Like its more powerful successor, the IGMS v2.2 combines an n-body gravitational simulator with simple galaxy modeling and 3-D visualization software plus an easy-to-use user interface. All necessary components are contained within the single file IGMS22.BAS. Any QBasic compiler should be capable of loading and running the program; however, the capabilities of the program may be limited depending on your QBasic version; if this is the case you may have to perform a minor modification to the code as described in the below paragraph.
There are a few problems with the software, though. Most significant is a memory limitation imposed as far as I can tell by the environment, which affects the program in two ways. First, the IGMS application is limited by a relatively tiny memory pool of about 500KB, imposing a low particle/max recording limit. In fact, depending on your computer and version of QBasic, this limit may be even lower and if this happens the memory allocation access will fail upon program compilation. If this happens, lower one of these limits (probably recordings). I wrote the program in version 6.2; under this version I was able to use 302 particles and 60 data recordings. Running on a different computer with version 7.1 the data recording limit had to be reduced to about 50; and using freeware version 1.1 the limit had to be reduced to a mere 20.
More seriously, the editor itself seems to be unable to hold the entire (66 KB!) program in memory; sometimes while editing lines of text will disappear and/or an error message will appear simply stating 'Out of Memory.' The more advanced versions of QBasic may have ways of dealing with these memory issues - I noticed version 7.1 has extended/expanded memory features - but version 6.2 did not as far as I could tell. Also, the program has more general bugs than IGMS v3.2, though as far as I can tell they're all very minor and have never caused the program to actually fail.
There is only one file to download, below. To get the file, simply click on the link. Your browser may try to open the file; if this happens return to this page and right-click on the link, then choose 'Save File As...'. Once the file has been downloaded you can open it with your version of QBasic and run by pressing F5. There is no manual for this version, although all its features are present in v3.2 and functions very similarly, so that manual would probably suffice. (Keep in mind instead one major retrotrajectory parameter changed, velocity[2.2] became eccentricity[3.2]. About 0.05-0.5 is the general range of galaxy velocities reasonable for use in this version.)
Max Galaxies: 2
Max Particles: 302
Max Recordings: 20-60, depending on compiler
Video Resolution: 640x480
Max. Colors: 16
Galaxy Mass Model: Central Point-Mass
Galaxy Disk Model: Disk of Concentric Massless-Particle Rings
Interaction Processing Time: 0.2 MHz s
Simulation Speed (800 MHz): 4000 interactions/second
Program Size: 66 KB (code)
Minimum System Requirements: 80486 Processer, 640KB RAM, 16-color VGA video card.
