Analyzing screen and message formats

When an application program communicates with a terminal, an editing procedure translates messages from the way they are entered at the terminal to the way the program expects to receive and process them.

The decisions about how IMS will edit your program's messages are based on how your data should be presented to the person at the terminal and to the application program. You need to describe how you want data from the program to appear on the terminal screen, and how you want data from the terminal to appear in the application program's I/O area. (The I/O area contains the segments being processed by the application program.)

To supply information that will be helpful in these decisions, you should be familiar with how IMS edits messages. IMS has two editing procedures:

• Message Format Service (MFS) uses control blocks that define what a message should look like to the person at the terminal and to the application program.
• Basic edit is available to all IMS application programs. Basic edit removes control characters from input messages and inserts the control characters you specify in output messages to the terminal.

Related reading: For information on defining IMS editing procedures and on other design considerations for IMS networks, see IMS Version 15.3 Communications and Connections.