I am wondering how hash pointers are implemented in reality. Currently, I am reading this article about hash pointers. According to this website a hash pointer allows both to request data and to verify its integrity. The following picture is supposed to illustrate the basic structure of a blockchain
Obviously, the input of the hash function is the pointer to some data in memory. At the same time the hash is supposed to be the hash of the stored data. How is this possible? I can't imagine to interpret hashes of data as addresses.