The VHDL access type will not be discussed in detail in this
module; it will be covered more thoroughly in the 'System Level VHDL'
module appearing in this collection of modules.
In brief, the access type is similar to a pointer in other
programming languages in that it dynamically allocates and deallocates
storage space to the object. This capability is useful for
implementing abstract data structures (such as queues and
first-in-first-out buffers) where the size of the structure may not be
known at compile time.
