fpp is the preprocessor used by the NAG Fortran compiler. It optionally accepts two filenames as arguments: input-file and output-file are, respectively, the input file read and the output file written by the preprocessor. By default standard input and output are used.
When used via nagfor, either because the input source file type was automatically recognised as requiring preprocessing (e.g. .ff90 files), or the -fpp option was used, the macro __NAG_COMPILER_RELEASE is automatically defined to be the integer release number (major*10+minor, e.g. 61 for release 6.1), and the macro __NAG_COMPILER_BUILD is automatically defined to be the build number (for release 6.1 this will have a value greater than 6100).