PGL Programmer's Reference Manual

Chapter 3 Bar Codes

Quiet Zone

Both ends of the bar code structure require blank quiet zones. The quiet

zones must 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. Be sure to provide sufficient space on the form for the quiet

zones.

Start/Stop Codes

The start/stop codes identify the leading and trailing end of the bar code. Each

of the Code 128 subsets uses a unique start code and a common stop code,

both automatically provided by the IGP/PGL. The start/stop code structure

permits bidirectional bar code scanning.

Code 128A Data Field

Although the command field does not allow the selection of Code A, the IGP/

PGL does encode these characters if found in the data.

Code 128B Data Field

The bar code symbol uses a series of varying width bars and spaces to

represent an extensive character set (96 ASCII characters and seven control

characters). The bars and spaces vary in width from one through four

modules. Each character consists of three bars and three spaces that total 11

modules.

Code 128C Data Field

The bar code symbol uses a series of varying width bars and spaces to

represent 100 pairs of numeric digits (00 through 99) and 3 control

characters. The bars and spaces vary in width from 1 through 4 modules.

Each character consists of three bars and three spaces that total 11 modules.

Readable Data

The optional readable data field provides a readable interpretation of the bar

code data. It can be printed above or below the bar code symbol.

Check Digit

The modulo-103 check digit is automatically calculated and inserted in the bar

code symbol. The check digit verifies accurate scanning. The start code is

included in the check digit algorithm.