How to declare const member functions?

If a member function does not alter any data in the class, then we may declare it as a const member function as follows:

void func(int , int) const;
float sum(float , float) const;

The qualifier const is appended to the function prototypes (in both declaration and definition). The compiler will generate an error message if such functions try to alter the data values of the data members of that class.

Some facts about static member functions in C++

Like static member variable, we can also have static member functions. A member function that is declared static has the following properties:

1. A static function can have access to only other static members (functions or variables) declared in the same class.
2. A static member function can be called using the class name (instead of its objects) as follows:

                   class-name  : :  function-name;

Situations where inline expansion may not work

The inline keyword merely sends a request, not a command, to the compiler. The compiler may ignore this request if the function definition is too large or too complicated and compile the function as a normal function.

Some of the situation where inline expansion may not work are:

1. For functions returning value, if a loop, a switch, or a goto exists.
2. For functions not returning values, if a return statement exist.
3. If functions contain static variables.
4. If inline functions are recursive.

What is difference between C & C++?

Following are the differences between C & C++:

C	C++
1. C is Procedural Language.	1. C++ is non Procedural i.e Object oriented Language.
2. No virtual Functions are present in C	2. The concept of virtual Functions are used in C++.
3. In C, Polymorphism is not possible.	3. The concept of polymorphism is used in C++. Polymorphism is the most Important Feature of OOPS.
4. Operator overloading is not possible in C.	4. Operator overloading is one of the greatest Feature of C++.
5. Top down approach is used in Program Design.	5. Bottom up approach adopted in Program Design.
6. No namespace Feature is present in C Language.	6. Namespace Feature is present in C++ for avoiding Name collision.
7. Multiple Declaration of global variables are allowed.	7. Multiple Declaration of global variables are not allowed.
8. In C scanf() Function used for Input. printf() Function used for output.	8. In C++ Cin>> Function used for Input. Cout<< Function used for output.
9. Mapping between Data and Function is difficult and complicated.	9. Mapping between Data and Function can be used using "Objects"
10. In C, we can call main() Function through other Functions	10. In C++, we cannot call main() Function through other functions.
11. C requires all the variables to be defined at the starting of a scope.	11. C++ allows the declaration of variable anywhere in the scope i.e at time of its First use.
12. No inheritance is possible in C.	12. Inheritance is possible in C++
13. In C, malloc() and calloc() Functions are used for Memory Allocation and free() function for memory Deallocating.	13.In C++,  new and delete operators are used for Memory Allocating and Deallocating.
14. It supports built-in and primitive data types.	14. It support both built-in and user define data types.
15. In C, Exception Handling is not present.	15. In C++, Exception Handling is done with Try and Catch block.
16. ANSI C recognizes only the first 32  characters in identifier names.	16. ANSI C++ places no limits on its length.
17.In ANSI C, we can assign a void pointer to a non-void pointer without using a cast to non-void pointer type. For example: void *ptr1; char *ptr2; ptr2=ptr1;	17. In ANSI C++ we must use cast operator as shown below: ptr2=(char *) ptr1;
18. ANSI C does not require an initializer; if none is given, it initializes the const to 0	18. C++ requires a const to be initialized.
19. In C character constants are stored as int, therefore, sizeof('a') is equivalent to sizeof(int)	19. In C++ char is not promoted to the size of int, and therefore, sizeof('a') is equivalent to sizeof(char)
20. In C, the global version of a variable cannot be accessed from within the inner block.	20. In C++, this problem is resolved by the introduction of a new operator : : called the scope resolution operator.
21. C notation for type casting is: (type) expression	21. C++ notation for type casting is: type (expression)
22. In C struct keyword is necessary while creating a object of structure. For example: struct student a;	22. In C++ struct keyword is not necessary while creating a object of structure. For example: student a;