Simplest Fortran Code Still Has an Error

Question

I'm learning Fortran for a new job and started writing some very, very basic programs. To compile, I'm using gcc version 4.6.2, and I'm working on Linux Suse OS (if that matters at all). I believe the version of Fortran I'm using is F90 or F95. The code is written using the VIM text editor.

Here is the program I've written

INTEGER, PARAMETER :: x = 2, y = 3
INTEGER            :: z = x+y

print *, z

That's it! Oh, and the lines are indented, They start on column 8, so indentation isn't an issue.

UPDATE 1 I have tried doing this like so:

PROGRAM print_stuff
        print *, z
END PROGRAM print_stuff

I also tried adding the IMPLICIT NONE statement to all of that and didn't get a change in the error. END UPDATE 1

I save, quit, and compile. The compiler returns this error:

Error: Unexpected end of file in 'practice1.f'

Anyone know what the problem is? I've even tried removing the print statement and just having the variable declarations but the same error occurs. It's keeping me from practicing Fortran at all!

just for fun the minimum fortran file you can compile is just the single line "end". Seriously is is possible you are failing to put a CR on the last line? (Though my compiler doesnt need it, i suppose some might) — agentp
If, for whatever reason, you are saving your file as *.f, then are you padding your lines of code with 7 or 8 spaces? Does changing the file name to practice1.f90 allow you to compile? — Kyle Kanos
Ok, so I realized just how little I know about Fortran today. The problem was that I wasn't declaring the variables inside the program. For some reason I thought it was ok to declare them in the very first lines of code and then start the program. Also, I'm using gfortran (now). Again, I know very little about this and didn't realize right away that gcc is for compiling C. I'm saving as .f and padding with 7 spaces. I'll save as .f90 from now on since apparently that's the best practice for writing in Fortran90 — Ryan Schuster
Aha. The order in which statements may appear in a Fortran program (or other compilation unit) is mandated by the language standard(s). See software.intel.com/sites/products/documentation/doclib/stdxe/… for an explanation. — High Performance Mark

High Performance Mark High Performance Mark · Accepted Answer · 2013-10-07T15:22:38

Your first version

INTEGER, PARAMETER :: x = 2, y = 3
INTEGER            :: z = x+y

print *, z

is NOT a valid Fortran program. Every valid program ends with the end statement. A 'program' without an end statement is not syntactically correct. Keep reading your introductory tutorial.

I suggest you get into the habit of starting your programs with a program statement, with a name, such as

program myprog

and ending them with

end program myprog

Strictly, neither the program statement nor a program name is necessary but they do make things look a bit more comprehensible.

Oh, and while I'm writing ... don't get into the habit of starting lines at column 8, that smacks of the now out-dated fixed-form source. If you are using a reasonable compiler (such as gcc) give your filenames the .f90 suffix and let your source code run free. All the while observing good habits of indentation of course.

EDIT in response to OP's edits

PROGRAM print_stuff
        print *, z
END PROGRAM print_stuff

and

INTEGER, PARAMETER :: x = 2, y = 3
INTEGER            :: z = x+y

print *, z
END

are both syntactically correct. Both gfortran (v4.1.2) and Intel Fortran (v13.0.1) compile both correctly and produce executables which execute.

Simplest Fortran Code Still Has an Error

1 Answers