Keyboard Layout

1. keyboard is a typewriter-style keyboard, which uses an arrangement of buttons or keys, to act as mechanical levers or electronic switches. Following the decline of punch cards and paper tape, interaction via teleprinter-style keyboards became the main input device for computers.

2. Keyboard Layout

3. A keyboard typically has characters engraved or printed on the keys and each press of a key typically corresponds to a single written symbol. However, to produce some symbols requires pressing and holding several keys simultaneously or in sequence. While most keyboard keys produce letters, numbers or signs (characters), other keys or simultaneous key presses can produce actions or computer commands. In normal usage, the keyboard is used to type text and numbers into a word processor, text editor or other program. In a modern computer, the interpretation of key presses is generally left to the software. A computer keyboard distinguishes each physical key from every other and reports all key presses to the controlling software. Keyboards are also used for computer gaming, either with regular keyboards or by using keyboards with special gaming features, which can expedite frequently used keystroke combinations. A keyboard is also used to give commands to the operating system of a computer, such as Windows' Control-Alt-Delete combination, which brings up a task window or shuts down the machine. Keyboards are the only way to enter commands on a command-line interface.

4. Keyboard Types Standard Standard "full-travel" alphanumeric keyboards have keys that are on three-quarter inch centers (0.750 inches, 19.05 mm), and have a key travel of at least 0.150 inches (3.81 mm). Desktop computer keyboards, such as the 101-key US traditional keyboards or the 104-key Windows keyboards, include alphabetic characters, punctuation symbols, numbers and a variety of function keys. The internationally common 102/105 key keyboards have a smaller 'left shift' key and an additional key with some more symbols between that and the letter to its right (usually Z or Y). Also the 'enter' key is usually shaped differently.[1] Computer keyboards are similar to electric-typewriter keyboards but contain additional keys. Standard USB keyboards can also be connected to some non-desktop devices.[2

5. Keyboard Types Laptop-size Keyboards on laptops and notebook computers usually have a shorter travel distance for the keystroke and a reduced set of keys. They may not have a numerical keypad, and the function keys may be placed in locations that differ from their placement on a standard, full-sized keyboard.

6. Keyboard Types Thumb-sized Smaller external keyboards have been introduced for devices without a built keyboard, such as PDAs, and smartphones. Small keyboards are also useful where there is a limited workspace.

7. PS2 & USB Connector The PS/2 connector is a 6-pin Mini-DIN connector used for connecting some keyboards and mice to a PC compatible computer system. Its name comes from the IBM Personal System/2 series of personal computers, with which it was introduced in 1987. 

8. Mouse Types Mechanical Mouse Optical /Laser Mouse Inertial Mouse 3-D Mouse Tactile Mouse A mouse is a pointing device that functions by detecting two-dimensional motion relative to its supporting surface. Physically, a mouse consists of an object held under one of the user's hands, with one or more buttons. It sometimes features other elements, such as "wheels", which allow the user to perform various system-dependent operations, or extra buttons or features that can add more control or dimensional input. The mouse's motion typically translates into the motion of a pointer on a display, which allows for fine control of a graphical user interface.

9. This mouse has two freely rotating rollers. They are located 90 degrees apart. One roller detects the forward–backward motion and other the left–right motion. Opposite the two rollers is a third one (white, in the photo, at 45 degrees) that is spring-loaded to push the ball against the other two rollers. Mechanical Optical mice make use of one or more light-emitting diodes (LEDs) and an imaging array of photodiodes to detect movement relative to the underlying surface, rather than internal moving parts as does a mechanical mouse. A laser mouse is an optical mouse that uses coherent (laser) light. Optical Mouse Often called "air mice" since they do not require a surface to operate, inertial mice use a tuning fork Inertial Mouse Also known as bats,[26] flying mice, or wands,[27] these devices generally function through ultrasound and provide at least three degrees of freedom. A recent consumer 3D pointing device is the Wii Remote. 3 – D mouse

10. Ajoystick is an input device consisting of a stick that pivots on a base and reports its angle or direction to the device it is controlling. Joysticks, also known as 'control columns', are the principal control in the cockpit of many civilian and military aircraft, either as a center stick or side-stick. They often have supplementary switches on them to control other aspects of the aircraft's flight. Many people use joysticks on computer games involving flight such as flight simulator. Joysticks are often used to control video games, and usually have one or more push-buttons whose state can also be read by the computer. A popular variation of the joystick used on modern video game consoles is the analog stick. Joysticks are also used for controlling machines such as cranes, trucks, underwater unmanned vehicles, wheelchairs, surveillance cameras and zero turning radius lawn mowers. Miniature finger-operated joysticks have been adopted as input devices for smaller electronic equipment such as mobile phones.

