Data input and output devices. Computer input devices

Ergonomic keyboards not only increase typist productivity and reduce overall fatigue during the workday, but also reduce the likelihood and severity of a number of diseases, such as carpal tunnel syndrome and osteochondrosis of the upper spine.

Mouse– manipulator-type control device.Moving the mouse 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 permanent dedicated interrupt for the mouse, and the computer's basic input and output system (BIOS), located in read-only memory (ROM), does not contain software to handle mouse interrupts.Due to this, the mouse does not work the first moment after turning on the computer. It requires the support of a special system program - a mouse driver.The driver is installed either when you connect the mouse for the first time, or when installing the computer's operating system.Although the mouse does not have a dedicated port on the motherboard, to work with it, use one of the standard ports, tools 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 a keyboard, a mouse cannot be directly used to enter character information - its control principle is event-based.Mouse movements and mouse button clicks are events from the point of view of its driver program.

A standard mouse has only two buttons, although there are custom mice with three buttons or two buttons and one rotary control.Recently, mice with a scroll wheel located between two buttons and allowing scrolling in any Windows application have become increasingly common.

In addition to a regular mouse, there are other types of manipulators, for example: trackballs, penmouses, infrared mice.The trackball, unlike a mouse, is installed 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 working surface, which is why trackballs are widely used in portable personal computers.

Penmouse is an analogue of a ballpoint pen, at the end of which, instead of a writing unit, there is a unit that records the amount of movement.

For computer games and in some specialized simulators, lever-type manipulators (joysticks) and similar joypads, gamepads and steering-pedal devices are also used. Devices of this type are connected to a special port on the sound card or to a USB port.

Touchpad(English touchpad - touch pad), touch panel - a pointing input device, used most often in laptops.

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 a number of 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 across the entire screen, you only need to move your finger a little (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.

It is a lever on a stand that can be tilted in two planes.The lever may contain various types of triggers and switches.

Scanner– a device for inputting graphic images into a computer. A sheet of paper with an image is placed into the scanner. The device reads it and sends it to the computer in digital form. During scanning, a powerful lamp and a ruler with many light-sensitive elements located on it in a row move smoothly along the sheet with the image. Typically, photodiodes are used as photosensitive elements. Each photosensitive element produces a signal proportional to the brightness of the reflected light from the section of paper located opposite it. The brightness of the reflected beam changes because the bright areas of the scanned image are much more reflective than the dark areas covered with paint. Color scanners have three groups of photosensitive elements that process red, green and blue colors, respectively. Thus, each point in the image is encoded as a combination of signals produced by photosensitive elements of the red, green and blue groups. The signal encoded in this way is transmitted to the scanner controller in the system unit.

Distinguish hand-held, pull-through and flatbed scanners. In hand-held scanners, the user himself guides the scanner along the surface of the image or text. Stretch scanners are designed to scan images on sheets of only a certain size. The pulling device of such scanners sequentially moves all sections of the scanned sheet over a stationary photosensitive matrix. The most widely used are flatbed scanners, which allow you to scan paper sheets, books and other objects containing images. Such scanners consist of a plastic case covered with a lid. The upper surface of the body is made of optically transparent material, on which the scanned image is placed. After this, the image is covered with a lid and scanning is performed. During the scanning process, a lamp with a light-sensitive matrix moves under the glass.

The main characteristics of scanners are reading speed, which is expressed by the number of pages scanned per minute (pages per minute - ppm), and resolution, expressed by the number of dots of the resulting image per inch of the original (dots per inch - dpi).

In modern tablets, the main working part is also a network of wires (or printed conductors), similar to the one in the Grafacons. This grid has a fairly large pitch (3-6 mm), but the mechanism for registering the position of the pen allows you to obtain a step for reading information much smaller than the grid pitch (up to 200 lines per mm).

There are different types of tablets based on their operating principle and technology. INelectrostatictablets register a local change in electrical n potential grids under the feather. INelectromagnetic- the pen emits electricity electromagnetic waves, and the grid serves as a receiver. In both cases, power must be supplied to the pen.

