Introduction to Advanced Operating System

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Advanced Operating System

M. Sc. Computer Science and Information Technology,Tribhuvan University

By

Bishnu Gautam


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Objectives of the course

Introduce the underlying principles of an

operating system, virtual memory and resource

management concepts. Exposer of current state of art research in

operating system

Exposure of distributed operating system, real-

time operating system and multimedia systems.

General OverviewAdvanced Operating System


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Why Learn about Operating Systems?

Tangible reasons

Build or modify a real operating system

Administer and use system well

Tune application performance

Intangibles reasons

Intrinsic curiosity Understand how much of your computer system works

Gain/apply knowledge in other areas of Computer Science Computer architecture and devices

Synchronization in programming languages Data structures and algorithms

Performance analysis

Challenge of designing large, complex systems

IntroductionAdvanced Operating System


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Course Overview1. Introduction -1week 2. Process, Memory and Storage Management -7weeks

First Internal Examination

3. System Protection and Security -2weeks4. Distributed Operating Systems, Distributed File

Systems -3weeks

5. Real-time Systems, Multimedia Systems -2weeks

Second Internal Examination -15weeks

Final Examination



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Books and References

Text Book:

1. Silberschatz, Galvin and Gagne, Operating System Concepts, 8th

Edition, John-Wiley.

References :

1. Research and Technical Papers

2. Tanenbaum, A. S.,Modern Operating Systems, 3rd Edition, PHI

3. Stallings, W., Operating Systems, Fourth Edition, Pearson.

4. Tanenbaum, A. S. and Woodhull, A. S., Operating Systems Design andImplementation, Second Edition, PHI.

Lab References:

Linux Manual, Linux Programming Manual and C book.



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Evaluation system

Total mark (75) = Assessment (15) + Semester (60)

Assessment marks is distributed as follows:

Assignments (5) + Internal Examination1 (5) + Internal

Examination2 (5) = 15

Assignments are basically Lab works and Case Studies,

each assignment will have a due date for submission and

demonstration, it is mandatory to submit their report with

in the due date. Home works will be assigned in class only for your

practice, not for submission, but sometime it may assigned

as an assignment.



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Introduction Computer System Structure

What is Operating Systems

Operating-System Structure

Operating-System Operations

Process Management

Memory Management

Storage Management

Protection and Security Distributed Systems

Special-Purpose SystemsReading: Textbook Chapter 1 & 2



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Computer System Structure

Computer system can be divided into four components:

Hardware provides basic computing resources

CPU, memory, I/O devices

Operating system Controls and coordinates use of hardware among various applications

and users

Application programs define the ways in which the system

resources are used to solve the computing problems of the users

Word processors, compilers, web browsers, database systems, video

games

Users

People, machines, other computers



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Computer System Structure



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What is an operating system?

An operating system (OS) is a collection of system programs that

together control the operation of a computer 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.

Provides an environment within which other programs can do

useful work.



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Two Functions of OS

OS as an Extended Machine

OS as a Resource Manager



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OS as an Extended MachineOS creates higher-level abstraction for programmer

Example: (Floppy disk I/O operation)

-disks contains a collection of named files

-each file must be open for READ/WRITE

-after READ/WRITE complete close that file

-no any detail to dealOS shields the programmer from the disk hardware and presents a simple fileoriented interface.

OS function is to present the user with the equivalent of an extendedmachine or virtual machine that is easier to program than the

underlying hardware.Challenges:

What are the right abstractions? How to achieve this?



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OS as a Resource Manager

-What happens if three programs try to print their output on the sameprinter at the same time?

-What happens if two network users try to update a shared document atsame time?

OS primary function is to manage all pieces of a complex system.Advantages:

Virtualizes resource so multiple users/applications can share

Protect applications from one another

Provide efficient and fair access to resourcesChallenges:

What mechanisms? What policies?



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OS evolution

Computer Generation, Component and OS Types

1st (1945-55) Vacuum Tubes User Driven

2nd (1955-65) Transistor Batch

3rd (1965-80) IC Multiprogramming

4th

(1980-present) PC Client Server/Distributed



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Operating System Structure Multiprogramming:Multiple jobs in memory at the same time. Each memory

space protected from each other. OS picks one, execute it for a while, stops (e.g.when programs reads for input or randomly), picks other to run.

Needed for efficiency

Single user cannot keep CPU and I/O devices busy at all times

One job selected and run viajob scheduling When it has to wait (for I/O for example), OS switches to another job

Timesharing (multitasking) is logical extension in which CPU switches jobsso frequently that users can interact with each job while it is running, creating

interactive computing

Response time should be < 1 second

Each user has at least one program executing in memory process

If several jobs ready to run at the same time CPU scheduling

If processes dont fit in memory, swapping moves them in and out to run

Virtual memory allows execution of processes not completely in memory



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Operating-System Operations

OS must insure that an incorrect program can not cause otherprograms to execute incorrectly, and must terminate the sucherroneous program.

