OS1

Operating Systems Concepts : 

© DOC, Imperial College, 2006 Operating Systems Concepts An introduction to the software that makes computers usable, ensures that systems can be made secure and provides the environment for software to be a marketable commodity Lecturer: Julie A. McCann (~jamm) Acknowledgement: Paul Kelly

What is an Operating System : 

© DOC, Imperial College, 2006 What is an Operating System The OS is software - it’s a program It “virtualises” your computer Your computer needs to be virtualised… trust me!! Because that’s what makes it possible to buy and sell computer programs And that’s a major economic activity

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© DOC, Imperial College, 2006 There are lots… Microsoft: Windows ME, Windows 2000, Windows CE Linux BSD (FreeBSD, NetBSD) Sun: Solaris IBM: AIX Compaq: Tru64 Unix, OpenVMS Hewlett-Packard: HP-UX Apple: MacOS-8, MacOS-X Symbian: EPOC PalmOS QNX VXWorks LynxOS MVS, AS/400 Many many more, mostly more-or-less Unix/POSIX compatible eg MESHIX Literally thousands of variants and research prototypes eg MACH, Plan9, Pebble, Go! Sun (again): the Java Virtual Machine is it??? JOS?? Various kinds of Unix Designed for handhelds Embedded real-time

Slide 4: 

© DOC, Imperial College, 2006 Opening up the software market More than 90% of all software products sold are designed for just one virtual machine This has been quite good for their business... Source: http://www.microsoft.com/msft/history.htm See also http://www-cs-students.stanford.edu/~kkoster/microsoft/

Overview of Course : 

© DOC, Imperial College, 2006 Overview of Course What is an OS Terminology Kinds of OS How does the OS work What principles underpin OS Operation What does an OS look like ‘under the bonnet’

Slide 6: 

© DOC, Imperial College, 2006 Recommended textbooks Modern Operating Systems. A Tanenbaum Prentice-Hall Operating Systems (4th edition). William Stallings, Prentice-Hall 2001 Operating Systems: a modern perspective (2nd edition). Gary Nutt, Addison Wesley, 2000

THERE IS NO SPOON : 

© DOC, Imperial College, 2006 THERE IS NO SPOON Read books – course built on classic authoritative textbook Exam designed to test your understanding and ability to apply it to new ideas Some exam questions will introduce an idea not covered in the course But will ask you to explore an idea using what you’ve learned The book might have even covered that!

Three waves of computing : 

© DOC, Imperial College, 2006 Three waves of computing

The first wave! : 

© DOC, Imperial College, 2006 The first wave!

Chapter 1: - Introduction to OS : 

© DOC, Imperial College, 2006 Chapter 1: - Introduction to OS 1945 to 1955 No operating system human operators What did the first operating system look like?

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© DOC, Imperial College, 2006 1956 to 1965 Transistors and batch systems , Clear distinction between designers, builders, operators, programmers, and maintenance personnel, I/O channel, Read ahead / spooling, Interrupts/ exceptions, Minimal protection, Libraries / JCL

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© DOC, Imperial College, 2006 1965 to 1980 ICs and Multiprogramming, System 360 and S/370 family of computers, Spooling (simultaneous peripheral operation on-line), Time sharing, On-line storage for System programs, User programs and data, Program libraries, Virtual memory, Multiprocessor configurations e.g. MULTICS

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© DOC, Imperial College, 2006 When people looked like this, we saw the next generation THE SECOND WAVE OF COMPUTING

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© DOC, Imperial College, 2006 1980-now Personal computers and workstations MS-DOS and Unix Massively parallel systems Pipelining Array processing / SIMD General multiprocessing / MIMD Symmetric multiprocessing / SMD Any process and any thread can run on any available processor Computer networks (communication aspect) -- network operating systems Distributed computing -- distributed operating systems Cray 2

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© DOC, Imperial College, 2006 Connection Machine 5

What is an OS : 

© DOC, Imperial College, 2006 What is an OS A program, C or C++ Loads and runs other programs Application programs might wish to: Draw on the screen Interact via a keyboard, mouse etc Access the hard disk (files) Communicate with other application programs The OS should provide a consistent way to do this Works on whatever hardware you have.

Virtual or Abstract Machines : 

© DOC, Imperial College, 2006 Virtual or Abstract Machines Effectively wraps the hardware to provide a ‘virtual’ machine Consistent interface to devices and services What are the limits/difficulties?

Challenges to the VM approach : 

© DOC, Imperial College, 2006 Challenges to the VM approach Performance machine too slow to run application, I want to safely run lots of applications! Resources - Machine too little memory

Overcoming VM challenges : 

© DOC, Imperial College, 2006 Overcoming VM challenges Most OSs solve this problem Uses virtual memory – paging Application or program requiring 100MBytes of memory can run on just 10 Mbytes of physical memory using VM Slowly mind! What if I want to run more than one program? Can you read mail and eat? – you have one brain Processor switch from one process to another Regularly, use a timer to interrupt the processor Most do this fairly (according to application needs) Time-slicing – scheduling and priority

Overcoming VM challenges : 

© DOC, Imperial College, 2006 Overcoming VM challenges What if the other programs behave maliciously e.g. try to steal my secrets? OS has privileged control over ‘address translation's hardware Each application allowed access to only own data Data is authenticated (i.e. user is allowed to access it) What if two applications try to access the same device at the same time eg printer? Fix with mutual exclusion – deadlock!

Lets look at an Operating System at work : 

© DOC, Imperial College, 2006 Lets look at an Operating System at work Julie put some program running on system Do ctrl/alt/del Start app Start another instance of application

Why are OSs fun? : 

© DOC, Imperial College, 2006 Why are OSs fun? Make application software commodity Abstraction make programming easier Challenging - security, performance, reliability Do fancy things with programs

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© DOC, Imperial College, 2006 http://www.doc.ic.ac.uk/~jamm/teaching/xpsucks.html

So what’s the third wave? : 

© DOC, Imperial College, 2006 So what’s the third wave? Mark Weiser

Ubiquitous Computing? : 

© DOC, Imperial College, 2006 Ubiquitous Computing? Involves many disciplines. Inspired by the social scientists, philosophers, and anthropologists paradigm shift? currently we expect the user to find ways to use the computer however we currently do not emphasise how the computer can find its own way to serve the user focus on HCI focus on security, privacy  big brother?

Current Technology : 

© DOC, Imperial College, 2006 Current Technology Thanks to M. Sloman for slides

Wearable : 

© DOC, Imperial College, 2006 Wearable Thanks to M. Sloman for slides

Intelligent Environment : 

© DOC, Imperial College, 2006 Intelligent Environment Fridge and cupboards tracks consumption and reorder your groceries Your car computer reminds you to pick up your order on the way home when you are near the supermarket. Thanks to M. Sloman for slides

Intelligent Environment - 2 : 

© DOC, Imperial College, 2006 Intelligent Environment - 2 Lights, air conditioning, TV automatically switch on and off when you enter or leave rooms Sit on your favourite chair and TV switches on to the program you usually watch at this time of the day Use communicator/pda for phone, remote control, keys payments, passport, health records, authenticator. Route input from ‘virtual’ keyboard to nearest suitable display. Automatic detection of new items to control and physical layout in a room or office, using computer vision. Thanks to M. Sloman for slides

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© DOC, Imperial College, 2006