Download - In put Devices and Media In order for a computer to do anything it must be told what to do
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In put Devices and Media
In order for a computer to do
anything it must be told what to do.
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The Keyboard
• The keyboard is the most common input device available. Nearly every computer comes with one. It has a series of keys similar to a typewriter.
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The Keyboard
• Each key has a letter, number, symbol or word on it.
• The user presses the key (or combination of keys) desired, causing a special code to be added to the keyboard buffer.
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The Keyboard• This code (known as an
ASCII code) remains in the buffer until the CPU is ready for it.
• It is then decoded and the computer takes the appropriate action — displaying a character, moving the cursor, and so on.
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The Keyboard
• Keyboards are best suited for data entry or typing text documents, even though they can be used for several other things.
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What Really is a Mouse• A mouse is a hand-
held device that is moved on the surface of the desk or on a mouse-pad.
• It has a ball underneath and usually two or more buttons (and maybe a wheel) on the top.
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How it works
• When the mouse is moved, this causes the ball to be moved. As the ball moves, the mouse pointer moves on the screen.
• When the pointer is over an item that the user wishes to select, he/she can click one of the mouse buttons.
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Mouse most commonly used for
• selecting a menu • command or
‘pressing’ a button on the screen
• highlighting icons and text
• a pointing device.
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Disadvantages of the mouse
• It is limited to objects on the screen
• When the ball gets dirty the mouse pointer moves erratically.
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WHAT IS IT ?
• A joystick is a device with a stick perpendicular to its base, as well as buttons on the stick and/or the base.
• designed to resemble those used in fighter jets in order for it to feel more realistic
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HOW DOES IT WORK
• It is primarily used in playing computer games or in virtual reality
• The user moves the stick, causing an object on the screen to be moved.
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• . When the user presses one of the buttons it usually triggers some appropriate action in the game or simulation, such as firing missiles.
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Advantages
• It gives the user the feeling of a more realistic action.
• It moves objects in any direction.
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Disadvantages• It is limited to certain
applications. • A program must be
specially written in order for a joystick to be used.
• it does not suit most applications anyway
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The Optical Mark Reader
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HOW DOES IT WORK?• An optical Mark Reader
(OMR) is a device that senses the presence of pencil and pen marks that are made on special forms.
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WHAT DO THEY LOOK LIKE?• Such forms usually have
several options with circles next to them. A person is asked to fill out the form by shading the circles for the correct options.
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WHAT IS IT USED FOR?
• This is an especially fast method of data entry for situations where a person is asked to choose various options such as questionnaires, multiple-choice exams or registration forms.
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Advantages
• Reduced cost of inputting large volumes of data
• Fast method of inputting data
• Less labour needed to input the data.
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Disadvantages• If options are not shaded
properly the machine may misread selections.
• Forms that are creased jam the machine, causing down time.
• Badly damaged forms have to be rewritten or keyed in manually.
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The Optical Character Reader
•A device that senses the presence of text by recognising the characters.
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HOW DOES IT WORK?
• When the document is scanned, a photo-electric device reads the characters, which are then converted to electrical signals.
• The signals represent patterns that give an indication of the characters involved.
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• it is a fast method of data entry for documents that were already typed/written.
• the accuracy of the input is dependent on the quality of the formation of characters.
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What is it used for?
• Capturing data from airline tickets
• Reading postal codes• Capturing data from
telephone and electricity bills
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Advantages
• Reduced cost of inputting large volumes of data
• Quick method of inputting data
• Less labour needed to input the data.
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Disadvantages
•The OCR may misread characters that are not formed properly.
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Touch sensitive devices
• A touch screen is another way to input data.
• It is a specially mounted screen that is sensitive to touch, so you do not need to use a keyboard or mouse.
• Banks, malls and restaurants use touch screens to provide information to the public.
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Touch sensitive devices
• A touch pad is a flat rectangular surface which also senses movement of a finger on its surface.
• These devices are usually found on notebook computers.
• A light pen is similar to a mouse, but you can move it over the screen and point at items on the screen to input data.
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Scanner
• A scanner allows you to transfer pictures, graphics and text to your computer.
• It scans the image from the top to the bottom, one line at a time and transfers it to the computer.
• You can then take that copy and use it in a paint program, send it out as a fax or print it.
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Microphone
• Data can be entered into a computer through a microphone.
• The computer responds to this data by carrying out instructions, such as printing a document or turning the spoken words into text in a word processor.
• These are called voice-activated or voice-input recognition systems.
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Digitiser
• Digitisers convert drawings and photographs into data for architects and makers of maps.
• You can use a digital camera to store pictures, not on film but in an electronic format.
• Pictures from the camera are then transferred to a computer using a cable and a computer program.
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Digitiser• Moving pictures can also be captured by a
computer using a video digitiser. • This method is often used by the television
industry to edit TV programmes. • With digital video cameras now available in
shops, video editing through computers will become commonplace.
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Direct data entry (DDE) devices