What allows multiple virtual operating systems to run on a single physical host computer?

The correct answer is the hypervisor, which is a crucial component in virtualization technology. A hypervisor enables multiple virtual operating systems, commonly referred to as virtual machines (VMs), to operate on a single physical host. It achieves this by abstracting the hardware resources of the physical machine and allocating them to each of the virtual machines as needed.

The hypervisor sits between the hardware and the operating systems. It can be classified into two types: Type 1 hypervisors (bare metal) which run directly on the hardware, and Type 2 hypervisors (hosted) which run on a conventional operating system. This architecture allows for efficient utilization of hardware, better resource management, and isolation between different operating systems.

In contrast, while a virtual machine manager is somewhat related, it typically refers to software that manages virtual machines, rather than the underlying technology that enables them to run. A system emulator imitates the architecture of another system but may not provide the full capabilities for running multiple operating systems on a single physical host. A cloud controller pertains to managing cloud services and resources and is not specifically designed for virtualization in the same way as a hypervisor.