Hey everybody, I am a mechanical engineer and new to Fortran(I have decent experience in programming in C, Matlab and understand languages similar to them). However the Fortran programming structure is new to me. Hence I am facing problems debugging a Fortran code. Here is the link of the code which I want to run. http://www2.meteo.uni-bonn.de/forsch...rtran/coad1d.f [Broken] I am using a Plato Fortran Compiler. It runs without showing error, but when I enter the values initially asked, the program stops mid-way showing an error: Run-time Error *** Error 112, Reference to undefined variable, array element or function result (/UNDEF) COURANT - in file help.for at line 149 [+01de] main - in file help.for at line 45 [+05dc] So there is an error in the Courant subroutine or error in calling it. Again i am a little unfamiliar to fortran subroutines but is it possible for any of you to also check what the problem here is ??? As far as i could see the variables inside the subroutine were declared beforehand. And the logic looks correct. Also is the declaration line 45 calling courant subroutine done correctly ??? Any help is appreciated. I have already received awesome help from you all here.