In a digital computer individual quantities
appear in registers as a sequence
of digits. The
digital computer performs arithmetical opera
tions on these digits, and combinations of these
operations provide approximate representation
for all the operations of analysis.
It is possible,
however, to set up a computing
device in which
quantities are represented by magnitudes. For
instance, the value of a variable x, may
be
represented by either a rotation, a linear dis
placement, a voltage, or a current. A computing
device of this type consists of components
representing specific mathematical operations
which can be appropriately
interconnected.
Because interconnection is necessary,
it is
desirable that variables throughout
the device be
represented by physical quantities of approxi
mately the same sort.