CPP32.EXE produces a file that lists a C or C++ program, in which all #include files and #define macros have been expanded. While you do not need to use the preprocessor during normal compilation, you may find the list file helpful for debugging purposes.  

Often, when the compiler reports an error inside a macro or an include file, you can get more information about what the error is if you can see the include files or the results of the macro expansions. In many multi-pass compilers, a separate pass performs this work, and the results of the pass can be examined. Because the CodeGear C++ compiler is a single-pass compiler, use CPP32 to get the first-pass functionality found  

For each file processed by CPP32, the output is written to a file in the current directory (or the output directory named by the -n option) with the same name as the source name but with an extension of .I.  

This output file is a text file containing each line of the source file and any include files. Any preprocessing directive lines have been removed, along with any conditional text lines excluded from the compile. Unless you use a command-line option to specify otherwise, text lines are prefixed with the file name and line number of the source or include file the line came from. Within a text line, any macros are replaced with their expansion text. Use the -Sr option to produce a file which doesn't have line numbers. You can then pass this file to the compiler (use the -P compiler option to force a C++ compile).