1. Lectutre-01 Introduction and Overview Somia Razzaq NFC IET
CS Operating Systems
Lectutre-01
Introduction and Overview
Somia Razzaq
NFC IET

2. Interaction is important!
Goals for today
What is an Operating System?
And – what is it not?
Why study Operating Systems?
How the course will proceed?
Course content
Grading
Regulations
Interaction is important!
Ask Questions!
Note: Some slides and/or pictures in the following lectures are adapted from author slides by Silberschatz, Galvin, and Gagne and some from different instructor lectures taken from internet.

3. Computer System
Hardware
Operating system
Applications programs
Users

4. Purpose of a Computer System
Computer systems consist of software and hardware that are combined to provide a tool to solve specific problems in an efficient manner
Execute programs

5. Layered View of a Computer System

6. Computer System Hardware
Keyboard
Mouse
Printer
RAM/ROM HD
Mem
Bus
System Bus
Monitor CD
Processor
Floating Point
Unit
Integer
Cache
Control

7. What is an Operating System?
A program that acts as an intermediary between a user of a computer and the computer hardware
A program that allocates and de-allocates computer system resources in an efficient, fair, and secure manner—a resource manager

8. Goals of Operating System
Operating system goals:
Execute user programs and make solving user problems easier
Make the computer system convenient to use
Use the computer hardware in an efficient manner

9. Technology Trends: Moore’s Law
Gordon Moore (co-founder of Intel) predicted in 1965 that the transistor density of semiconductor chips would double roughly every 18 months.
2X transistors/Chip Every 1.5 years
Called “Moore’s Law”
Moore’s Law
Microprocessors have become smaller, denser, and more powerful.
How many transistors you think a processor would have?
10s? 1000s? Millions?
Alright.. About ten million transistors.. In January 1995, the Digital Alpha microprocessor had 9.3 million transistors. Six years later, a state of the art microprocessor contained more than 40 million transistors. Isn’t it complex!
Until 2002 the curve kept going higher exponentially like this.
At Intel and other manufacturers started to panic as they had made transistor so small that they pondered what we gonna do now to keep the curve moving

10. ManyCore Chips: The future is here
Intel 80-core multicore chip (Feb 2007)
80 simple cores
Two floating point engines /core
Mesh-like "network-on-a-chip“
100 million transistors
65nm feature size
Frequency Voltage Power Bandwidth Performance
3.16 GHz V 62W Terabits/s Teraflops
5.1 GHz 1.2 V 175W Terabits/s Teraflops
5.7 GHz V 265W Terabits/s Teraflops
“ManyCore” refers to many processors/chip
64? 128? Hard to say exact boundary
How to program these?
Use 2 CPUs for video/audio
Use 1 for word processor, 1 for browser
76 for virus checking???
Parallelism must be exploited at all levels

11. Computer System Organization
Computer-system operation
One or more CPUs, device controllers connect through common bus providing access to shared memory
Concurrent execution of CPUs and devices competing for memory cycles

12. Functionality comes with great complexity!
Pentium IV Chipset
Proc
Caches
Busses
Memory
I/O Devices:
Controllers
adapters
Disks
Displays
Keyboards
Networks
Pentium 4 is already getting old as Intel is coming up with some new chipsets
This complexity gives us some very interesting stuff
It gives us networking, gamming, graphics, efficiency.. Loads more

13. Sample of Computer Architecture Topics
Input/Output and Storage
Disks, WORM, Tape
RAID
Emerging Technologies
Interleaving
Bus protocols
DRAM
Coherence,
Bandwidth,
Latency
Memory
Hierarchy
L2 Cache
Network
Communication
Other Processors
Addressing,
Protection,
Exception Handling
L1 Cache
VLSI
Instruction Set Architecture
Pipelining, Hazard Resolution,
Superscalar, Reordering,
Prediction, Speculation,
Vector, Dynamic Compilation
Pipelining and Instruction
Level Parallelism

14. Example: Some Mars Rover (“Pathfinder”) Requirements
Pathfinder hardware limitations/complexity:
20Mhz processor, 128MB of DRAM, VxWorks OS
cameras, scientific instruments, batteries, solar panels, and locomotion equipment
Many independent processes work together
Can’t hit reset button very easily!
Must reboot itself if necessary
Must always be able to receive commands from Earth
Individual Programs must not interfere
Better not crash antenna positioning software!
Further, all software may crash occasionally
Automatic restart with diagnostics sent to Earth
Periodic checkpoint of results saved?
Certain functions time critical:
Need to stop before hitting something
Must track orbit of Earth for communication
Why processor is so limited?
What if you had to move the rover paying attention to every little component? Taking care of the motors, measuring soil/distances, coordinating with the controller at Earth…!
Distance 186 light secs to 21 light minutes one-way
Nearly two earth years
If you have to move the rover with consideration to every little complexity.. Including taking care of all the motors, measuring the soil/distance and talking to the co-pilot.. How difficult would that be?
Why processor is so limited? Power consumption!
Blue screen of death? Help! Game over! What happens if rover gets the blue screen of death? What we want is if it crashes, we want to figure out a way if the main system is down we should be able to reboot it atleast.. Rover should always be able to get signals from earth.. Restart, send diagnostics to earth – bug fixing!
Certain functions are higher priority than others.. You better stop before you hit someone.. Prioritization is important
It’s a fun example to think what would be your core requirements not only in terms of hardware but software too.
We can do that using an OS

