Input/output devices and memory storages
Input devices:
Keyboard
In computing, a keyboard is an input device, partially modeled after the typewriter keyboard, which uses an arrangement of buttons or keys, to act as mechanical levers or electronic switches. 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.
A computer keyboard distinguishes each physical key from every other and reports all keypresses to the controlling software. 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 Windows.
Different types, different layouts (notebook), new trends ..
Mouse (mechanical, optical, laser, wireless /cordless)
The oldest mouse design is the classic "mouse ball" design (mechanical mouse). This model of mouse operates by using a small ball that rolls against two bars. One bar controls vertical mouse movement, the other controls horizontal movement. Unlike some other kinds of computer mouses, this model requires frequent cleaning.
They are being replaced with optical mouses. These kinds of mouses replace the mouse ball with an optical display that uses a LED (light-emitting diode) and photodiodes to detect any mouse movement against a flat surface. Not only does this technology provide more accurate and reliable movement for the mouse, but also requires little maintenance. Laser mouse is a type of optical mouse which uses laser beam.
Trackball mouse (up-side-down mouse) is completely stationary on the desk. While these kinds of computer mouses have become extremely rare, with only one company still producing new models, they are still widely used by corporate offices as well as by people who have crippling illnesses that would make using a standard mouse hardly possible.
Gaming mouse is a type of optical mouse that has much more functionality than the standard mouse. Gaming mouses, in addition to the two main buttons and scroll bar, come equipped with many other buttons that allow users to adjust everything from the mouse sensitivity to assigning functions to the additional buttons that are placed near where the thumb rests.
3D mouses are a technology that companies have been toying around with since the 1990s. Commonly referred to as "wands," these mouses operate by using a motion-sensing device that determines the location, speed and direction of the wands, and adjusts the pointer on the screen to comply with movements. The first piece of electronics to popularize the 3D mouse technology was the Nintendo Wii.
Touchpad
A touchpad (also trackpad) is a pointing device consisting of specialized surface that can translate the motion and position of a user's fingers to a relative position on screen. They are a common feature of laptop computers and also used as a substitute for a computer mouse where desk space is scarce.
Digitizing tablet
A graphics tablet (or digitizing tablet, graphics pad, drawing tablet) is a computer input device that allows one to hand-draw images and graphics, similar to the way one draws images with a pencil and paper. These tablets may also be used to capture data or handwritten signatures.
A graphics tablet (also called pen pad or digitizer) consists of a flat surface upon which the user may "draw" an image using an attached stylus, a pen-like drawing apparatus. The image generally does not appear on the tablet itself but, rather, is displayed on the computer monitor. Some tablets however, come as a functioning secondary computer screen that you can interact with directly using the stylus.
Some tablets are intended as a general replacement for a mouse as the primary pointing and navigation device for desktop computers.
Microphone , camera, video camera, webcameras
Scanner
scanner is a device that optically scans images, printed text, handwriting, or an object, and converts it to a digital image.
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.
Joystick, gamepad
Output devices
Display device (display screen, monitor)
Monitor
CRTs produce images when the moving electron beam inside the large cathode tube moves back and forth, firing electronic beams at phosphor dots on the inside of the glass tube line by line. The phosphors in your CRT are chemicals that emit red, green, or blue light when struck by electrons. The smoothness of the image is determined by the scan rate of the beam (screen flicker increases as the speed decreases).
LCD monitors, liquid crystal displays, are flat panels. This digital technology was first invented in 1971.Initially used in watches and calculators, its functionality was quickly adopted and began redefining computer, medical, and industrial electronics. In computing, LCDs have been used for years in laptops, and later as flat panel computer screens, as well as being integrated into new technology television screens. It took until 2003 for the volume of these flat screens to escalate and capture half the monitor market. In 2005, LCD monitors exceed CRTs sales by more than 2-to-1.
There are no cathode ray tubes in the very thin LCD monitors. Instead, thin "sandwiches" of glass contain liquid-crystal filled cells (red, green and blue cells ) that make up a pixel. Arrays of TFTs (thin film transistors) provide the voltage power causing the crystals to untwist and realign so that varying amounts of light can shine through each, creating images. This particular sensitivity to light makes LCD technology very useful in projection (such as LCD front projectors), where light is focused through LCD chips
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CRT
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LCD
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Advantages
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Work better for multiple resolution
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Less eyestrain
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Contrast (dark is darker)
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Half of CRT energy consumption
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Flat
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Light, easy movable
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Disadvantages
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Radiation emission
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Best view – straight
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Size and weight
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Energy consumption
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Flickering
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Heating
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Data projektor
A device that projects computer output onto a white or silver fabric screen that is wall, projecting green or interactive board.. It is widely used in classrooms and auditoriums for instruction and slide presentations.
