Fortran compiling error Two main programs
<p>I've been trying to write this program for fortran where the pressure of a gas is calculated using the Van der Waals equation and everytime I've scrapped the entire code and started over because everything I do comes back with an error, even when I try using answers from other questions. I'm new to fortran and I know my syntax is probably all over, if someone could just please tell me where I'm going wrong it would be greatly appreciated. </p>

<pre><code>    !Named program EquationOfState
 program EquationOfState
    implicit none
    real :: pressure
    write(*,*) 'pressure of Ideal Gas = '
    write(*,*) 'pressure calculated with Van der Waals equation = '

end program EquationOfState

!Prompt user to input values for density == d, and temperature == t
   write(*,*) "Enter density of gas"
   read(*,*) d
   write(*,*) "Enter temperature conditions"
   read(*,*) t
   write(*,*) "The pressure of the gas is", pressure


function pressure(d, t)
  real(kind=4) :: pressure_IdealGas
  real, intent(in) :: d, t
  real, parameter :: R = 286.9_4

pressure = d * R * t

end function pressure
</code></pre>

<p>with this error</p>

<pre><code> program EquationOfState
                        1
HWL_4.f90:14.36:

   write(*,*) "Enter density of gas"
                                    2
Error: Two main PROGRAMs at (1) and (2)
</code></pre>