Difference between revisions of "Advanced-C++/C2/Static-Members/English"

Static keyowrd.

Static data memeber.

Static member functions.

We will do this with the help of examples.

Ubuntu OS version 11.04

gcc and g++ compiler v. 4.6.1

Static means fixed, which cannot change.

The word justifies its meaning.

If a variable is defined as static, it means that it is initialized.

It will remain in the memory till the end of the program.

Static variables are initialized to zero before the first object is created.

A static function may be called by itself without depending on any object.

To access a static function we use,

classname :: staticfunction();

I have already typed the code on the editor.

stat.cpp

Let me explain the code now.

#include <iostream>

using namespace std;

class statex

{

private:

int x;

public:

static int sum;

Then we have a static variable sum declared as public.

static int sum;

statex()

{

sum++;

x=sum;

}

In this we have incremented sum.

Then the value of sum is stored in x.

static void stat()

{

cout << "Result is: " << sum<<"\n";

}

In this we print the sum.

void number()

{

cout << "Number is: " << x<<"\n";

}

};

Here we print the number x

The class is closed here.

int statex::sum=0;

To access a static variable we write as:

datatype classname::static var name.

Now the storage is allocated to variable sum.

It is initialized to 0.

int main()

statex o1, o2, o3;

As o1, o2 and o3.

o1.number();

o2.number();

o3.number();

statex::stat();

Using the class name and scope resolution operator.

cout<< “Now static var sum is ” <<o1.sum<< “\n”;

return 0;

Ctrl, Alt and T keys simultaneously

g++ static.cpp -o stat

To execute

Type

./stat

g++ static.cpp -o stat

To execute

Type

./stat

Output

Number is: 0

Number is: 1

Number is: 2

Number is: 3

Now static var sum is 3

Output

Let me resize the window.

The first object gives the value as 0

Then we have the value as 1 ie x =1

The second object gives the value as 1

And the third object gives the value as 2

Then we call the stat function which gives the value of sum.

Result is sum.

Hence this will gived the value as 3.

Thus the final output we have is.

Static var sum is 3.

statex 01, 02, 03, 04;

Click on Save

Press the arrow key twice.

Again Press the arrow key twice.

Output

Result is 4

Now static var sum is 4

As the 4th object is created.

Come back to the slides.

Summary

In this tutorial, we have seen,

static keyword.

Static variable

eg. static int sum;

Static function.

eg. static void stat()

Assignment

Create a class that declares a static variable.

Decrement the variable.

And print the value.

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