A Short Introduction to
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Introduction to Barcodes
Here is some information that will give you a basic introduction to
barcodes. If you need more details about particular barcodes, check out our
page on Different Types of Barcodes.
And we are always happy to answer questions; just give us a call or send us
an e-mail message.
How does a
Each character is represented by a pattern of wide and
narrow bars. A barcode reader uses a photosensor to convert the
barcode into an electrical signal as it moves across a barcode. The
scanner then measures the relative widths of the bars and spaces, translates
the different patterns back into regular characters, and sends them on to a
computer or portable terminal.
Every barcode begins with
a special start character and ends with a special stop character. These
codes help the reader detect the barcode and figure out whether it is being
scanned forward or backward.
Some barcodes may include a checksum character just
before the stop character. A checksum is calculated when the barcode is
printed using the characters in the barcode. The reader performs the same
calculation and compares its answer to the checksum it read at the end of
the barcode. If the two don't match, the reader assumes that something is
wrong, throws out the data, and tries again.
There are different
barcode symbologies, each with its own particular pattern of bars. The
UPC code used on retail products is an
all-numeric code; so is the Interleaved 2 of
5 Code. Code 39 includes upper case
letters, digits, and a few symbols. Code
128 includes every printable and unprintable ASCII character code.
What's a 2-D code?
symbols are generally square or rectangular patterns that encode data in two
dimensions. They fall into two general categories: 'Stacked
barcodes' are constructed like a layer cake of barcodes stacked on on top of
the other; they can be read by special 2-D scanners or by many CCD and laser
scanners with the aid of special decoding software. 'Matrix Codes' are
built on a true 2-D matrix; they are usually more compact than a stacked
barcode, and they can be read only by a true 2-D scanner. The primary
advantage of 2-D codes is the ability to encode a lot of information in a
small space. The practical limit for a standard barcode depends on a
number of factors, but 20 to 25 characters is an approximate maximum; 2-D
symbols can encode from 100 to about 2,000 characters. The next time
you receive a package from United Parcel Service look for a 1-inch square
label with a pattern of dots and a small bullseye in the center. This is a
MaxiCode label, and it is used by UPS
for automatic destination sortation. Two other popular 2-D codes are
What barcode symbology should I use?
Are there any industry standards that your codes will
have to conform to, or is an important customer insisting on a specific
label format? If so, you will probably have to use whatever barcode
they want. If you are marking a retail product,
UPC-A is the code used in the USA and
EAN-13 is used in the rest of the world.
If you are shipping containers to the U.S. Government you will need to
adhere to the LOGMARS specification
(which uses Code 39). If the application is strictly
for internal use and you can choose anything you want, do you now or will
you ever need to encode letters as well as numbers? If so,
Code 39 or
Code 128 would be a good choice. If you need only numbers,
Interleaved 2 of 5 would do the job
although Code 128 tends to be more
robust and just as compact for numeric data. If you have to encode a
lot of data, take a look at PDF-417. If you need to squeeze a
small or modest amount of data into a really small space, then
DataMatrix might be a good choice.
Depending on the details of your application there may be other codes to
consider. If you need help deciding what type of code to use
send us an email describing your requirements and
we'll try to help.
How do I get a retail code
for my new product?
Have a look at our
FAQ about marking retail products.