Fur trade marten furs could generate in international markets spurred a "fur fever" in which many Russians moved to Siberia as independent trappers. From 1585 to 1680, tens of thousands of sable and other valuable pelts were obtained in Siberia each year. The primary way for the Muscovite state to obtain furs was by exacting a fur tribute from the Siberian natives, called a "yasak". "Yasak" was usually a fixed number of sable pelts which every male tribe member who was at least fifteen years old had to supply to Russian officials. Officials enforced "yasak" through coercion and by taking hostages, usually
PC Paintbrush to work in color. When Paintbrush was released the following year, "PCPaint" had already added 16-color support for the PC's 64-color Enhanced Graphics Adapter (EGA), and Paintbrush followed with the PC's advantage of EGA support as well. (The EGA supported 64 colors, of which any 16 could be on the screen at a time in normal use.) Also following the lead of Mouse Systems and "PCPaint", one of the first pieces of software on the PC to use a computer mouse pointing device, the earliest versions of Paintbrush were distributed by Microsoft, with a mouse included. Both Microsoft and their