Object-oriented programming languages enable you to declare classes, create derived classes (subclass), and send messages to the objects instantiated from a class. This is the essence of object-oriented programming and part of the object-oriented extensions that Objective-C adds to C. To ensure that everything operates smoothly, compiler directives are available that enable you to inform the compiler of your classes by using @class and #import.


#import "Superclass.h"
@interface ClassName : Superclass {
instance variable declarations;
method declarations
@property(attributes) instance variable declaration;


#import "ClassName.h"
@implementation ClassName
@synthesize instance variable ;
method definitions

Message Syntax

[receiver message]


#import “filename.h”
Guarantees that a header file will be included only once.


@class ClassName;
Clues the compiler into user defined types.