xtrs is a Radio Shack TRS-80 Model I/III/4/4P emulator for Unix and the X Window System. It includes lower case, the real time clock, hi-res graphics, serial port, parallel printer, mouse, cassette, sound and music output, 5" and 8" floppy disk drives in single and double density, and even hard disk drives. The emulated floppy and hard disk file formats are compatible with the popular MSDOS-based emulators by Jeff Vavasour, Matthew Reed, and David Keil, and (if you choose a capable enough file format), all features of the original TRS-80 floppy disk controller are emulated. Under Linux, physical floppy disk drives are also supported. Physical cassettes can be read and written too. The user interface is a bit spartan, but it gets the job done.