Von neuman

Von Neumann Computers [e-mail] Rudolf Eigenmann Purdue University

David J. Lilja University of Minnesota [e-mail] January 30, 1998

1 Introduction
The term von Neumann computer has two common meanings. Its strictest de nition refers to a speci c type of computer organization, or architecture," in which instructions and data are stored together in a common memory. This type of architecture is distinguished from the Harvard" architecture in which separate memories are used to store instructions and data. The term von Neumann computer" also is used colloquially to refer in general to computers that execute a single sequence of instructions, which operate on a single stream of data values. That is, colloquially, von Neumann computers are the typical computers available today. There is some controversy among historians of technology about the true origins of many of the fundamental concepts in a von Neumann computer. Thus, since John von Neumann brought many of these concepts to fruition in a computer built at the Princeton Institute for Advanced Study see Figure 1, many people in the eld of computer science and engineering prefer to use the term Princeton" computer instead of von Neumann" computer. The intention of this terminology is to acknowledge the important concepts introduced by many other individuals while not over-emphasizing von Neumann's contributions. Recognizing that many people in addition to von Neumann contributed to the fundamental ideas embodied in this widely adopted computer architecture, this article nevertheless uses the colloquial version of the term von Neumann computer to refer to any computer with the fundamental characteristics described in Section 3. The term Princeton architecture" is then used to distinguish between computers with the split Harvard and uni ed Princeton memory organizations.

History
The von Neumann computer concept was developed in the 1940s when the rst electronic computers were