252
Chapter 7Bar Codes
Readable Data
The human readable data field provides a readable interpretation of the bar
code data. It can either be suppressed or printed above or below the bar code
symbol.
Check Digit
The modulo-10 check digit is automatically calculated and inser ted in the bar
code symbol. The check digit verifies accurate scanning. The number system
character is included in the check digit algorithm.
UPC-E
The UPC-E bar code structure is shown in Figure 23 and described below.
Figure 23. UPC-E Structure
Quiet Zone
Quiet zones extend on both ends of the bar code to permit the scan to begin
and end in a blank area. You must provide sufficient space (minimum of
seven modules) on the form for the quiet zones. The number system
character is also printed automatically in the left quiet zone.
Start/Stop Codes
The start/stop codes are special character codes marking those portio ns of
the bar code. These codes are automatically provided.
Number System Character
The number system character field for all UPC-E bar codes must be zero.
Data Field
The bar code symbol uses a series of varying width bars and spaces to
represent a limited character set (numbers 0-9 and Special Characters St art
and Stop). The bars and spaces vary in width from one through four modules.
Each character consists of two bars and two spaces that total seven modules.
For UPC-E, eleven digits are expected, which are compressed down to the
six encoded symbol characters.
QUIET
ZONE
QUIET
ZONE
DATA
FIELD
START
CODE STOP
CODE
NUMBER
SYSTEM
CHARACTER
N
OPTIONAL
CHECK
DIGIT
HEIGHT
C
CHECK
DIGIT
CHARACTER
NUMBERSYSTEM
CHARACTERFIELD READABLE
DATAFIELD
2-or 5-
DIGIT
ADD-ON
CODE
FIELD
SR,SC
POSITION