Rational Programming Patterns for System z

The Screen entity

A Screen belongs to a Dialog and is considered as a list of fields.

A Screen is constituted of:

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.

The default options of the Screen itself become the default options of the fields which make up a Screen. Each field is characterized by:

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.

Generation

The development of a Dialog/Screen is independent of the environment. The generated online application is portable.

After describing and defining a Dialog and its constituting Screens, you can generate them. The generation automatically produces the following elements:
  • Screen maps

    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...).

  • Online programs
    An online program is the sequence of the following processing:
    • Message reception,
    • Validation processing,
    • Processing of received information,
    • Output formatting,
    • Display.
    All the processing associated with a given Screen is generated in a single program which applies to this Screen only.
    This basic principle ('one Program for one Screen') has many advantages:
    • The program is independent of the structure and content of the Dialog,
    • The size of the online programs is homogeneous
    • The maintenance and implementation are easy.
    Part of the generated processing is implicitly generated from the Screen description:
    • The technical processing (reception, formulation, and display of messages, initialization of fields),
    • The processing 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 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.

  • Screen Flow

    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.

    Depending on the environment, the Dialog can be generated:
    • Either in one single monitor program which is called by each online program during the dispatching phase (example: IMS),
    • Or in each of the online program (example: CICS).
Note: For the instances imported from Pacbase, the skeleton language of the local generation is identical to the Pacbase skeleton language. This piece of information is retrieved from the extraction of the Pacbase models and from the import. It is stored in the Library.

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


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