Who’s in charge in there? 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 Phone OSes Windows *nix iOS Linux MacOS X Phone OSes iOS Android

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 OS maps to Nice, orderly OS maps to Main memory Hard drive (Virtual Memory)

Other Resources Hard Disk Abstraction: Allocation: Programs ask for files ("MyEssay.doc"), OS deals with details Allocation: What users/programs get to work with which files

Other Resources Monitor: Abstraction Allocation: How exactly to draw to screen Allocation: What program's get to draw in what order

Other Resources Monitor: Abstraction Allocation: How exactly to draw to screen Allocation: What program's get to draw in what order