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Types of Software
• Application Software : Does things we want to do
• System Software : Does things we need doneLow level details
Operating System
• Operating System : Software that manages the operation of a computer
• Not all computational systems have an OS– Early computers– Embedded systems
Operating Systems
• PC Operating Systems– Windows– *nix• Linux• MacOS X
• Phone OSes– iOS– Android– Windows
Operating Systems
• What is Linux?https://www.youtube.com/watch?v=5ocq6_3-nEw
Resource Scarcity
• Resources scarce in– Time• Processor• IO / Disk
– Space• Memory• Disk
• OS responsible for allocating scarce resources
Resources - Processes
• OS manages what process(es) are running– Programs take turns on processor• Run until time limit or need to wait• OS handles all hardware events
http://computerscience.chemeketa.edu/cs160Reader/OperatingSystems/ProcessManagement.html
Resources - Memory
• Main Memory : – Where running programs & data are stored– Computer may have ~4 or 8 billion bytes– Programs can "use" up to 200 trillion bytes
(48 bit addresses)
Virtual Address Space
• Program uses virtual addresses– Nice, orderly
• OS maps to – Main memory – Hard drive (Virtual Memory)
Other Resources
• For Keyboard, Monitor, Network, Disks, Printer, OS provides:– Abstraction:• Hides ugly details (how bits are stored on disk),
provides abstract interface ("MyEssay.doc")
– Allocation:• Who gets to use what when
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