Apple's programming interface (API) for the Mac desktop and iOS mobile operating systems.  MacOS and iOS applications are generally programmed in Apple's Xcode development environment using the Objective-C and Swift programming languages.  Cocoa provides the framework for the Mac, and Cocoa Touch is the version for mobile devices.  See 
Xcode, 
macOS, 
iOS, 
Classic Environment, 
Carbon and 
application framework.