Roles of an OS Appl­ication software Programs that help us solve real-world problems Systems software Programs that manage a computer system and interact with hardware Oper­ating system System software that manages computer resources and provides an interface for system intera­ction Intera­ction The operating system in its relative position among computer system elements. Memory, Process, and CPU Management Mult­ipr­ogr­amm­ing The technique of keeping multiple programs in main memory at the same time, competing for the CPU Memory manage­ment The act of keeping track of how and where programs are loaded in main memory Proc­ess The dynamic repres­ent­ation of a program during execution Process manage­ment The act of keeping track of inform­ation for active processes CPU schedu­ling The act of determ­ining which process in memory is given access to the CPU so that it may execute Time­sha­ring A system in which CPU time is shared among multiple intera­ctive users at the same time Virtual machine The illusion created by a timesh­aring system that each user has a dedicated machine Main­frame A large, multi-user computer often associated with early timesh­aring systems Dumb terminal A monitor and keyboard that allow the user to access the mainframe computer in early timesh­aring systems

Memory Management Logical address A reference to a stored Logical address value relative to the program making the reference Physical address An actual address in the main memory device Address binding The mapping from a logical address to a physical address