Storage Class in C

Types of Storage Classes

In C Programming Language, there are four types of storage classes.

1. Auto Storage Class
   • This is the default storage class for all the variables declared inside a function or a block.
   • There is no need for writing the auto keyword while writing the C program.
   • Example:

   #include <stdio.h>  
   
   void display() {
       auto int x = 10;
       printf("Value of auto variable x inside function: %d\n", x);
   }
   
   int main() {
       display();
       return 0;
   }
   

2. Extern Storage Class
   • Extern storage stands for external storage.
   • Extern means that the variable is declared outside the block where it is used.
   • Example:

   #include <stdio.h>
   
   extern int x;
   
   int main() {
       printf("Value of extern variable x: %d\n", x);
       return 0;
   }
   
   int x = 20;
   

3. Register Storage Class
   • Register storage class is almost the same as the auto storage class.
   • Register storage basically stores a variable into the CPU register rather than RAM for faster access.
   • Example:

   #include <stdio.h>
   
   int main() {
       register int x = 30;
       printf("Value of register variable x: %d\n", x);
       return 0;
   }
   

4. Static Storage Class
   • This storage class is used to declare static variables which are popularly used while writing programs in the C language.
   • Static variables have a property of preserving their value even after they are out of their scope.
   • Example:

   #include <stdio.h>
   
   void display() {
       static int x = 40;
       printf("Value of static variable x inside function: %d\n", x);
       x++;
   }
   
   int main() {
       display();
       display();
       return 0;
   }
   

These storage classes play a crucial role in determining the scope, lifetime, and visibility of variables in C programs.