<Ul> <Li> the Atlas Supervisor for the Atlas </Li> <Li> THE multiprogramming system for the Electrologica X8 (software based virtual memory without hardware support) </Li> <Li> MCP for the Burroughs B5000 </Li> <Li> MTS, TSS / 360 and CP / CMS for the IBM System / 360 Model 67 </Li> <Li> Multics for the GE 645 </Li> <Li> the Time Sharing Operating System for the RCA Spectra 70 / 46 </Li> </Ul> <Li> the Atlas Supervisor for the Atlas </Li> <Li> THE multiprogramming system for the Electrologica X8 (software based virtual memory without hardware support) </Li> <Li> MCP for the Burroughs B5000 </Li>

When is virtual memory used and for what purpose