The CALL statement transfers  control  to  a  BASIC  subprogram  or  other
  callable  routine.  You can pass optional arguments to the routine and can
  specify how these arguments are to be passed.   When  the  called  routine
  finishes executing, control returns to the calling program.

  Example

  CALL SUB1 BY REF (A$, Z BY VALUE, D$() BY DESC)