11. image scanner—often abbreviated to just scanner—is a device that optically scans images, printed text, handwriting, or an object, and converts it to a digital image. Hand-held scanners, where the device is moved by hand, have evolved from text scanning "wands" to 3D scanners used for industrial design, reverse engineering, test and measurement, orthotics, gaming and other applications. Mechanically driven scanners that move the document are typically used for large-format documents, where a flatbed design would be impractical. Modern scanners typically use a charge-coupled device (CCD) or a Contact Image Sensor (CIS) as the image sensor, whereas older drum scanners use a photomultiplier tube as the image sensor. A rotary scanner, used for high-speed document scanning, is another type of drum scanner, using a CCD array instead of a photomultiplier. Other types of scanners are planetary scanners, which take photographs of books and documents, and 3D scanners, for producing three-dimensional models of objects.

12. Scanner Types Drum Scanner Drum scanners capture image information with photomultiplier tubes (PMT), rather than the charge-coupled device (CCD) arrays found in flatbed scanners and inexpensive film scanners. Reflective and transmissive originals are mounted on an acrylic cylinder, the scanner drum, which rotates at high speed while it passes the object being scanned in front of precision optics that deliver image information to the PMTs. Most modern color drum scanners use three matched PMTs, which read red, blue, and green light, respectively. Light from the original artwork is split into separate red, blue, and green beams in the optical bench of the scanner.

13. Flat Bed / CCD Scanner A flatbed scanner is usually composed of a glass pane (or platen), under which there is a bright light (often xenon or cold cathode fluorescent) which illuminates the pane, and a moving optical array in CCD scanning. CCD-type scanners typically contain three rows (arrays) of sensors with red, green, and blue filters.

14. CIS( Contact Image Sensor )scanning consists of a moving set of red, green and blue LEDsstrobed for illumination and a connected monochromaticphotodiode array for light collection. Images to be scanned are placed face down on the glass, an opaque cover is lowered over it to exclude ambient light, and the sensor array and light source move across the pane, reading the entire area. An image is therefore visible to the detector only because of the light it reflects. CIS Scanner

15. Film Scanner Hand Scanner Other Scanner Types Smart Phone Scanner

16. Digitizer : (also graphic tablet , digitizing tablet, graphics pad, drawing tablet or pen tablet) is a computer input device that enables a user to hand-draw images and graphics, similar to the way a person draws images with a pencil and paper. These tablets may also be used to capture data or handwritten signatures. It can also be used to trace an image from a piece of paper which is taped or otherwise secured to the surface. Capturing data in this way, either by tracing or entering the corners of linear poly-lines or shapes is called  as digitizing. Digitizer

17. light pen is a computerinput device in the form of a light-sensitive wand used in conjunction with a computer's CRT TV set or monitor. • It allows the user to point to displayed objects or draw on the screen in a similar way to a touch screen but with greater positional accuracy. • It was long thought that a light pen can work with any CRT-based display, but not with LCD screens. • However, in 2011 Fairlight Instruments released its Fairlight CMI-30A, which uses a 17" LCD monitor with light pen control. Light Pen

18. A light pen is fairly simple to implement. A light pen works by sensing the sudden small change in brightness of a point on the Screen. It uses an  interrupt, at which point the scan position can be read from a special register, or computed from a counter or timer. The pen position is updated on every refresh of the screen.

19. Touch Screen • A touch screen is an electronic visual display that can detect the presence and location of a touch within the display area. • The term generally refers to touching the display of the device with a finger or hand. Touch screens can also sense other passive objects, such as a stylus. • Touchscreens are common in devices such as game consoles, all-in-one computers, tablet computers, and smartphones.

20. Used in • Smart Phone • Tablet PC • PDA • The touch screen has two main attributes. First, it enables one to interact directly with what is displayed, rather than indirectly with a pointer controlled by a mouse or touchpad. • Secondly, it lets one do so without requiring any intermediate device that would need to be held in the hand (other than a stylus, which is optional for most modern touch screens). • Such displays can be attached to computers, or to networks as terminals. • They also play a prominent role in the design of digital appliances such as the personal digital assistant (PDA), satellite navigation devices, mobile phones, and video games.

