6.10 Declarations & initialization

6.10 Declarations & initialization

• Variables must be declared.
• Alphabetic order and comments help.
• Multiple variables can be declared in a single declaration.

    int i, j, k, l, m, n;
    

• Initialization may also be done.

    int i = 1, j =2;
    const double pi = 3.1415926535897932384626433;
    

• Storage class specifiers and Type specifiers precede identifiers.
• Storage class specifiers  

  extern	Symbol is passed to the linker
  static	Symbol is NOT passed to the linker
  	exists for the duration of the program.
  auto	Limits storage duration, not useful
  register	Instructs compiler to use registers.
  	pointers are NOT allowed.

• Type specifiers  

  void	It doesn't exist
  char	a single character
  short	often 16 bits
  int	the default size on the machine
  long	often 32 bits
  float	floating point
  double	64 bit floating point
  signed	the default anyway
  unsigned	no negative values,
  	but twice the range.

• Type Qualifier  

  const	You can't change it.
  volatile	"Something" else might change it.

6.10 Declarations & initialization