The SET EDITOR command enables you to specify any editor that is
    installed on your system. In general, the command line specified
    as parameter to the SET EDITOR command is spawned and executed in
    a subprocess.

    On Alpha and Integrity servers, if you use EDT, LSEDIT, or
    TPU, you can start these editors in a more efficient way.
    You can specify /CALLABLE_EDT or /CALLABLE_TPU which causes the
    callable versions of EDT and TPU respectively, to be invoked
    by the EDIT command. In the case of TPU, you can also specify
    a command line that is executed by the callable editor.

    On Alpha processors, you can use /CALLABLE_EDT or /CALLABLE_TPU,
    but not /CALLABLE_LSEDIT.

    Related commands:

       EDIT
       (SET,SHOW,CANCEL) SOURCE
       SHOW DEFINE