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NOTE: Bill Powers’s work Living Control Systems III : The Fact of Control (2008) with updated Windows programs is recommended. These programs and the book explaining them provide an excellent introduction to PCT. The programs are available for free download at, mirrored here, but you do need the book to get full benefit from them. The programs themselves are superior in many ways to the programs discussed below. Here is a for the book.

This web page features programs created by Bill Powers prior to 2008.

The programs can be downloaded in zipped program packages that hold the program and its documentation in separate folders: docs and program. When you unzip, ask for subfolders. The documentaton of these early programs yields additional insight for the serious student of PCT.

PCT Tutorials and Simulations

Running PCT demos    by Dag Forssell
Notes on running PCT demos on Windows computers

Pulleys — A demonstration of control    by Bill Powers
Here is a very clear demonstration that shows a simple experiment. Bill’s comments on the demo highlight the obvious: Neither the behavioristic Stimulus-Response (S-R) idea that the environment makes us do things (which permeates our culture) nor the current cognitive psychology idea that the brain evaluates what is going on and issues commands to our muscles is viable. Contemporary psychology has no valid concept of how individual behavior works.
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DEMO1 and DEMO2 tutorial programs — DOS    by Bill Powers
The best way to get a sense of how control works is to play with physical control systems. The most readily accessible control systems available for this purpose may be model aircraft servos. You can feel them strain as you apply disturbances or change the reference signal, just like you strain when you arm-wrestle and change your mind about where you want your arm to be when the wrestling starts. DEMO1 and DEMO2 (DOS programs, study in sequence) are excellent tutorials that introduce and review the basics. Studying DEMO1 and DEMO2 with care is essential to understanding PCT.

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DEMO1 and DEMO2 tutorial programs — Java    by Bill Powers
Adam Matics has undertaken to faithfully convert Powers' original DOS programs (shown above) to Javascript versions you can run in your browser. More conversions to come.

DEMO3 tutorial program — Windows    by Bill Powers
In an email November 1, 2004, Bill said: "I am working on a new version of Demo1 — it should probably be called Demo3. This is only a partial version, but I think it contains enough to be of general interest."
     If a later version of Bill’s effort is located, this pdf and the program will be changed/replaced.
     NOTE: It may be a good idea to change the screen resolution for your monitor to 800 x 600 before running the program. The program runs only full screen and will display well at this resolution.

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Track Analyze — Windows    by Bill Powers
This Windows program expands on DEMO1, Compensatory tracking, with additional detail and analysis. The program computes parameters for, and runs a simulation designed to replicate your own results.

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E-COLI — DOS    by Bill Powers
This interactive DOS program demonstrates that living organisms can achieve efficient results with some very "dumb" processes.

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Crowd — Windows    by Bill Powers
Demonstrates how familiar "crowd behaviors" emerge from independent agents each controlling simple perceptions that have nothing to do with such phenomena. Windows version (2004).

Bill suggested: The 2008 version from LCSIII. Very similar, runs better.

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2008 Windows program:

Crowd — DOS    by Bill Powers
The DOS version (1989) of the same Crowd simulation.

Note that the documentation for the old version may be very informative.

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Inverted Pendulum — DOS and Windows    by Bill Powers
Animals standing or walking on one or two legs are always falling to one side or the other, especially if the wind blows or the ships deck moves. To see how we keep our balance, it is well to study and inverted pendulum (balancing an upside-down broom by supporting the handle end in the palm of your hand). This demo shows that a few simple control systems are an excellent start when you set out to reverse engineer a standing, walking animal. DOS demo

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Square Circle — DOS    by Bill Powers
This DOS demo shows clearly that you do NOT control your behaviors. They are your means to control your perceptions – the outcome you want.

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Little Man One — DOS    by Bill Powers
This program demonstrates a model of pointing. You can move a target around in three dimensions while a model person reaches out to touch it, following it as it moves. There are five lower-order control systems and three higher-order control systems that run the model; you can alter the basic parameters of all systems to see the effects. The model person uses binocular vision in three dimensions to detect depth information; all visual information is computed from reasonably accurate optical computations that calculate the finger and target angles that each eye will see.

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Little Man One — Windows    by Bill Powers
This program is an updated, more user friendly version of the original DOS program. The same description applies.

Note that the documentation for the old version is very informative.

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Arm with 14 degrees of freedom — DOS    by Bill Powers
This DOS program simulates an entire arm with 14 degrees of freedom. You will see that the neural structure required to control an arm with its many joints can be remarkably simple.

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Multiple Control Systems / PCT and Engineering Control Theory    by Bill Powers
Newcomers have sometimes concluded that PCT cannot be valid because people cannot be described as a single control system, they're not that simple. Of course they aren't. As in any science, we simplify for purposes of experiment (as in pursuit tracking) or explanation (as in the rubber band demos). When you perform a rubber band demo, many muscle groups are actively controlling, including your left big toe if you are standing up at the time. This Windows program demonstrates that hundreds of interdependent control loops can be "in control" at the same time, despite widely varying reference signals. Thus it demonstrates that the suggested PCT and HPCT hieararchy with thousands of control loops active simultaneously is very realistic.

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