C Programming language

Storage classes define the scope and lifetime of the variable and function within a C program.

Types of storage classes in C :

1. Auto storage class : This is the default storage class for local variable.

   {
   	int num;
   	auto int month; 
   }
   

2. Register storage class : This is used to define the local variable that should be stored in register instead of RAM.

   {
   	register int miles;
   }
   

3. Static storage class : This is the default storage class for global variables.

   {
   	int num;
   	static int count;
   	main()
   	printf(“%d”,count);
   }
   

4. Extern storage class : Extern is used to give a reference of a global variable that is visible to all the program files.

   int count=5;
   main()
   {
   	write_extern();
   }
   ////////////////////////
   void write_extern(void);
   extern int count;
   void write_extern(void)
   {
   	printf("count is %i\n", count);
   }
   

Here extern keyword is being used to declare count in another file.