What is the structure of a PDB file?

Question

I am trying to understand how a debugger uses PDB file. It would probably be a small file system in itself. Could someone help me understand the structure of the PDB file?

Answer 1

According to MSDN, its impractical:

Because the format of the .pdb file generated by the postcompiler tools undergoes constant revision, exposing the format is impractical

A debugger would use the DIA SDK to access the data inside them, meaning you don't really need to know its structure.