/sys$common/syshlp/helplib.hlb DTM, SPAWN, Command Qualifiers, /PROMPT  *Conan The Librarian (sorry for the slow response - running on an old VAX)

   /PROMPT[=string]

   Specifies the prompt string for the subprocess. If you specify the
   /PROMPT qualifier but do not specify a string, the default prompt
   is displayed. The default is to copy the current prompt string
   from the parent process.