This article is about the ways in which C# and C++ are similar and where these languages differ. You are familiar with the concepts of OOP language. You may have already studied one such language, called C#. If not, then there is no problem.

In this session, you will learn about:

  • Variables and data types
  • Storing data in a variable and displaying data on the screen
  • Creating and executing a C++ program
  • Classes in C++
  • Member functions
Before we start the session, let us revisit the features of Object-Oriented Programming (OOP) language.

oop

In order to perform a specific task on a computer, you need to write a set of instructions known as a program. While creating a program, you may need to temporarily store some values by using variables.

Variables and Data Types

The syntax to declare a variable is:
  • <data type><variable name>;
Examples:
  • int num1;
  • char chr;
Data types can be categorized into the following types:

type

The following table lists the common built-in data types used in C++ and C#.

Data Type Number of Bytes in C++ Number of Bytes in C#
char 1 2
int 2 or 4 4
float 4 4
double 8 8

data type

The data type equivalent to string in C++ is a character array.

The following table shows the use of a string variable and a character array.

C# C++
string str = “India”; char str[] = “India”;



area

Let us see how these objects are used in C++

In C++, we use predefined objects to store and display data.

data

Storing Data in a Variable and Displaying Data on the screen
  1. #include<iostream.h>
  2. int num1, num2, sum;
  3. cout<<“Enter number 1”<<endl;
  4. cin>>num1;
  5. cout<<“Enter number 2”<<endl;
  6. cin>>num2;
  7. sum = num1 + num2;
  8. cout<<“The sum is:”<<sum;
header

Once you have created a C++ program, you need to compile and execute it. Let us now compile and execute a C++ program,
  • Similar to C#, a C++ program must contain the main() function.
  • C++ is not a pure object-oriented language like C#.
  • Therefore, you can create a program in C++ without using a class as in the following code:
    1. #include < iostream.h >
    2. void main()
    3. {
    4. int num1, num2, sum;
    5. cout << “Enter number1” << endl;
    6. cin >> num1;
    7. cout << “Enter number2” << endl;
    8. cin >> num2;
    9. sum = num1 + num2;
    10. cout << “The sum is: ” << sum;
    11. }
Classes in C++

Object-oriented programming languages, such as C# and C++, use classes to group objects having common attributes.
  • A class is declared by using the class keyword.
  • The syntax of a class in C++ is:
class<class_name>
{
...
};

In C#, a program cannot be created without a class. However, in C++ you can create a program with/without a class.

A class consists of:
  • Attributes: Represented using member variables
  • Behaviors: Represented using member functions

Member Functions

Functions

A function consists of the following parts:
  • Declaration: Syntax for declaring a function:
<return type><function name><function parameters>;
  • Definition: Syntax for defining a function:
<return type><function name><function parameters>
{
... }

member

The following table shows the use of member functions in C# and C++.

C# (function declared and defined inside the class body)C++ (function declared and defined inside the class body)
C++ (function declared inside and defined outside the class body)

  1. class Sum
  2. {
  3. public void Add()
  4. {
  5. //Function Body
  6. }
  7. }
  1. class Sum
  2. {
  3. void Add()
  4. {
  5. //Function Body
  6. }
  7. };
  1. class Sum
  2. {
  3. void Add(); //Declaration
  4. };
  5. void Sum::Add() //Definition
  6. {
  7. //Function Body
  8. }


Now, let us see how the same function can be modified to accept the numbers as arguments. Consider the following code snippet in which the Add() function accepts two numbers from a user and adds them:
  1. class Sum
  2. {
  3. void Add(); //Declare the member function
  4. };
  5. void Sum::Add() //Defining the member function
  6. {
  7. int num1, num2, sum;
  8. cout << “Enter number 1” << endl;
  9. cin >> num1;
  10. cout << “Enter number 2” << endl;
  11. cin >> num2;
  12. sum = num1 + num2;
  13. cout << “The sum is: ” << sum;
  14. }
Types of Function Arguments

A function can have the following types of arguments:
  • Default arguments
  • Constant arguments
The following table shows the use of default and constant arguments.

Default arguments Constant arguments
void Add(int iNum1=10, int iNum2=20)
{
//Function Body
}		 void Add(constint iVar1, constint iVar2)
{
//Function Body
}