Where's the source code for __builtin__?

[John Machin]

On 25/04/2007 9:32 AM, Dustan wrote:
> I've been paging through the source code for various C modules in
> python, and wanted to find the source of some of the builtin
> functions. I searched through the Modules, Objects, Python, and Parser
> folder, searched docs.python.org, searched the archived messages of
> this group, searched the web, and got absolutely nowhere in finding a
> __builtin__.c, or anything that contains the builtin source code.
> 
> Help?
> 

What's the 2nd file (in alphabetical order) in the Python folder?