computer mouse.
Rice. 3. A gamepad that combines the functionality of a keyboard, gamepad, and tablet.
Transmission of sound and graphic information
To simplify the input of graphics, there is a special type of peripheral devices - graphic tablets.
With their help, you can transfer information to a PC by drawing on the surface, as on paper. The use of these peripherals is important for the development of drawings and the creation of design projects.
In order to bring a ready-made image and even text to a PC, they use it.
Scanners can be black and white and color, manual and desktop (which, in turn, are divided into roller and flatbed).
Need to know: A flatbed scanner allows you to scan any flat image - from a book, from a sheet of almost any size (if the formats do not match, scanning is carried out in parts). The roller version provides continuous scanning, but is only suitable for sheet materials.
Rice. 4. Scanning tablet device.
To transfer information to a PC in the form of a video recording, web cameras are used that connect to the system unit via USB or wirelessly.
They are also suitable for networking.
The camera can be equipped in order to record not only the image, but also the sound.
If this possibility is not provided, the recording should be carried out using an external device.
Rice. 5. Webcam with 1080p resolution.
The need to use microphones arises when transmitting audio information and the lack of built-in options that are typical for laptops.
However, even mobile computers sometimes need to connect an external device through a special 3.5 mm jack. For example, to get better sound.
The gaming devices for output include helmets and - although they can be used not only for games.
Rice. 7. Periphery for information output.
Output of graphic information
The main device for displaying graphic information from a computer is a video card. With its help, the data can be converted into a static image or video.
Rice. 8. External video card with two coolers.
The video card transmits the image to the monitor, which consists of a screen, a power supply and several control boards.
To connect this peripheral to a PC, different ports located directly on the graphics card can be used:
- on old computers - ;
- on more modern ones - DVI;
- on the latest models - and DisplayPort.
Rice. 9. Types of connectors for connecting a monitor.
Need to know: The difference between monitors and TVs is the lack of speakers (although some models have built-in speakers). Therefore, you can use them to receive a television signal only if you have a tuner on your computer (video card). At the same time, most TVs can be used as monitors.
To enlarge the image transmitted from the computer, peripheral devices such as projectors are used.
With their help, a picture or video is projected onto any flat (and preferably plain and light) surface.
Some projector models have built-in speakers and a card reader for reading information from external media, although most require a connection to a computer via USB, video input, and even Wi-Fi.
There are also projection devices that support 3D technology.
Rice. 10. Compact projector with USB connection.
While the top versions are almost a full-fledged computer - even with the operating system installed.
Rice. 11. AIO VR Sky CX-V3 virtual reality glasses with Android 5.1 OS.
The peripherals intended for static output of images include printers (and their special case - plotters).
With their help, a text or picture is applied to a solid medium - paper or film.
More modern devices allow you to get not a flat, but a three-dimensional image.
Peripherals are connected to the computer either using special ports (LPT1), or via a universal USB connector, or wirelessly.
Rice. 12. Compact home 3D printer.
Audio output
Speakers are used to convert information into an audio signal.
These include speakers, which are an almost indispensable attribute of a modern desktop computer, as a rule, not equipped with built-in speakers.
Laptops do not need external devices due to the presence of their speakers in the case.
However, to increase the volume and sound quality, even mobile computers can be connected (via a 3.5 mm jack or, in rare cases, via USB) external speakers.
You can do without an additional speaker system and when used as a monitor.
However, to transmit sound to only one user (in order not to disturb other people), you should use their more miniature variety - headphones.
Devices are connected to a stationary PC through a standard connector.
At the same time, some models can also be equipped with a microphone, which makes them more convenient for network communication or sound recording.
Rice. 13. Speakers and headphones.
