Pointers and Multidimensional Arrays

To simplify the discussion, let's use a small array. Suppose you have this declaration:

int zippo[4][2]; // an array of arrays of ints

The zippo, being the name of an array, is the address of the first element of the array. In this case, the first element of zippo is itself an array of two ints, so zippo is the address of an array of two ints. Let's analyze that further in terms of pointer properties:

• Because zippo is the address of the array's first element, zippo has the same value as &zippo[0]. Next, zippo[0] is itself an array of two integers, so zippo[0] has the same value as &zippo[0][0], the address of its first element, an int. In short, zippo[0] is the address of an int-sized object, and zippo is the address of a two-int-sized object. Because both the integer and the array of two integers begin at the same location, both zippo and zippo[0] have the same numeric value.

• Adding 1 to a pointer or address yields a value larger by the size of the refered-to object. In this respect, zippo and zippo[0] differ, because zippo refers to an object two ints in size, and zipp[0] refers to an object one int in size. Therefore, zippo + 1 has a different value from zippo[0] + 1.

• Dereferencing a pointer or an address (applying the * operator or else the [] operator with an index) yields the value represented by the refered-to object. Because zippo[0] is the address of its first element, (zippo[0][0]), *(zippo[0]) represents the value stored in zippo[0][0], an int value. Similarly, *zippo represents the value of its first element, zippo[0], but zippo[0] itself is the address of an int. It's the address &zippo[0][0], so *zippo  is &zippo[0][0]. Applying the dereferencing operator to both expressions implies that **zippo equals *&zippo[0][0], which reduces to zippo[0][0], an int. In short, zippo is the address of an address and must be dereferenced twice to get an ordinary value. An address of an address or a pointer of a pointer is an example of double indirection.

  注意：

  zippo = *zippo = &zippo

  这暗示着数组名是一个指向自身的指针！