The C Programming Language - Pointers

1.6 Pointer to Arrays
A pointer always increments or decrements by the number of bytes of the data type
to which it points. For a char this would be one byte, for a double it would be 4 or 8
bytes depending on the system.
To illustrate this, in the following example we create an int array and store four values
in it. Instead of the "usual" access to the elements of the array, we now use a pointer
to access the first element in the array, and then increment the pointer three times in
the for loop. This moves the pointer to the next position in the array.
/* example 133 – pointer to arrays */
#include
int main (void)
{
int ivar[] = {2, 8, 5, 9};
int *iptr;
iptr = ivar; // ivar is an array, therefore we need no address operator &
for (int i = 0; i < 4; i++) {
printf("Address of ivar[%d] = %p\n", i, iptr );
printf("Value of ivar[%d] = %d\n", i, *iptr );
}
iptr ++; // move to the next position
}
return 0;
Address of ivar[0] = 0060FEE8
Value of ivar[0] = 2
Address of ivar[1] = 0060FEEC
Value of ivar[1] = 8
Address of ivar[2] = 0060FEF0
Value of ivar[2] = 5
Address of ivar[3] = 0060FEF4
Value of ivar[3] = 9
As you can see, the array ivar[] was stored at address 0x0060FEE8. This is also the
address of the first element with the content 2. The value of the pointer was then
increased by 4 bytes. So the next address in the array for the 2nd element is
0x0060FEEC, whose content is the value 8. This allows access to the individual
elements of an array. It is noticeable here that the & operator for an address
assignment is missing. This is because according to the ANSI-C standard, an array name
represents a pointer to the 1st element of the array. Another notation would be e.g.
ptr_a = &a[0]; The address of the 1st element of array a is also passed to the pointer
ptr_a with this command.
The C Programming Language by Heimo Gaicher – Chapter Pointers 16