Doubt in variable declaration and definition in C

Replies

• 

  gaurav.bhorkar

  When you write extern int a; - it is a declaration not a definition. The extern keyword says that the variable is defined outside the function block.
  
  The following code will explain this:
  

  void func( );
  
  void main ( )
  {
      func ( );
  }
  
  void func ( )
  {
      extern int var; //declaring a variable var which is outside the scope of this function (i.e. our global variable)
      printf ("%d", var);
  }
  
  int var = 10; //Defining a global variable. This can be in another file also

  Note that we have declared (and defined) our global variable 'var' outside the func( ) block, and also way below the func ( ).
  Had we defined the global variable 'var' above the func() block, we wouldn't have to declare it using the extern keyword.