CPU modes (also called processor modes, CPU states, CPU privilege levels and other names) are operating modes for the central processing unit of some computer architectures that place restrictions on the type and scope of operations that can be performed by certain processes being run by the CPU. This design allows the operating system to run with more privileges than application software. Multiple modes can be implemented—allowing a hypervisor to run multiple operating system supervisors beneath it, which is the basic design of many virtual machine systems available today.