Xcode is not a language but an IDE (Integrated Development Environment) its a program that helps you do edit and debug your code.  Any language you can program on OS X you can also on linux or windows.  I'm assuming the books you got were on Objective-C.  The first few chapters may talk about setting up Xcode but just skip over those if you are using a different IDE.  Check out gcc to compile any other Objective-C program.  If you really did pick up a book to learn how to operate Xcode exclusively but can't run it on your system just don't learn it is my advice.