Editing Register machine (section)

=== Hartmanis (1971) ===
By 1971, Hartmanis has simplified the indexing to [[indirection]] for use in his RASP model.<ref name="Hartmanis_1971"/>

'''Indirect addressing:''' A pointer-register supplies the finite state machine with the address of the target register required for the instruction. Said another way: The ''contents'' of the pointer-register is the ''address'' of the "target" register to be used by the instruction. If the pointer-register is unbounded, the RAM, and a suitable RASP built on its chassis, will be Turing equivalent. The target register can serve either as a source or destination register, as specified by the instruction.

Note that the finite state machine does not have to explicitly specify this target register's address. It just says to the rest of the machine: Get me the contents of the register pointed to by my pointer-register and then do xyz with it. It must specify explicitly by name, via its instruction, this pointer-register (e.g. "N", or "72" or "PC", etc.) but it doesn't have to know what number the pointer-register actually contains (perhaps 279,431).