IBCA
Foundation and Implementation Guide (LIG)
8.
Appendix - How Bar Codes Work
(rev November 2008)
8.1
How Bar Codes Work
Bar
codes work in much the same way that Morse Code works. Instead of using dots and
dashes to create unique patterns that represent letters or numbers, wide and
narrow bars and spaces are used; hence, the name "bar" code.
For
example, in International Morse Code, the number "3" is represented by
• • • – – (three DOTS and two DASHES). One bar code symbology
(Interleaved 2 of 5) encodes the number three (3) in five (5) bars or spaces as
shown below.
(The number "3"
is encoded in 5 elements, 2 wide elements and 3 narrow elements)
Changing
the position of the wide elements creates different patterns which can represent
different numbers. For example, the number "8" is still encoded in 5
elements but the wide ones are placed in different positions as shown below:
As
you can see, the bar code is nothing more than a machine readable code
representing any kind of data that your information system uses. Just as Morse
Code can encode any message, bar codes have the capability to encode virtually
any string of numbers or text. Bar code can encode a company’s present item
numbers, purchase order numbers, etc.
Using
bar code has exactly the same effect as hiring a fast and accurate typist. From
a systems perspective, whether the data is key entered or bar code entered makes
no difference whatsoever.
8.2
Symbologies
There
are many different types of bar codes. Each uses a series of varying width bars
and spaces to encode numbers and / or letters and / or special characters. Some
bar code symbologies were designed to
encode only numbers while others can encode numbers, letters and even special
computer control characters.
Symbology
|
Character
Set
|
Number
of Bars and Spaces per character
|
GS1
12 (U.P.C.)
|
Numbers Only
|
2 bars, 2 spaces
|
GS1
13 (EAN)
|
Numbers Only
|
2 bars, 2 spaces
|
Interleaved 2 of 5
|
Numbers Only
|
5 bars or 5 spaces
|
Code 39
|
Numbers and Letters
|
5 bars, 4 spaces
|
GS1
128 (Code 128)
|
Numbers and Letters and
special characters.
|
3 bars, 3 spaces
|
Different
bar code symbologies are to bar code as typefaces are to human readable text.
Changing the typeface does not change the content of the message. Today’s bar
code readers can easily be configured to automatically read different
symbologies in the same way a person can automatically distinguish between HELVETICA and COURIER
typefaces.
8.3
Bar Code Systems
If
bar code is only a machine readable typeface, what is a bar code system?
A
bar code system consists of three components which collectively replace the
keyboard:
- Bar code symbol
encoding a text string / item number into wide and narrow bars and spaces that
can be detected by a bar code scanner.
- Bar code scanner
that can "see" the bars and spaces and transmit the pattern to a
reader.
- Bar code reader
that can "decode" the pattern of wide and narrow spaces into the
number or text string that they represent and transmit the decoded message to a
computer that reacts as though the data was typed in.
The
illustration above compares bar code data entry to manual data entry systems
because bar code is a data entry system, not a business information system. Bar
code "feeds" any business information system.
For
the sake of comparison, consider the table below showing examples of data entry
systems and business information systems. Any of the data entry systems shown on
the left could feed any of the business information systems shown on the right.
Examples
of Data Entry Systems
|
Examples
of Business Information Systems
|
Hand Writing followed by keyboard data entry
|
Order Entry Systems
|
Bar code data entry
|
POS Price Look Up Systems
|
Magnetic Stripe Input
|
WIP Tracking Systems
|
Optical Character Recognition (OCR)
|
Purchase Order Systems
|
Voice Recognition
|
Invoicing Systems
|
Handwriting Recognition
|
Inventory Control Systems
|
8.4
Bar Code Compatibility with Existing Computer Systems
Sometimes
companies think they can’t use bar code until their present business
information system is "bar code compatible." In one sense, every
business information system is already bar code compatible because by the time
it reaches the host computer, the bar code has already been decoded. The host
computer does not have to be programmed to understand how to decode bar codes.
Bar
code compatibility is more a printing issue than a decoding issue. The real
measure of a system’s bar code compatibility is its ability to print bar codes
from within the business information system. For example:
- Can
it print pick tickets with a bar code representation of the item number?
- Can
it print a production traveler with a bar coded representation of the work order
number?
- Can
it print receiving tickets with a bar coded representation of the storage
location?
- Can
it print bar coded carton labels meeting industry standards?
Note:
If your present system cannot print bar codes, this doesn’t mean that you
can’t use bar code technology until it can. Many companies start with bar code
by purchasing stand-alone bar code labeling packages.
8.5
Summary of How Bar Codes Work
Bar
code is a machine readable typeface capable of encoding any string of numbers or
letters. It is used because it is a fast and accurate alternative method of data
entry. All existing business information systems can accept bar code data entry
just as they can accept keyboard data entry. The method of data entry
technically doesn’t make any difference whatsoever.
Practically,
however, it makes a lot of difference. Keyboard data entry has proven itself to
be a time-consuming, inaccurate and expensive way to enter repetitive data. Bar
code, on the other hand, has proven itself to be a fast, highly accurate and
inexpensive way to enter repetitive data.
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