REXX is the major EXEC language for VM/CMS. It has gotten a lot of good press over the last few years, and has gathered so much support both within and outside IBM that it is now a component of the SAA - Systems Application Architecture - that will someday transcend the IBM product line.

For the first time, TSO/E Version 2 includes a REXX processor. This means that there are two different CLIST languages to learn under TSO; however it also implies that applications written in REXX can be transported between operating systems.

The TSO/E REXX implementation does not inherently require TSO/E services, and so therefore you can execute REXX applications in ANY address space.

REXX execs can call other execs, and full recursion is supported (an exec can call itself). Variables are dynamically scoped; they become available when you assign values to them, and they go away when the subroutine in which they were created returns control to its caller. REXX has no GOTO instruction; it contains a full complement of so-called structured programming primitives.

At a TSO terminal, a user cannot tell the difference between a CLIST and an exec without looking at its source code. You invoke both types of programs in the same way.