Graphical Aids for Stochastic Processes

Award-Winning Educational Software

GRAPHICAL AIDS FOR STOCHASTIC PROCESSES (GASP) is an award-winning interactive tutorial in the theory of stochastic processes by Bob Fisch and David Griffeath. This DOS package is divided into 6 modules, A-F, on the subjects of Bernoulli Trials, Random Walks, Markov Chains, Poisson Processes, Branching & Queueing, and Brownian Motion, respectively. Once the software is installed, simply run GASP_x, where x is the desired module letter.

The distinguishing feature of GASP is state-of-the-art interactive microcomputer animation and an arcade style that makes the program fun to use. A "cartoon" of a toad jumping randomly between a princess and a dragon illustrates random walk (click the thumbnail image above for a snapshot). Another graphic shows "random people" at the bank to explain queueing. Users can interact with the program at any time - to change parameter values in the animations, read explanatory text screens, and so forth. Many topics are presented as challenging games.

The Interface
When you start the program, the first thing you will see is a title screen. If you are not familiar with the simple user interface, BE SURE TO PRESS THE FUNCTION KEY F1 (usually in the upper left corner of the keyboard) IMMEDIATELY AFTER THE TITLE SCREEN APPEARS in order to call up a help screen which explains keyboard control common to all modules. Later on, you can enter F1 at any time for additional help. By making use of the help screens and windows you will catch on quickly.

Keyboard control is so simple that anyone can learn how GASP works within a few minutes, using only the program's help windows. We recommend that you start right in on Module A, which is deliberately paced more slowly than subsequent modules, in order to learn by doing. But if you prefer, you can read the following summary of the interface.

Each module has eight text screens, accessed with function keys F2 through F9. F1 displays a help screen that summarizes the very simple GASP interface. F10 shows a table of contents for screens F2 through F9. To load the first text screen, press F2. Every text screen has a companion graphics animation; ESC switches back and forth between text and graphics. Each text screen refers to its companion animation as "the current graphic," "the companion graphics screen" or some such phrase.

In text mode, the screen displays only one sentence initially. Hit Ins to call up additional sentences at your own pace until the screen is full. In graphics mode, A turns the animation on/off, S turns the sound effects on/off and R restarts any animation. Windows pop up on the graphics screen asking you to input data, choose parameter values and so on. Always remember to use ENTER (CR) to end input and remove windows. A stop sign icon alerts you if the animation is stopped: press A to start. Whenever you don't recall your options, simply hit F1 and a help window will appear. Pressing F1 a second time displays the main summary of commands.

Download and Registration
GASP is currently distributed as shareware. You may use the tutorial for 30 days to evaluate its usefulness. If at the end of that time you are satisfied with GASP as a product, you can register it. The basic registration fee for a single user of GASP is $25. See below for details on site licenses.

The complete, uncrippled software package is available by anonymous ftp from:

psoup.math.wisc.edu/pub

The file gasp.exe is a self-extracting DOS program that installs the complete software package in the current location when it is executed. We recommend running it from a \gasp directory. The tutorial runs well under Windows 3.x / 95 ; icons for a program group are included.

Cheques or Postal Orders should be made out to GASP Software and sent to:
GASP Software
c/o David Griffeath
Mathematics Dept.
University of Wisconsin
Madison WI 53706

You may fill out an order form and send it along with your cheque or Postal Order to the above address.

Additional Features
There are a few useful interface elements of GASP which are not documented within the program:

(1) If you want to run the program without sound effects (in a library say, or because you hate noise), just type GASP_A QUIET at the DOS prompt.

(2) All text screens will fill automatically (rather than sentence by sentence in response to the Ins key) if you type GASP_A TEXT at the DOS prompt. (QUIET and TEXT can both be entered, in either order, separated by a space.)

(3) When displaying GASP with a large screen projection device (e.g., for in-class demos) you may want to black out the video temporarily without disabling the animation. By simultaneously entering CTRL and PGDN you can alternately blank and restore the active screen.
Best of luck in life,
R.F. and D.G.

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