A computer
architecture
conceived by mathematician
John von Neumann, which forms the
core of nearly every computer system in use today (regardless
of size). In contrast to a
Turing machine, a von Neumann
machine has a
random-access memory (RAM) which means that
each successive operation can read or write any memory
location, independent of the location accessed by the previous
operation.
A von Neumann machine also has a
central processing unit
(CPU) with one or more registers that hold data that are
being operated on. The CPU has a set of built-in operations
(its
instruction set) that is far richer than with the
Turing machine, e.g. adding two
binary integers, or
branching to another part of a program if the binary integer
in some register is equal to zero (
conditional branch).
The CPU can interpret the contents of memory either as
instructions or as data according to the
fetch-execute cycle.
Von Neumann considered parallel computers but recognized the
problems of construction and hence settled for a sequential
system. For this reason, parallel computers are sometimes
referred to as non-von Neumann architectures.
A von Neumann machine can compute the same class of functions
as a universal
Turing machine.
http://salem.mass.edu/~tevans/VonNeuma.htm.