Carbon is a transitional technology allowing compatibility of applications written for earlier versions of the Mac OS with Mac OS X.
Cocoa is an object-oriented API in which all future OS X programs will be written. For developers writing software for OS X this means adjusting to two new environments to create applications and to access the enhanced features of the new OS, Cocoa and Carbon. Mac OS X, Apple's newest operating system for the Macintosh platform, is profoundly different from its earlier versions because of its similarity to the UNIX operating system.
