# Beginner fortraner: messing up arithmatic

• Fortran
Hi All.
I am trying to rewrite a program that i have in matlab to one in fortran. as i chug along, i am comparing the results and i am getting funny answers. This is the program in have in fortran so far:

ccccccccccccccccccccccccccccccccccccccccccccccccc
program main
implicit none
ccccccccccccccccccccccccccccccccccccccccccccccccc
integer Nstep, Xstep
double precision x, t, dt, dx
double precision K1, K2, Vmax, KM, P, Po
double precision Co, Qo, Cop,DeltaQ
double precision A1, A2, A3
cccccccccccccccccccccccccccccccccccccccccccccccccc
t = 1.0d0
x = 0.5d0
Xstep=2**8
dx=1/Xstep
dt=0.0005d0
Nstep=t/dt
Co = 275.0d-6
Vmax = 14.50d-9
ccccccccccccccccccccccccccccccccccccccccccccccccccccccccccccccccccc
print *, "t, x,Nstep, Xstep dx,dt",t,x,Nstep, Xstep,dx,dt
print*, "Co, Vmax", Co, Vmax
ccccccccccccccccccccccccccccccccccccccccccccccccccccccccccccccccccc
return
end

the results i get when i run it with f77 f1.f (f1.f is what i called the file) is this:
t, x,Nstep, Xstep dx,dt 1. 0.5 1999 256 0. 0.0005
Co, Vmax 0.000275 1.45E-08

with the first line i have major problmes: Nstep=1/.0005 and should be 2000, why is it 1999 ............and dx=1/Xstep=0 but it should be equal to .0039

why am i getting such funny results?