PROGRAM SIMPLE_PLOT

      PARAMETER (MaxPts = 21)

      INCLUDE 'SYS$LIBRARY:GKSDEFS.BND'

      REAL xPts(MaxPts)                   

      REAL yPts(MaxPts)                   

      WsId    = 1

      WRITE(6,100)
100   FORMAT('$Enter Marker #:')
      READ(5,101) IMARK
101   FORMAT(I5)
      CALL GOPKS(5)                     ! open GKS with UNIT 5 as the error file

      CALL GOPWK(WsId,gconid,gwsdef)	! open Workstation with default conid

      CALL GACWK(WsId)
      SCALE = 1.0/(MAXPTS-1)
          do i=1,MAXPTS
            xPts(i) = (i-1)*SCALE
            yPts(i) = (i-1)*SCALE
          enddo
      CALL GPL(MAXPTS,xPts,yPts)
      IF(IMARK .NE. 0) THEN
          CALL GSMK(IMARK)
          CALL GPM(MAXPTS,xPts,yPts)
      END IF
      CALL GUWK(WSID,1)
      READ 110,NCHAR,CH
110   FORMAT(Q,A)

      CALL GDAWK(WsId)
      CALL GCLWK(WsId)
      CALL GCLKS()

      END