Wacom created technology based on electromagnetic resonance , when the grid both emits and receives a signal. In this case, the signal emitted by the grid is used to power the pen, which, in turn, sends a response signal, which is not just a reflection of the original one, but a newly generated one, which, as a rule, carries additional information identifying a specific pen, as well as data on the pressure applied, fixation/position of controls on the pointer, whether the working tip of the pen or its “eraser” is used (if such functions are provided in it). Therefore, no separate power supply is required for such a device. But when operating electromagnetic tablets, interference from emitting devices is possible, in particular monitors. Some are based on the same operating principle. touchpads.

There are tablets that come with pens that can register pressure. Typically, the registration mechanism is based on the use of variable capacitor. In particular, this type of sensor is used in pens for Wacom tablets. Registration can also be done using component with variable resistance or variable inductance . There are implementations based onpiezoelectric effect. When you press the pen within the working surface of the tablet, under which a grid of conductors is laid, a potential difference arises on the piezoelectric plate, which allows you to determine the coordinates of the desired point. Such tablets do not require a special pen at all and allow you to draw on the working surface of the tablet as on a regular drawing board.

In addition to pen coordinates, modern graphics tablets can also determine pressure pen on the working surface, tilt, direction of rotation in the plane of the tablet and the force of compression of the pen with your hand.

Also, a set of graphics tablets may include a mouse together with a pen, which, however, does not work like a regular one.computer mouse, but on the same principle as the pen. This mouse can only work on a tablet. Since the resolution of a tablet is much higher than the resolution of a conventional computer mouse, using a mouse + tablet combination allows you to achieve significantly higher accuracy when entering.

Graphics tablets are used both for creating images on a computer in a way that is as close as possible to how images are created on paper, and for general work with interfaces that do not require relative input (although entering relative movements using a tablet is possible, it is often inconvenient).

In addition, they are convenient to use for transferring (rendering) ready-made images to a computer.

Input device

Introduction

Input devices are those devices through which information can be entered into a computer. Their main purpose is to implement an impact on the machine. The variety of input devices produced has given rise to entire technologies from touch to voice. Although they work on different principles, they are intended to implement one task - to allow a person to communicate with a computer. Graphic information input devices are widely used due to the compactness and clarity of the way they present information to humans. Based on the degree of automation of the search and selection of image elements, graphic information input devices are divided into two large classes: automatic and semi-automatic. In semi-automatic graphic information input devices, the functions of searching and selecting image elements are assigned to a person, and the transformation of the coordinates of the read points is performed automatically. In semi-automatic devices, the process of searching and selecting image elements is carried out without human intervention. These devices are built either on the principle of scanning the entire image, followed by its processing and conversion from a raster representation to a vector one, or on the principle of line tracking, which ensures reading of graphic information presented in the form of graphs, diagrams, and contour images. The main areas of application of graphic information input devices are computer-aided design systems, image processing, training, process control, animation and many others. These devices include scanners, encoding tablets (digitizers), light pens, touch screens, digital cameras, video cameras, computer keyboards, mice, and others.

The Keyboard is designed to enter information from the user into the computer.

The keyboard, despite strong competition from the mouse, is the main input device. Its dominant position is unlikely to change until a reliable and inexpensive system for recognizing human speech is created.

Keyboard with plastic pins

Plastic and rubber are used to make such keyboards. Pressing a key on such a keyboard often feels exceptionally soft. If you don't look at the screen, you don't know whether a key is pressed or not. Another drawback of these keyboards is vibration, which causes the effect of a key opening repeatedly if it is pressed incorrectly. Thus, it can easily happen that when you press a key, the corresponding symbol is displayed on the screen several times. For a device that types touch-type or at high speed, this is an extremely undesirable side effect.

Clicky keyboard

The above phenomena do not exist in the clicky keyboard. When you press a key on such a keyboard, the mechanical resistance of the key increases the deeper it is pressed. To overcome this resistance you need to expend a certain force, after which the key moves very easily. This ensures unambiguous contact.

