WHAT IS ISPF?

WHAT IS ISPF? Consider the Interactive System Productivity Facility (ISPF) program product an extension of the MVS Time Sharing Option (TSO...

WHAT IS ISPF?
Consider the Interactive System Productivity Facility (ISPF) program product an extension of the MVS Time Sharing Option (TSO) host system on which it runs. ISPF services complement those of the host system to provide interactive processing. ISPF is similar to a control program or access method in that it provides services to dialogs (applications) during their execution.

The types of services provided by ISPF are:
• Display services
• File-tailoring services
• Variable services
• Table services
• Miscellaneous services • Dialog test facility, including: o Setting breakpoints o Tracing usage of dialog services and dialog variables o Browsing trace output in the ISPF log data set o Examining and updating ISPF tables o Interactively invoking most dialog services. A dialog receives requests and data from a user at a terminal. The dialog responds by using ISPF services to obtain information from, or enter information into, a computer system. WHAT IS A DIALOG? To understand the dialog interface, you must first understand what a dialog is. A dialog is the interaction between a person and a computer. It helps a person who is using an interactive display terminal to exchange information with a computer. The user starts an interactive application through an interface that the system provides. The dialog with the user begins with the computer displaying a panel and asking for user interaction. It ends when the task for which the interactions were initiated is completed. A dialog developer creates the parts of a dialog, called dialog elements. Each dialog application is made up of a command procedure or program, together with dialog elements that allow an orderly interaction between the computer and the application user. The elements that make up a dialog application are: • Functions • Variables • Command tables • Panel definitions • Message definitions • File-tailoring skeletons • Tables. A dialog does not necessarily include all types of elements, particularly tables and skeletons, which certain kinds of applications do not use. WHAT DOES A DIALOG DO? You can use ISPF to simplify the programming that provides interactive application operations. Operations performed during dialog execution include: • Identifying to the user choices of available processing routines • Invoking a requested routine, based on the user's choice • Prompting the user to enter data • Reading the data into a work area • Checking the data to verify that it is appropriate for the application If the data is not appropriate for the application: o Identifying the error to the user o Prompting the user to enter new data and verifying that data If the entered data is in the proper form: o Displaying any information requested by the user o Processing or storing the user's data, then advising the user of its disposition • Creating sequential output data sets or reports • Providing online messages, help, and tutorial displays to help users understand application processing. DEVELOPING A DIALOG A developer, using an editor such as the PDF editor in Option 2 of ISPF, develops a dialog by creating its various elements at a terminal and storing them in libraries. You can use any available editor when creating dialog elements. However, in addition to an editor, ISPF provides special facilities to aid dialog development. Examples of these facilities are: • A VIEW facility for displaying source data or output listings • Utilities to simplify data handling • Programming-language processing facilities • Edit models for messages, file-tailoring skeletons, panels, and DTL source • Library access services for accessing both ISPF libraries and other data sets. • Figure 1 shows a developer using ISPF to create and test dialog elements. As shown in the figure, panel definitions, message definitions, and file-tailoring skeletons are created prior to running the dialog. These dialog elements are saved in libraries. The developer stores the program (after compilation) or command procedure in an appropriate system program library. During dialog testing, tables of data, log entries, and file-tailoring output data sets can be created by dialog processing. ISPF creates the log data set the first time the user performs some action that results in a log message, such as saving edited data or submitting a job to the batch machine. ISPF creates the list data set the first time a user requests a print function or executes a dialog that issues a LIST service request. When the developer completes the functions, panel definitions, and any other dialog elements required by the application being developed, the dialog is ready to be processed under ISPF.