NOTE: Bill Powers’s work Living Control Systems III : The Fact of Control (2008-2009) with updated Windows programs is recommended. These programs and the book explaining them provide an excellent introduction to PCT.

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	running_pct_demos.pdf
DEMO1 and DEMO2 tutorial programs    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.	Program+Document ZIP: demo1.zip demo2.zip Program uncompressed demo1 program demo2 program Document only: demo1.pdf demo2.pdf
Track Analyze    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.	Program+Document ZIP: track_analyze.zip Program uncompressed track analyze program Document only: track_analyze.pdf
E-COLI    by Bill Powers This interactive DOS program demonstrates that living organisms can achieve efficient results with some very "dumb" processes.	Program+Document ZIP: e-coli.zip Program uncompressed ecoli program Document only: PDF ecoli.pdf
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).	Program+Document ZIP: crowd_win.zip Program uncompressed crowd win program Document only: crowd_win_demo.pdf
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.	Program+Document ZIP: crowd_dos.zip Program uncompressed crowd dos program Document only: crowd_dos_demo.pdf
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	Program+Document ZIP: inverted_pendulum.zip Program uncompressed inverted win program inverted dos program Document only: inverted_pendulum.pdf
Square Circle    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.	Program+Document ZIP: square_circle.zip Program uncompressed square circle program Document only: square_circle.pdf
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.	Program+Document ZIP: arm_one_dos.zip Program uncompressed arm one dos program Document only: arm_one_dos_descr.pdf arm_one_dos_calc.pdf
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.	Program+Document ZIP: arm_one_win.zip Program uncompressed arm one win program Document only: arm_one_win_calc.pdf
Arm with 14 degrees of freedom    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.	Program+Document ZIP: 14_deg_freedom.zip Program uncompressed 14_deg_freedom dos Document only: 14_deg_freedom.pdf
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.	Program+Document ZIP: multiple_control.zip Program uncompressed multiple cont win Document only: multiple_control.pdf