Pointers, Arrays, and Structures(Chapter 5 of The C++ Programming Language)

　　No object is allocated with the address 0 . Consequently, 0 acts as a pointer literal, indicating that a pointer doesn’t refer to an object.

　　The declarator operator that makes a pointer constant is *const. There is no const* declarator operator, so a const appearing before the * is taken to be part of the base type. For example:

　　char *const cp;   // const pointer to char

　　char const* pc;   // pointer to const char

　　const char* pc2; // pointer to const char