PRC

The Palm Resource Compiler (PRC) format is sometimes considered to be an e-book format because a number of electronic readable documents have this extension, but it's not really a specific format of that type; it's merely a variant of the PalmOS Database format (used on Palm devices) which uses .prc as its extension instead of the more common .pdb to designate a resource for Palm devices. An e-book is one of the sorts of resource which may be stored this way, and some e-book readers use it. The format is the same as MOBI, but with a different extension.