I write thermodynamic Engineering applications for large electric power plants. One such program is very large and I'm having trouble compiling the application. I'm using Visual Basic 5. In this application there are a large number of double presision variable names and a considerable number of subroutines to support the code. I'm looking for some general programming ideas for very large applications? I've considered breaking the application into several small sections that call each other. The problem is this, the solution which the program arrives at is done iteratively. You start with an initial reasonable guess and then the entire code executes repeatedly. With each iteration, it uses the results from the previous iteration. I want a smooth seamless look on the screen with a text or picture box where I can display intermediate data as the iterative process progresses. Breaking the application into several modules which call each other, makes this difficult and does not look very smooth on the screen. Any tips would be greatly appreciated. Perhaps a suggestion for some further reading might be helpful (a suggested book). Thanks in advance for your time and consideration.