(a) voluntary user action, e.g. copying a file from disk to memory in order to edit it;
(b) system software, e.g. transfer of a page between swapping device and memory when a page fault occurs;
(c) system hardware, e.g. movement of a set of words from memory to cache when a word within the set is accessed.
At a given level of the hierarchy the operating system will control what fraction of that level is to be allocated to each process. This can clearly only occur where control is by system software, and refers most particularly to the allocation of memory to a process, or to the allocation of space on the swapping device. Movement between disk and magnetic tape is often separately treated as archiving. See also storage protection.
"memory management." A Dictionary of Computing. . Encyclopedia.com. (August 14, 2018). http://www.encyclopedia.com/computing/dictionaries-thesauruses-pictures-and-press-releases/memory-management
"memory management." A Dictionary of Computing. . Retrieved August 14, 2018 from Encyclopedia.com: http://www.encyclopedia.com/computing/dictionaries-thesauruses-pictures-and-press-releases/memory-management