KeyRus was a DOS-based TSR device driver for keyboard and display, written by the Donetsk student and hacker Dmitry Gurtyak in 1989. It was widely distributed in the USSR and outside of the country free of charge. The last version of KeyRus was released in 1994, not long before Gurtyak suddenly died.
KeyRus was distributed primary via electronic bulletin boards and Nikolai Bezroukov's Softpanorama electronic magazine. KeyRus loaded fonts into the EGA/ VGA and provided keyboard layout changes. Initially it could change only between the Russian and Latin layouts, but later became more configurable. Its distribution included the layout and font editors.
Later versions of KeyRus utilized the original font compression technique - they were stored in memory being packed and unpacked just before loading into the graphics adapter. That allowed KeyRus to occupy a minimum of the DOS limited memory space.