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Legacy of Old Code: Software Old Enough to Get a Drivers License

Following up on my nostalgia for ten years on the web, I also reflected on what was likely the first educational software I ever created, back in 1987.

As a Geology grad student at Arizona State University with a few programming courses as an undergrad, I was handed the opportunity to run a computer lab (14 Apple Mac Plus-es, no hard drive, one 300 kps modem, and a LaserWriter printer).

Upon request of a geophysics professor, I wrote a little application, Gravity Simulation (Talwani Method) designed to help students understand how a surface measured gravity profile (measuring variations in the earth’s gravity over a linear traverse) could help identify subsurface (anomalies, e.g. ore bodies, buried volcanic lavas, etc).

Exciting, eh? There is more…

snapshot of program
This program is very crude, interface wise. It was written in FORTRAN on and for a Mac Plus. It does not use the mouse- all input are via the keyboard. However, it does teach students about the way different shaped anomalous bodies or ones of different densities could yield the same gravity curve.

This program will allow you to create different subsurface bodies in order to match a given gravity anomaly pattern. As you know there are an infinite number of mass distribution and body geometries that will cause the same local variation in gravitational attraction.

The anomaly is calculated for a user specified polygon based on the method of Talwani et al , 1959.

Sure, everyone know the Talwani, method, right?

Anyhow, the program is more or less a math and logic problem, and setting up ways to modfiy and calculate the gravity differences between a geometric buried “blob” that has a density contrast with the surrounding rock.

I wrote this in 1987 on a Mac Plus using MacFORTRAN and get this. This 1987 software still runs on my 2003 Apple G4! (in MacOS 9 Classic mode), but runs exactly the same as it did back in the late 1980s.

To contrast, I have a CD-ROM project last updated in December 2000 that ran on PCs using Windows 3.1/95/NT/2000 but must be completely re-coded to make it run on Windows XP, a shelf like of less than 3 years. Pfffffffttt on that.

Yes, I have my Mac bias, but to be able to have software running that soon will old enough to be drafted, well, it is hard to top that, 95% of the market and all.

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Profile Picture for Alan Levine aka CogDog
An early 90s builder of the web and blogging Alan Levine barks at on web storytelling (#ds106 #4life), photography, bending WordPress, and serendipity in the infinite internet river. He thinks it's weird to write about himself in the third person.


  1. Whoah… That’s some old stuff…

    I’ll have to dig up my original Hypercard stack… “HyperCELL” – a cellular biology tutorial I wrote back in the day… Don’t have Classic installed, so I’ll have to hunt for a system that can run MacOS9 if I can find the stack (probably on an old floppy… ;-)

  2. Most common mistake with getting CGIs to work is setting permissions correctly to execute. I already comment in your blog, but I think Director/Shockwave would be a snatch for doing your project.

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