Operators and Expressions in c++

Operators in C++:-

• All C operators are valid in C++ also.
• In addition, C++ introduces some new operators.
• Other new operators are:-

           ::         Scope resolution operator
           ::*       Pointer to member declarator
           ->*      Pointer to member operator
           .*        Pointer to member operator
         delete    Memory release operator
         endl      Line feed operator
          new     memory allocation operator
          setw     field width operator

• Various Operators and their parts are as follows:-

Scope Resolution Operator:-

• Like C, C++ is also a block-structured language.
• We know that the same variables name can be used to have different meanings in different blocks.
• The scope of the variable extends from the point of its declaration till the end of the block containing the declaration.
• A variable declared inside a block is said to be local to that block.
• Example:

        {
              int i=10;

              {
                  int i=1;
               }
         }

• Here, the inner block which contains int i=10, and the outer block which contains int i=1 are nested.
• In C, the global scope of a variable cannot be accessed from within the inner block.
• C++ resolves this problem by introducing the (::) operator called as Scope resolution operator.
• 
  
• Syntax:

     :: variable_name;
This operator allows access to the globle scope of a variable.

Member dereferencing operator:- 

• A member dereference operator operates on a pointer variable.
• It returns the location value i.e. l- value in memory pointed to by the variable's value.
• Dereferencing operator is denoted as '* ' 
• Syntax:-

        *pointer_variable

• C++ provides a set of three pointer to member operators.

Operator	Function
…..*	To declare a pointer to a member of a class.
*	To access a member using object name and a pointer to that member.
->*	To access a member using a pointer to the object and a pointer to that member.

Memory management operators:-

• C uses malloc( ) and calloc( ) functions to allocate memory dynamically and the free( ) function to free dynamically allocated memory at runtime.
• Similarly, C++ supports these functions. It defines unary operators new and delete, that perform the task of allocating and freeing the memory in a better way.
• An object can be created by using new keyword and destroyed by using delete, as & when required.
• An object created inside a block with new, will remain in existence throughout the program until it is explicitly destroyed by using delete.
• The new operator can be used to create objects of any type.
• Syntax:-

             pointer_variable= new data_type;

            example:-

               p=new int;

               q=new float;

• The new operator can be used to initialize memory.
• Syntax:-

        pointer_variable=new data_type(value);

          example:- Here, value specifies the initia value,

             int *p=new int(25);

             float *q= new float(7.5);

• The new operator can be used to create a memory space for any data type including user defined types such as arrays, structures and classes.
• Syntax:-

         pointer_variable= new data_type(size);

 Here, size specifies the number of elements in the array.

• When we don't need a data object, it is destroyed to release the memory space for reuse.
• Syntax:-

       delete pointer_variable;

        The pointer_variable is the pointer that points to a data object created with new.

         example:-

           delete p;

           delete q;

• If we want to free a dynamically allocated array, then
• Syntax:-

      delete[size] pointer_variable;

example:-  delete[ ] p;

Manipulators:-

• Manipulators are the operators that are used to format the data display.
• The most commonly used manipulators are endl and setw.
• The endl manipulator, when used in an output statement, it terminate a line i.e. to end a line.
• It produce a newline.
• example:-

       //code

         cout<<"m="<<m<<endl

         cout<<"m="<<m<<endl

         cout<<"m="<<m<<endl;

      //code

• The setw manipulator stands for set width.
• It is used to specify the minimum number of character positions on the output a variable will consume.
• example:-

       cout<<setw(5)<<sum<<endl;

Here, setw(5) specifies a field width 5 for printing the value of the variable sum.

Expressions and their types:-

• An expression is a combination of operators, constants and variables arranged as per the rules of the language.
• It may also contain function calls which return values.
• It may consist of one or more operands, and zero or more operators to produce a value.
• Following are the types of expressions:-

1. Constant Expressions
2. Integral Expressions
3. Float Expressions
4. Pointer Expressions
5. Relational Expressions
6. Logical Expressions
7. Bitwise Expressions

• Expressions can be the combination of the expressions mentioned above. These expressions are known as compound expressions.

1. Constant Expression:-

    Constant expressions consist of only constant values.

2.Integral Expressions:-

    Integral Expressions are the expressions which produces integer results after implementing all the automatic and explicit type conversions.

3.Float Expressions:-

   Float expressions are the expressions which produce floating point results after all conversions.

4.Pointer Expressions:-

   Pointer expressions produce address values.

5.Relational Expressions:-

   Relational expressions yield results of type bool which takes a value true or  false.Relational expressions are also known as Boolean expressions.

6.Logical Expressions:-

   Logical expressions combine two or more relational expressions and produces bool type results.

7.Bitwise Expressions:-

   Bitwise expressions are used to manipulate data at bit level. They are basically used for testing or shifting bits.

So here it is all about operators and expressions in C++.