If you have never encountered large programs before, its sheer size will be overwhelming. The rest is part of SimKit. Each code library directory consists of two sub-directories build and src .
Source code is always in the src sub-directory.
Other file prefixes usually mean the file will be located in a code library attached to a traffic model. Opening the traffic directory reveals an even larger set of directories, most of which are code libraries for the traffic models. The model directory has a similar structure to the code libraries, but in addition contains a third sub-directory, tests , in which the user data files are placed. The bin directory contains architecture sub-directories, within which symlinks to the actual executable will be found. The lib directory contains architecture sub-directories, into which make places the .a executable libraries.