UPC-A
251
The modulo-10 data field check digit for both SSCC-18 and SCC-14 is printed
in the bar code as the second half of the last number pair using subset C. It is
displayed in the human-readable data field as the twentieth byte for SSCC-18
or the sixteenth byte for SCC-14.
ASCII Emulation automatically calculates the modulo-10 check digit for
SSCC-18 if only 17 data digits are provided following the application identifier
of 00.
UPC-A
The UPC-A bar code structure is shown in Figure 22 and described below.
Figure 22. UPC-A 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 are responsible for providing 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/Center/Stop Codes
The start/center/stop codes are special character codes marking those
portions of the bar code. These codes are automatically provided.
Number System Character
The number system character field allows you to provide a code to a class or
type of item. The first character in the data field is used as the number system
character.
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 Start,
Center, 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. The symbol coding of the left data field is different from the right
data field to permit read direction sensing.
QUIET
ZONE
START CODE CENTER CODE
CHECK DIGIT FIELD
STOP CODE
LEFT DATA
FIELD
RIGHT DATA
FIELD
HEIGHT
QUIET
ZONE
OPTIONAL READABLE
SR, SC
POSITION
N
NUMBER
SYSTEM
CHARACTER
C
CHECK DIGIT
CHARACTER
NUMBER SYSTEM
CHARACTER FIELD
DATA FIELD
2- or 5-
DIGIT
ADD-ON
CODE
