CHAPTER (4) Input & Output Emad Salem

The Input units: 1) Keyboard. 2) Mouse. 3) Scanner. 4) Voice Input. 5) Touch Screens. 6) Digital Cameras. 7) Joystick.

1) Keyboard: Most personal computer keyboards include: 1. Function keys: top of the keyboard. 2. The main keyboard: in the center. 3. The numeric keys: from 0 to 9, to the right. 4. Extended keyboards: have additional keys between the main keyboard and the numeric keys. (like: Home, End, Page up, Page Down,..) 5. Status lights: in the upper-right corner.

1) Keyboard:

Function KeysFunction Keys: 12 keys, from F1 to F12. The function keys are an easy way to give certain commands to the computer. What each function key does is defined by the particular software you are using.

Main Keyboard The Escape key, Esc, is used in different ways by different programs; often it allows you to "escape" the program. The Tab key allows you to tab across the screen and set tab stops as you would on a typewriter. Capitals Look, When the Caps Lock key is pressed, uppercase letters are produced. The Shift key allows you to produce uppercase letters and the upper symbols shown on the keys.

Main Keyboard The Control key, Ctrl, is pressed in combination with other keys to initiate commands as specified by the software. The Alternate key, Alt, is also used in combination with other keys to initiate commands. The Backspace key is most often used to delete a character to the left of the cursor, moving the cursor back one position. (The cursor is the flashing indicator on the screen that shows where the next character will be inserted). The Enter key moves the cursor to the beginning of the next line. It is used at the end of the paragraph, for instance.

2) Mouse: A mouse, which has a ball on its underside, is rolled on a flat surface, usually the desk on which the computer sits or perhaps a separate flat item called a mouse pad. The rolling movement causes a corresponding movement of a pointer on the screen. The pointer can be a number of shapes but is most often an arrow. A mouse usually has two buttons, the left for common actions and the right for operating system or application-defined actions. Actions with the mouse consist of positioning the pointer and then clicking (sometimes double-clicking) a button. Move the mouse pointer to the desired place in the screen text, then click the button to set the insertion point, or cursor. (The insertion point can also be moved by pressing various keyboard keys.) The next text typed will begin at the insertion point.

3) Scanner: There was a time when the only way to transfer an existing document into the computer was to retype it. Now, however, a scanner can convert text or even a drawing or picture into computer-recognizable data by using a form of optical recognition. Optical recognition systems use a light beam to scan input data and convert it into electrical signals, which are sent to the computer for processing.

Scanner types: 1. Flatbed scanner: typically scans one sheet at a time. it can be used to scan bound documents. 2. Sheetfeed scanner: motorized rollers feed the sheet across the scanning head. However, sheetfeed scanners are less versatile than flatbed scanners and are more errors. 3. Handheld scanner : the least expensive and least reliable of the three. For example: ( wand reader and bar-code reader) wand readerbar-code reader

OCR software: If you want to scan text and then be able to edit it using word processing, you need special software--usually called OCR software, for optical character recognition--that can identify the individual letters as opposed to treating the entire text document as one big picture. Most scanners come accompanied by OCR software.

4) Voice Input: Speaking to a computer, known as voice input or speech recognition, is another form of source input. Speech recognition devices accept the spoken word through a microphone and convert it into binary code (0 and 1) that can be understood by the computer.

5) Touch Screens: One way of getting input directly from the source is to have a human simply point to a selection.

6) Digital Cameras: Digital camera takes photos that it stores internally on a chip; there is no film. The photos can then be sent by cable directly to your computer. Once in the computer, the photos can be edited with the software that accompanied the camera.

7) joystick: Video graphics are well known to people who like to play arcade games; their input device is a joystick, a sort of quickly reacting mouse with a handle that allows fingertip control of figures on the screen.joystick

The Output units: 1. Screen. 2. Printers. 3. Voice Output.

1) Screen: A user's first interaction with a computer screen may be to view the screen response to that user's input. When data is entered, it appears on the screen. Screen output is known in the computer industry as Soft copy because it is intangible and temporary, unlike Hard copy, produced by a printer on paper, which is tangible and can be permanent.oft copyHard copy

Flat Screens: Another type of screen technology, a flat display often seen on watches and calculators. LCD screens are commonly used on laptop computers. Flat screen monitors are more expensive than other types.

2) Printers: A printer is a device that produces information on paper output. Most printers have two orientation settings, portrait and landscape mode. The default setting is portrait mode.

Printers types: A- Laser printers: Laser printers use a light beam to help transfer images to paper. Laser printers print 600 or 1200 dpi (dots per inch), producing extremely high quality results. Laser printers print a page at a time at impressive speeds, using technology similar to that of a photocopier. Organizations use laser printers to produce high-volume, customer-oriented reports. Low-end black-and-white laser printers for use with personal computers can now be purchased for a few hundred dollars. Color laser printers are more expensive.

B- Ink-jet printers: Ink-jet printers, which spray ink from multiple jet nozzles. can print in both black and white and several different colors of ink to produce excellent graphics. However, the print quality of an ink-jet printer, although more than adequate, usually will not match that of a laser printer. Nor will the printing be as speedy. Furthermore, ink-jet printers need a fairly high quality of paper so that the ink does not smear. Nevertheless, low-end ink-jet printers, which cost just a few hundred dollars, are a bargain for users who want color output capability. Unfortunately, they have also become vehicles for counterfeiters.

3) Voice Output: Voice output through the speakers.