Input (grade 6): Releases of Mac OS X are named after big cats: for example, Mac OS X v10 .6 is usually referred to by Apple and users as "Snow Leopard".
Output (grade 7): Mac OS X releases are named after kinds of "big cats" and have a version number that starts with 10. The newest version of Mac OS X is called "Snow Leopard" and is version 10.6.