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- 1. 1.1 Silberschatz, Galvin and Gagne ©2013
Operating System Concepts – 9th Edition
Course Introduction
Course Name: Operating Systems
Credit Hours: 3 (2-3)
Contact Hours: 2-3
Pre-requisites: Data Structures
Reference Materials: (or use any other standard and latest books)
1. Operating Systems Concepts, 9th edition by Abraham Silberschatz
2. Modern Operating Systems, 4th edition by Andrew S. Tanenbaum
3. Operating Systems, Internals and Design Principles, 9th edition by William
Stallings
- 4. 1.4 Silberschatz, Galvin and Gagne ©2013
Operating System Concepts – 9th Edition
Chapter 1: Introduction
What Operating Systems Do
Computer-System Organization
Computer-System Architecture
Operating-System Structure
Operating-System Operations
Process Management
Memory Management
Storage Management
Protection and Security
Kernel Data Structures
Computing Environments
Open-Source Operating Systems
- 5. 1.5 Silberschatz, Galvin and Gagne ©2013
Operating System Concepts – 9th Edition
Objectives
To describe the basic organization of computer systems
To provide a grand tour of the major components of operating systems
To give an overview of the many types of computing environments
To explore several open-source operating systems
- 6. 1.6 Silberschatz, Galvin and Gagne ©2013
Operating System Concepts – 9th Edition
What is an Operating System?
An operating system manages a computer’s hardware.
It also provides a basis for application programs and acts
as an intermediary between the computer user and the
computer hardware
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
- 7. 1.7 Silberschatz, Galvin and Gagne ©2013
Operating System Concepts – 9th Edition
What is an Operating System?
An operating system is large and complex, it must be
created piece by piece.
Each of these pieces should be a well-delineated portion
of the system, with carefully defined inputs, outputs, and
functions.
- 8. 1.8 Silberschatz, Galvin and Gagne ©2013
Operating System Concepts – 9th Edition
Computer System Structure
Computer system can be divided into four components:
1. Hardware – provides basic computing resources
CPU
Memory
I/O devices
2. Operating system
Controls and coordinates use of hardware among
various applications and users
- 9. 1.9 Silberschatz, Galvin and Gagne ©2013
Operating System Concepts – 9th Edition
Computer System Structure
3. 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
4. Users
People, machines, other computers
- 11. 1.11 Silberschatz, Galvin and Gagne ©2013
Operating System Concepts – 9th Edition
What Operating Systems Do: User View
On Personal Computer (PC) Users want
convenience, ease of use
Don’t care about resource utilization
But shared computer such as mainframe or
minicomputer must keep all users happy. The
operating system in such cases is designed to
maximize resource utilization
- 12. 1.12 Silberschatz, Galvin and Gagne ©2013
Operating System Concepts – 9th Edition
What Operating Systems Do: User View
Users of dedicate systems such as workstations have
dedicated resources but frequently use shared resources
from servers. Therefore, their operating system is
designed to compromise between individual usability and
resource utilization.
Handheld computers are resource poor, optimized for
usability and battery life
Some computers have little or no user interface, such as
embedded computers in devices and automobiles
- 13. 1.13 Silberschatz, Galvin and Gagne ©2013
Operating System Concepts – 9th Edition
Operating System Definition: System View
OS is a resource allocator
Manages all resources
Decides between conflicting requests for efficient and
fair resource use
OS is a control program
Controls execution of programs to prevent errors and
improper use of the computer
- 14. 1.14 Silberschatz, Galvin and Gagne ©2013
Operating System Concepts – 9th Edition
Operating System Definition (Cont.)
No universally accepted definition
“Everything a vendor ships when you order an operating
system” is good approximation
But varies wildly
“The one program running at all times on the computer”
is the kernel. Everything else is either a system program
(ships with the operating system) or an application
program.
