Section 12.1
Peripherals
12.1 Input Devices
There are several methods of data capture:
- Data may be keyed in.
- Document readers.
- Direct capture methods.
- Graphical input device.
12.1.1 Key To Disk Systems
Such a system is used in a batch environment where several thousand documents need to be
keyed in every day.
Step 1
A key station operator runs the data entry program and keys in a batch of data.
Step 2
As the batch is entered, it is validated.
Step 3
The whole batch is stored on disk.
Step 4
The source documents are re-typed by another operator.
Step 5
The original batch is verified and discrepancies are checked and corrected.
Step 6
The completed batch is transferred to the mainframe for processing (either on
tape or electronically).
The scanner shines a bright light onto the image been scanned while a mirror
reflects a strip of the image onto a bank of photosensors.
The photosensors convert the light into an electrical current.
An analogue to digital converter converts the current into a bit pattern.
12.1.5 Magnetic Ink Character Recognition (MICR)
Most banks use MICR for processing cheques.
The ink head used to print the characters at the bottom of the cheque contains
iron oxide which can be magnetised during processing.
12.1.6 Optical Mark Recognition (OMR)
OMR devices work by scanning marks in certain positions on a form.
Uses of OMR
OMR forms can be used where answers are sought to 'closed' questions.
Examples:
- Scanning multiple choice tests.
- Market research questionnaires.
- Selecting courses at Havant College.
12.1.7 Magnetic Strip Card Readers
Cash machines (ATMs) use a keypad and a magnetic strip card as input devices.
The bank card is encoded with:
- The customer's account number and sort code.
- The PIN number which is encrypted.
- The withdrawal limit.
- The amount withdrawn so far (in the current day).
When a customer inserts the bank card and enters a PIN number which is then
checked against the PIN on the card and if possible, the PIN number held in the
customer's record on the bank computer.
If the customer then wishes to withdraw cash the following checks are made:
- The customer's account balance on the banks central computer.
- The withdrawal details on the card.
Smart cards incorporate a microchip (with memory) instead of a magnetic
strip.
Typically a smart card can store in excess of 10Kb
Uses of Smart Cards
- Telephone cards (makes fraud more difficult)
- Mondex (a system designed to replace conventional money)
- As a door key
12.1.9 Touch Screens
A touch screen allows the user to provide input by touching an area of the
screen.
Uses of Touch Screens
- Industrial environments
- Retail order processing
- Public information systems
In general they are useful when the operator is moving but not so useful when
the operator is at a desk.
12.1.10 Other Pointing Devices
Graphics Tablets
A graphics tablet is a flat rectangular plate on which a stylus is placed.
Uses of Graphics Tablets
- Tracing a drawing
- Computer aided design
Pen Stylus Input
Palmtop computers use a pen-stylus in conjuntion with a touch sensitive screen
as a pointing device.
Mice And Trackballs
These are the most commonly used pointing devices.
Trackballs may be used where a robust or compact pointing device is required.
12.1.11 Electronic Point Of Sales (EPOS)
Most EPOS systems use barcodes.
The Barcode Reader
A LASER beam passes rapidly across the barcode on the item been purchased.
The reflected light is picked up by a photosensitive cell and the numeric code
is calculated.
The price and description of the item can then be looked up in a master file.
12.1.12 Electronic Funds Transfer At The Point Of Sales (EFTPOS)
Most Point of Sales 9POS) terminals can automatically deduct money from the
customers bank account. Such systems are known as EFTPOS systems.
At the same time the retailers account is electronically credited.
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