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Operating Systems Who’s in charge in there? Types of Software • Application Software : Does things we want to do • System Software : Does things we need done Low 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 Varieties of OSes • Embeded Varieties of OSes • Batch – Submit list of jobs Varieties of OSes • Real Time / Dedicated What do the do? • API : Application Programming Interface • Set of functions software can do • OS provides API to other programs for – Reading files – Using a network – Drawing windows – Getting mouse position What do they do? • Manage hardware resources – Provide an abstraction for resources – Allocate scare resources 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 • Hard Disk – Abstraction: • Programs ask for files ("MyEssay.doc"), OS deals with details – Allocation: • What users/programs get to work with which files Other Resources • Monitor: – Abstraction • How exactly to draw to screen – Allocation: • What program's get to draw in what order Other Resources • Monitor: – Abstraction • How exactly to draw to screen – Allocation: • What program's get to draw in what order