Code 128
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Code 128
The Code 128 structure is shown in Figure 10 and described belo w.
Figure 10. Code 128Structure
Quiet Zone
Both ends of the bar code structure require blank quiet zones. The qui et
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
Thest art/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 ASCII Emulation.

Code 128A Data Field

Subset A operates in the manual mode only. Subset A data characters
include mostly normal printable ASCII characters which require no subset
switching and can be entered directly.

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 fou r
modules.Each character consists of three barsand 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.
DATAFIELD QUIETQUIET START STOP
LOWERGUARD BAND
CODE CODEZONE ZONE
OPTIONALREADABLE DATA FIELD
CHECKDIGIT
OPTIONAL
SR,SC
HEIGH
T
POSITION
UPPERGUARD BAND