The Electronical Numerical Integrator and Computer (ENIAC) was built at the Moore School of Engineering, University of Pennsylvania, and has been hailed as the first large-scale electronic computer in the world. In this project we wrote the first software simulation of the ENIAC. The simulation is written in Java and runs as a Java applet on any computer connected to the Internet.

 The main difficulty encountered in simulating the ENIAC is that it did not use software. The program was hardwired by special programming assistants. Figure 1 below shows the cycling unit of the ENIAC, the initiating unit, and two accumulators. The user can activate the switches and connect accumulators with transmission lines for digits or pulses. Once the program has been “cabled”, the machine can run at the velocity desired by the user.

 This simulation provides computer science students with a better understanding of the architecture and programming of the ENIAC. The simulation was shown in 2004 in Germany and the US, and is currently online at zuse.zib.de.

In the simulation of the ENIAC, up to 20 accumulators, two constants units, and other units can be assembled. Appropriate signal lines allow the user to perform tabular computations, iterations, and even to insert “if-then” commands. Since the machine is so large, the simulation allows the user to zoom in or out of the machine to get a better impression of the overall cabling. The figures below show some screenshots of the simulator.

 This project was pursued by Till Zoppke under my supervision.