Some inputs have a list of predefined values. The items in this list are constants. The input can be set to one of the constants or to a formula that uses the constants. A constant can only be used inside the expression of its input. To refer to a constant of an input in the expression of another input a constant link must be used (see the Constant links subsection of the Links section later in this chapter). For example, some constants for the CodeType of the CodeReader step are:
Code39.
UPCA.
DataMatrix.
Maxicode.
These constants are not available to another property of the same or another step unless a constant link is used.