program test_rounding
implicit none
real(4):: x, y
x = 1.7                              ! 1.70000004768372
write(*,'(A4,F16.14)') 'x = ', x
y = 2.3                              ! 2.29999995232628
write(*,'(A4,F16.14)') 'y = ', y
y = x + y
write(*,'(A4,F16.14)') 'v = ', y     ! 4.0000000000000

write(*,*)

x = 1.7                              ! 1.70000004768372
write(*,'(A4,F16.14)') 'x = ', x
y = 0.3                              ! 0.30000001192093
write(*,'(A4,F16.14)') 'y = ', y
y = x + y             
write(*,'(A4,F16.14)') 'v = ', y     ! 2.0000000000000
end program