Instructions for using the computers in Harkness

Math 215 - Instructions for using the computers in Harkness 114

Here is some information about using software relevant to Math 215 on the computers in Harkness 114.

To use Netscape, click on the icon that appears when you first get into Windows NT.
To use Telnet, click on "Start" in the lower left couner, then move the cursor to the Program Menu and then to the Internet group.
To save work done on the a Harkness computer you can use the FTP program to transfer files to/from another computer account such as one on uhura. The FTP program can be found in the same menu as the telnet program above.
To use Winfract (the Windows version of Fractint), go to the Math 215 group on the Program Menu and click on Winfract. There is also a DOS version of the program. If you have the use a PC you can download it from the Fractint site. It has some features not available in the Windows version, but it does not work well within Windows. It works best when run from DOS.

To get the bifurcation diagram first shown in class on 1/21 from Winfract, pull down the Fractals menu, select Fractal Formula, and then choose biflambda. For greater speed, go the the View menu and be sure that Pixel Update is off. In the DOS version, go to the Main Menu, select Fractal Types and then choose biflambda.
To get the version of the Mandelbrot set first shown in class on 1/26 from Winfract, pull down the Fractals menu, select Fractal Formula, and then choose lambda, and then right-click. Experiment with colors by choosing vrious options on the Color menu.

The program Mathematica can be run from the Mathematica group in the Program Menu.
To download a Mathematica Notebook from the web, such as the one in the Cobweb Diagram Learn Section, click on the Mathematica icon near the top of the page. This will cause a file to be donloaded and Mathematica to be opened. There are several easy but necessary things that you must do next.

A dialog box labelled "Autosave Package" will appear. Click on the "Create Autosave Package" Button in loweright.

A notebook window entitled "Sequences--Cobeweb Diagrams" will appear. Evaulate the second cell by putting the cursor near "Cobweb[f,.." and pressing Shift-Enter. Answer Yes to the diaglog box that appears.

A cobweb diagram should appear. You can modify it by editing the equations above it and pressing Shift-Enter again.

There are some QBasic programs that can be found a run by going to the "Shortcut to ClassData" folder, and from there to the Mth215/Qbasic folder. I will say more about these later.
The Microsoft GifAnimator (in the Math 215 group on the Program Menu) can be used to view animations created with the help of the Dos version of Fractint. This animationprocess involves several steps. I will illustrate by describing the production of an animation that shows Julia sets corresponding to various points on the edge of the period 2 bud of the Mandelbrot set.

Decide what you want to do. Write down the instructions you would like Fractint to have.
Fractint must be given a set of instructions in the form of a key file. A good example is demo.key, which can be found in c:\mth215\fractint, the directory where Fractint 18.2 is stored. It is called when demo.bat is run, which takes about 20 minutes and is rather entertaining. The key file that is relevant to this example is julia2x.key. It is tedious to write such files by hand, and it is better to write a program that does it for you. I wrote a Pascal program for this purpose, julia2.pas. Similar programs can be written in QBasic, C, or any other language you have access to.
Execute the key file. This can be done from the DOS prompt with the command

fractint autokey=play autokeyname=julia2x.key sound=off

This particular key file creates and saves 72 images. Fractint has a default file naming system which causes these files to be named Fract001.gif through Fract072.gif. This will take some time, depending on the number and sizes of the images created and on the speed of the computer you are using.

Open the MS GIF Animator. Click on the blank page icon in the upper left corner to create a new file. The gif files created above must be inserted as frames one by one. (Can anyone think of a more efficient way to do this?) This can be done more easily by dragging and dropping from the Windows Explorer. Name your file and save your work as a gif file for future use. The sample file here is julia2x.gif, which is about 1.3 MB in length. If you click on this your browser will show a series of Julia set images, one on top of the other. You should save the file so you can view it with the animator.

This page was last revised on March 19, 1998.

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