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

Varieties of OSes Embeded

Varieties of OSes Batch – Submit list of jobs

Varieties of OSes Real Time / Dedicated

Operating Systems PC Operating Systems – Windows – *nix Linux MacOS X Phone OSes – iOS – Android – Windows

Operating Systems What is Linux?

What do they do? Manage hardware resources – Provide an abstraction – 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

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

Abstraction Abstractions provided via API (Application Programming Interface) Set of functions software can do OS API Features – Functions (blocks) to Read files Use a network Draw windows Get mouse position