Text Compressed for Readability (.tcr)
The TCR file extension stands for Text Compressed for Readability, originally used by Psion Series 3 palmtop devices in the early 1990s. It stores eBooks in a proprietary format that offers better compression than PalmDOC, making it suitable for the limited storage of handheld devices. Despite the discontinuation of Psion devices, TCR files can still be read using modern eReaders like Sumatra PDF.