Time Sharing Operating System, or TSOS, is a discontinued operating system for RCA mainframe computers of the Spectra 70 series. TSOS was originally designed in 1968 for the Spectra 70/46, a modified version of the 70/45. TSOS quickly evolved into the Virtual Memory Operating System (VMOS) by 1970. VMOS continued to be supported on the later RCA 3 and RCA 7 computer systems. While Sperry – now Unisys – discontinued VS/9, the BS2000 variant, now called BS2000/OSD, is still offered by Fujitsu and used by their mainframe customers primarily in Germany and other European countries.