Static data members and static member function, C/C++ Programming

Static Data Members:

A data member inside the class can construct as static data member.   There are few

guidelines to be followed when declaring static data member.

  • It is declared as a private data member.
  • Only one copy of the static data member is created any numbers of objects are created from that class. Therefore the static data member will be same for all the objects created.
  • The static member must be defined outside the class like function with class name.
  • The static member can be initialized in the definition and can be used only within its class.

 

The following program will give clear difference between static data count and regular data number members.  The static data is common to all objects but regular data is unique to its object.

 

class item

{int number; static int count; public:

void getdata()

{++count;

number=count;

}

void putdata(void)

{cout<<"Count is "<

cout<<"Number is "<

}

};

int item::count=0;

int main()

 

 

{           clrscr();

item x,y,z; //Three object produced from class item x.getdata();

y.getdata();

z.getdata();

x.putdata(); The count is 3 and number is 1

y.putdata(); The count is 3 and number is 2 z.putdata(); The count is 3 and number is 3

return 0;

}

 

Static Member Function:

The static member function can be specified like static data member.  It works asc a static member data except the static member data is used in static member function.

Rules of Static Member function are given below:

  • The static member function can read static data member only from its class.
  • The static member function is called using class name not object name. class_name::static_function_name( ); It can also be called using object.static_fun( ).

 

The given program will illustrate how the static member function is worked.

 class find

{static int count;

int code;

public:

static void showcount(void)

{cout<<"Count is " <

}

void setcode(void)

{code = ++count;

}

void setcount(void)

{ cout<<"Code is " <

}

};

int find ::count=0;

int main()

{clrscr();

find x,y,z;

x.setcode(); // Code and count is 1. y.setcode(); //Code and count is 2 find::showcount(); //Count is 2

 

z.setcode(); //Code and count is 3 find::showcount(); //Count is 3

 

x.setcount(); // Code is 1 for object x.

 

 

 

 

y.setcount(); // Code is 2 for object y. z.setcount(); // Code is 3 for object z.

 

x.setcode(); // Code and count is 4. y.setcode(); //Code and count is 5 z.setcode(); //Code and count is 6 find::showcount(); //Count is 6

//The value of code will increase from its previous value of that object.

x.setcount(); // Code is 4 for object x. y.setcount(); / Code is 5 for object x. z.setcount(); // Code is 6 for object x.

return 0;

}

 

Since the count is declared as static it has only one copy irrespective of number of objects created.   When static count function called again and again it will increase count for all the objects created simultaneously therefore the count will be uniform for all object, but for the data member code it is unique for each object created because it is not a static data member.  Therfore from the above example there will only one value for count data member irrespective of number of objects constructed since it is a static data member, where as for code data member the value will be different for each object.

Posted Date: 9/20/2012 7:56:45 AM | Location : United States







Related Discussions:- Static data members and static member function, Assignment Help, Ask Question on Static data members and static member function, Get Answer, Expert's Help, Static data members and static member function Discussions

Write discussion on Static data members and static member function
Your posts are moderated
Related Questions
Expected output of the program: 1. Consider the following programs. For each, indicate whether the program is correct. If yes, what is the expected output? If not, what is the

M em b e r d e r e f e r e n c i ng o p e r a t o r s: T h e s e op e r a t o r s w i l l b e d i s c u s s e d l a t

Ba s i c r u l e s o f C + + p r o g r a m : ·     I t m u s t h a v e o n l y o n e m a i n f u n c ti o n ·

Write a program that predicts users age: Write a program that predicts users' age (0-128 years old) with at most 7 questions. The game starts with asking the user whether he/s

program area under the curve y=f(x) between x=a & y=b, integrate y=f(x) between the limits of a & b   Solution: #include float    start_point,            /* GLOBAL V

A body which has three forces acting on it is in equilibrium. One force is 3N to the North and the other is 4N to the west. What us the magnitude and direction of the third force?

Write a program to find the area under the curve y = f(x) between x = a and x = b, integrate y = f(x) between the limits of a and b. The area under a curve between two points can b

Selecting Array Elements Implement the following C++ code in assembly language, using the block-structured .IF and .WHILE directives. Assume that all variables are 32-bit signed in

Given an integer n and a permutation of numbers 1, 2 ... , n-1, n write a program to print the permutation that lexicographically precedes the given input permutation. If the given

Selection Sort using this a nested for loop to iterate through and compare the array elements. If the value of an element with lower index is greater than the value of an element w