Variables and variable classes

Much of the information displayed within dialog elements is derived directly from the tags used to define it. Other information is obtained dynamically when the application is running, such as:

Data that the user supplies
Data that the application supplies
Data that ISPF supplies.

In all of these cases, the data is derived from values specified in variables.

DTL provides you with tags to declare variables and to define the characteristics of these variables using variable classes. Variables and variable classes are considered global because they can be referred to by more than one element within the same source file. All variables referred to by dialog elements should be declared. Variable names and variable classes should be used consistently throughout dialog elements that are used in the same application.

Variables declared using DTL are accessible to your application through the dialog variable pools and variable services provided by ISPF. Within ISPF display processing, all variable values are in character format. ISPF transforms display variables between their dialog program format and internal display processing character format when retrieving and storing variable values.

Note: Although the conversion utility processes all of the variable information provided in your DTL source file and issues suppressible warning messages for missing VARDCL tags during the processing of several other tags, such as DTAFLD and LSTCOL, ISPF does not require any of the tags described in the topic to generate a valid ISPF panel.

The conversion utility supports the SOURCE tag as an alternative means of placing variable processing and validation statements directly into the ISPF panel.