Convert sounds into a form that can be processed by the system unit. By far the most widely used audio-input devices are the microphone. Audio input can take many forms, including the human voice and music.
VOICE RECOGNITION SYSTEM
Use a microphone, a sound card, and special software. These systems allow users to operate computers and to create documents using voice commands. Portable voice recognition systems are widely used by doctors, lawyers, and others to record dictation. These devices are able to record several hours before connecting to a computer system to edit, store, and print the dictated information. Some systems are even able to translate dictation from one language to another, such as from English to Japanese.
WHAT IS OUTPUT
Is a processed data or information. Output typically takes the form of text, graphic, photos, audio, and/ or video. For example, when you create a presentation using a presentation graphics program, you typically input text and graphics. You also could include photographs and even add voice narration. The output would be the completed presentation.
Output devices are any hardware used to provide or to create output. They translate information that has been processed by the system unit into a form that humans can understand. There are wide ranges of output devices. The most widely used are monitors, printers, and audio-output devices
MONITOR
Known as display screens, monitors present visual image of text and graphics. The output is often referred to as soft copy. Monitors vary in size, shape, and cost.
Features
Clarity refers to the quality and sharpness of the displayed images. It is function of several monitor features, including resolution, dot pitch, refresh rate, size, and aspect.
Resolution
One of the most important features. Image are formed on a monitor by a series of dots or pixels (picture elements). Resolution is expressed as a matrix of these dots or pixels.
For examples; many monitors today have a resolution of 1,600 pixels columns by 1,200 pixel rows for a total of 1,920,000 pixels. The higher a monitor’s resolution (the more pixels), the clearer the image produced.
Dot (pixels) pitch
The distance between each pixel. Most newer monitors have a dot pitch of 3.1 mm (31/100th of a millimetre) or less. The lower the dot pitch (the shorter the distance between pixels), the clearer the image produced.
Refresh rate
Indicates how often a displayed image is updated or refresh. Most monitors operate at a rate of 75 hertz, which means that the monitor is refreshed 75 times each second. Image displayed on monitors with refresh rates lower than 75 hertz appear to flicker and can cause eye strain. The faster the refresh rate ( the more frequently image are redrawn), the better the quality of image displayed.
Size or active displayed area
Measured by the diagonal length of a monitor’s viewing area. Common sizes are 15, 17, 19, 21, and 24 inches.
Aspect ratio
Determined by the width of a monitor divided by its height. Common aspect ratio for monitors are 4: 3 (standard, similar to traditional television pictures) and 16: 10 (wide screen).
FLAT-PANEL MONITORS
Are the most widely used type of monitor today. Compared to the other types, they are thinner, more portable, and require less power to operate.
Almost all today’s flat-panel monitors are LCD (Liquid crystal display).
There are two basic types:
1. Passive-matrix or Dual-scan monitors: create images by scanning the entire screen. This type require very little power, but the clarity of the image is not as sharp
2. Active-matrix or thin film transistor (TFT) monitor: do not scan the down the screen; instead, each pixel is independently active. They can display more color with better clarity. Active-matrix monitors are more expensive and require more power.
CATHODE-RAY TUBES
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Until recently, the most common type of monitor for the office and the home was the cathode-ray tube (CRT). These monitor are typically placed directly on the system unit or on the desktop. CRTs are similar in size and technology to televisions. Compared to other types of monitors, their primary advantages are low cost and excellent resolution. Their primary disadvantages are that they are bulky, are less energy efficient, and occupy a considerable amount of space on the desktop.
There are several different categories of CRT monitors, which are apart by the mask used:
1. FST-Invar (Flat Square Tube), whose phosphors are round. these monitors use a grid called ashadow mask. they give the right colours overall, but have the disadvantage of distorting and darkening the image at the corners.
2. Mitsubishi's Diamondtron tubes and Sony's Trinitron, whose masks are made up of vertical slots (called an aperture grille or tension mask), which lets through more electrons and therefore gives a brighter image.
OTHER MONITOR
E-BOOK READERS are handheld, book-sized devices that display text and graphics. Using content downloaded from the web or from special cartridges, these devices are used to read newspaper, magazines, and entire books.
eBook readers take it one step further. One device holds about a library and gives you as many of your favorite book titles at your fingertips as you could ever really want. Plus, they make it easy to take notes, save clippings of quotations and highlight passages we want to be able to find again. eBook readers are about readability. They are designed to make your reading experience more enjoyable and less of a hassle. Nobody wants to take a stack of books with them on a business trip or long roadtrip. They’re convenient, portable and good for the environment. In fact, the only real downside we can see to an electronic book over a real paper book is that you’ll have a few more problems if you accidentally spill your coffee on it or get splashed at the pool.
DATA PROJECTORS are specialized devices similar to slide projectors. These devices, however, connect to microcomputers and project computer output just as it would appear on a monitor. Data projectors are commonly used for presentation almost anywhere from the classroom to the boardroom.
HIGH-DEFINITION TELELVISION (HDTV) delivers a much clearer and more detailed wide-screen picture than regular television. Because the output is digital, users can readily freeze video sequences to create high-quality still image. The video and still image can then be digitized, edited, and stored on disk for later use. This technology is very useful to graphics artists, designers, and publishers.
