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Example

#include<iostream.h>

int funct( int); // function prototype

int main()

{

int count, value; // count is a local auto variable

for(count = 1; count<= 10; count++)

value = funct( count);

cout<<count<<‘\t’<<value<<endl;

return 0;

}

int funct( int x)

{

static int sum = 100; // sum is a local auto variable

sum += x;

return sum;

}

The output of the above program:

1 101

2 103

3 106

4 110

5 115

6 121

7 128

8 136

9 145

10 155

Since sum has a permanent memory space it retains the same value in the period of time between leaving function and again entering it later.

Note:

  1. The initialization of static variables is done only once when the program is first compiled. At compile time, the variable is created and any initialization value is placed in it. Thereafter, the value in the variable is kept without further initialization each time is called. (compile-time initialization).
  2. All static variables are set to zero when no explicit initialization is given.

Register variables

Register variables have the same time duration as automatic variables. The only difference between register and automatic variables is where the storage for the variable is located.

Register variables are stored in CPU’s internal registers rather than in memory.

Examples:

register int time;

register double difference;

Global variable storage classes

Global variables are created by definition statements external to a function. Once a global variable is created, it exists until the program in which it is declared is finished executing.

Global variables may be declared as static or extern (but not both).

The purpose of the extern storage class is to extend the scope of a global variable beyond its normal boundaries. To understand this, we must notice that the programs we have written so far have always been contained together in one file. Thus, when you have saved or retrieved programs, you have only needed to give the computer a single name for your program. Larger programs typically consist of many functions stored in multiple files and all of these files are compiled separately. Consider the following exaple.

Example:

//file1

int a;

float c;

static double d;

.

.

int main()

{

func1();

func2();

func3();

func4();

.

}

int func1();

{

.

.

}

int func2();

{

.

.

}

//end of file1

//file2

double b;

int func3();

{

.

.

}

int func4();

{

.

.

}

//end of file2

Although the variable a has been declared in file1, we want to use it in file2. Placing the statement extern int a in file2, we can extend the scope of the variable a into file2.

Now the scope of the variable a is not only in file1, but also in func3 and func4.

//file1

int a;

float c;

static double d;

.

.

int main()

{

func1();

func2();

func3();

func4();

.

}

extern double b;

int func1();

{

.

.

}

int func2();

{

.

.

}

//end of file1

//file2

double b;

extern int a;

int func3();

{

.

.

}

int func4();

{

extern float c;

.

.

}

//end of file2

Besides, placing the statement extern float c; in func4() extends the scope of this global variable, created in file1, into func4(), and the scope of the global variable b, created in file2, is extended into func1() and func2() by the declaration statement extern double b; placed before func1().

Questions & Answers

what is variations in raman spectra for nanomaterials
Jyoti Reply
I only see partial conversation and what's the question here!
Crow Reply
what about nanotechnology for water purification
RAW Reply
please someone correct me if I'm wrong but I think one can use nanoparticles, specially silver nanoparticles for water treatment.
Damian
yes that's correct
Professor
I think
Professor
what is the stm
Brian Reply
is there industrial application of fullrenes. What is the method to prepare fullrene on large scale.?
Rafiq
industrial application...? mmm I think on the medical side as drug carrier, but you should go deeper on your research, I may be wrong
Damian
How we are making nano material?
LITNING Reply
what is a peer
LITNING Reply
What is meant by 'nano scale'?
LITNING Reply
What is STMs full form?
LITNING
scanning tunneling microscope
Sahil
how nano science is used for hydrophobicity
Santosh
Do u think that Graphene and Fullrene fiber can be used to make Air Plane body structure the lightest and strongest. Rafiq
Rafiq
what is differents between GO and RGO?
Mahi
what is simplest way to understand the applications of nano robots used to detect the cancer affected cell of human body.? How this robot is carried to required site of body cell.? what will be the carrier material and how can be detected that correct delivery of drug is done Rafiq
Rafiq
what is Nano technology ?
Bob Reply
write examples of Nano molecule?
Bob
The nanotechnology is as new science, to scale nanometric
brayan
nanotechnology is the study, desing, synthesis, manipulation and application of materials and functional systems through control of matter at nanoscale
Damian
Is there any normative that regulates the use of silver nanoparticles?
Damian Reply
what king of growth are you checking .?
Renato
What fields keep nano created devices from performing or assimulating ? Magnetic fields ? Are do they assimilate ?
Stoney Reply
why we need to study biomolecules, molecular biology in nanotechnology?
Adin Reply
?
Kyle
yes I'm doing my masters in nanotechnology, we are being studying all these domains as well..
Adin
why?
Adin
what school?
Kyle
biomolecules are e building blocks of every organics and inorganic materials.
Joe
anyone know any internet site where one can find nanotechnology papers?
Damian Reply
research.net
kanaga
sciencedirect big data base
Ernesto
Introduction about quantum dots in nanotechnology
Praveena Reply
what does nano mean?
Anassong Reply
nano basically means 10^(-9). nanometer is a unit to measure length.
Bharti
do you think it's worthwhile in the long term to study the effects and possibilities of nanotechnology on viral treatment?
Damian Reply
absolutely yes
Daniel
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Source:  OpenStax, Programming fundamentals in c++. OpenStax CNX. Jul 29, 2009 Download for free at http://cnx.org/content/col10788/1.1
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