In put Devices and Media In order for a computer to do anything it must be told what to do.
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.
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.
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.
The Keyboard Keyboards are best suited for data entry or typing text documents, even though they can be used for several other things.
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.
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.
Mouse most commonly used for selecting a menu command or pressing a button on the screen highlighting icons and text a pointing device.
Disadvantages of the mouse It is limited to objects on the screen When the ball gets dirty the mouse pointer moves erratically.
The Joystick
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
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.
. When the user presses one of the buttons it usually triggers some appropriate action in the game or simulation, such as firing missiles.
Advantages It gives the user the feeling of a more realistic action. It moves objects in any direction.
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
The Optical Mark Reader
HOW DOES IT WORK? An optical Mark Reader (OMR) is a device that senses the p resence of pencil and pen marks that are made on special forms.
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.
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.
Advantages Reduced cost o f inputting large volumes of data Fast method of i nputting data L ess labour needed to input the data.
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.
The Optical Character Reader
The Optical Character Reader A device that senses the presence of text by recognising the characters.
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.
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.
What is it used for? Capturing data from airline tickets Reading postal codes Capturing data from telephone and electricity bills
Advantages Reduced cost of inputting large volumes of data Quick method of inputting data Less labour needed to input the data.
Disadvantages The OCR may misread characters that are not formed properly.
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.
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.
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.
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.
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.
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.
Direct data entry (DDE) devices