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.
fb2 The .fb2 filename extension refers to the open XML based eBook format known as FictionBook. The file format was developed by Dmitry Gribov with an initial release in 2004, quickly gaining popularity in Russia. The format is open which in this context means it has no compatibility with digital rights management technologies. The structure of the format splits the contents of the data into three sections; title information, XML document information, and finally information about the paper edition which is optional.