TCR, Psion Series 3 eBook File (.tcr)
The TCR eBook file format
Files with the TCR extension are a by now deprecated e-book file format. Originally, the format has been developed by Psion Teklogix for their Psion Series 3 devices. The Psion Series 3 devices and the proprietary TCR format have been developed in the 1990s, but have since been abandoned in favor of more popular and more widely supported e-book formats. However, there are still some mobile and desktop readers that are able to handle, open and display TCR files.
Technical details of TCR files
TCR files, like any e-book files, can contain the text of the e-book, but only very basic and limited formatting. The TCR format provided, at the time of release, a better compression ratio than it's immediate competitors.