User`s guide

Defining Your Own Commands
You can define your own commands or change the definition of existing commands
to use in place of DCL commands.
The UCL (User Command Linkage) command-interpreter utility and the UCF
(User Command First) command-interpreter utility both enable you to define your
own commands. For more information, see Defining Your Own Commands in the
Introduction to RT–11.
1–18 Using RT–11 Commands