OS X can run two different kinds of programs, each with different characteristics: Cocoa and Carbon.
The explanation involves a little bit of history and a little bit of logic. To take full advantage of Mac OS X’s considerable technical benefits, software companies had to write new programs for it from scratch. So what should Apple have done—sent out an email to the authors of the 18,000 existing Mac programs, suggesting that they throw out their programs and rewrite them from the bottom up?
At most big software companies, that suggestion would wind up on the Joke of the Week bulletin board.
Instead, Apple gave software companies a choice:
Update the existing programs (Carbon). If programmers were willing to put some effort into getting with the OS X program, they could simply adapt, or update, their existing software.
The resulting software looks and feels almost like a true OS X program—you get the crash protection, the good looks, the cool-looking graphics, the Save sheets, and so on—but behind the scenes, the bulk of the computer programming is the same as it was in Mac OS 9. These are what Apple calls Carbonized programs, named for the technology (Carbon) that permits them to run on OS X.
For years, many famous Mac programs were simply Carbonized: Photoshop versions before CS3, FileMaker before version 11, Microsoft Office before version 2011, and so on. Believe it or not, the Finder itself was a Carbon program until Snow Leopard (Mac OS X 10.6) came along. After ...