GALAXIES IN COLLISION
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The original algorithm is by M.C. Schroeder and Neil F. Comins, and was
published in ASTRONOMY, December 1988, p. 90.

The present implementation, which includes some minor revisions to the
algorithm, is by Luigi M. Bianchi.  A previous version for the Hercules
card, named GC3DH.EXE, was released in 1989.

The initial screen prompts for the "target" galaxy data and for the
"intruder" galaxy initial position and velocity.  The target galaxy
consists of a core and a number of rings of stars around the core.
You specify the number of rings (try 5) and the number of stars per
ring (try 50).  You are then prompted for initial conditions of the
target galaxy.  A few examples are listed on the screen, and you can
experiment with other values.  Finally you are asked to specify the
number of time steps (try 500).

Then watch...  At any time you can end the program with the ESC key.

                                   *

Hardly any error checking is used, to reduce size and increase speed.
This is especially obvious in the data entry component--improper data
messes up the screen (no damage done, just annoying!).

An 80x87 is used, if present.  The program has been written for a
VGA graphic card only.  The 640x480x16 mode is used.

                                   *

Questions and comments can be sent to the program's author:

Luigi Bianchi þ 414 Atkinson College þ York University 
4700 Keele Street þ North York þ Ontario M3J 1P3 þ Canada
E-M: lbianchi@yusol.bitnet þ compuserve 72060,3723