Recently, I received an operational Power Mac G5 with the dual 2.0GHz processor configuration from 2005. This is the first Macintosh computer I've owned, although I'm not exactly short of computers otherwise; I own five x86 computers running Windows or Linux, along with a modified Wii running Linux, and I have an ARM-based Raspberry Pi on the way. Suffice it to say that I don't really "need" the Power Mac, particularly not for internet browsing, word processing or other light computer tasks. That said, I want it to earn its keep, as it were. I'm an IT student at the moment, and I have enough computers running Linux not to just want to turn the Power Mac into Yet Another Standard Development Box. Therefore I'm looking for tasks to do specifically with Mac OS X. Having ruled out iOS development because of the age of the computer, my mind has turned to Mac OS X development. I had a couple of questions to do with that. Given that the Power Mac is running Mac OS X 10.4 Tiger, I was wondering how close that operating system is to Lion. Specifically, are Universal Binaries still supported on Lion? If not, could I write a GUI application in Tiger using Objective-C and port the source code over directly to Lion, expecting it to compile without any changes required?