What is .M?? file?
Class implementation file used by programs written in Objective-C; begins with the @implementation directive; initializes variables and functions that can be referenced by other Objective-C source files; may also reference header (.H) files.
Objective-C is most commonly used to implement applications for Apple's Mac OS X and iOS operating systems. Apple's Cocoa API provides the Objective-C programming interface for Mac OS X, and the iOS API provides the programming interface for the iOS platform.
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