My research into numerical simulations of many-body (N-body) gravitational interactions spans over 40 years, and is reported in several publications and my book. I have developed a set of FORTRAN codes which describe the dynamics very closely, and these are regarded by many as the de facto standard. I have explained below how you can download these codes for execution on your local computer system.
NBODY6 code tree from Doxygen documentation can be found here.
For those of you with an FTP tool, you can access my public N-Body directory at ftp://ftp.ast.cam.ac.uk/pub/sverre/. Your browser (such as Microsoft's Internet Explorer) should present you with an FTP viewer window when you click on this link. If so, you should be able to copy whole code group directories at a time.
Otherwise please use the links below to identify and download the specific files that you need.
At any time if you'd like further information, please do contact me.