Structure of c++ program

Structure of c++ program

The structure of a C++ program consists of several components that help in organizing the code efficiently. Outline of a basic C++ program structure are as follows:

+----------------------------------------------+
| Preprocessor Directives             |
+----------------------------------------------+
| Namespace Declaration             |
+----------------------------------------------+
| Global Variables (Opt)                |
+----------------------------------------------+
| Function Prototypes (Opt).        |
+----------------------------------------------+
| The main() Function                   |
+----------------------------------------------+
| User-Defined Functions (Opt).  |
+----------------------------------------------+
| Classes and Objects (Opt)           |
+----------------------------------------------+

1. Preprocessor Directives

These are instructions that are processed before compilation begins.

Example:

#include <iostream> // Includes the standard input-output stream library

2. Namespace Declaration

Defines the scope of identifiers used in the program.

Example:

using namespace std; // Allows using standard C++ library functions without prefixing 'std::'

3. Global Variables (Optional)

Declared outside functions and accessible from any function.

Example:

int globalVar = 10;

4. Function Prototypes (Optional)

Declaration of functions before main().

Example:

void displayMessage(); // Function prototype

5. The main() Function

The entry point of the C++ program.

Example:

int main() 

{

    cout << "Hello, World!" << endl;

    return 0;

}

6. User-Defined Functions (Optional)

Functions written by the programmer to perform specific tasks.

Example:

void displayMessage() 

{

    cout << "This is a user-defined function." << endl;

}

7. Classes and Objects (Optional in Basic Programs)

Used in object-oriented programming to define templates for objects.

Example:

class Car 

{

public:

    string brand;

    void showBrand() 

    {

        cout << "Car Brand: " << brand << endl;

    }

};

Example of a Complete C++ Program

#include <iostream>  
using namespace std;  
void displayMessage(); // Function prototype
class Car  // Class definition

{
public:
    string brand;
    void showBrand() 

   {
        cout << "Car Brand: " << brand << endl;
    }
};
int main() 

{  
    cout << "Hello, World!" << endl;  
    displayMessage(); // Function call
    Car myCar;  
    myCar.brand = "Toyota";  
    myCar.showBrand();  
    return 0;  
}
void displayMessage() 

{  
    cout << "This is a user-defined function." << endl;  

}