C++ Refresher - Part One

• 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.



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:



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

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”;

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

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



Storing Data in a Variable and Displaying Data on the screen


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.