Object-orientated programming approach

Constants 

There are two ways of creating constants in C++.  

1. Using the qualifier const.
2. Defining a set of integer constants using enum. (Ex. enum {x = 100, y = 50, z = 200}. )

A value declared as const cannot be modified by a program.   

Declaration of Variables      

In C++, all the variables must be declared before they are used in executable statements. They can be declared anywhere in the programme but before using them. 

Dynamic Initialization of Variables:

C ++ permits initialization of the variables at runtime. This is called as dynamic initialization. For example:   

             float area= 3.14 *rad*rad;  

             float avg = sum/i;  

Observe that declaration and initialization of variable can be done simultaneously at a place where the variable is used for the first time. 

Reference Variable 

A reference variable provides an alternative name (alias) for a previously defined variable. A reference variable is created as follows. 

data - type & reference - name =  variable – name 

Operators in C++ 

1. << insertion operator: << is insertion or put to operator. It inserts (or sends) the contents of the variable on its right to the object on its left. 
2. >> Extraction operator: The operator>> is extraction operator or get from operator. It extracts (or takes) the value from the keyboard and assigns it to the variable on its right.  
3. Scope Resolution operator: A C + + program may contain a block within a block. Declaration of variable in an inner block hides a declaration of same variable in an outer block. Therefore, each declaration will cause reference to a different data object. Scope resolution operator can be used to uncover a hidden variable. It has the form:  

variable - name.  

This operator allows access to a global version of variable. 

Memory management operators 

C++ defines two unary operators new and delete, to perform task of allocating memory dynamically at run time and freeing memory. The new operator can be used to create objects of any type. It has the form:  

pointer - variable = new data type;  

Manipulators 

Manipulators are operators that are used to format the data display. The most used manipulators are endl and setw.  

The endl operator is like '\ n'. It causes a line feed to be inserted. 

The manipulator setw specifies fieldwidth. 

Structure of C + + program 

Typically, a  C ++program contains four sections.