Grass source code

[Sastry V. Dhara]

I was reading through the source code of Grass. 
There is not much of documentation/comments in most of the
programs.

For example, I am unable to figure out the basic data-structure
used to store the data.

I chanced upon a file named "btree.h" and assumed the B-Tree format is
used .

Any comments on where to look ?

Thanks.

Sastry