Printer
Three basic types:, Ink-jet(bubble-jet) printers, laser
Other types: wax, thermal
Important: price, operating costs (one page), quality (resolution DPI), speed (pager/min), noise, colour print
Dot matrix printers: low price, low operating costs (0,1 Kč per page), carbon copy, low quality, noisy
Ink-jets(bubble-jets) printers spray ionized tiny drops of ink onto a page to create an image. This is achieved by using magnetized plates which direct the ink's path onto the paper in the desired pattern. Almost all ink-jets offer a color option as standard, in varying degrees of resolution. Ink-jet printers are capable of producing high quality print which almost matches the quality of a laser printer. A standard ink-jet printer has a resolution of 300 dots per inch, although newer models have improved on that. As a rule color link-jet printers can also be used as a regular black and white printer.
Laser printers operate by shining a laser beam to produce an image on a drum. The drum gets in touch with toner and the electrically charged portions of the drum pick up toner powder. The powder on the drum is transferred onto the page. . Finally, using a combination of heat and pressure, the powder is fixed (fused) onto the paper. Laser printers print very fast, and the supply cartridges work a long time. Color laser printers use the same toner-based printing process as black and white ( B/W) laser printers, except that they combine four different toner colors. Color laser printers can also be used as a regular black and white laser printer.
Plotter
Plotters differ from printers. They draw lines using a pen. As a result, they can produce continuous lines, whereas printers can only simulate lines by printing a closely spaced series of dots. Multicolor plotters use different-colored pens to draw different colors.
In general, plotters are considerably more expensive than printers. They are used in engineering applications where precision is mandatory.
Speakers
Head phones
Input output device
Modem, touch screen, electronic musical devices
Memory storages
Hard disk
HD is a non-volatile storage device that stores digitally encoded data on rapidly rotating platters with magnetic surfaces.
Nearly every desktop computer and server today contains one or more hard-disk drives. Every mainframe and supercomputer is normally connected to hundreds of them. HD may be interna lor external. These billions of hard disks do one thing well -- they store changing digital information in a relatively permanent form. They give computers the ability to remember things when the power goes out.
A single hard disk usually consists of several platters. Each platter requires two read/write heads, one for each side. All the read/write heads are attached to a single access arm so that they cannot move independently. Each platter has the same number of tracks, and a track location that cuts across all platters is called a cylinder.
Characteristics:
· Capacity (40 GB – 1TB)
· Speed of spinning (7200rpm)
· Cache memory (8MB)
· Seek (přístupová doba)
Other electromagnetical memory storages:
Floppy disk(1.44MB since 1970s – extremely long)
Zip
Tape (backup)
Optical data storages
Compact Disk (CD-ROM, CD-R, CD-RW) 700MB
Digital versatile disk (DVD, DVD-R, DVD-RW) 4,7 GB – 17,8 (both sides, dual layer)
HighDensity DVD, 15GB – 30 GB (dual layer)
Blue-ray, 25GB – 50GB (dual layer)
Holografic Versatile Disk, 500GB
Electronic data storage
Memory cards
USB flash drives
Memory stick
A solid-state disk or drive (SSD), also called a flash drive, is the next generation hard disk.The name is from standard hard disks, but in reality an SSD uses a special kind of memory chip with erasable and writeable cells that can hold data even when power is off.
Sources:
(srpen 2009) webopedia: www.webopedia.com
Computer data storage, srpen 2009, z Wikipedia: http://en.wikipedia.org/wiki/Computer_data_storage
Computer mouses, http://www.ehow.com/about_5052324_kinds-computer-mouses.html
Laser printer, srpen 2009, How stuff works: http://computer.howstuffworks.com/laser-printer2.htm
Lorna Bointon, A. B. (2008). Learm Office 2007. Dublin: Blackrock Education Centre.
Roubal, P. (2005). Informatika a výpočetní technika pro střední školy. Brno: CP Books, a. s.