C Programming language

  Storage Classes In C Language

Storage classes define the scope and lifetime of the variable and function within a C program.
Types of storage classes in C :

• Auto storage class

• Register storage class

• Static storage class

• Extern storage class
  
  Auto storage class : This is the default storage class for local variable.
  For example:
  {
  int num;
  auto int month;

  
  }
  Register storage class : This is used to define the local variable that should be stored in register instead of RAM.
  For example.
  {
  register int miles;
  }
  Static storage class : This is the default storage class for global variables.
  For example.
  {
  int num;
  static int count;
  main()
  printf(“%d”,count);
  }
  Extern storage class : Extern is used to give a reference of a global variable that is visible to all the program files.
  File 1: main.c

  
  int count=5;
  
  main()
  {
  write_extern();
  }
  File 2: write.c

  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.