21. A charge-coupled device (CCD) is a device for the movement of electrical charge, usually from within the device to an area where the charge can be manipulated • The CCD is a major technology for digital imaging. • In a CCD image sensor, pixels are represented by p-doped MOS capacitors.  • These capacitors are biased above the • Although CCDs are not the only technology to allow for light detection, CCD image sensors are widely used in professional, medical, and scientific applications where high-quality image data is required Working : An image is projected through a lens onto the capacitor array (the photoactive region), causing each capacitor to accumulate an electric charge proportional to the light intensity at that location. A one-dimensional array, used in line-scan cameras, captures a single slice of the image, while a two-dimensional array, used in video and still cameras, captures a two-dimensional picture corresponding to the scene projected onto the focal plane of the sensor.

22. Once the array has been exposed to the image, a control circuit causes each capacitor to transfer its contents to its neighbor (operating as a shift register). • The last capacitor in the array dumps its charge into a charge amplifier, which converts the charge into a voltage. By repeating this process, the controlling circuit converts the entire contents of the array in the semiconductor to a sequence of voltages. • In a digital device, these voltages are then sampled, digitized, and usually stored in memory; in an analog device (such as an analog video camera), they are processed into a continuous analog signal (e.g. by feeding the output of the charge amplifier into a low-pass filter) which is then processed and fed out to other circuits for transmission, recording, or other processing.

23. An output device of computer hardware is used to communicate the results of data processing carried out by an computer to the outside world. Examples. Speaker Head Phone Printer Monitor • A liquid crystal display (LCD) is a flat panel display,  that uses the light modulating properties of liquid crystals . • Liquid Crystals do not emit light directly. • They are used in a wide range of applications, including computer monitors, television, instrument panels, aircraft cockpit displays,signage, etc. LCD Liquid Crystal Display

24. They are common in consumer devices such as video players, gaming devices, clocks, watches, calculators, andtelephones. • LCDs have replaced cathode ray tube (CRT) displays in most applications. • They are available in a wider range of screen sizes than CRT and plasma displays, and since they do not use phosphors, they cannot suffer image burn-in. LCDs are, however, susceptible to image persistence. [1] • LCDs are more energy efficient and offer safer disposal than CRTs. • Its low electrical power consumption enables it to be used in battery-oweredelectronic equipment. • It is an electronically modulated optical device made up of any number of segments filled with liquid crystals and arrayed in front of a light source (backlight) or reflector to produce images in color or monochrome. LCD Liquid Crystal Display

25. Printer is a peripheral which produces a text or graphics of documents stored in electronic form, usually on physical print media such as paper or transparencies. • Many printers are primarily used as local peripherals, and are attached by a printer cable or, in most new printers, a USB cable to a computer which serves as a document source. • a few modern printers can directly interface to electronic media such as memory cards, or to image capture devices such as digital cameras and scanners; • some printers are combined with scanners or fax machines in a single unit, and can function as photocopiers. • Printers that include non-printing features are sometimes called multifunction printers (MFP), multi-function devices (MFD), or all-in-one (AIO) printers. features.

26. Types of Printers Toner Based Printer Liquid Inject Printer Solid Ink Printer Inkless Printer Thermal Printer UV Printer Typewriter Printer Daisy Wheel Printer Dot Matrix Printer Line Printer Pen Based Plotter Teli typewriter Printer Photography Printers Barcode Printer Spark Printer Electrolytic Printer

27. Operation of Inkjet Printer Inkjet printing, like laser printing, is a non-impact process. Ink is emitted from nozzles while they pass over media. • The operation of an inkjet printer is easy to visualize: liquid ink in various colors being squirted onto paper and other media, like plastic film and canvas, to build an image. • A print head scans the page in horizontal strips, using the printer's motor assembly to move it from left to right and back again, while the paper is rolled up in vertical steps, again by the printer. • A strip (or row) of the image is printed, then the paper moves on, ready for the next strip. • To speed things up, the print head doesn’t print just a single row of pixels in each pass, but a vertical row of pixels at a time.

28. For most inkjet printers, the print head takes about half a second to print the strip across a page. On a typical 8 1/2"-wide page, the print head operating at 300 dpi deposits at least 2,475 dots across the page. Inkjet Printer Laser Printer Laser Printers are commonly used printers that are known for its rapid printing abilities. The other marked feature of a laser printer is the high quality text and graphics printing. It works basically on the principle of xerographic printing process. However, it is different from the analog photocopying machines in which the image produced is the result of direct scan of a laser beam on the photoreceptor of the printer.

29. laser printer is a common type of computer printer that rapidly produces high quality text and graphics on plain paper. As with digital photocopiers and multifunction printers (MFPs), laser printers employ a xerographic printing process, but differ from analog photocopiers in that the image is produced by the direct scanning of a laser beam across the printer's photoreceptor.