I'm a programmer and system administrator with more than 15 years of experience on Windows and Linux. I recently switched to OS X, using a MacBook Pro. Can anybody point me to the OS X documentation where I can find everything about OS X, from the files system and utilities, up to philosophy and architecture?
Here is the OS X Yosemite v10.10 Documentation.
You can always find developer resources on the Apple Developer sites. You can find other OS X documentations there, as well as iOS documentations. Other resources, such as feature descriptions, revision histories, upcoming changes, and user agreements can be found there, also.
The best of luck in your programming endeavours!