RESOURCE MANAGEMENT System Resources

What resources are managed in a computer system?

Primary memory (RAM) Secondary storage (hard drive/disk storage) Central Processing Unit (CPU) Graphical Processing Unit (GPU) Network bandwidth/connectivity Screen resolution Sound processor

How do resources differ on different systems?

Cost vs. Performance No need to spend money on extra hardware if it is not needed Examples: Screens for mainframes and servers Hard drives for cell phones GPU for an e-book

What problems could occur from limited resources?

Limited memory  use of secondary storage as memory Secondary storage is slower  time lost Limited CPU  programs run slower or system stalls Limited GPU  choppy, undetailed graphics Limited network connectivity  constant buffering and delays

Operating System Roles Hardware management Communicating with all hardware Resource monitoring processor time, memory usage, etc. Coordinating concurrent processing multiple programs (processes) running at the same time Memory management each program has their own space in memory **Operating system hides the complex activities above from the user!**

Multi-processing/Multi-tasking Memory allocation Load program from hard drive into a section of memory (RAM) Time-slicing (sharing CPU time across programs) Giving a particular program a “slice” of time to run Priority A program can be given “priority” if it’s more important e.g. window in focus, streaming services

Virtual Memory What happens when you run too many programs and all of the memory is used up? What other storage is there? How do we keep some memory free at all times?

Virtual Memory Terms Paging / Swapping Moving program data between memory and disk Where do you see this stuff? pagefile.sys in windows /swap space in linux Whenever you use up all your RAM and your hard drive goes crazy. Optimizations Whole programs do not have to fit in memory contiguously (all in one section) Prevents memory segmentation Pre-emptive paging

Discussion: Why are there different operating systems? Mac OS X vs. iOS Ubuntu Linux vs. Android Advantages? (Hint: think in terms of design)

How does the OS represent hardware devices? Hardware complexities are hidden from the user by the OS Hardware is simplified and represented virtually by the OS Examples Mouse pointer File tree and drive letters Others?

OS  Hardware Communication How does the OS know “when” to communicate with hardware? Interrupt vs. Polling What do you think they mean?