A Screen belongs to a Dialog and is considered as a list of fields.
These fields can be grouped into categories (top, bottom, repetitive). The processing is executed category by category.
The presentation and display default options defined in the Dialog Definition can be modified at the Screen level.
These presentation options can be changed in each call of Data Element on the Screen.
The elements called in the Screen are used to build the Screen layout and determine the processing of the Screen data.
The processing of the data external to the Screen is determined by the call of Segments. For each of them, it is determined by the specification of its physical characteristics (type of organization...) and type of use (read, update...). You can indicate additional processing with specific code.
The development of a Dialog/Screen is independent of the environment. The generated online application is portable.
The physical description of the generated Screen is internal to the program for a number of environments and is external for others. The code to generate, which can either be in native mode or in a more evolved language (BMS for IBM-CICS, MFS for IBM-IMS, FORMS for BULL...).
A number of options taken into account at generation time (external names of standard files, terminals in use...) can be modified in the -GG Lines.
Finally, the processing that is specific to a given Screen, described in specific code, complement the standard processing in order to obtain the complete generation of an online program.
The screen flow is the part of the Screen description which animates a Dialog. It ensures the branching of the different Screens according to various scenarios.
Screen branching is performed with reserved Data Elements PF keys or characters, depending on the environment.
For explanations on the generated Screen, see the OnLine Systems Development manual which you can find at the following URL:
http://www-01.ibm.com/support/docview.wss?rs=37&uid=swg27005477