Information systems are used widely in shops and in the
distribution of goods and one area in which their use is
particularly important is supermarkets. Computer systems are used in a variety of ways in the modern, large supermarket,
from stock control to maintaining temperatures in fridges and freezers. In this section we will look in more detail at these systems in one particular large supermarket, which is part of a national chain.
The supermarket uses several computers which are located in a room known as the system office and form the
supermarkets own Local Area Network. These computers are
used to control the stock and are connected to the checkouts. These are the 'branch computers'. The computers are multifunctional, and each can access the data, which gives the management a number of access points.
Admin and stock control staff now have access to hand held
computers, SEC (Shelf Edge Computers). These are used for
price changes, creating stock pictures (information on stock totals) and for forecasting deliveries.
Like many companies, they have experimented with giving
customers hand held scanners to enter their own shopping.
The experiment has been discontinued due to huge stock
losses, staff called them ‘Shop and Rob’ rather than ‘Shop and Go’. The company is currently looking at developing a
better system to get round these problems.
Each product to be sold must have an identifying code
number which is different from that of every other product.
Different sizes of the same product even need different code numbers. These code numbers are printed onto the labels or
packaging of the product in the form of bar codes.
Located at each checkout is an ELECTRONIC POINT OF
SALE ( EPOS ) till. This
EPOS till comprises a keyboard, a digital display, a scanner which reads bar codes, a set of scales, a printer, a credit / debit card reader and a till drawer. Each till also has its own base to which all of the above is attached. It is the base unit which is connected by cables to the branch computer in the
supermarket's system office.
Bar codes are made up of a set of black lines and white
Look at the bar code. You can see that it is split into two
halves, and each half is contained within two thin black
The diagram shows the pattern of lines for each digit on the bar code. Notice that the pattern for a digit on the right hand half of a bar code is the opposite of the one on the left hand half.
Many bar codes today use the European Article Number or
EAN. This is a thirteen
digit number which can be used to uniquely identify a product. Using the bar code shown as an example :
a) The first 2 digits represent the country from which the
company producing the
product comes. 50 - U.K.
b) The next five digits represent the company which produced the product. 00208 - Lyons Tetley Ltd.
c) The following five digits represent the product. 02100 - 80 Tea bags.
d) The last number is a check digit. This is used to make sure the bar code has been read correctly.
So 5000208021000 is the EAN for a box of 80 Tetley tea
The bar codes on products are read by the EPOS tills at the
checkouts. This is
achieved by using a scanner, which sends out infra-red laser beams via a set of mirrors, enabling the bar code to be read at most angles.
When an item is passed over the scanner, the black and white parts of the code are detected by the laser, as the black parts reflect very little light whilst the white parts reflect most of the
light. This is converted into electrical pulses which are sent along the cables to the branch computer. The branch
computer then searches its stock file for the product matching the EAN number. When this record is located the price and
description of the product is extracted and sent back to the EPOS till at the checkout which then shows this item and
price on the digital display, prints them on a receipt and adds...