Will updating my MacBook Pro to OSX Yosemite delete/ruin my current files on desktop I'm currently working on an Xcode project that I have on my desktop. I'm currently using OSX version 10.9.5. If I update my mac to OSX Yosemite 10.10.3, will this delete all my projects/files with Xcode 6.1 that I have on desktop that i'm working on?
It probably won't, but just to be safe, it never hurts to take a backup! Take a Time Machine backup of your hard drive, and then upgrade. Worst-case scenario, you lose your Xcode files, in which case you can just wipe your hard drive and restore from the backup.