A one dimensional array is really just a pointer to a set of data.
int a [5] = { 0, 1, 2, 3, 4 };
int *ptr_a;
int x;
/* point pa to the first element of a */
ptr_a = &a[0]; /* or just "ptr_a = a" */
/* copy the value of a[0] into x */
x = *ptr_a;
Since ptr_a points to a particular memory address then, by
definition, (ptr_a + 1) will point to the next address and
(ptr_a - 1) will point to the previous one.
/* copy the value of a[1] into x */
x = *(ptr_a + 1);
Therefore, *(ptr_a + i) is the same as a[i]
One difference between a pointer and an array name
ptr_a = a; /* legal */
ptr_a++; /* legal */
a = ptr_a; /* not legal */
a++; /* not legal */
