In OOP, a class basically represents a type or category of objects that share the same
set of data fields or properties, and perform the same set of actions. Different from Java
but quite similar to C++, the definition of a class in Objective-C is composed of two
sections, interface and implementation [2]. These two sections can be put in either the
same file or separate files. The data fields of a class are declared within curly braces
inside the interface section. The interface section also contains the method headers for the
actions available in that class. The implementation details of each method are put in the
implementation section.