The document discusses the scope of variables in C programming. It defines variables as storage locations that hold temporary data. Variables can be declared locally within a function or globally outside of all functions. Local variables are only accessible within their declaration block, while global variables can be accessed from any function. The document provides examples of local and global variable declarations and discusses best practices around their use.

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SCOPE OF VARIABLES IN C

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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

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