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 may 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 and, for each of them, by the specification of its physical characteristics (type of organization...) and type of use (read, update...). You can indicate additional processing via specific code.
The development of a Dialog/Screen is independent of the environment. This allows the generated online application to be 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 the generated processings are implicitly generated from the Screen Description. These are the technical processings (reception, formulation and display of messages, initialization of fields) as well as the processings generated from the detailed analysis of an online program (validations and updates, data access).
A number of options taken into account at generation time (external names of standard files, terminals used, etc) can be modified in the -GG Lines section of the -G Lines tab.
Finally, the processings that are specific to a given Screen, described in specific code, complete the standard processings 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, the sequence of the Screens defined and analyzed and which ensures the branching of the different Screens according to various scenarii.
Screen branching is performed via reserved Data Elements PFKEYs or characters, depending on the environment.
For explanations on the generated Screen, refer to the On-Line Systems Development manual which you can find at the following URL:
http://www-01.ibm.com/support/docview.wss?rs=37&uid=swg27005477