16066 storage classs

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STORAGECLASS


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INTRODUCTION

We all know C++ is blocked structured language, so wecan use the same variable in the C++ program inseparate blocks i.e when we declare a variable it isavailable only to that block of program.

The area or block of the C++ program where thevariable can be accessed is known as Scope ofvariable

Area or scope of the variable depend where on itsstorage class i.e where and how it is declared.

Storage class of the variable tells the compiler1. Storage area of the variable

2. Initial value of the variable

3. Scope of variable

4. Life of the variable i.e how long it would be active


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Broadly storage class is classified as

Local variable:-it is visible to the function in which it is

declared. Declared inside the function

Global variable :-it is visible to all the functions and it is

outside the function. the proper place of declaring of

global variable is at the beginning of the main program


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TYPESOFSTORAGECLASS

1. Automatic variable

2. External variable

3. Static variable

4. Register variable


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AUTOMATICVARIABLE

It is a default storage class to be used within a

program or file.

defined and accessed within the function

Local variables is also automatic variables b/c it isautomatically created (when function is called) and

automatically destroyed (when execution of function

is complete)

Auto variables are stored on to stack, which

provides temporary storage

Its default initial value is garbage value.


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EXAMPLE

#include

#include

void main()

{

int a=10;

void func();

Cout


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EXTERNALVARIABLE

The variable that are available to all the functions

i.e entire program they can be accessed

The scope of the variable is global.

Its initial value is zero


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EXAMPLE

#include

#include

int a;

void main()

{

void func1(),func2();

a=a+1;

cout


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void func1()

{

a=a+10;

cout


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STATICVARIABLE

It is a storage similar to auto except that the

variable once defined anywhere do not die till

program ends

the value of the variable will also be retained but

will be accessed only by the function declaring it

Static storage variable have initial value as zero


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EXAMPLE

Void main()

{

void func();

func();

func();func();

getch();

}

Void func()

{static int a=0;

a++;

cout


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REGISTERVARIABLE

We can also keep some variables in the cpu

register(high speed memory near to the processor)

instead of memory.

The keyword registertells the compiler that variable

is kept on the cpu register, since register is faster

than memory access

Register has Limited space, so if not space

available it will treat variable as auto variables


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EXAMPLE

#include

#include

void main()

{

register int m=1;

for(;m


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SUMMARY

STORAGE CLASS LIFE TIME SCOPE

Auto Local Local(within function)

External Global Global (in all function)

Static Global Local

Register Local Local


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void main()

{

func();func();

}

void func()

{ auto int i=0;register int j=0;

static int k=0;

i++; j++; k++;

printf( \n %d %d %d, i, j, k);

}

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