An object file is a file that contains billets of executable code and/or data. It cannot be executed by itself (even if it contains all the code for an executable), as the information stored in such files is only used by a linker when building the final executable; otherwise, all the code and data within the file is not bound to any address, and only hints are provided. Detailed information on the Microsoft object file format, as well as the PE executable format specifications, may be obtained at http://www.microsoft.com/whdc/system/platform/firmware/PECOFF.mspx. Visit this URL, click on the Download button, and select pecoff.docx.