15. How do we tame complexity?
Every piece of computer hardware is different
Different CPU
Pentium, PowerPC, ColdFire, ARM, MIPS
Different amounts of memory, disk, …
Different types of devices
Mice, Keyboards, Sensors, Cameras, Fingerprint readers
Different networking environment
Cable, DSL, Wireless, Firewalls,…
Questions:
Does the programmer need to write a single program that performs many independent activities?
Does every program have to be altered for every piece of hardware?
Does a faulty program crash everything?
Does every program have access to all hardware?
Dell commercial.. Making your machine separately for you
Your comp is different from other ones.. Different CPUs, keyboards, memories, finger print readers

16. OS Tool: Virtual Machine Abstraction
Application
Operating System
Hardware
Physical Machine Interface
Virtual Machine Interface
Software Engineering Problem:
Turn hardware/software quirks  what programmers want/need
Optimize for convenience, utilization, security, reliability, etc…
For Any OS area (e.g. file systems, virtual memory, networking, scheduling):
What’s the hardware interface? (physical reality)
What’s the application interface? (nicer abstraction)
Hardware is complicated.. I would put an OS .. It will provide an interface which is simple and similar for everybody
e.g., a USB drive is far more different than the hard drive in your computer.. No motor.. Disk spinning but you use both in quite a similar manner
Making sense?
We are trying to make things easier for the programmers.. You may want to be programmers of advanced complex apps in near future
Older programmers had to be pretty much specialized in a lot many details. Now all the programmers need not be of the same engineering mind set.. Ppl with different creativity capabilities can do different things in their own specialized areas without worrying about the underlying architectural details of hardware, computer organization, memory and IO details.

17. What does an Operating System do?
Silerschatz and Galvin: “An OS is Similar to a government”
Begs the question: does a government do anything useful by itself?
Coordinator and Traffic Cop:
Manages all resources
Settles conflicting requests for resources
Prevents errors and improper use of the computer
Facilitator:
Provides facilities that everyone needs
Standard Libraries, Windowing systems
Make application programming easier, faster, less error-prone
Some features reflect both tasks:
E.g. File system is needed by everyone (Facilitator)
But File system must be Protected (Traffic Cop)

18. So what is this course all about?
What we’ll be covering? and
How we shall proceed?

19. Tentative Course Outline
Week #
Module
Topics 1
Introduction
Introduction to the course
Operating System Concepts
System Structures 2
Process Concepts
Process Scheduling
Process Operations
Inter process Communication
Communication in Client Server Systems 3
Multithreaded Programming
Overview
Multithreading Models
Thread Libraries 4
Basic Concepts
Scheduling Criteria
Scheduling Algorithms
Thread Scheduling

20. Course Outline Week # Module Topics 5 Synchronization Overview
Critical Section Problem
Semaphores
Monitors 6
Deadlocks
System Model
Deadlock Characterization
Methods for handling Deadlocks
Deadlock Prevention 7
Memory Management
Background
Swapping
Contiguous Memory Allocation
Paging

21. Course Outline Week # Module Topics 8 Mid Term Exam 9 Virtual Memory
Demand Paging
Copy-on-Write
Page Replacement
Allocation of Frames
Thrashing 10
File System
File Concept
Access Methods
Directory and Disk Structure
File System Mounting
11-12
Secondary Storage Structure
Overview of Mass Storage Structure
Disk Structure
Disk Scheduling
RAID Structure Overview

22. Course Outline Week # Module Topics 12-13 I/O Systems Overview
Hardware
Application I/O Interface
Kernel I/O Subsystem
Transforming Requests to Hardware Operations
Streams
13-14
Protection
Goals
Principles
Domain
Access Matrix
Access Control 15
Security
The issue
Threats
Cryptography
Authentication
Defense 16
Distributed Operating Systems
An overview of Distributed Operating System Concepts

23. Tentative Lab Exercise Plan
Module
Week
Lab 1
Process Creation in Java
RMI Example (Optional)
Week 2
Lab 2
Threads in Java
Week 3
Lab 3
Threads in Java (priority scheduling example)
Week4
Lab 4
Synchronization in Java
Week 5
Lab 5
Deadlock Example with handling of deadlocks in Java
Week 6
Lab 6
Memory Management Exercise
Week 8
We’ll also be playing with Linux Operating System later on in the second half of the course

24. Textbook
Operating System Concepts – 7/8th Edition Silberschatz, Galvin, and Gagne (Textbook)
Modern Operating Systems,3rd Edition, Tanenbaum A.S., (Reference)

25. Grading Scheme Quizzes 5% (unannounced/announced) Assignment 5%
Attendance/
Class participation 5%
Midterm Exam: 30%
Final Exam: 50%
Term Assignment %

26. Academic Dishonesty Policy
Copying all or part of another person's work, or using reference material not specifically allowed, are forms of cheating and will not be tolerated. A student involved in an incident of cheating will be subject to strict disciplinary action as per the institute’s policies.
The instructor may take actions such as:
require repetition of the subject work,
assign a'zero' grade to the subject work,

27. Remember
Interaction is important!