I m a windows application developer and want to develop a phone tool application(to read and write phonebook, calendar, media files) under Mac OS. This phone tool needs UI and USB interface or COM port access. I want to know the application roadmap or architecture for my phone tool. I have several more detailed questions: a. How do I select develop environment or tool? To use XCode? b. How to write a module like DLL under windows? c. What function or class can I use to access USB port or COM port? d. To use which language to develop? C or C++ or Object-C? Any answers would be appreciated. A book or URL would be good. Thanks.