- 15. 1.15 Silberschatz, Galvin and Gagne ©2013
Operating System Concepts – 9th Edition
Computer Startup
bootstrap program is loaded at power-up or reboot
Typically stored in ROM or EPROM, generally known
as firmware
Initializes all aspects of system
Loads operating system kernel and starts execution
- 16. 1.16 Silberschatz, Galvin and Gagne ©2013
Operating System Concepts – 9th Edition
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
- 17. 1.17 Silberschatz, Galvin and Gagne ©2013
Operating System Concepts – 9th Edition
Computer-System Operation
I/O devices and the CPU can execute concurrently
Each device controller is in charge of a particular
device type
Each device controller has a local buffer
- 18. 1.18 Silberschatz, Galvin and Gagne ©2013
Operating System Concepts – 9th Edition
Computer-System Operation
CPU moves data from/to main memory to/from local
buffers
I/O is from the device to local buffer of controller
Device controller informs CPU that it has finished its
operation by causing an interrupt
- 19. 1.19 Silberschatz, Galvin and Gagne ©2013
Operating System Concepts – 9th Edition
Common Functions of Interrupts
Interrupt transfers control to the interrupt service routine
generally, through the interrupt vector, which contains
the addresses of all the service routines
Interrupt architecture must save the address of the
interrupted instruction
A trap or exception is a software-generated interrupt
caused either by an error or a user request
An operating system is interrupt driven
- 20. 1.20 Silberschatz, Galvin and Gagne ©2013
Operating System Concepts – 9th Edition
Interrupt Handling
The operating system preserves the state of the CPU
by storing registers and the program counter
Determines which type of interrupt has occurred:
polling
vectored interrupt system
Separate segments of code determine what action
should be taken for each type of interrupt
- 21. 1.21 Silberschatz, Galvin and Gagne ©2013
Operating System Concepts – 9th Edition
I/O Structure
After I/O starts, control returns to user program only upon
I/O completion
Wait instruction idles the CPU until the next interrupt
Wait loop (contention for memory access)
At most one I/O request is outstanding at a time, no
simultaneous I/O processing
- 22. 1.22 Silberschatz, Galvin and Gagne ©2013
Operating System Concepts – 9th Edition
I/O Structure
After I/O starts, control returns to user program without
waiting for I/O completion
System call – request to the OS to allow user to wait
for I/O completion
Device-status table contains entry for each I/O
device indicating its type, address, and state
OS indexes into I/O device table to determine device
status and to modify table entry to include interrupt
- 23. 1.23 Silberschatz, Galvin and Gagne ©2013
Operating System Concepts – 9th Edition
Storage Definitions and Notation Review
Computer storage is generally measured and manipulated
in bytes and collections of bytes.
1. a kilobyte, or KB, is 1,024 bytes
2. a megabyte, or MB, is 1,0242 bytes
3. a gigabyte, or GB, is 1,0243 bytes
4. a terabyte, or TB, is 1,0244 bytes
5. a petabyte, or PB, is 1,0245 bytes
- 24. 1.24 Silberschatz, Galvin and Gagne ©2013
Operating System Concepts – 9th Edition
Storage Definitions and Notation Review
The basic unit of computer storage is the bit. A bit can contain one of two values, 0 and 1.
All other storage in a computer is based on collections of bits. Given enough bits, it is
amazing how many things a computer can represent: numbers, letters, images, movies,
sounds, documents, and programs, to name a few. A byte is 8 bits, and on most computers
it is the smallest convenient chunk of storage. For example, most computers don’t have an
instruction to move a bit but do have one to move a byte. A less common term is word,
which is a given computer architecture’s native unit of data. A word is made up of one or
more bytes. For example, a computer that has 64-bit registers and 64-bit memory
addressing typically has 64-bit (8-byte) words. A computer executes many operations in its
native word size rather than a byte at a time.
Computer storage, along with most computer throughput, is generally measured and
manipulated in bytes and collections of bytes.
