The class libraries are grouped together in the assemblies they belong. Each directory here represents an assembly, and inside each directory we divide the code based on the namespace they implement. In addition, each assembly directory contains a Test directory that holds the NUnit tests for that assembly. We use a new build system which is described by various README files in mcs/build The build process typically builds an assembly, but in some cases it also builds special versions of the assemblies intended to be used for testing. * Missing implementation bits If you implement a class and you are missing implementation bits, please use the attribute [MonoTODO]. This attribute can be used to programatically generate our status web pages: [MonoTODO] int MyFunction () { throw new NotImplementedException (); } Ideally, write a human description of the reason why there is a MonoTODO, this will be useful in the future for our automated tools that can assist in developers porting their code. Do not use MonoTODO attributes for reminding yourself of internal changes that must be done. Use FIXMEs or other kinds of comments in the source code for that purpose, and if the problem requires to be followed up on, file a bug. * Tagging buggy code If there is a bug in your implementation tag the problem by using the word "FIXME" in the code, together with a description of the problem. Do not use XXX or obscure descriptions, because otherwise people will not be able to understand what you mean. * Tagging Problematic specs. If the documentation and the Microsoft implementation do differ (you wrote a test case to prove this), I suggest that you edit the file `mcs/class/doc/API-notes' so we can keep track of these problems and submit our comments to ECMA or Microsoft and seek clarification. Sometimes the documentation might be buggy, and sometimes the implementation might be buggy. Lets try to identify and pinpoint which one is the correct one. Sometimes the specification will be lame (consider Version.ToString (fieldCount) where there is no way of knowing how many fields are available, making the API not only stupid, but leading to unreliable code). In those cases, use the keyword "LAMESPEC". * Coding considerations and style. In order to keep the code consistent, please use the following conventions: http://www.mono-project.com/community/contributing/coding-guidelines/