Pressing and releasing a key is accompanied by a click, hence the name. Clicky keyboards are preferred over non-clicky keyboards because they can be assured of a relatively clean keystroke.

To connect the keyboard, a cable about 1 m long is used, which has a 5-pin DIN connector or a 6-pin Mini-DIN (PS/2).

The keyboard is one of the most important devices that determines the conditions for comfortable work on a PC. The main element of a keyboard is the keys. When purchasing a keyboard, you should test it thoroughly to determine whether the keyboard's mechanics suit your individual needs. It almost doesn't matter what materials are used for the keyboard case and keys. It can be either plastic or metal. Color and other aspects are not as important from a functional point of view as the keyboard mechanics used.

Along with the keyboard, the mouse is the most important means of entering information into the computer. The mouse is a small box with several buttons that easily fits in the palm of your hand. Mice are usually produced with two or three buttons, but special models have more than three buttons (for example, Internet mouse). Together with a wire for connecting to a computer, this device really resembles a mouse with a tail. Some application programs are designed to work only with a mouse, but allow the mouse to be replaced by commands entered from the keyboard.

For optimal functioning, the mouse must move on a flat surface - special mouse pads are usually used.

Optical-mechanical mouse

Despite the name, this is a very ordinary mouse. The movements of the rubber-coated metal ball contained inside are recorded by two plastic rollers located at right angles to each other (X and Y axis). These rollers have a disk with raster holes at the end (similar to a wheel with spokes). When you move the mouse across the mousepad, the ball sets in motion the rollers with disks in contact with it. Each disk is located between the light source and the photosensitive element, which, in the order in which the photosensitive elements are illuminated, determine the direction and speed of the mouse's movement.

Optical mouse

An optical mouse works on principles similar to the operation of an optical-mechanical mouse, only the movement of the mouse is not recorded by mechanical rollers. An optical mouse sends a beam to a special mouse pad. This beam, after being reflected from the mat, enters the mouse and is analyzed by electronics, which, depending on the type of signal received, determines the direction of movement of the mouse, based either on the angles of incidence of the light or on a special backlight. The advantage of such a mouse is reliability and reliability. Reducing the number of mechanical components leads to an increase in its service life.

Infrared mice

The godfathers of the infrared mouse were televisions, VCRs, etc. with remote control. An infrared radiation receiver is installed next to or on the computer, which is connected to the PC by cable. Mouse movement is detected using already known mechanics and converted into an infrared signal, which is then transmitted to the receiver. The advantage of free movement is somewhat reduced by the inherent disadvantage. For flawless transmission of the infrared signal, “eye” contact must always be established between the receiver and transmitter. You cannot block the emitter of such a mouse with books, heat-absorbing or other materials, since with low signal power the mouse will not be able to transmit the signal to the PC. Infrared mice are equipped with a rechargeable battery or a regular battery.

Radio mouse

A more interesting alternative is to transmit information from the mouse via a radio signal. In this case, there is no need for eye contact between the receiver and the transmitter. The operation of such mice may be disrupted by external interference.

Based on the principle of operation, a Trackball can best be compared to a mouse that lies on the table with its belly up.

There are two main ways to connect mice (wired): through a serial port - a 9-pin Sub-D connector and through a 6-pin PS/2 connector.

A scanner is an automatic graphic information input device. There are several types of scanners, differing in the way the reading mechanism (its head) and the original move relative to each other: manual, roll, flatbed, projection and drum.

A handheld scanner is the simplest type of scanner. Here, the role of the drive of the reading mechanism is performed by the human hand, and the nature of the work of this type of scanner is somewhat reminiscent of a mouse. Obviously, how evenly the user moves the scanner depends on the degree of distortion of the image transmitted to the computer. The main advantages of this type of scanners include small overall dimensions and relatively low price, while the disadvantages arise from the design principle. Using such scanners, it is impossible to enter an A4 format image in one pass, since the reading head is small in size (standard width is 105 mm). Modern hand-held scanners can provide automatic “gluing” of images, that is, they form a whole image from separately entered parts. In general, it is very difficult to achieve high image quality with their help, so hand-held scanners can be used for a limited range of tasks. In addition, they are completely devoid of the “intelligence” inherent in other types of scanners.

