Input Devices : Summary

Input Devices : Summary

1.	An input device transfers data from the outside world into a computer.

2.	There are two different categories of input device. They are : Manual Input Devices : User must enter data into the computer by hand. Direct Data Entry (DDE) Devices : Transfers information automatically from a source document such as a form or barcode into the computer.

3.	Important criteria for comparing input devices are : suitability to application, input speed, cost and reliability.

4.	There are many different input devices available. The key features of each input device are outlined in the table below.

Manual Input Devices
Input Device	Example Use	Advantage	Disadvantage
QWERTY Keyboard	Word processing.	Typists can use with ease to enter any textual data.	Relatively slow.
Concept Keyboard	Children's toys, tills in restaurants / pubs.	Can be operated by novices or people who can not manage a normal keyboard.	Needs to be customised for each application.
Touch Screen	Information system in tourist office window.	Can be used where a mouse or keyboard might get wet or dirty.	Tiring to keep touching screen.
Light Pen	Drawing on screen.	Cheap to manufacture.	Extremely inaccurate and awkward to use.
Mouse	Moving a pointer on screen.	Easy for novices to use for drawing or to choose options off the screen.	Requires a lot of space to use.
Tracker Ball	Moving a pointer on screen.	Does not need as much space as a mouse.	Not as intuitive to use as a mouse.
Touch Pad	Moving a pointer on screen.	Does not need as much space as a mouse.	Not as intuitive to use as a mouse.
Joystick	Playing games or controlling robots.	Allows fast, natural directional interaction needed for games.	Not as accurate as a mouse for selecting options from screen.
Graphics Tablet	Producing technical drawings.	Allows digitising of images with great accuracy.	Expensive unless you use it a lot.
Scanner	Transferring printed images onto a computer.	Cheap and fast method of getting graphics into a computer.	Images take up a lot of storage space.
Digital Camera	Including photographs in newsletters and DTP work.	No film required, no delay getting negatives processed.	Camera can only store a limited number of images, resolution is usually not very good.
Video Capture	Reads still or moving video images into computer. e.g. Video Digitiser, Webcam.	Can capture moving images.	Captured video files require a lot of storage space.
Voice Recognition (Microphone)	Telephone banking, automatic dictation.	Can be operated by inexperience users, can be used remotely by telephone.	Can only understand a few words or one person.
MIDI	Input and output of music via instruments.	Quicker and easier than entering music through computer keyboard.	Instruments and computer require MIDI ports.
Remote Control	Operating a TV from remote location.	More convenient than having to move to TV to operate it.	Can be lost, some controls do not work all functions of device.
Biometric Devices	Security applications where a person must be identified by fingerprint/iris e.g. passport.	More reliable identification than password, signature etc.	People are worried about personal data stored about them being misused.
Sensors	Control systems.	Many types available, automatic input of physical quantities.	May require calibration.
Direct Data Entry (DDE) Devices
Input Device	Example Use	Advantage	Disadvantage
Barcodes	Supermarket stock control.	Quick and easy to enter data under non-ideal condition, cheap to print bar-codes.	Only numbers can be stored in bar-codes.
Magentic Ink Character Recognition	Reading information from cheques.	Very fast and secure : numbers can not be changed by overwriting and not damaged by folding.	Expensive to buy reader and ink.
Magnetic Stripe Codes	Used to store a small amount of information on the back of credit cards	Simple and cheap to produce.	Can be damaged by magnetic fields or scratching.
Smart Cards	Petrol station points cards, satellite TV decoder cards, debit cards.	Can store a lot of information.	People worried about what information could be stored.
Optical Mark Recognition	Marking exam scripts, lottery tickets.	Fast and accurate.	Instructions have to be followed exactly by person marking the form.
Optical Character Recognition	Used to read printed text into the computer, reading postcodes to sort letters.	Fast method of reading text into a computer.	Not 100% accurate, OCRed documents must be checked manually.

5.
A turnaround document is a document which :

Has some information printed onto it by a computer.

Has more information added to it by a human.

Is fed back into a computer to transfer the added information into the computer.

6.
A Portable Data Entry Terminal (PDET) is a handheld computer that can be used to enter data into a computer system as an alternative to a turnaround document.