von Neumann machine

Updated About encyclopedia.com content Print Article Share Article
views updated

von Neumann machine Any computer characterized by the following concepts:

(a) the main units are a control unit, ALU, memory, and input and output facilities;

(b) programs and data share the same memory, thus the concept of a stored program is fundamental;

(c) the control unit and ALU, usually combined into a central processor (which may contain internal storage – accumulators and other registers), determine the actions to be carried out by reading instructions from the memory.

It follows that a program for a von Neumann machine consists of a set of instructions that are examined one after another; a program counter in the control unit indicates the next location in the memory from which an instruction is to be taken. It also follows that the data on which the program operates may include variables: storage locations can be named so that the stored value may be subsequently referenced or changed during execution of the program.

The vast majority of present-day computers are von Neumann machines. The name is taken from that of the American, John von Neumann. Compare non von Neumann architecture.