As far as I remember, the two extensions are mostly interchangeable, and are only used as a convention to indicate whether a given file contains an executable application or data.
Palm OS doesn't really have a concept of files; everything's a record-oriented database, containing either resources, including executable code, or data. Palm Desktop would just queue up every .prc or .pdb for copying during the next HotSync. (I've never tested it, but presumably renaming a .prc to .pdb and installing it would lead to it being backed up as a .prc.)
For some reason, Mobipocket (which was originally a Palm OS based ebook format) has landed on using .prc over .pdb for their books, which are definitely not executable, so every once in a while I stumble over a book with a .prc extension and it annoys me ever so slightly – it'll work, but that should be a .pdb :)
IIRC PalmOS prc and pdb are similar, in that they both contain PalmOS data, but pdb was meant to just for data and prc was meant to include executable resources too. PalmOS borrows a massive amount from 68K Mac. Codewarrior used to be the default compiler, and PalmOS uses resources in a similar way - though the actual file format is different IIRC. PalmOS apps are basically modified 68K Mac code (library?) resources. There was a tool that converted ThinkPascal generated binaries of whatever the type I don;t remember was, to prc files. SARC was what it was called.
Palm OS doesn't really have a concept of files; everything's a record-oriented database, containing either resources, including executable code, or data. Palm Desktop would just queue up every .prc or .pdb for copying during the next HotSync. (I've never tested it, but presumably renaming a .prc to .pdb and installing it would lead to it being backed up as a .prc.)
For some reason, Mobipocket (which was originally a Palm OS based ebook format) has landed on using .prc over .pdb for their books, which are definitely not executable, so every once in a while I stumble over a book with a .prc extension and it annoys me ever so slightly – it'll work, but that should be a .pdb :)