The Computer: abstract set of rules, defined the Universal Machine that may be imagined the ordered modus operandi. The formal approach is defined the Von Neumann architecture that may be supposed the ideally stated procedure.
It may be defined the Turing Machine that may be visualised as the abstract method. The Computer is not in any sense apparatus and is the ordered table of instructions that can be made in many ways. It is defined the Universal Machine that may be supposed the abstract modus operandi performing a computation. The formal procedure is defined the Abstract Machine that may be thought the formalized 'ideal clerk'.
See also Inscription,