DEM Source files.

I recently downloaded a program called DEM it is designed to make mesh files . The question I have is where do you find the necassary source files. I have been looking on line without much luck. I thought I had found a source file but when I try to open it I get a file to long message Any info would be appreaciated 8)
I found this program from avsim.
I found this program from avsim.