A kilobyte, or KB, is 1,024 bytes
a megabyte, or MB, is 1,0242 bytes
a gigabyte, or GB, is 1,0243 bytes
a terabyte, or TB, is 1,0244 bytes
a petabyte, or PB, is 1,0245 bytes
Computer manufacturers often round off these numbers and say that a megabyte is 1
million bytes and a gigabyte is 1 billion bytes. Networking measurements are an exception
to this general rule; they are given in bits (because networks move data a bit at a time).
- 26. 1.26 Silberschatz, Galvin and Gagne ©2013
Operating System Concepts – 9th Edition
Direct Memory Access Structure
Used for high-speed I/O devices able to transmit
information at close to memory speeds
Device controller transfers blocks of data from buffer
storage directly to main memory without CPU intervention
Only one interrupt is generated per block, rather than the
one interrupt per byte
- 27. 1.27 Silberschatz, Galvin and Gagne ©2013
Operating System Concepts – 9th Edition
Storage Structure
Main memory – only large storage media that the CPU
can access directly
Random access
Typically volatile
Secondary storage – extension of main memory that
provides large nonvolatile storage capacity
- 28. 1.28 Silberschatz, Galvin and Gagne ©2013
Operating System Concepts – 9th Edition
Storage Structure
Magnetic disks – rigid metal or glass platters covered
with magnetic recording material
Disk surface is logically divided into tracks, which are
subdivided into sectors
The disk controller determines the logical interaction between
the device and the computer
Solid-state disks – faster than magnetic disks,
nonvolatile
Various technologies
Becoming more popular
- 29. 1.29 Silberschatz, Galvin and Gagne ©2013
Operating System Concepts – 9th Edition
Storage Hierarchy
Storage systems organized in hierarchy
Speed
Cost
Volatility
Caching – copying information into faster storage
system; main memory can be viewed as a cache for
secondary storage
Device Driver for each device controller to manage I/O
Provides uniform interface between controller and kernel
- 31. 1.31 Silberschatz, Galvin and Gagne ©2013
Operating System Concepts – 9th Edition
Caching
Important principle, performed at many levels in a
computer (in hardware, operating system, software)
Information in use copied from slower to faster storage
temporarily
Faster storage (cache) checked first to determine if
information is there
If it is, information used directly from the cache (fast)
If not, data copied to cache and used there
Cache smaller than storage being cached
Cache management important design problem
Cache size and replacement policy
- 32. 1.32 Silberschatz, Galvin and Gagne ©2013
Operating System Concepts – 9th Edition
Computer-System Architecture
Most systems use a single general-purpose processor
Most systems have special-purpose processors as well. Such as
disk, keyboard, and graphics controllers;
The operating system cannot communicate with these
(special-purpose) processors; they do their jobs
autonomously
- 33. 1.33 Silberschatz, Galvin and Gagne ©2013
Operating System Concepts – 9th Edition
Computer-System Architecture
Multiprocessors: Such systems have two or more
processors in close communication, sharing the computer
bus and sometimes the clock, memory, and peripheral
devices
Multiprocessor systems first appeared prominently
appeared in servers and have since migrated to
1. Desktop
2. Laptop systems
3. Mobile devices
4. Smartphones and Tablet computers
- 34. 1.34 Silberschatz, Galvin and Gagne ©2013
Operating System Concepts – 9th Edition
Computer-System Architecture
Multiprocessors systems growing in use and importance
Also known as parallel systems, tightly-coupled systems
Advantages include:
1. Increased throughput
2. Economy of scale
3. Increased reliability – graceful degradation or fault
tolerance
The ability to continue providing service proportional to the
level of surviving hardware is called graceful
degradation. Some systems go beyond graceful
degradation and are called fault tolerant, because they
can suffer a failure of any single component and still
continue operation
- 35. 1.35 Silberschatz, Galvin and Gagne ©2013
Operating System Concepts – 9th Edition
Computer-System Architecture
Multiprocessing systems are of two types:
1. Asymmetric Multiprocessing: the relationship
between multicore processors (heterogeneous or
homogeneous) of asymmetric multiprocessing is a
master-slave relationship
2. Symmetric Multiprocessing: All processors of
same type (may be either heterogeneous or
homogeneous) of symmetric multiprocessing are
peers;
- 36. 1.36 Silberschatz, Galvin and Gagne ©2013
Operating System Concepts – 9th Edition
Computer-System Architecture
More specifically, each CPU in symmetric multiprocessing
runs the same copy of the OS, while in asymmetric
multiprocessing, they split responsibilities typically,
therefore each may have specialized (different) software
and roles.
