program Example1
! This file: http://ftp.aset.psu.edu/pub/ger/fortran/hdk/example1.f90
!
!
!=== Example of numeric breakdown;
!    For example try: A=10000., X=0.00001
!    and see P computed as:  -68.7  in Single Precision
!                       or: -119.2. in Double Precision.
!    Note that P is algebraically equal to 1.0 for all A and X<>0.
!
!  Penn State Information Technology Services
!  Graduate Education and Research Services (GEaRS)
!  Skip Knoble - 1981

       integer, parameter :: PRECISION = selected_real_kind(6)
!       integer, parameter :: PRECISION = selected_real_kind(15)
!
       real(kind=PRECISION) :: P,A,X
       DO
         PRINT *, "Evaluating P=((A+X)**2 - A**2 - 2*A*X)/X**2"
         PRINT *, "Please enter A and X (or Zeros to Quit):"
         READ *, A,X
         IF (A == 0 .OR. X == 0) EXIT
         P=((A+X)**2 - A**2 - 2.0*A*X)/X**2
         print *, "P is algebraically equal to 1."
         print *, "P=",P," A=",A," X=",X
       END DO
       print *, "** Example 1 Ended **"

end program Example1