In roll scanners, the scanning head stands still, and the paper moves relative to it using a feeding mechanism (as in a dot-matrix printer). The main advantage - at a relatively low price of the scanner - is the ability to input documents in A4 format. However, you can scan a book only after first dividing it into separate sheets.

Flatbed (the most common type) scanners, in which the scanning head moves relative to the paper using a stepper motor, do not have this drawback. Originally used for scanning opaque originals. Almost all models have a removable cover, which allows you to scan “thick” originals (magazines, books). Additionally, some models can be equipped with a single sheet feeding mechanism. Recently, many leading companies in the production of flatbed scanners have begun to additionally offer a slide module (for scanning transparent originals). The slide module has its own light source located on top. This slide module is installed on a flatbed scanner instead of a simple cover and turns it into a universal one.

In projection scanners, the reading part moves using a micromechanism. Their appearance resembles a photographic enlarger. Some of these scanners do not use a special light source; natural light is sufficient. Although projection scanners provide high-resolution and high-quality scanning of small format slides (usually no larger than 4 by 5 inches in size), documents, books, adding the ability to enter projections of three-dimensional objects into a computer, they have a significant drawback - low scanning speed. There are two modifications: with a horizontal and vertical arrangement of the optical reading axis.

The main difference between drum scanners is that the original is fixed on a transparent drum, which rotates at high speed. The reading element is located as close as possible to the original. This design provides the highest scanning quality. Typically, three photomultiplier tubes are installed in drum scanners, and scanning is carried out in one pass. In order to reduce the cost, “younger” models from some companies use a photodiode as a reading element instead of a photomultiplier. Drum scanners are capable of scanning opaque and transparent at the same time.

There are only two types of originals: transparent (negative and positive slides), which are scanned in transmitted light, and opaque, scanned in reflected light. Opaque originals are either analogue images - photographs, or discrete ones - illustrations from printed publications.

In addition, information input devices include:

JOYSTICK - (eng. Joystick = Joy + Stick) - a control device in computer games. It is a lever on a stand that can be tilted in two planes. The lever may contain various types of triggers and switches. The word “joystick” is also commonly used to refer to a control lever, for example, in a mobile phone.

In Russian, the control handle of industrial mechanisms and vehicles (airplanes, etc.) is never called a joystick (unlike the English joystick).

LIGHT PEN - (English lightpen, also - stylus, English stylus) - one of the tools for entering graphic data into a computer, a type of manipulator.

Externally, it looks like a ballpoint pen or pencil connected by a wire to one of the computer’s I/O ports. Typically, a light pen has one or more buttons that can be pressed by the hand holding the pen. Inputting data using a light pen involves touching or drawing lines with the pen on the surface of the monitor screen. A photocell is installed in the tip of the pen, which registers the change in screen brightness at the point with which the pen comes into contact, due to which the corresponding software calculates the position “indicated” by the pen on the screen and can, depending on the need, interpret it in one way or another, usually as a reference to an object displayed on the screen or as a drawing command. The buttons are used similarly to the buttons of a Mouse-type manipulator - to perform additional operations and enable additional modes.

The light pen was common during the proliferation of EGA graphics cards, which usually had a connector for connecting a light pen. The light pen cannot be used with regular LCD monitors.

DIGITIZER (with a light pen) - A graphics tablet (or digitizer, digitizer, from the English digitizer) is a device for entering handwritten drawings directly into a computer. Consists of a pen and a flat tablet that is sensitive to pressure or proximity of the pen.

