The programs used in lecture were written in a language called cT, which was developed at Carnegie-Mellon University. In order to run them, you need the cT executor program which, fortunately, is freely distributable under the terms of the cT licensing agreement. If you already have the cT executor on your machine and you only want to download an individual program, click here to get the individual (zipped) files.

Otherwise, do you want to:

run the programs on this machine?
take them with you and run them on another machine?

To run the programs here

For those who are experienced at this sort of thing:

• Press the shift key and click here to download the file "ctx01.zip", which contains the programs and everything you need to run them.
• Unzip ctx01.zip using StuffIt, then to run the file xxx.ctb you open it with ctx.exe.

For those who haven't done this very much:
This may look like a long, drawn-out procedure, but it's pretty straightforward.

1. Hold down the shift key and click here. This will bring up a dialogue box labelled "Save As...".
2. In this dialogue box, to the right of the "Save in:" box, there is a yellow icon with an upward-pointing arrow on it. Click on this icon repeatedly until "Desktop" appears in the "Save in:" box (and the icon turns grey -- you can't go up any farther).
3. Click on the "Save" button near the bottom of the dialogue box. The dialogue box will then go away, and after a moment an icon labelled "ctx01.zip" will appear on your desktop, probably just below the Internet icon.
4. Double-click on the "ctx01.zip" icon on the desktop. A dialogue box labelled "StuffIt Expander" will appear for a while, then it will go away.
5. When the "StuffIt Expander" box goes away, click on the "ctx01.zip" icon and drag it to the recycle bin. Where it was, you should now see a yellow folder labelled "Ctx01".
6. Double-click on the "Ctx01" folder. You now get a window showing lots of files with names like "Helvbo08.fpc". You are interested in the files which end in ".ctb".
7. (Optional) To make it easier to find the program you want to run, you could click on the "View" item on the menu at the top of the window, then click on the "Arrange Icons" item on the menu that appears, then click on "by Type" on the new submenu that appears. This will put all the .ctb files together, near the left side of the window.
8. Click on the program you want to run.
9. Click on "File" on the menu bar at the top of the window. When the menu appears, click on "Open with...". A new dialogue box will appear.
10. Click on the button that says "Other...", near the bottom of the dialogue box.
11. In the window that now appears, click on the icon labelled "ctx.exe", then click on the button marked "Open".
12. You are now back on the "Open with..." window. Click on the button marked "OK". This runs the program.

When you are finished running programs, drag the yellow "Ctx01" folder on the desktop to the Recycle Bin.

To run the programs at another machine

For those who are experienced at this sort of thing:

• To run the programs, you will need the cTx distribution package, which contains the executor ctx.exe and all the font files that it needs. If you don't already have it, you can download a zipped version by...
  • shift-clicking here to get a package containing only ctx.exe and the font files, or
  • shift-clicking here to get a package containing ctx.exe, the font files, and all the programs I have loaded so far.
• If you don't have a zip/unzip utility, you can download the self-extracting shareware program pkz204g.exe from Pkware by shift-clicking here.
• If you already have everything you need, then you can just go to the list of programs and download the one(s) you want.

For those who haven't done this very much:

I can't be very explicit, because a lot depends on whether your home computer is running Windows or Windows '95. You will need at least some familiarity with your computer. But then, if it's your computer, you probably do.

1. Put a disk in the disk drive of the computer.
2. If you don't have an unzip program on your computer at home, download the shareware program PKZ204g:
   • Hold down the shift key and click here.
   • In the "Save As ...'' dialogue box, to the right of the "Save in:'' box, click on the up icon until "My Computer" appears in the "Save in:'' box. [If you get all the way up to "Desktop", then click on the little down arrow next to the white "Save in:" area.] Then click on "3-1/2 Floppy (A:)", which is under "My Computer".
   • Click on the Save button. You will get a "Saving Location" box, and it will take some time for the program to download. (This takes time because you're downloading from a remote location. If you don't seem to be getting anywhere, click on the Cancel button and try again.)
3. If you don't have ctx.exe and all that it needs to run:
   • Hold down the shift key and click here.
   • If the "Save As..." box doesn't come up saying "3-1/2 Floppy": In the "Save As..." dialogue box, to the right of the "Save in:" box, click on the up icon until "My Computer" appears in the "Save in:" box. [If you get all the way up to "Desktop", then click on the little down arrow next to the white "Save in:" area.] Then click on "3-1/2 Floppy (A:)", which is under "My Computer".
   • Click on the Save button. You will get a "Saving Location" box, and it will take some time for the program to download.

To run any of the programs (say, "name.ctb", for example):

1. Either exit Windows, or double-click on the "MS-DOS Prompt" icon in the "Main" program group (these programs will not run in a window);
2. Use the "cd" (change directory) command to change to the directory which ct.exe and the program are in;
3. Start the program by typing the command
   ctx name at the command-line prompt.

Here are the programs:

• nitesky1, which produces a time lapse animation of the motion of the stars around the sky, facing celestial north. Used in lecture on 8/28 and 9/4.
• sidereal, which shows the rotation of a planet while it orbits the sun. Used in lecture on 9/4.
• nitesky3.
• epicycle.
• retrogrd.