CLIST
Template:Short description Template:One source CLIST (Command List) (pronounced "C-List") is a procedural programming language for TSO in MVS systems. It originated in OS/360<ref>Template:Cite book </ref> Release 20 and has assumed a secondary role since the availability of Rexx in TSO/E Version 2. In its basic form, a CLIST program is a list of commands to be executed in strict sequence (like a DOS batch file (*.bat) file). OS/VS2 R3.6 (MVS) added If-Then-Else logic and loop constructs to CLIST.<ref>Template:Cite book </ref> The term CLIST is also used for command lists written by users of NetView.<ref name="clist">Template:Cite web</ref>
CLIST is an interpreted language. That is, the computer must translate a CLIST every time the program is executed. CLISTs therefore tend to be slower than programs written in compiled languages such as COBOL, FORTRAN, or PL/1. (A program written in a compiled language is translated once to create a "load module" or executable.)
CLIST can read/write MVS files and read/write from/to a TSO terminal. It can read parameters from the caller and also features a function to hold global variables and pass them between CLISTs. A CLIST can also call an MVS application program (written in COBOL or PL/I, for example). CLISTs can be run in backgroundTemplate:Efn-lrTemplate:Efn-lr. CLISTs can display TSO I/O screens and menus by using ISPF dialog services.
Compare the function of CLIST with that provided by REXX.
Example programs
<syntaxhighlight lang="rexx" line highlight="10">
PROC 0 WRITE HELLO WORLD!
</syntaxhighlight>
Adding If-Then-Else logic: <syntaxhighlight lang="rexx" line highlight="10">
/********************************************************************/
/* MULTI-LINGUAL "HELLO WORLD" PROGRAM. */
/* */
/* THIS CLIST, STORED AS USERID.TSO.CLIST(TEST), CAN BE INVOKED */
/* FROM THE ISPF COMMAND LINE AS SHOWN IN THE FOLLOWING EXAMPLE: */
/* */
/* COMMAND ===> TSO TEST SPANISH */
/* */
/********************************************************************/
PROC 1 LANGUAGE
IF &LANGUAGE = SPANISH THEN +
WRITE HOLA, MUNDO
ELSE IF &LANGUAGE = FRENCH THEN +
WRITE BONJOUR, MONDE
ELSE +
WRITE HELLO, WORLD
EXIT
</syntaxhighlight>