Structure of C++ Program

A typical C++ program would contain four section.
They are Main function program, Member functions definitions, Class declaration and Include files.
These sections may be placed in separate code files and then compiled independently or joined.

Structure of C++

INCLUDE FILES IN C++

Header File is a file that allows programmers to separate certain elements of program’s source code into reusable files.

Header file contains forward declaration of classes, variables and identifiers.

C++ DECLARATION

A Declaration introduces one or more name into a program.
Declaration can be occur more than once in a program.
Therefore classes, structures, enumerated and user-defined types can be declared for each compilation unit.
The constraint on this multiple declaration is that all declaration must be identical.

Example for C++ Declaration

// Declare and define int variables i and j.
int i;
int j = 10;

// Declare enumeration suits.
enum suits { Spades = 1, Clubs, Hearts, Diamonds };

// Declare class CheckBox.
class CheckBox : public Control
{
public:
            Boolean IsChecked();
    virtual int     ChangeState() = 0;
};

// Declare and define int variables i and j.

int i;

int j = 10;

// Declare enumeration suits.

enum suits { Spades = 1, Clubs, Hearts, Diamonds };

// Declare class CheckBox.

class CheckBox : public Control

{

public:

Boolean IsChecked();

virtual int ChangeState() = 0;

};

MEMBER FUNCTIONS IN C++ PROGRAM

Classes can contain data and function. These functions are referred to as “member functions”.
Any non-static function declared inside a class declaration is considered as a member function.

It is a common practice to organize a program into separate files.
The class declarations are placed in a header file and the definitions of member functions go into another file.
This approach enables the programmer to separate the abstract specification of the interface (class definition) from the implementation details (member functions definition).
The main program that uses the class is placed in a third file which “includes” the previous two files as well as any other files required .

Client-Server Model

This approach is based on the concept of client-server model.
The class definition including the member functions constitute the server that provides service to the main program known as client.
The client uses the server through the public interface of the class.