Provide hardware support to differentiate between at least two modesof operations.

1. User mode . execution done on behalf of a user.

User programs runs in user mode, which permits only the subset ofinstructions to be executed and subset of features to be accessed.

2. Kernel mode (or supervisor mode) . execution done on behalfof operating system.

OS runs in kernel mode, giving it access to the complete hardware.

Mode bit is added to the hardware of the computer to indicate thecurrent mode: kernel(0) and user(1).



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Dual-Mode OperationWhen an trap or interrupt occurs hardware switches from user modeto the kernel mode. Thus, whenever the OS gains control of computer,

it is in kernel mode. The system always switches to user mode before

passing control to the user program.

Privileged instructions can be issued only in kernel mode.

Advantages:

protect OS from errant users and errant user from one another.



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Process Management

A process is a program in execution. A process needs certainresources, including CPU time, memory, files, and I/O

devices, to accomplish its task.

The operating system is responsible for the following activitiesin connection with process management.

Process creation and deletion.

Process suspension and resumption.

Provision of mechanisms for:

process synchronization

process communication

deadlock handling



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Memory Management

Memory is a large array of words or bytes, each with its own

address. It is a repository of quickly accessible data shared

by the CPU and I/O devices.

The operating system is responsible for the followingactivities in connections with memory management:

Keep track of which parts of memory are currently being used and

by whom.

Decide which processes to load when memory space becomesavailable.

Allocate and deallocate memory space as needed.



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File Management

A file is a collection of related information defined by its creator.

Commonly, files represent programs (both source and object

forms) and data.

The operating system is responsible for the followingactivities in connections with file management:

File creation and deletion.

Directory creation and deletion.

Support of primitives for manipulating files and directories.

Mapping files onto secondary storage.

File backup on stable (nonvolatile) storage media.



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I/O Management

All computers have physical devices for acquiring input

and producing output.

The I/O system consists of: A memory management component that includes buffering,caching, and spooling.

A general device-driver interface.

Drivers for specific hardware devices.

Disk management.



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Protection and SecuritySituation: a computer system has multiple users and allows theconcurrent execution of multiple processes, then access to data mustbe regulated.

Required mechanisms that ensures files, memory segments, CPU, andother resources can be operated on by only those processes that have

gained proper authorization from the operating system Protection mechanism for controlling access of processes or usersto resources defined by the OS

Security defense of the system against internal and external attacks Huge range, including denial-of-service, worms, viruses, identity theft, theft of service

Systems generally first distinguish among users, to determine who can

do what User identities (user IDs, security IDs) include name and associated number User ID then associated with all files, processes of that user to determine access control Group identifier (group ID) allows set of users to be defined and controls managed Privilege escalation allows user to change to effective ID with more rights



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Distributed Systems

A distributed system is a collection of physically separate, possibly

heterogeneous, computer systems that are networked toprovide the users

with access to the various resources that the system maintains.

Access to a shared resource increases computation speed,functionality, data availability, and reliability

Network Operating System provides features between systems across

network

Communication scheme allows systems to exchange messages Illusion of a single system



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Special-Purpose Systems

The computer systems whose functions are more limited and whose

objective is to deal with limited computation domains

Real-time embedded systems most prevalent form of

computers Vary considerable, special purpose, limited purpose OS, real-time OS

Multimedia systems

Streams of data must be delivered according to time restrictions

Handheld systems PDAs, smart phones, limited CPU, memory, power

Reduced feature set OS, limited I/O



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System callsSystem calls provide the interface between a process and the operatingsystem. Typically written in a high-level language (C or C++)

Mostly accessed by programs via a high-level Application Program Interface(API) rather than direct system call use

Three most common APIs are Win32 API for Windows, POSIX API for POSIX-based systems (including virtually all versions of UNIX, Linux, and Mac OS X),and Java API for the Java virtual machine (JVM)

Example: ReadFile() function in the Win32 APIa function for reading from a file


HANDLE filethe file to be readLPVOID buffera buffer where the datawill be read into and written fromDWORD bytesToReadthe number ofbytes to be read into the bufferLPDWORD bytesReadthe number ofbytes read during the last readLPOVERLAPPED ovlindicates ifoverlapped I/O is being used


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Home Works

HW #1:

1. Textbook: (Ch. 1) 1.1, 1.3, 1.4, 1.6, 1.7, 1.8, 1.13,1.19 & 1.21

2. Textbook: (Ch. 2) 2.1, 2.2, 2.14, 2.8 & 2.19,

2. What does the CPU do when there are no programs to run?3. What must user programs be prohibited from writing to the

memory locations containing the interrupt vector?

4. Classify the following applications as batch-oriented or interactive.

a) Word processing

b) Generating monthly bank statementsc) Computing pi to a million decimal places

5. What is a purpose of system calls?


Documents

Introduction to Advanced Operating System