SUBROUTINE  VISHO (X,Y,N,I,PL)

C     [HORIZONS]
C     SUBROUTINE WHICH UPDATES THE HORIZONS FOR THE HIDDEN LINE
C     SUBROUTINES.  THE ACTUAL WORK IS DONE BY VISBO, BUT VISHO
C     CONTAINS THE WORK ARRAYS NEEDED IN THE SIMPLEST APPLICATIONS,
C     AVOIDING THE NECESSITY TO DEFINE THEM SEPARATELY FOR EACH
C     INDIVIDUAL PROGRAM.
C     X(N)   ARRAY OF ARGUMENTS
C     Y(N)   ARRAY OF FUNCTION VALUES
C     I      DIRECTION OF PEN MOVEMENT
C     PL     PEN MOVEMENT SUBROUTINE
C     [29-MAY-74]

      EXTERNAL    PL
      VIRTUAL   X(1),Y(1)
      VIRTUAL   X0(701),T0(701),B0(701)
      VIRTUAL   X1(701),T1(701),B1(701)
      COMMON/VIS/ N0
      DATA        M/701/

      CALL VISBO (X1,T1,B1,M,X0,T0,B0,N0,X,Y,N,I,PL)
      RETURN

      END