User`s manual

A–8 Bar Codes
Bar Code Character Set
Different bar code styles allow certain parts of the ASCII character set to be
used. Some styles allow only the numerals 0 – 9, while others allow the full
ASCII character set, and still others allow variations in between.
START, STOP, and CENTER Code Characters
The START/STOP characters identify the beginning and end of the bar code
symbol to the bar code reader. The START code is at the left end of the
symbol, next to the most significant character. The STOP code is at the right
end of the symbol, next to the least significant character.
Some bar code styles have a CENTER character code. This code divides the
characters so that a digit that appears on both sides of the CENTER code can
have a certain bar pattern on the left side that differs from the pattern on the
right side. This is possible because the digits to the left of the CENTER
character code are usually coded in odd parity, while the digits to the right of
the CENTER bar are coded in even parity.
Quiet Zone
Both ends of the bar code structure require blank quiet zones. The quiet
zones should be at least 0.25 inches wide and completely blank to ensure
accurate reading of the START/STOP codes and to prevent adjacent bar
codes from overlapping. The operator is responsible for providing sufficient
space on the form for the quiet zones.
Intercharacter Gap
The intercharacter gap separates the last bar in one character from the first
bar of the next character. The intercharacter gap is required in styles where
each character begins and ends with a dark bar.
Number of Characters in a Bar Code
There is no set number of characters for all bar codes. Some styles have a
specific number of characters necessary for making individual bar codes (for
example, UPC–A uses an 11–character symbol). Code 39, however, uses
character symbols of variable length.