Fortran Error Meanings - error-handling

Question

I have been following books and PDFs on writing in FORTRAN to write an integration program. I compile the code with gfortran and get several copies of the following errors.
1)Unexpected data declaration statement at (1)
2)Unterminated character constant beginning at (1)
3)Unclassifiable statement at (1)
4)Unexpected STATEMENT FUNCTION statement at (1)
5)Expecting END PROGRAM statement at (1)
6)Syntax error in data declaration at (1)
7)Statement function at (1) is recursive
8)Unexpected IMPLICIT NONE statement at (1)
I do not know hat they truly mean or how to fix them, google search has proven null and the other topics on this site we about other errors. for Error 5) i put in Program main and end program main like i might in C++ but still got the same result. Error 7) makes no sense, i am trying for recursion in the program. Error 8) i read implicit none was to prevent unnecessary decelerations.
Ill post the code itself but i am more interested in the compiling errors because i still need to fine tune the array data handling, but i cant do that until i get it working.
Program main
implicit none
real, dimension(:,:), allocatable :: m, oldm
real a
integer io, nn
character(30) :: filename
real, dimension(:,:), allocatable :: alt, temp, nue, oxy
integer locationa, locationt, locationn, locationo, i
integer nend
real dz, z, integral
real alti, tempi, nuei, oxyi
integer y, j
allocate( m(0, 0) ) ! size zero to start with?
nn = 0
j = 0
write(*,*) 'Enter input file name: '
read(*,*) filename
open( 1, file = filename )
do !reading in data file
read(1, *, iostat = io) a
if (io < 0 ) exit
nn = nn + 1
allocate( oldm( size(m), size(m) ) )
oldm = m
deallocate( m )
allocate( m(nn, nn) )
m = oldm
m(nn, nn) = a ! The nnth value of m
deallocate( oldm )
enddo
! Decompose matrix array m into column arrays [1,n]
write(*,*) 'Enter Column Number for Altitude'
read(*,*) locationa
write(*,*) 'Enter Column Number for Temperature'
read(*,*) locationt
write(*,*) 'Enter Column Number for Nuetral Density'
read(*,*) locationn
write(*,*) 'Enter Column Number for Oxygen density'
read(*,*) locationo
nend = size(m, locationa) !length of column #locationa
do i = 1, nend
alt(i, 1) = m(i, locationa)
temp(i, 1) = log(m(i, locationt))
nue(i, 1) = log(m(i, locationn))
oxy(i, 1) = log(m(i, locationo))
enddo
! Interpolate Column arrays, Constant X value will be array ALT with the 3 other arrays
!real dz = size(alt)/100, z, integral = 0
!real alti, tempi, nuei, oxyi
!integer y, j = 0
dz = size(alt)/100
do z = 1, 100, dz
y = z !with chopped rounding alt(y) will always be lowest integer for smooth transition.
alti = alt(y, 1) + j*dz ! the addition of j*dz's allow for all values not in the array between two points of the array.
tempi = exp(linear_interpolation(alt, temp, size(alt), alti))
nuei = exp(linear_interpolation(alt, nue, size(alt), alti))
oxyi = exp(linear_interpolation(alt, oxy, size(alt), alti))
j = j + 1
!Integration
integral = integral + tempi*nuei*oxyi*dz
enddo
end program main
!Functions
real function linear_interpolation(x, y, n, x0)
implicit none
integer :: n, i, k
real :: x(n), y(n), x0, y0
k = 0
do i = 1, n-1
if ((x0 >= x(i)) .and. (x0 <= x(i+1))) then
k = i ! k is the index where: x(k) <= x <= x(k+1)
exit ! exit loop
end if
enddo
if (k > 0) then ! compute the interpolated value for a point not in the array
y0 = y(k) + (y(k+1)-y(k))/(x(k+1)-x(k))*(x0-x(k))
else
write(*,*)'Error computing the interpolation !!!'
write(*,*) 'x0 =',x0, ' is out of range <', x(1),',',x(n),'>'
end if
! return value
linear_interpolation = y0
end function linear_interpolation
I can provide a more detailed description of the exact errors, i was hoping that the error name would be enough since i have a few of each type.

Answer 1

I think I can spot a few serious errors in your code sample. The syntax error is that you have unbalanced parentheses in the exp(... statements. They should be like this:
tempi = exp(linear_interpolation(alt, temp, size(alt), alti) ) ! <- extra ")"
nuei = exp(linear_interpolation(alt, nue, size(alt), alti) )
oxyi = exp(linear_interpolation(alt, oxy, size(alt), alti) )
It's precisely things like this that can produce long strings of confusing errors like you're getting; therefore the advice Dave and Jonathan have given can't be repeated often enough.
Another error (the "unclassifiable statement") applies to your loops:
do(i=1, nend)
! ...
do(z=1, 100, dz)
! ...
These should be written without parentheses.
The "data declaration error" stems from your attempt to declare and initialise multiple variables like
real dz = size(alt)/100, z, integral = 0
Along with being positioned incorrectly in the code (as noted), this can only be done with the double colon separator:
real :: dz = size(alt)/100, z, integral = 0
I personally recommend always writing declarations like this. It must be noted, though, that initialising variables like this has the side effect of implicitly giving them the save attribute. This has no effect in a main program, but is important to know; you can avoid it by putting the initialisations on a separate line.