# The Von Neumann Machine¶

John Von Neumann was an important figure in the history of computing.

His contributions to that history really began when he authored this document in 1945:

## World War II¶

Back in 1945 – World War II was still going on – John Von Neumann was thinking about the whole business of computing. He published his paper as part of work to build an electronic computing machine, and started the world on a whole new track.

Note

As a computer professional, you should read some of these early papers to get a feel for how these machines came into being. I recommend this paper, and others by George Boole, and Alan Turing as well.

Von Neumann explained to the world (in 1945) how an electrical device with a Stored Program could process information. Although he did not come up with these ideas alone (he was working with a team of scientists and engineers building this first machine), Von Neumann was the first to write everything down in a way that was clear and easy to understand. We call the architecture he described, a “Von Neumann Architecture” but major features of the architecture should be properly attributed to others, like Eckert and Mauchly who built the first stored program machine at the University of Pennsylvania in 1943 (ENIAC). Today, Alan Turing is credited with having come up with some of the basic principles that led to the development of the computer as well.

His Computing Mechanism consisted of four fundamental parts:

• A Central Arithmetic Unit (CA) to do the number crunching
• A Control Unit (CU) to manage the machine
• A Memory Unit (M) to store programs and data
• An Input/Output Unit (IO) to get things into and out of the machine

## How the parts are organized¶

As obvious as this might seem today, back when Von Neumann was doing his work, few people really had any idea what an automatic calculating device should look like, so this paper was hugely important to those people who set out to build one. The first machines to come out were huge, used immense amounts of electricity, broke often, but they worked!

A computer is really just a fancy electronic device that does very simple things. There is nothing magic about this. A human could act as the Control Unit, a piece of paper could function as the Memory, a calculator as the Central Arithmetic Unit, and the keys and display of the calculator as the Input/Output device.

To this day, most computers follow this basic architecture. This course focuses on creating programs for the most fundamental part of the modern computer - the Control Unit, or the Central Processor Unit (CPU). In today’s computer systems, the control unit and the arithmetic-logic-unit are packaged in a single integrated circuit. We will concentrate on one of the most popular of these chips - the CPU of most IBM-PC class of computers. Specifically, we will look at the Intel Pentium processor, and later at two much different chips - called microcontrollers.

## Von Neumann’s Machine¶

The first electronic computing machine was actually constructed in England. It was called EDVAC. The first such machine in the US was Eniac, built at Penn State. There is some debate, even today, over which machine came first, but Von Neumann’s place in history was assured by his paper, which was widely circulated and became a handbook for further development of electronic computers.

This beast weighed in in tons, and was huge in all its glory. It was also fragile!