Arrays and Pointers
If you are not already familiar with pointers, you should review the
Spark Note on
memory and pointers.
All of this time we have been using our array variable with the syntax
[<index>] to index into the array. We, will now discuss
the actual value stored in the array variable. You may
have guessed that an array variable holds an entire array the same way
that an integer value holds an entire integer. This is not
the case. Instead, the array value itself is just a pointer to the
memory address where the array begins, as illustrated in the following
image:
Figure 1.1: Pointer to Array
This is the reason that you cannot simply assign the value of one
array into another array and expect it to create a new copy. Instead,
if you have two array variables, and you assign one to the other it
will simple mean that you are assigning the address where the first
array starts into the second array so that they both point to the same
chunk of memory.
Figure 1.2: Array Assignment
If you were planning to use a variable to store only an address, then
you would not necessarily want to allocate a chunk of memory when you
declared it. To achieve such a variable you could either use the
syntax for declaring a pointer:
int *arr_p;
Or you could declare it as you would a normal array but just leave the
square brackets empty.
int arr_p[];
In the next section we will discuss more of the implications of arrays
being pointers.
