From the very beginning, this book teaches Fortran in a style suitable for use on large projects. It emphasizes the importance of going through a detailed design process before any code is written, using a top-down design technique to break the program up into logical portions that can be implemented separately. It stresses the use of procedures to implement those individual portions, and the importance of unit testing before the procedures are combined into a finished product. Finally, it emphasizes the importance of exhaustively testing the finished program with many different input data sets before it is released for use.
In addition, this book teaches Fortran as it is actually encountered by engineers and scientists working in industry and in laboratories. One fact of life is common in all programming environments: Large amounts of old legacy code that have to be maintained. The legacy code at a particular site may have been originally written in Fortran IV (or an even earlier version!), and it may use programming constructs that are no longer common today. For example, such code may use arithmetic IF statements, or computed or assigned GO TO statements. Chapter 18 is devoted to those older features of the language that are no longer commonly used, but that are encountered in legacy code.