Establishes a scope search list that is like the default search
    list (0,1,2, . . . ,n), numeric scope specified as the command
    parameter. Scope 0 is the PC scope, and n is the number of calls
    in the call stack.

    When using SET SCOPE/CURRENT, note the following conventions and
    behavior:

    o  The default scope search list must be in effect when the
       command is entered. To restore the default scope search list,
       enter the CANCEL SCOPE command.

    o  The command parameter specified must be one (and only one)
       decimal integer from 0 to n.

    o  In screen mode, the command updates the predefined source,
       instruction, and register displays SRC, INST, and REG,
       respectively, to show the routine on the call stack in which
       symbol searches are to start.

    o  The default scope search list is restored when program
       execution is resumed.