I am using a huge 'C' library to be build CFD app. The library contains fortran interfaces, so, I am willing to write a nice GUI in fortran to simulate a chemical process. The problem that arises is this one: The library contains a lot of printf streams and that goes nowhere in windows app. What I want to know is: Is there a way to redirect to a file [ open(6,.....) ?] or to a MessageBox those streams with fortran statements?