"Symbology" is the
term used to describe the rules specifying the way
that data is encoded into the bars and spaces. It
is similar to a language. When humans communicate
via the spoken or written word, any language can be
used provided that both parties agree to and are proficient
in the choice.
The same concept is used in bar code. A bar code symbol
consists of a number of printed bars and intervening spaces.
The width of the bars and spaces, as well as the number
of each, is determined by a specification for that symbology.
Depending on the data to be communicated, several different
Symbologies can be used.
There are two types of bar code Symbologies:
Continuous and Discrete. Discrete bar codes start with
a bar, end with a bar, and have a space between characters,
referred to as an intercharacter gap. Continuous bar
codes start with a bar, end with a space, and have no
intercharacter gap. The most popular Symbologies are
listed as follows:
Code 39 And
Code 39 Mod 43
UPC A
UPC E0 And
UPC E1
EAN 13 And
EAN 8
Code 93
Interleaved
2 of 5 And Interleaved 2 of 5 Mod 10
Code 128
Codabar
MSI
Code 39 And Code 39 Mod
43
Code 39 was the first alphanumeric
symbology to be developed. It is the most commonly used
bar code symbology because it allows numbers, letters, and
some punctuation to be bar coded. It is a discrete and variable
length symbology. Every Code 39 character has five bars
and four spaces. Every character encodation has three wide
elements and six narrow elements out of nine total elements,
hence the name. Any lower case letters in the input are
automatically converted to upper case because Code 39 does
not support lower case letters. The asterisk (*) is reserved
for use as the start and stop character. Bar code symbols,
which contain invalid characters, are replaced with a checked
box to visually indicate the error. The Code39 mod 43 symbol
structure is the same as Code 39, with an additional data
security check character appended. The checkcharacter is
the modulus 43 sum of all the character values in a given
data string. The list of valid characters for the Code 39
bar code includes:
The capital
letters A to Z
The numbers
0 to 9
The space character
The symbols
- . $ / + %
U.P.C. A
The
Universal Product Code (U.P.C.,) has been successfully employed
in the supermarket industry since 1973. It is designed to
uniquely identify a product and its manufacturer. It is
a fixed length, numeric, continuous symbology. Every character
has four elements. The U.P.C., Version A (U.P.C., A) bar
code is used to encode a 12 digit number. The first digit
is the number system character, the next five are the manufacturer
number, the next five are the product number, and the last
digit is the checksum character.
U.P.C. E0 And U.P.C.
E1
U.P.C. E0 stands for Universal Product
Code Version E zero. U.P.C. E0 is a zero suppression form
of U.P.C. A and is used by pre-arrangement with the Uniform
Code Council. The first character in this symbology, the
number system character, is always 0 (zero). The ten digit
input string consists of the five digit manufacturer's number
and the five digit product code. The four rules for proper
product numbers are as follows:
1.If the last 3 digits in the Manufacturer's
number are 000, 100, or 200, valid Product Code numbers
are 00000-00999. 2.If the last 3 digits in the Manufacturer's
number are 300, 400,500, 600, 700, 800 or 900 valid
Product Code numbers are 00000-00099. 3. If the last
2 digits in the Manufacturer's number are 10, 20, 30,
40, 50, 60, 70, 80 or 90, valid Product Code numbers
are 00000-00009. 4. If the Manufacturer's number does
not end in zero (0), valid Product Code numbers are
00005-00009.
U.P.C. E1 stands for Universal Product
Code Version E1, it is also a numeric only and fixed
length code, and is typicallyused for shelf labeling
in the Retail environment. The length of the input string
for U.P.C. E1 is 6 numeric characters.
EAN 13 And EAN 8
The
European Article Numbering system (abbreviated as EAN) is
a superset of U.P.C. An EAN scanner can decode U.P.C., but
the reverse is not necessarily true.
EAN has two versions: EAN 13 and EAN
8, both are fixed length and numeric only. EAN 13 encodes
13 digits and EAN 8 encodes 8 digits.
Code 93
Code
93 is an Alphanumeric, variable length and continuous symbology.
Code 93 encodes all 128 ASCII characters. Forty-three of
code 93's character set correspond to code 39's character
set, and 4 additional characters are used as control characters
when encoding the full ASCII character set in code 93's
expanded mode. Each character is encoded with 9 modules
composed in a pattern of 3 bars and 3 spaces. Each bar and
space width may be one, two,three or four modules wide.
Interleaved 2 of 5 And
Interleaved 2 of 5 Mod 10
Interleaved
2 of 5 is a continuous, self-checking numeric symbology
primarily used in industrial and retail applications. We
use I 2 of 5 and I 2 of 5 Mod 10 to represent Interleaved
2 of 5 and Interleaved 2 of 5 Mod 10 respectively in the
bar code font list. The Uniform Code Council recognizes
the I 2 of 5 symbology for Shipping Container marking. I
2 of 5 pairs characters together and encodes the first of
the pair in five bars and the second of the pair in the
five interleaved
spaces. In other words, all the odd-positioned data is encoded
in bars, and all of the even-positioned data is encoded
in the spaces. Two of five bars are wide, similarly two
of five spaces are wide. A complete I 2 of 5 barcode symbol
consists of the start code (two narrow bars and two narrow
spaces), the data characters, and the stop code (one wide
bar, a narrow space, and a narrow bar). I 2 of 5 requires
an even number of digits to encode information. Interleaved
2
of 5 Mod 10 symbol structure is the same as I 2 of 5, with
an additional data security check digit appended. The check
digit is a modulus 10 sum. Interleaved 2 of 5 Mod 10 requires
an odd number of digits to encode information.
Code 128
Code
128 is variable length, continuous and alphanumeric symbology.
Characters in Code 128 consists of three bars and three
spaces such that the total character width is 11 modules.
Bars and spaces may be one, two, three, or four modules
wide. Code 128 B is a full alpha-numeric bar code that supports
both upper and lower case character, plus four function
control codes. The four function codes are inputted as follows:
FNC1
FNC2
FNC3
FNC4
Code 128 C is a numeric only bar code.
UCC is the name given to a specially defined subset
of Code 128; it is used most often for shipping containers.
UCC is numeric only, always 19 data characters, starts
with a special Function 1 character and includes a Mod
10 check digit.
Codabar
Codabar
is a discrete, variable length, self-checking symbology.
Each character is represented by a standalone group of four
bars and three intervening spaces. The character set of
Codabar consists of 16 characters: the digits 0-9, and the
special characters: $, :, /, ., +, -. There are four different
start/stop characters (a, b, c, d) that are encoded as one
bar and two spaces.
MSI
MSI
is a variable length, numeric only symbology. It is typically
found on Shelf Pricing Labels in a Retail Store. This bar
code always has a modulus 10 checksum at the end. We can
also add an additional modulus 10 or modulus 11 checksum
to the bar code before the final checksum. They are represented
as MSI+10, MSI+10+10, MSI+11+10 respectively in the bar
code font list.
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