- 37. 1.37 Silberschatz, Galvin and Gagne ©2013
Operating System Concepts – 9th Edition
How a Modern Computer Works
A von Neumann architecture
- 39. 1.39 Silberschatz, Galvin and Gagne ©2013
Operating System Concepts – 9th Edition
A Dual-Core Design
Uniform memory access (UMA) is a shared
memory architecture used in parallel computers.
All the processors in the UMA model share the physical
memory uniformly.
In a UMA architecture, access time to a memory location
is independent of which processor makes the request or
which memory chip contains the transferred data.
- 40. 1.40 Silberschatz, Galvin and Gagne ©2013
Operating System Concepts – 9th Edition
A Dual-Core Design
Non-uniform memory access (NUMA) is a computer
memory design used in multiprocessing, where the
memory access time depends on the memory location
relative to the processor.
Under NUMA, a processor can access its own local
memory faster than non-local memory (memory local to
another processor or memory shared between
processors).
- 42. 1.42 Silberschatz, Galvin and Gagne ©2013
Operating System Concepts – 9th Edition
A Dual-Core Design
Systems containing all chips vs. blade servers
Chassis containing multiple separate systems
- 43. 1.43 Silberschatz, Galvin and Gagne ©2013
Operating System Concepts – 9th Edition
Clustered Systems
They are composed of two or more individual systems—or
nodes—joined together.
Like multiprocessor systems, but multiple systems working
together
Usually sharing storage via a storage-area network (SAN)
Provides a high-availability service which survives failures
Some clusters are for high-performance computing (HPC)
Some have distributed lock manager (DLM) to avoid conflicting
operations
- 45. 1.45 Silberschatz, Galvin and Gagne ©2013
Operating System Concepts – 9th Edition
Operating System Structure
Multiprogramming is needed for efficiency.
Multiprogramming is also the ability of an operating
system to execute more than one program on a single
processor machine.
More than one task/program/job/process can reside into
the main memory at one point of time.
A computer running excel and firefox browser
simultaneously is an example of multiprogramming.
- 47. 1.47 Silberschatz, Galvin and Gagne ©2013
Operating System Concepts – 9th Edition
Operating System Structure
Timesharing (multitasking) is the ability of an
operating system to execute more than one task
simultaneously on a single processor machine.
Though we say so but in reality no two tasks on a
single processor machine can be executed at the
same time.
Actually CPU switches from one task to the next task
so quickly that appears as if all the tasks are
executing at the same time.
More than one task/program/job/process can reside
into the same CPU at one point of time.
- 48. 1.48 Silberschatz, Galvin and Gagne ©2013
Operating System Concepts – 9th Edition
Memory Layout for Multiprogrammed System
- 49. 1.49 Silberschatz, Galvin and Gagne ©2013
Operating System Concepts – 9th Edition
Operating System Structure
Multiprocessing is the ability of an operating system
to execute more than one process simultaneously on
a multi processor machine. In this, a computer uses
more than one CPU at a time.
- 50. 1.50 Silberschatz, Galvin and Gagne ©2013
Operating System Concepts – 9th Edition
Operating-System Operations
Interrupt driven by hardware
Software error or request creates exception or trap
Division by zero, request for operating system
service, infinite loop, processes modifying each
other or the operating system
Dual-mode operation allows OS to protect itself and
other system components
User mode and kernel mode
- 51. 1.51 Silberschatz, Galvin and Gagne ©2013
Operating System Concepts – 9th Edition
Operating-System Operations
Mode bit provided by hardware
Provides ability to distinguish when system is
running user code or kernel code
Some instructions designated as privileged,
only executable in kernel mode
System call changes mode to kernel, return from
call resets it to user
- 52. 1.52 Silberschatz, Galvin and Gagne ©2013
Operating System Concepts – 9th Edition
Process Management
A process is a program in execution. It is a unit of work
within the system. Program is a passive entity, process is
an active entity.
