在以下声明中，使用指针有何区别？

Question

char *array[size];
char (*aPointer)[size];

I'm pretty new to C++ and currently I'working on an assignment.And I noticed there are two different(maybe?) use of pointer. Can anyone please tell me what are the difference between them? Thank you

Answer 1

char *array[size] declares an array of size pointers to char s.

char (*aPointer)[size] declares a pointer to an array of size char s.

Just for the sake of completeness, there's also char *cPointer , which declares a pointer to a char , which could be the first one in an array. The difference between that and aPointer is a semantic one. The memory layout will be identical. For example, aPointer + 1 will return a pointer that points to a location size bytes after the one pointed to by aPointer , while cPointer + 1 will return a pointer that points to a location one byte after the one pointed to by cPointer .

So char *array[size] declares something like this:

 array      +--------+
+------+    | a char |
| a[0] +--->+--------+
+------+
| a[1] +--->+--------+
+------+    | a char |
| ...  |    +--------+
+------+

Of course, each of the char s pointed to could be the first element of an array as well:

 array      +--------+--------+--------+
+------+    | a char | a char |  ...   |
| a[0] +--->+--------+--------+--------+
+------+
| a[1] +--->+--------+--------+--------+
+------+    | a char | a char |  ...   |
| ...  |    +--------+--------+--------+
+------+

char (*aPointer)[size] declares something like this:

 aPointer
+--------+    +--------+
|        +--->+ a char |
+--------+    +--------+
              | a char |
              +--------+
              |  ...   |   aPointer + 1
              +--------+    +--------+
                        <---+        |
                            +--------+

char *cPointer could declare something like this:

 cPointer
+--------+    +--------+
|        +--->+ a char |   cPointer + 1
+--------+    +--------+    +--------+
              | a char +<---+        |
              +--------+    +--------+
              |  ...   |
              +--------+

Note that in all of those examples, the pointers don't initially point to anything. You have to point them at something yourself.

Answer 2

The first declares an array of size pointers to char . The second declares a pointer to an array of size elements of type char .

You can think of it as the [] operator binding more strongly than * . Start reading declarations like this one at the identifier and work your way outwards. In the first case, we see the identifier array . Next to it we have [] as well as * . The [] binds more strongly than * , so it applies first. Thus, array is an array of something. Next applies the * , so array is an array of pointers to something. The only thing that's left is the type specifier char , thus array is an array of pointers to char . The second case works analogously, only there we have parentheses which force the * to apply before the [] .