Main user characteristics:

Working area - The working area is usually equal to one of the standard paper formats (A7-A0). The cost is approximately proportional to the area of ​​the tablet. It is more convenient to work on large tablets.

Resolution - The resolution of the tablet is the step at which information is read. Resolution is measured in dots per inch (dpi). Typical resolution values ​​for modern tablets are several thousand dpi.

Degrees of Freedom - Degrees of freedom describes the number of quasi-continuous characteristics of the relative position of the tablet and pen.

The minimum number of degrees of freedom is 2 (X and Y positions of the projection of the sensitive center of the pen), additional degrees of freedom can include pressure, tilt of the pen relative to the plane of the tablet.

TOUCHPAD (English touchpad - touch pad), touch panel - a pointing input device, used most often in laptops.

Principle of operation. The operation of touchpads is based on measuring the capacitance of the finger or measuring the capacitance between the sensors. Capacitive sensors are located along the vertical and horizontal axes of the touchpad, which allows you to determine the position of your finger with the required accuracy.

Since the device operates by measuring capacitance, the touchpad will not work if you move a non-conductive object, such as the base of a pencil, over it. If you use conductive objects, the touchpad will only work if there is sufficient contact area. (Try touching the touchpad with your finger only slightly.) Wet fingers make the touchpad difficult to operate.

TOUCH SCREEN - designed to control devices by simply touching the screen. Touch screens have proven to be the most convenient way for humans to interact with machines. The use of touch screens has a number of advantages that are not available when using any other input devices: increased reliability, resistance to harsh external influences (including vandalism), and an intuitive interface.

Touch screens are used in payment terminals, information kiosks, trade automation equipment, pocket computers, operator panels in industry.

Principle of operation. The touch screen is a glass structure placed on the surface of the display that displays the navigation system. The required system function is selected by touching the corresponding image on the screen. The touch screen controller processes the coordinates of the touch point and transmits them to the computer. Special software starts the selected function.

1. Keyboard. The keyboard keys are connected to a pin matrix. Each key or key combination is assigned its own number (code). There is a separate microprocessor inside the keyboard. Each press of a key closes a contact. In this case, in accordance with the contact matrix, the microprocessor generates a code for the pressed key. This code is stored in a special area (microprocessor buffer) and becomes available for processing by software. The keyboard driver is usually supplied with the operating system. This program allows the user to select the alphabet and implement the key layout.

All keys can be divided into the following groups:

Alphanumeric keys;

Cursor keys;

Special control keys;

Function keys;

Additional keyboard.

Function keys F1-F12 are located at the top of the keyboard. These keys are designed for various special actions; they are programmable and have their own purpose for each software product.

2. Manipulators. Mouse manipulator– a command input device, which is a small device with several keys. Moving the mouse pointer across the screen is done by moving the mouse across the table. There are mechanical, optical and wireless devices. The mechanical device consists of a rubber ball that rotates when the mouse moves, and two mutually perpendicular rollers. The roller rotation sensors transmit signals to the computer. The “tail” of wires through which signals travel gives the device the name “mouse.” Electronic motion devices use the principle of processing reflected light pulses from the surface on which the mouse moves. Such devices are much more reliable than mechanical ones. Mice are produced that transmit information to the computer via an infrared channel (wireless). The characteristic of a mouse is resolution. It is measured in dpi (dot per inch - dots per inch). If a mouse has a resolution of 900 dpi and is moved 1 inch (2.53 cm) to the right, then the mouse drive receives information through the microcontroller about a shift of 900 units to the right. The ballistic effect is the dependence of the accuracy of mouse positioning on the speed of its movement. The mouse driver is supplied with the device. Modern operating systems contain drivers for most manipulators of this type and automatically select the most suitable one when you turn on the computer.

Joystick- control device for computer games. It is a lever on a stand that can be tilted in two planes. The lever may contain various types of triggers and switches. The word “joystick” is also commonly used to refer to a control lever, for example, in a mobile phone.

