TR-DOS and Beta disc were developed by Technology Research Ltd (UK), in 1984.
[1][2] A clone of this interface is also used in the Russian Pentagon and Scorpion machines.
It became a standard in Russia and most disk releases for the ZX Spectrum, especially of modern programs, are made for TR-DOS as opposed to other disk systems.
[5] Unofficial versions with various enhancements and bug-fixes have been released since 1990, with the latest being 6.10E (2006).
Current emulators support TR-DOS disk images in the formats .TRD or .SCL.