Process needs resources to accomplish its task
CPU, memory, I/O, files
Initialization data
Process termination requires reclaim of any reusable
resources
Single-threaded process has one program counter
specifying location of next instruction to execute
Process executes instructions sequentially, one at a
time, until completion
- 53. 1.53 Silberschatz, Galvin and Gagne ©2013
Operating System Concepts – 9th Edition
Process Management
Multi-threaded process has one program counter per
thread
Typically system has many processes, some user,
some operating system running concurrently on one or
more CPUs
Concurrency by multiplexing the CPUs among the
processes / threads
- 54. 1.54 Silberschatz, Galvin and Gagne ©2013
Operating System Concepts – 9th Edition
Process Management Activities
The operating system is responsible for the following
activities in connection with process management:
1. Creating and deleting both user and system processes
2. Suspending and resuming processes
3. Providing mechanisms for process synchronization
4. Providing mechanisms for process communication
5. Providing mechanisms for deadlock handling
- 55. 1.55 Silberschatz, Galvin and Gagne ©2013
Operating System Concepts – 9th Edition
Memory Management
All data in memory before and after processing
All instructions in memory in order to execute
Memory management determines what is in memory
when
Optimizing CPU utilization and computer response to
users
- 56. 1.56 Silberschatz, Galvin and Gagne ©2013
Operating System Concepts – 9th Edition
Memory Management
Memory management activities
Keeping track of which parts of memory are currently
being used and by whom
Deciding which processes (or parts thereof) and data
to move into and out of memory
Allocating and deallocating memory space as
needed
- 57. 1.57 Silberschatz, Galvin and Gagne ©2013
Operating System Concepts – 9th Edition
Storage Management
File-System management
Files usually organized into directories
Access control on most systems to determine who can
access what
OS activities include
Creating and deleting files and directories
Primitives to manipulate files and dirs
Mapping files onto secondary storage
Backup files onto stable (non-volatile) storage media
- 58. 1.58 Silberschatz, Galvin and Gagne ©2013
Operating System Concepts – 9th Edition
Performance of Various Levels of Storage
- 59. 1.59 Silberschatz, Galvin and Gagne ©2013
Operating System Concepts – 9th Edition
Migration of Integer A from Disk to Register
Multitasking environments must be careful to use most recent value, no
matter where it is stored in the storage hierarchy
Multiprocessor environment must provide cache coherency in
hardware such that all CPUs have the most recent value in their cache
Distributed environment situation even more complex
Several copies of a datum can exist
Various solutions covered in Chapter 17
- 60. 1.60 Silberschatz, Galvin and Gagne ©2013
Operating System Concepts – 9th Edition
I/O Subsystem
One purpose of OS is to hide peculiarities of hardware devices from the
user
I/O subsystem responsible for
Memory management of I/O including buffering (storing data
temporarily while it is being transferred), caching (storing parts of data
in faster storage for performance), spooling (the overlapping of output
of one job with input of other jobs)
General device-driver interface
Drivers for specific hardware devices
- 61. 1.61 Silberschatz, Galvin and Gagne ©2013
Operating System Concepts – 9th Edition
Protection and Security
Protection – any mechanism for controlling access of
processes or users to 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
- 62. 1.62 Silberschatz, Galvin and Gagne ©2013
Operating System Concepts – 9th Edition
Write answers to exercise question from 1.1 to 1.11
Only handwritten neat and clean homework will be
accepted.
Page size and page quality through out the
course should remain the same.
Throughout this course, homework should be
submitted to CR in next class after the class
attendance.
Homework