Classes consist of both state and behavior Here state means data(variables) and behavior is functions.

    class city
{
 private:
 char name[10];
 public:
 void putdata()
 {
   //block of code }};

Classes allowed private, protected, and public data members and member function. By default all data is private.

    class city
{
 private
 char name[10];
protected:
  int postalcode;
 public:
 void putdata()
 {
   //block of code
 }
};

A member function can be defined inside or outside of the class.
If we define member function outside the class then we use a scope resolution operator.

    class city
{
 private
 char name[10];
 int postalcode;
 public:
 void putdata();
};
void city ::putdata()
{
 
   //block of code

}
}

We also create an array of objects in the main function.

    class city
{
 private
 char name[10];
 int postalcode;
 public:
 void putdata();
};
void city ::putdata()
{
 
   //block of code

}
}

Objects can be passed as a parameter to function.
Objects can be returned from the function.

 void city (city c1)   // pass by value
{
 c1.put_data();
}
};
int main()
{
 city c2;
 c2.put_data(c2);  	
}