TR-DOS is a disk operating system for ZX Spectrum with Beta disc and Beta 128 disc interface. TR-DOS and Beta disc were developed by Technology Research Ltd (UK), in 1985. Most disk releases for ZX Spectrum (especially modern programs) are made for TR-DOS.
Latest firm version is 5.03 (1986).
Latest hack versions are 6.10E (in Mr Gluk Reset Service) and vTR-DOS (for ATM computer). Both versions have been released in (2006). More than 30 different hacks are known (first one dates back to 1990).
TR-DOS handles SS/DS, SD/DD floppy disks. All modern versions support ramdisk and some versions support hard disks (with .trd disk images = 640k).