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SCOPE OF VARIABLES IN C

3. Disclaimer: This presentation is prepared by trainees of
baabtra as a part of mentoring program. This is not official
document of baabtra –Mentoring Partner
Baabtra-Mentoring Partner is the mentoring division of baabte System Technologies Pvt . Ltd

4. Variable
• In computer programming, a variable is
a storage location
• The variable name is the usual way to
reference the stored value
• Element of the Programing Language.

5. Variable(cntnd)
• Hold data temporary.
• Value Lost as soon as program terminate
• Declaration:
data type variable name;
int a;

6. Scope
• The scope of a variable is the block of code where
the variable is valid for use
• If declaration is made outside the bodies of all functions and
outside the main program is called global variable
• A local declaration is one that is made inside the body of a function
• It is possible to declare the same identifier name in different parts
of the program

7. Scope(cntnd)
• Undisciplined use of global variables may lead to confusion and
debugging difficulties
• The use of global variable is not encouraged due to the lack of
protection of data

8. Scope of Variables
• Scope refers to the visibility of variables.
• 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.

9. Local variables
• Declared inside a function or Block.
• They are unknown to other functions and to the main
program
• They are recreated each time a function is executed or
called.
• They can be used only by statements that are inside that
function or block of code.

10. Example
int sum(int a, int b)
{
int total;
total=a+b;
}

11. Global variable
• Declared out side of all Functions used within the program
• A global variable can be accessed by any function.
• They remains in the memory as long as the program is
executing.
• They do not get recreated if the function is recalled.
• i.e. a global variable is available for use throughout
your entire program after its declaration.

12. Global variable eg:-
#include <stdio.h>
void get_students( void ) ;
int num_stud ;
main() {
get_students() ;
printf( "The number of students is %dn", num_stud ) ;
}
void get_students( void ) {
num_stud = 12 ;
}

13. 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.

14. Difference between Global and Local
Variables
#include<stdio.h>
int sum(int, int);
int total; // Global variable declaration
main(){
int a,b; // Local variable declaration
a=10,b=5; // initialization
total=sum(a,b);
Printf(“%d”,total); // Print result
}
sum(int c, int d){
total=c+d;
return total;
}

15. • Example
#include<stdio.h>
int f1();
int a=10;
main()
{
int a=20;
int b=f1();
printf(“%dn % d”, a , b);
}
f1(int x)
{
x=a;
return x;
}
Using local variable ‘a’
Using global variable ‘a’
Output
20
10

17. 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=12
a=7
b=17
x=7
a=17
c=119

18.  Thank you 

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