Light pen– one of the tools for entering graphic data into a computer. Externally, it looks like a ballpoint pen or pencil connected by a wire to one of the computer’s I/O ports. Typically, a light pen has one or more buttons that can be pressed by the hand holding the pen. Inputting data using a light pen involves touching or drawing lines with the pen on the surface of the monitor screen. A photocell is installed in the tip of the pen, which registers the change in screen brightness at the point with which the pen comes into contact, due to which the corresponding software calculates the position “indicated” by the pen on the screen and can, depending on the need, interpret it in one way or another, usually as a reference to an object displayed on the screen or as a drawing command. The buttons are used similarly to the buttons of a mouse manipulator - to perform additional operations and enable additional modes.

3. Scanner– a device for converting graphic information into digital information. The function of a scanner is to obtain an electronic copy of a document created on paper. The lamp illuminates the scanned text, the reflected rays fall on a photocell consisting of many photosensitive cells. Each of them acquires an electrical charge when exposed to light. The analog-to-digital converter assigns a numerical value to each cell, and this data is transmitted to the computer. Scanners are hand-held and desktop (portable page or sheet-fed, flatbed, slide scanners, drum scanners); they can be black and white (up to 64 shades of gray) and color (256 - 16 million colors).

Hand-held scanners look like a large “mouse” that the user moves over the scanned image. However, manual movement of the device along the paper and the small size of the scanned area do not provide sufficient speed and require careful joining of individual sections of the image.

The main distinguishing feature of a flatbed scanner is that the scanning head moves relative to the stationary paper. They are simple and easy to use, allowing you to scan images from individual sheets, as well as from books and magazines.

With handheld page scanners, the paper moves relative to the scanning head. They are quite compact, but it is unlikely that you can scan a drawing from a book with them. This type of scanner is used to input document pages in formats from business cards to A4; the automatic paper feeding system ensures uniform scanning across the entire width of the sheet.

Slide scanners are highly specialized devices designed to capture images from transparent material (photographic film) with high resolution and image quality. They have a pronounced professional orientation and high cost.

Drum scanners are professional stationary devices designed for use in printing and scanning large-format images. The main advantages are high scanning speed and accuracy due to a permanently fixed scanning element and high uniformity of rotation of the drum with the scanned image placed on it.

The main characteristics are:

Resolution (optical resolution), that is, the number of recognizable dots (pixels) per inch;

Scanning speed is a performance indicator that is equal to the time spent processing one line of an image;

Dimensions of the scanned sheet (scanning area);

Bit width - determines the maximum number of colors or shades of gray that the scanner can perceive.

The scanner driver is designed to control the scanning process and configure basic scanner parameters. Sometimes drivers are supplemented with means for manipulating scanned images (change brightness, contrast, etc.). Scanners can be used to simply transfer pictures (photos, drawings, etc.) into computer memory or onto a display screen, or for quickly entering text documents. In the second case, it is necessary to extract (recognize) letters, numbers, spaces, tabs, columns from a graphic image, that is, convert the image into text format. Optical character recognition programs are designed to convert scanned texts into text codes.

4. Touch devices. Digitizer(graphics tablet) is a device for entering handwritten drawings directly into a computer. Consists of a pen and a flat tablet that is sensitive to pressure or proximity of the pen.

Main user characteristics:

The working area is usually equal to one of the standard paper formats (A7-A0);

Resolution – step of reading information;

The number of degrees of freedom describes the number of characteristics of the relative position of the tablet and the pen. The minimum number of degrees of freedom is 2 (X and Y positions of the projection of the sensitive center of the pen), additional degrees of freedom may include pressure, tilt of the pen relative to the plane of the tablet.

Touchpad(touchpad) is a pointing input device, most often used in laptops. Touchpads work by measuring the capacitance of your finger or measuring the capacitance between the sensors. Capacitive sensors are located along the vertical and horizontal axes of the touchpad, which allows you to determine the position of your finger with the required accuracy. Since the device operates by measuring capacitance, the touchpad will not work if you move a non-conductive object, such as the base of a pencil, over it.