A pointer type variable holds the address of a data object or a function. A pointer can refer to an object of any one data type; it cannot refer to a bit field or a reference.
Some common uses for pointers are:
- To access dynamic data structures such as linked lists, trees, and queues.
- To access elements of an array or members of a structure or C++ class.
- To access an array of characters as a string.
- To pass the address of a variable to a function. (In C++, you can also use a reference to do this.) By referencing a variable through its address, a function can change the contents of that variable.
Note that the placement of the type qualifiers volatile and const affects the semantics of a pointer declaration. If either of the qualifiers appears before the *, the declarator describes a pointer to a type-qualified object. If either of the qualifiers appears between the * and the identifier, the declarator describes a type-qualifed pointer.
The following table provides examples of pointer declarations.
| Declaration | Description |
|---|---|
| long *pcoat; | pcoat is a pointer to an object having type long |
| extern short * const pvolt; | pvolt is a constant pointer to an object having type short |
| extern int volatile *pnut; | pnut is a pointer to an int object having the volatile qualifier |
| float * volatile psoup; | psoup is a volatile pointer to an object having type float |
| enum bird *pfowl; | pfowl is a pointer to an enumeration object of type bird |
| char (*pvish)(void); | pvish is a pointer to a function that takes no parameters and returns a char |
 nullptr_t pnull; |
pnull is a null pointer that does not point to any valid object or function. |