ENIAC Simulator

This is a simulator for the ENIAC, the first electronic general-purpose computer, built in 1946.

Demo

The demo is set up to run three pre-configured programs. Select one and then follow the directions for running the machine. (Read below for how to write your own programs!)

You can view it at http://eniac-simulator.herokuapp.com/.

Or, fire up the ENIAC locally by performing these operations:

• Run foreman start
• Visit http://localhost:5000/

How do I write an ENIAC program?

An ENIAC "program" consists of the wiring together of different units, and the units' settings (dials, knobs, etc). Let's say you wanted to write a program that simply lets the user enter two numbers, and then it would add them to produce a sum. Here's how you could wire up and configure the ENIAC do accompliash that:

1. Let the user load X into the top row of the Constant Transmitter
2. Let the user load Y into the bottom row of the Constant Transmitter
3. Set the initializer unit to kick off these operations (over control line 0) when the ENIAC is started:
   • Constant Transmitter sends top number (over digit tray 0)
   • Accumulator 0 receives number (over digit tray 0)
   • Kick off the next operations over control line 1
4. The next operations:
   • Constant Transmitter sends top number (over digit tray 0)
   • Accumulator 1 receives number (over digit tray 0)
   • Kick off the next operations over control line 2
5. The next operations:
   • Accumulator 0 transmits contents (over digit tray 1)
   • Accumulator 1 receives number, adding to its contents (over digit tray 1)

At the completion of this program, Accumulator 1 holds X+Y.

Even this simple program takes about 50-100 lines of configuring and wiring up: https://github.com/jimlindstrom/eniac-simulator/blob/master/public/test_programs/test_add_two_constants_once.js

To see more complex programs, browse these tests: https://github.com/jimlindstrom/eniac-simulator/tree/master/public/test_programs

What's built?

I've focused on building enough to get a flavor for what it was like to program the ENIAC. What's included in this simulator so far is:

• Initiating Unit
• Cycling Unit
• Master Programmer
• Constant Transmitter (1)
• Accumulator (2)
• Buses

Not yet tackled are:

• Multiplier
• Function Table
• Divider and Square Rooter
• Printer
• Card Reader

(Refer to TODO.txt for a development roadmap.)

References

• ENIAC Operating Manual
• Report on THE ENIAC