Here is public domain source code that any would-be programmer/astrologer can use as the core for any sort of astrology program a person wants to make. This source code uses the Astrodienst Swiss Ephemeris (click here) to do all planetary and house calculations. Please see Astrodienst's web page for the details of the Swiss Ephemeris license (click here) and other documentation.
AstroSrc contains natal chart interpretations, daily transit interpretations, single and dual chartwheels, two types of keyword features, 7 different house systems, my AstroLine graphic planetary display, a meanings form that allows you to select and read various natal interpretations for any planet in a house, sign, or aspect, plus any rising sign, a natal chart report writer, a daily transit report writer, plenty of option settings, help files, a Tip of the Day feature, and an astrology font that can be used in any word processor application. Since this is free source code, there is currently no automatic atlas feature in the program, except the ability to interface with the ACS DOS atlas. There are geographic lists of about 2300 cities, though.
The source code here given is perhaps not written like they teach in colleges of computer science. Okay, I am an engineer first and a programmer second. It may not be fancy or elegant, but it works. And it works well.
Download everything in one .zip file below:
Download AstroSrc - v134 source code.zip, 2,977,605, 05 Nov 2007. Once
downloaded, simply create a new directory, then unzip astrosrc.zip into that directory. Then double-click on
astrosrc.vbp to open AstroSrc in your Visual Basic environment. Go from there. Of course you can always
just simply run astrosrc.exe and use the program as is. But this isn't preferred because my Astro123 program
has everything AstroSrc has and more.