DBG> SET ATSIGN USER:[JONES.DEBUG].DBG
  DBG> SET OUTPUT VERIFY
  DBG> @CHECKOUT
  %DEBUG-I-VERIFYICF, entering command procedure CHECKOUT
   SET MODULE/ALL
   SET BREAK SUB1
   GO
  break at routine PROG5\SUB2
   EXAMINE X
  PROG5\SUB2\X:  376
       . . .
  %DEBUG-I-VERIFYICF, exiting command procedure MAIN
  DBG>

      In this example, the SET ATSIGN command establishes
      that debugger command procedures are, by default,
      in USER:[JONES.DEBUG] and have a file type of .DBG.
      The @CHECKOUT command executes the command procedure
      USER:[JONES.DEBUG]CHECKOUT.DBG. The debugger echoes commands
      in the command because of the SET OUTPUT VERIFY command.