Black and Wiliam (1998a) also noted that for assessment to function formatively, the feedback information had to be used, and thus the differential treatments that are incorporated in response to the feedback are at the heart of effective learning.
A hypervisor is a unique type of software that allows a computer to run more than one operating system (OS). Through a process known as virtualization, the software tricks each OS into thinking it has exclusive access to a particular set of hardware.
The virtualization software, or the hypervisor, offers caching technology that can be used to cache changes to the virtual hardware or the virtual hard disk for writing at a later time. This technology enables a user to discard the changes done to the operating system, allowing it to boot from a known state.