C  Example for the call of subroutine DIFEX1
C
C  Explicit Extrapolation Integrator
C  for Non-Stiff Systems of Ordinary Differential Equations
C  (Based on the Explicit Mid-Point Discretization)
      IMPLICIT DOUBLE PRECISION(A-H,O-Z)
      DIMENSION Y(2)
      EXTERNAL FCN
C
C  Print Parameter KFLAG
C  KFLAG=0 : No Output
C  KFLAG=1 : Integration Monitor
C  KFLAG=2 : Intermediate Solution Points T, Y(1),...
C  KFLAG=3 : Integration Monitor and Intermediate Solution Points
C
      KFLAG=11
C  Number of Differential Equations
      N=2
C  Starting Point of Integration
      T=20.D0
C  Initial Values Y(T)
      Y(1)=0.1411796119452533D+02
      Y(2)=0.2400000608244010D+01
C  Final Point of Integration
      TEND=0.D0
C  Desired Accuracy
      TOL=1.D-5
C  Maximum Permitted Stepsize
      HMAX=2.5D0
C  Initial Stepsize Guess(Here=TOL)
      H=TOL
C  Call of DIFEX1 with these Parameters
      CALL DIFEX1 (N,FCN,T,Y,TEND,TOL,HMAX,H,KFLAG)
C
      WRITE(6,101) T,(Y(I),I=1,N)
101   FORMAT('  SOLUTION AT T=  ',E25.16,/,10X,4E25.16)
      STOP
      END
      SUBROUTINE FCN(N,T,Y,DY)
C
C  Example E5 from Testset DETEST (Due to Hull et al.)
      IMPLICIT DOUBLE PRECISION(A-H,O-Z)
      DOUBLE PRECISION Y(N),DY(N)
C
      DY(1)=Y(2)
      DY(2)=DSQRT(1.D0+Y(2)*Y(2))/(25.D0-T)
C
      RETURN
      END