Each allocated chunk of memory is a node of a universal chain of dynamcially allocated objects. This linked list is invisible to the user’s code. However, this mechanism does allow the interpreter or virtual machine to scan through all allocated chunks of memory.
Furthermore, each chunk of allocated memory also knows its own index in the universal table of pointers.
When a new chunk of memory is allocated, the interpreter or virtual machine finds an unused pointer in the universal table of pointers, and make that entry associated with the chunk of memory.