VMOS meaning in General ?

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.

RCA was in the computer business until 1971 when it sold its computer business to Sperry Corporation. Sperry renamed TSOS to VS/9 and continued to market it into the early 1980s. In the mid seventies, an enhanced version of TSOS called BS2000 was offered by the German company Siemens.

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.

As the name suggests, TSOS provided time sharing features. Beyond that it provided a common user interface for both time sharing and batch, which was a big advantage over IBM's OS/360 or its successors MVS, OS/390 and z/OS.