What is an Operating System p opend ing Systems g It is an extended machine top-down view H Hides the messy details which must be performed H Presents user with a virtual machine. easier to use g It is a resource manager bottom-up view m Each program gets time with the resource e.g. Multiple programs run on one CPU H Each program gets space on the resource e.g. main memory is divided up among several running programs Gao Haichang, Software School, Xidian UniversityOperating Systems Gao Haichang , Software School, Xidian University 8 What is an Operating System? It is an extended machine top-down view Hides the messy details which must be performed. Presents user with a virtual machine, easier to use. It is a resource manager bottom-up view Each program gets time with the resource e.g. Multiple programs run on one CPU. Each program gets space on the resource e.g. Main memory is divided up among several running programs