mobi The .mobi filename extension is an eBook file format developed by French company MobiPocket for their ebook readers for mobile phones and PDAs. The company was later acquired by book reseller and online store company Amazon in 2005, a deal which included the mobi format asset. The mobi file format is mostly associated with the mobipocket software package as well as early versions of Amazon's kindle ebook reader device. The format is considered cross platform given its compatibility with several devices including most smartphones that have compatible readers installed. But although mobi files still exist in circulation, the format was superseded by Amazon's AZW format when support and further development of mobi ceased in 2011.
tcr The .tcr filename extension is a compressed text file format for eBooks and text associated with eBook reader software developed by Psion, a London based techonology company. The format has its beginnings in the early 90's and was designed for use on the PDAs released by the company, particularly the Series 3 handheld PDA. Though the format is proprietary and was intended for exclusive use on Psion devices, today, a few eBook reader applications can open files encoded in this format. As PDAs eventually lost there popularity, the format was discontinued when Psion eventually pulled out of the PDA market.