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Scope of variable in C

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4. Scope of variable
•Refers to where variables can be referenced
•There are three places where variables can be declared in c
programming language
1. Local variable
2. Global variable
3. Formal parameters

5. Local variable
• Variables that are declared inside a function or block
are called local variables.
• They can be used only by statements that are inside
that function or block of code.
function_1()
{
data_type a;
}

6. • Example
#include<stdio.h>
main()
{
int a=5;
++a;
printf("%d", a);
increment();
return 0;
}
void increment()
{
++a;
printf("%d", a);
}
Error : function is trying to access
local variable of main()

7. Global variable
• Global variables in c have their declaration outside
the function definition of all functions used within the
program.
• They remains in the memory as long as the program
is executing.

8. • Example
#include<stdio.h>
int a=5;
main()
{
++a;
printf("%dn", a);
increment();
return 0;
}
void increment()
{
++a;
printf("%dn",a);
}
Output
6
7

9. Nested scope
• Local variables of same name can be nested inside global
variables.
int total = 5;
int main ( )
{
int total = 4;
….
}
int sub1 ( ) {
int i = total;
}
Nested scope

10. • 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

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