This document discusses the scope of variables in C programming. It defines three places where variables can be declared: locally within a function or block, globally outside of functions, and as formal parameters in function definitions. Local variables only exist within the function they are declared in and are recreated each time the function is called. Global variables can be accessed by any function and persist even when the declaring function ends. The document provides examples of local, global, and formal parameter variables and discusses best practices for using each type. It concludes by explaining some common use cases for global variables.

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SCOPE OF VARIABLES IN C

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4. •Region of the program where a defined variable can
have its existence .
•3 places where variables can be declared in C
programming language:
 Inside a function or a block -local variables
 Outside of all functions - global variables
 In the definition of function parameters-formal parameters.
What Actually Scope Of A Variable Mean??

5. What are local variables ???
•It exists only inside the specific function that creates them.
•They are unknown to other functions and to the main
program.
•Local variables cease to exist once the function that created
them is completed.
•They are recreated each time a function is executed or
called.

6. EXAMPLE
int sum(int a, int b)
{
int tot;
tot=a+b;
}

7. •These variables can be accessed by any function
comprising the program.
•They do not get recreated if the function is recalled.
What are global variables
???

8. EXAMPLE
#include<stdio.h>
int sum(int, int);
int tot;
main()
{
int a=10,b=5;
tot=sum(a,b);
}
sum(int c, int d)
{
tot=c+d;
return tot;
}

9. #include <stdio.h>
int sqr( int x ) ;
main()
{
int i , j ;
sqr( i ) ;
printf( "%d %dn", i, j ) ;
}
int sqr( int x )
{
j = x * x ; }
SIMPLE EXAMPLE ILLUSTRATING
SCOPE OF VARIABLES

10. CORRECT METHOD
#include <stdio.h>
int sqr( int x ) ;
main()
{
int i , j ;
sqr( i ) ;
printf( "%d %dn", i, j ) ;
}
int sqr( int x )
{ int j;
j= x * x ; }

11. LOCAL VARIABLES Vs
GLOBAL VARIABLES
Using local variables allows to focus attention on smaller more
manageable pieces of the program. Globals forces to keep track
of how they're being used throughout the entire system.
While working with other people, you must coordinate who's
creating which global variables. It is not valid to create two
globals of the same name.
The effects of algorithm steps reduces the cases of unexpected
behavior.
Localizing the effects of algorithm steps makes the program
easier for others to understand.

12.  If the two functions need to communicate, then we
generally need global variables.
If the entire program is built around some central data
and if access to that data is needed in nearly every
function and particularly if that is a large data structure,
then it makes sense to make such data global.
When do we use global variables ???

13. A Final Implementation with an Example
#include <stdio.h>
int f1( void ) ;
int f2( int x, int a ) ;
int a ;
main()
{ int a, b, c ;
a = 7 ;
b = f1() ;
c = f2( a, b ) ;
printf( "%dn %dn %dn", a, b, c ) ;
}
int f1( void )
{ a = 12 ;
printf( "%dn ", a ) ; return( a + 5 ) ;
}
int f2( int x, int a )
{ printf( "%dn ", a ) ; return( x * a ) ;
}
OUTPUT
12
17
7
17
119
a=7,12
a=7,12,7
b=17
x=7
a=7,12,7,17
c=119

14. CONCLUSION
Scope of variable was explained. It defines the existence or
the availability of variables in a program.
Types of scope was discussed. Scope depends upon the type
of variable declaration.
Global and Local variables were briefly explained.

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