Skip to main content

C++ Storage Classes

C++ Storage Classes

Storage class is used to define the lifetime and visibility of a variable and/or function within a C++ program.

Lifetime refers to the period during which the variable remains active and visibility refers to the module of a program in which the variable is accessible.

There are five types of storage classes, which can be used in a C++ program

  1. Automatic
  2. Register
  3. Static
  4. External
  5. Mutable
Storage ClassKeywordLifetimeVisibilityInitial Value
AutomaticautoFunction BlockLocalGarbage
RegisterregisterFunction BlockLocalGarbage
MutablemutableClassLocalGarbage
ExternalexternWhole ProgramGlobalZero
StaticstaticWhole ProgramLocalZero

Automatic Storage Class

It is the default storage class for all local variables. The auto keyword is applied to all local variables automatically.

  1. {   
  2. auto int y;  
  3. float y = 3.45;  
  4. }  

The above example defines two variables with a same storage class, auto can only be used within functions.


Register Storage Class

The register variable allocates memory in register than RAM. Its size is same of register size. It has a faster access than other variables.

It is recommended to use register variable only for quick access such as in counter.

Note: We can't get the address of register variable.

  1. register int counter=0;    

Static Storage Class

The static variable is initialized only once and exists till the end of a program. It retains its value between multiple functions call.

The static variable has the default value 0 which is provided by compiler.

  1. #include <iostream>  
  2. using namespace std;  
  3. void func() {    
  4.    static int i=0; //static variable    
  5.    int j=0; //local variable    
  6.    i++;    
  7.    j++;    
  8.    cout<<"i=" << i<<" and j=" <<j<<endl;    
  9. }    
  10. int main()  
  11. {  
  12.  func();    
  13.  func();    
  14.  func();    
  15. }  

Output:

i= 1 and j= 1
i= 2 and j= 1
i= 3 and j= 1

External Storage Class

The extern variable is visible to all the programs. It is used if two or more files are sharing same variable or function.

  1. extern int counter=0;    

Anurag Rana Educator CSE/IT

Comments

Popular posts from this blog

JAVA Scrollbar, MenuItem and Menu, PopupMenu

ava AWT Scrollbar The  object  of Scrollbar class is used to add horizontal and vertical scrollbar. Scrollbar is a  GUI  component allows us to see invisible number of rows and columns. AWT Scrollbar class declaration public   class  Scrollbar  extends  Component  implements  Adjustable, Accessible   Java AWT Scrollbar Example import  java.awt.*;   class  ScrollbarExample{   ScrollbarExample(){               Frame f=  new  Frame( "Scrollbar Example" );               Scrollbar s= new  Scrollbar();               s.setBounds( 100 , 100 ,  50 , 100 );               f.add(s);               f.setSize( 400 , 400 );               f.setLayout( null );               f.setVisible( true );   }   public   static   void  main(String args[]){           new  ScrollbarExample();   }   }   Output: Java AWT Scrollbar Example with AdjustmentListener import  java.awt.*;   import  java.awt.event.*;   class  ScrollbarExample{        ScrollbarExample(){               Frame f=  new  Frame( "Scro

Difference between net platform and dot net framework...

Difference between net platform and dot net framework... .net platform supports programming languages that are .net compatible. It is the platform using which we can build and develop the applications. .net framework is the engine inside the .net platform which actually compiles and produces the executable code. .net framework contains CLR(Common Language Runtime) and FCL(Framework Class Library) using which it produces the platform independent codes. What is the .NET Framework? The Microsoft .NET Framework is a platform for building, deploying, and running Web Services and applications. It provides a highly productive, standards-based, multi-language environment for integrating existing investments with next-generation applications and services as well as the agility to solve the challenges of deployment and operation of Internet-scale applications. The .NET Framework consists of three main parts: the common language runtime, a hierarchical set of unified class librari

Standard and Formatted Input / Output in C++

The C++ standard libraries provide an extensive set of input/output capabilities which we will see in subsequent chapters. This chapter will discuss very basic and most common I/O operations required for C++ programming. C++ I/O occurs in streams, which are sequences of bytes. If bytes flow from a device like a keyboard, a disk drive, or a network connection etc. to main memory, this is called   input operation   and if bytes flow from main memory to a device like a display screen, a printer, a disk drive, or a network connection, etc., this is called   output operation . Standard Input and Output in C++ is done through the use of  streams . Streams are generic places to send or receive data. In C++, I/O is done through classes and objects defined in the header file  <iostream> .  iostream  stands for standard input-output stream. This header file contains definitions to objects like  cin ,  cout , etc. /O Library Header Files There are following header files important to C++ pro