Mode Selection - Printronix L7032 Programmer's Reference Manual

Chapter 3
Bar Codes
Data Field
Code 128 bar codes support a full ASCII character set: Subset A provides
standard alphanumeric keyboard characters, control and special characters;
subset B includes all standard alphanumeric keyboard characters, lowercase
alphabetical characters, and special characters; subset C provides 100 digit
pairs, from 00 through 99 inclusive, plus special characters. Table 32 lists the
full Code 128 character set.
Control characters, identified by a "greater than" (>) symbol, introduce Special
Function Control Codes so that you can manually supply control codes to shift
between subsets as described in the "Mode Selection" section, below. The
bars and spaces vary in width from 1 through 4 modules. Each character
consists of 3 bars and 3 spaces that total 11 modules.
Readable Data
The optional readable data field provides a readable interpretation of the bar
code data. Bar code data is printed below the horizontal bar code symbol, and
to the left of a vertical bar code symbol. The lower guard band is provided
when the readable data field is selected. The readable data field is available
only in the automatic mode.
Check Digit
For Code 128, 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.

Mode Selection

VGL generates Code 128 bar codes in one of two modes: automatic or
manual.
Automatic Mode
VGL creates the shortest possible bar code by automatically sending the
subset switch characters (characters preceded by >) to switch from subset B
into subset C whenever strings of four or more consecutive numeric
characters are provided. As long as the data includes ordinary keyboard
characters and no subset switch, VGL switches in and out of subsets B and C
automatically before and after numeric character strings. Start codes, stop
codes, and check digits are generated automatically.
NOTE: The code >0 is not a special character; VGL recognizes >0 as the
"greater than" character (>) on a standard ASCII chart.
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