PROGRAM NUMDIF
      DOUBLE PRECISION DFW,DBW,DCR,F,X,H
      F(X)=DSIN(X)
      H=1.0D-1
      WRITE(*,*)'Give X : '
      READ(*,*)X
      DO 100 I=1,10
          DFW=(F(X+H)-F(X))/H
          DBW=(F(X)-F(X-H))/H
          DCR=(F(X+H)-F(X-H))/2/H
          WRITE(*,300)DBW,'\\\\'
          H=H/10
  100 CONTINUE
  300 FORMAT(1H ,F22.15,A2)
      END