SUBROUTINE Y_VIEWPORT(LUS,X1,X2,Y1,Y2)
C
C----------------------------------------------------------------------
C.IDENTIFICATION: Subroutine Y_VIEWPORT
C.LIBRARY:        GRAPHSERV
C.AUTHOR:         L.Chiappetti - IFCTR Milano
C.VERSIONS:       0.0 - 25 Jun 93 - Prototype
C.                0.0a- 19 Jul 94 - using stream I/O (ddf)
C.                0.1 - 17 Aug 94 - officialized + common clientside.inc
C.PURPOSE:        send opcode to set up viewport       
C.SYNTAX:         CALL Y_MOVE (x,y)
C.PARAMETERS:     REAL x1,x2,y1,y2    viewport corner coordinates
C----------------------------------------------------------------------
C                                           
      REAL X1,X2,Y1,Y2
      INTEGER LUS(2)
      INTEGER IERR
      INCLUDE 'clientside.inc'
      OPCODE=101
*     WRITE(LUS(1),IOSTAT=IERR)OPCODE,X1,X2,Y1,Y2  
      RARGS(1)=X1
      RARGS(2)=X2
      RARGS(3)=Y1
      RARGS(4)=Y2  
      CALL Z_WRITE_STREAM(LUS(1),IBUF,20)
      RETURN
      END