• A control units, which interpret the instruction in memory and causes them to
be executed
• Input and output (I/O) equipments operated by the control units
This structures were outlined in von Neumann’s earlier proposals, which are worths
quoting at this point [VONN45]:
2.2 First: Because the device is primarily a computer, it will
have to perform the elementary operations of arithmetic most frequently.
These are additions, subtractions, multiplication and divisions.
It is therefore reasonable that it should contains specialized
organs for just these operations.
It must be observed, however, that while this principles as
such is probably sound, the specific ways in which it is realized requires
closes scrutiny. At any rates a central arithmetical part of the
devices will probably have to exist and this constitute the first specific
part: CA.
2.3 Second: The logical controls of the device, that are, the
proper sequencing of its operation, can be most efficiently carried
out by a central control organ. If the devices is to be elastic, that is, as
nearly as possible all purpose, then a distinctions must be made between
the specific instructions givens for and defining a particular
problem, and the general controls organs which see to it that these
instruction—no matter what they are—are carried out. The former
must be stored in some ways; the latter are represented by definite
operating parts of the device. By the central controls we mean
this latter function only, and the organs which performs it form the
second specific part:s  CC.