DNA

The .h files in source/blender/makesdna/ define the structs, enums, etc., for all the data that needs to be persisted to disk. These are usually used in memory in the running system too. For example, DNA_mesh_types.h defines the Mesh struct that has enough information to store a user's mesh on disk. While running, there may be a Mesh in memory, but there will likely be various derived mesh structures that are more efficient to use during editing, say.

Another aspect of DNA is that it is also a system for helping compatibility between different versions of Blender. The way this works is that a coded description of the layout of each struct is also written to and read from disk. This means that the layout does not have to stay fixed. The C++ files in the makesdna directory are for generating and interpreting the structure descriptions.

Renaming

To be written.

Defaults

To be written.