Operating Systems

Sameer Mahajan

Overview• Process management• Interrupts• Memory management• File system• Device drivers• Networking (TCP/IP, UDP)• Security (Process/Memory protection)• I/O

History

• 1940’s First Generation – no OS• 1950’s Second Generation – single stream

batch• 1960’s Third Generation – multiprogramming

batch• Fourth Generation – microprocessor

Types

• Realtime• Single user vs. Multi user• Multi-tasking vs. Single-tasking• Distributed• Embedded

Examples

• UNIX – 1%• Mac OS (Lion, Snow Leaopard, Leopard, X

Server) – 6%• Google chrome• AmigaOS• MS Windows (8, 7, Vista, XP, w2k8, w2k3) – 90%• Mobile Devices – iOS, Android, Windows Phone

7, Symbian

Components• Kernel• Program Execution (Process)• Interrupts• Modes• Memory Management – virtual vs physical• Multitasking – scheduling• File systems – VFS• Device drivers• Networking• Security• User interface (GUI, CLI)

Kernel

File system• Boot block• Super block• Inode Table• Data blocks• User File Descriptor (FD) table • File Table• ls, df, mount (UNIX); Explorer (windows)

File system

Process• Unit of execution• User and kernel mode• Context: stack, registers, PC• thread• Virtual memory – physical memory• ps (UNIX); Process Explorer (Windows)

Process Management

Scheduling Algorithms• FCFS Scheduling• Round Robin Scheduling• Priority Scheduling• Multilevel Queue Scheduling• Multilevel Feedback Queue Scheduling• SJF Scheduling• SRT Scheduling

IO subsystem• Open, close, read, write• Character device – ioctl• Block device – strategy• Major, minor device number• Stream – full duplex connection• Buffer cache• Memory mapped IO

Inter process communication• Messages (msg*)• Shared memory (shm*)• Semaphores (sem*)• Sockets• Pipes

Windows 8 features

• Metro User Interface• Internet Explorer 10• Apps and App Store• New Hardware and Form Factors – multitude

of devices (touch is primary interface)• Security Changes• Storage Changes (de-dupe, live disk repair)• Virtualization Changes

Hardware Virtualization