doc The .doc filename extension is a native file extension used by the closed source document processing application Microsoft Office Word. Initially developed and used by Microsoft since 1983, the filename extension .doc continues to be supported natively even in the most recent iteration of the word processing application Microsoft Office Word 2013. The more recent .docx filename extension however was introduced by Microsoft in Office Word 2007, becoming the default filename extension. Documents to be saved in the .doc format are saved as Word 97, 2003 documents.
pdb The .pdb filename extension refers to the program database file format authored by Microsoft. The format is used for storing debugging information about executable files and programming libraries or DLL files. The pdb format was designed to ease the debugging process of executables and program modules by decoupling the debugging information from the end of the program or class library itself to allow the integrated debugger and linker to access the pdb files directly. It doing so, the PDB format facilitates the stepping into/out of runtime libraries. The format and its internals remain the proprietary asset of Microsoft.