Types of CLISTs

A CLIST can perform a wide range of tasks, but most fall into one of three general categories.

CLISTs that perform routine tasks
CLISTs that are structured applications
CLISTs that manage applications written in other languages.

These are described in this section.

CLISTs that perform routine tasks

As a user of TSO/E, you will probably perform certain tasks on a regular basis. These tasks might involve entering TSO/E commands to check on the status of data sets, to allocate data sets for particular programs, or to print files.

You can write CLISTs that significantly reduce the amount of time that you have to spend on these routine tasks. By grouping all the instructions required to perform a task in a CLIST, you reduce the time, number of keystrokes, and errors involved in performing the task and increase your productivity. A CLIST can consist of TSO/E commands only or a combination of TSO/E commands and CLIST statements.

CLISTs that are structured applications

The CLIST language includes the basic tools you need to write complete, structured applications. Any CLIST can invoke another CLIST, which is referred to as a nested CLIST. CLISTs can also contain separate routines called sub-procedures. Nested CLISTs and sub-procedures let you separate your CLISTs into logical units and put common functions in a single location. Specific CLIST statements let you:

Define common data for sub-procedures and nested CLISTs
Restrict data to certain sub-procedures and CLISTs
Pass specific data to a sub-procedure or nested CLIST.

For interactive applications, CLISTs can issue ISPF commands to display full-screen panels. Conversely, ISPF panels can invoke CLISTs, based on input that a user types on the panel.

CLISTs that manage applications written in other languages

Suppose you have access to applications written in other programming languages, but the interfaces to these applications might not be easy to use or remember. Rather than write new applications, you can write CLISTs that provide easy-to-use interfaces between the user and such applications.

A CLIST can send messages to, and receive messages from, the terminal to determine what the user wants to do. Then, based on this information, the CLIST can set up the environment and issue the commands required to invoke the program that performs the requested tasks.