PRODUCT : Turbo C++ NUMBER : 809 VERSION : All OS : DOS DATE : September 17, 1991 PAGE : 1/1 TITLE : Using CPP to Resolve Mysterious Compiler Errors The preprocessor CPP.EXE can be used when you are not sure how #include is working, how #define macros are being expanded or how the various #if directives are being evaluated, among other things. The default CPP output file name will be the same name as the input source file with a .I extension. The output from CPP is often useful when you are getting error messages during compilation and the reason is not clear when viewing the source code. If your source code contains complex macros that take several arguments CPP will show you exactly what the final expansion will be, which can also be helpful when trying to find the source of a subtle problem.