Variables in C programming can have local, global, or formal (parameter) scope. [1] Local variables are declared within a function and can only be accessed within that function. [2] Global variables are declared outside of functions and can be accessed anywhere. [3] Formal parameters declared in a function signature take precedence over global variables of the same name within that function.

1. Scope Rules
Prepared By: Mr. Sangram A. Patil
Assistant Professor PVPIT,Budhgaon

2. Scope of Variables
 A scope in any programming is a region of the program where a defined variable
can have its existence and beyond that region variable cannot be accessed. There
are three places where variables can be declared in C programming language −
 Inside a function or a block which is called local variables.
 Outside of all functions which is called global variables.
 In the definition of function parameters which are called formal parameters.

3. Local Variables
 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.
 Local variables are not known to functions outside their own.
void main()
{
int a,b; // Local Variables
a=10;
b=20;
printf(“A=%d n B=%d”,a,b);
}

4. Global Variables
 Global variables are defined outside a function, usually on top of the program.
 Global variables hold their values throughout the lifetime of your program and
they can be accessed inside any of the functions defined for the program.
 A global variable can be accessed by any function.
 That is, a global variable is available for use throughout your entire program after
its declaration.

5. Global Variables
#include<stdio.h>
int x=500; //global Variable
void main()
{
int a,b; // Local Variables
a=10;
b=20;
printf(“A=%d n B=%d”,a,b);
printf(“nX=%d”,x);
}

6. Formal Variable
 Formal parameters, are treated as local variables with-in a function and they take
precedence over global variables.
#include<stdio.h>
int a=50;
void main()
{
int a=10,b=20,c;
printf(“n value of a in main(): %d”,a);
C=sum(a,b);
printf(“n value of c in main(): %d”,c);
}
int sum(int a,int b);
{
printf ("value of a in sum() = %dn", a);
printf ("value of b in sum() = %dn", b);
return a+b;
}