GCSE ICT - Input devices

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5.3.1 Input devices: identification and use

Revision Points: (Full course)

Candidates are expected to:
- identify a range of data collection methods additional to those listed in 5.1.2 i.e. OMR, OCR, MICR, bar-code reader, touch screens, graphics tablet, voice input;
- identify common uses of different data collection methods e.g. MICR in banking, Bar-code reader in supermarket stock control;
- describe the comparative advantages and disadvantages of using the range of different data collection methods above and 5.1.2;

Touch screen

These are devices which enable a use to control a computer by touching an area of the screen.

Touch screens work by the user either breaking criss-crossing infra-red beams or by pressure making an electrical connection between two layers of conducting plastic.

Advantages:

Software can alter the screen while it is running making it more flexible than a printed overlay (concept) keyboard
No extra peripherals are needed apart from the touch screen monitor itself

Disadvantage:

Not suitable for inputting large amounts of data
Selecting detailed objects can be difficult with fingers

Bar code reader

An simplified animation showing how a laser beam scans over a barcode

A bar code is made up vertical lines (bars) and spaces. The sequence of bars and spaces of different thickness represents a sequence of numbers. Bar codes are commonly found on packaging and the code gives information about the country of manufacture, the name of the manufacturer and the product itself.

A bar code reader uses a laser beam to read the code. The laser beam moves over the barcode and is reflected by the lighter bars and absorbed by the darker bars. The reader converts the pattern of reflected and non-reflected laser light into a digital code which is unique to that product. The last number on the barcode is a check digit. If this does not match the check digit calculated from the other numbers in the barcode then an error beep is produced.

Bar codes and readers are most often seen in supermarkets and retail stores, but a large number of different uses have been found for them. They are also used to take inventory in retail stores; to check out books from a library; to track manufacturing and shipping movement; to sign in on a job; to identify hospital patients; and to tabulate the results of direct mail marketing returns.

Advantages:

Bar codes are a fast and reliable method of inputting data. They can be read even when they are on curved surfaces or upside down and the check digit that is included in the code makes it reasonably good at rejecting errors.

Disadvantages:

Input is limited to a number code. An extra layer of packaging is needed for multi-pack goods because they need a different barcode to the one on the individual items.

Graphics tablet

A flat pad which you can write or draw on with a pressure sensitive stylus (like a pen).

The movement of the stylus and the pressure are mirrored by the drawing on the monitor screen. Used for art work and Computer Aided Design (CAD). Better designs can record up to 256 levels of pressure to control the brush pressure used in more advanced graphics software.

Buttons on the side act as mouse buttons to allow selections from menus etc.

Advantages:

Natural to use for anyone familiar with a pen. Can record levels of pressure unlike other point and click devices.

Disadvantages:

Can be awkward to access menus and make selections. Larger designs (A4 for example) are expensive.

Optical character recognition (OCR)

This uses an ordinary scanner to take a digital image of printed or even hand-written text.

The OCR software then converts the image of the text into an actual text file by recognising each character.

The text file can then be edited using a word processor. OCR is also used to automatically recognise post codes on letters at sorting offices.

Advantages:

Can convert large amounts of text into a digital form that can be edited in a word processor etc. Advanced versions can recreate tables and columns and even produce web-pages from original text.

Disadvantages:

Recognition can be poor, particularly with poor-quality originals and unusual fonts. Best suited to large volumes of text where the set-up time is more worthwhile.

Optical mark reader (OMR)

Similar to a bar code reader but uses infra-red light to scan marks on prepared forms such as multiple-choice examination answer sheets or lottery tickets.

The infra-red light is not reflected when it scans over a mark and the position of the mark is passed back to the computer. The software then matches up the position of the mark with the information on the sheet.

This provides a very fast and accurate method of inputting large amounts of data, provided the marks have been made accurately and clearly.

Advantages:

A quick and generally reliable way of inputting large volumes of simple data.

Disadvantages:

Limited to fairly simple data capture such as selections from a menu or marking thinks present or absent. Cannot be used for text input and number input requires the number to be broken down into 0-9, 10-100 etc.

Magnetic Ink Character Recognition (MICR)

This uses special ink which contains iron particles that can be magnetised and then read when the printed numbers passes through a MICR reading machine.

The MICR reading machine will only recognise numbers printed in a standard font using special magnetic ink. This provides a high level of security because any attempt to alter the magnetic ink printout with normal ink will be ignored.

Because it is expensive, MICR it is mainly used by banks. The account number, the cheque number and the branch number are pre-printed on a cheque.

When you receive a cheque and deposit it in your bank they print the amount and your account details on the cheque in magnetic ink.

It then sent to a clearing bank to be read by another MICR reading machine and the correct amounts are automatically transferred between accounts by computers.

Advantages:

Provides a high level of security and automation to the processing of cheques

Disadvantages:

The readers and printers are relatively expensive (although this could help reduce fraud)