class lecture on input & output devices(part1)

class lecture on input & output devices(part1)

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  BAF Shaheen EnglishMedium School(SEMS)
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  Std: Ѵ Section : Bluebell/Lavender Subject: Computer Studies Subject Teacher: Shah Md. Shariful Islam Date: 28-12-11
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  Input devices  Objectives Afterthe completion of this topic we will learn  Definition of input devices in the context of any computer based system.  Detail about various kinds of input devices  Uses of the input devices.  Advantages and disadvantages.
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  Definition for inputdevices Input devices are hardware devices that allow data to be input into a computer. For example keyboard, mice, barcode reader are known as input devices.
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  keyboards  The mostcommon input devices and are used to input text, numbers and instructions into the computer.  Most used layout is “QWERTY”.  Recently developed keyboard is “Ergonomic keyboard”.  An ergonomic keyboard is a computer keyboard designed with ergonomic considerations to minimize muscle strain and a host of related problems. Typically such keyboards are constructed in a V shape, to allow right and left hands to type at a slight angle more natural to the human form.
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   Designed toreduce health related problems like carpal tunnel syndrome or repetitive strain injury(RSI) associated with the standard keyboard.
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   Uses  Keyboardsare used to input data into applications software(e.g. text into word processors, numbers into spreadsheets, etc).  They are also used for typing in commands to the computer(e.g. Prnt Scrn, Ctrl+P to print out, etc.) • Advantages  Keyboards enable fast entry of new text into a document.  They are a well-tried technology and a well-known method of entry.  Most people find them easy to use.  It is easy to do verification checks as data is entered, as it appears on the screen simultaneously.
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   Disadvantages  Userswith limited arm/wrist use can find keyboards hard to use.  Entering data using a keyboard is slow when compared to direct data entry (e.g. optical mark recognition).  Keyboards are fairly large devices that devices that use up valuable desk space.
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   The conceptkeyboard  It uses icons or phrases instead of standard letters.  Often used in fast food restaurants, offices and shops, where a single key represents an item. • Advantages  It enables fast data entry, as there is no need to type in whole commands.  They are waterproof, which is useful in a restaurant environment.  These keyboards are tamper proof and so are useful in certain applications, preventing people from keying information which could potentially corrupt the computer system.
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  Concept keyboard
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   Numeric keypads A numeric keypad is used to enter numbers only(although some have a function key ot allow input of alphabetic characters). • Uses  Numeric keypads are used in automatic teller machines(ATMs), where customers can key in their personal identification number(PIN), and amount of money etc.  Telephones have numeric keypads to allow phone numbers, etc. to be keyed in.
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   Electronic pointof sale(EPOS) terminals have numeric keypads in case the barcode reader fails to read the barcode and the number has to be keyed in manually by the operator.  Chip and PIN devices have numeric keypads for entry of PIN, amount of money etc.  They are used to enable fast entry of numeric data into a spreadsheet.
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  Electronic point ofsale(EPOS) terminals
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   Advantages  Numerickeypads are faster than standard keyboards for entry of numeric data.  Since many are small devices(e.g. mobile phones) they are very easy to carry around. • Disadvantages  They can be difficult to use, due to very small keys.  It is difficult to use them for entering text.  Sometimes the order of the numbers on the keypad isn’t intuitive.
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   Mice  Amouse is a pointing device that functions by detecting two-dimensional motion relative to its supporting surface. • Usually two kinds of mice are found on the basis of their working principles • Mechanical mice
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   A ballis used underneath the mouse to detect movement, so by moving the mouse around the user can control the position of a pointer on the screen.  Usually two buttons are there; left button is used to select and the right button is used bring up drop-down menus.  Many mice also have scroll button which speeds up the process of moving through a document.
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   Optical mice They make use of one or LED(light-emitting diode) and an imaging array of photodiodes to detect movement relative to the underlying surface.
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  • The cordlessmouse doesn’t need any wire to connect with the computer. • Advantages  It has no moving parts and it also doesn’t pick up any dirt.  Since it has no ‘skidding’ problem like the older ones it improves performances.
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   Uses  Micecan be used for opening, closing, and minimizing software.  They can be used for grouping, moving and deleting files.  They are very useful when editing images.  Mice are used for controlling the position of a pointer on the screen to allow selection from a menu or selecting an icon and for scrolling up and down/left to right.
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   Advantages  Itcan be faster to select an option using a mouse rather than a keyboard.  Mice enable rapid navigation through applications and the internet.  Mice are small and so take up little area. • Disadvantages  People with restricted hand/wrist movement can find it hard to operate a mouse.  Mice are easily damaged and older type of mouse also quickly becomes clogged up with dirt.  They are difficult to use if there is no flat surface readily available.
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   Touchpads  Touchpadsare used in many laptop computers as a pointing device.  The pointer is controlled by the user moving their finger on the touchpad and then gently tapping it to simulate the left hand button of a mouse.  They also have buttons under the touchpad which serve the same function as the left and right buttons on a mouse.
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   Advantages  Itcan be faster to select an option using a touchpad rather than a keyboard.  Touchpads enable rapid navigation through applications and the internet.  Since the touchpad is integrated into the laptop compute, there is no need for a separate mouse, aiding portability.  They can be used even when there are no flat surfaces available. • Disadvantages  It can be more difficult to control the pointer when compared with a mouse.  They are more difficult to use when doing certain operations such as “drag and drop”.