COMS 4118
Operating Systems
Spring 2005
Abhinav Kamra
kamra@cs.columbia.edu
http://www.cs.columbia.edu/~kamra/teaching/
Operating System Concepts
Silberschatz, Galvin and Gagne 2002
1.1
Abhinav Kamra
Computer Science, Columbia University
Course Contents
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Processes
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Process Management
Inter-process Communication
Process Scheduling
Process Synchronization (to access very popular data)
Deadlocks
Memory Management
Virtual Memory
File Systems
I/O Systems
Interrupt Handling
Operating System Concepts
Silberschatz, Galvin and Gagne 2002
1.2
Abhinav Kamra
Computer Science, Columbia University
Logistics
 Lectures
 Tuesdays and Thursdays
 9:30am – 10:45am
 Exams
 No mid-term exam
 4-5 “Quizzes”
 A Comprehensive Final Exam
Operating System Concepts
Silberschatz, Galvin and Gagne 2002
1.3
Abhinav Kamra
Computer Science, Columbia University
Logistics (continued)
 Homework Assignments
 None
 Grading
 Quizzes: 25%
 Programming Assignments: 50%
 Final Exam: 25%
Operating System Concepts
Silberschatz, Galvin and Gagne 2002
1.4
Abhinav Kamra
Computer Science, Columbia University
Logistics (continued)
 Programming Assignments
 2-3 small assignments
 One “big” assignment (A Real OS)
 OSKit and VMWare
 An MP3 CD Player OS
Operating System Concepts
Silberschatz, Galvin and Gagne 2002
1.5
Abhinav Kamra
Computer Science, Columbia University
Chapter 1: Introduction
 What is an Operating System?
 Mainframe Systems
 Desktop Systems
 Multiprocessor Systems
 Distributed Systems
 Clustered System
 Real -Time Systems
 Handheld Systems
Operating System Concepts
Silberschatz, Galvin and Gagne 2002
1.6
Abhinav Kamra
Computer Science, Columbia University
“I think that there is a world
market for five computers”
- Thomas J. Watson (1945)
Operating System Concepts
Silberschatz, Galvin and Gagne 2002
1.7
Abhinav Kamra
Computer Science, Columbia University
What is an Operating System?
 A program that acts as an intermediary between a user of
a computer 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.
Operating System Concepts
Silberschatz, Galvin and Gagne 2002
1.8
Abhinav Kamra
Computer Science, Columbia University
Why Study Operating Systems?
 We want to have an efficient O/S because it
 consumes more resources than any other program.
 is the most complex program.
 is necessary for any use of the computer.
 is used by many users.
 Efficiency is measured through
 Functionality
 Performance: Time and Utilization
 Convenience and Cost
Operating System Concepts
Silberschatz, Galvin and Gagne 2002
1.9
Abhinav Kamra
Computer Science, Columbia University
Goals of This Course
 Understand what an operating system is
 Understand the key components of an operating system
 Have a deeper understanding of common operating systems in
the market (e.g. Windows, Unix, MS-DOS) and the issues
associated with them
 To be able to use performance measures
Operating System Concepts
Silberschatz, Galvin and Gagne 2002
1.10
Abhinav Kamra
Computer Science, Columbia University
Computer System Components
1. Hardware – provides basic computing resources (CPU,
memory, I/O devices).
2. Operating system – controls and coordinates the use of
the hardware among the various application programs for
the various users.
3. Applications programs – define the ways in which the
system resources are used to solve the computing
problems of the users (compilers, database systems,
video games, business programs).
4. Users (people, machines, other computers).
Operating System Concepts
Silberschatz, Galvin and Gagne 2002
1.11
Abhinav Kamra
Computer Science, Columbia University
Abstract View of System Components
Operating System Concepts
Silberschatz, Galvin and Gagne 2002
1.12
Abhinav Kamra
Computer Science, Columbia University
Operating System Definitions
 Resource allocator – manages and allocates resources.
 Control program – controls the execution of user
programs and operations of I/O devices .
 Kernel – the one program running at all times (all else
being application programs).
Operating System Concepts
Silberschatz, Galvin and Gagne 2002
1.13
Abhinav Kamra
Computer Science, Columbia University
Operating Systems Ease the Pain
 Performs the interface task with the hardware (file operations, memory
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paging, etc.) which should have been done by the user if the OS did not
exist
High-level interface (GUI, command line a.k.a. CUI)
The O/S’s capability for multi-user and multi-tasking utilize the hardware
efficiently
Makes visible the “virtual” component of the system
Allows program interaction
Operating System Concepts
Silberschatz, Galvin and Gagne 2002
1.14
Abhinav Kamra
Computer Science, Columbia University
Why are Operating Systems Difficult to
Create and Maintain?
 Size
 Too big for one person; current systems have millions of lines of code
and involve 10-100 man years to build
 Lifetime
 Operating systems remain longer than the programmers who
originally wrote them. Code is written and rewritten and original intent
is forgotten (Unix designed to be cute, small system - now several
volumes thick!)
Operating System Concepts
Silberschatz, Galvin and Gagne 2002
1.15
Abhinav Kamra
Computer Science, Columbia University
Why are Operating Systems Difficult to
Create and Maintain?
 Complexity
 The system must do difficult things -- deal with ugly I/O
devices, multiplexing/juggling act, handle errors
 Multitasking
 Must do several things at once.
 General purpose
Operating System Concepts
Silberschatz, Galvin and Gagne 2002
1.16
Abhinav Kamra
Computer Science, Columbia University
A Brief History: Early 1950’s,
Mainframes Rule!
 Early systems
 No O/S! Programmer is also operator
 Large machines run from a console; programs loaded through switches and
card readers
 Simple batch systems were the first real OS
 Setup time was a problem -> hire an operator
 Operator ran related jobs together
 O/S was a simple program stored in one part of memory
 Loads a single job from card reader into memory
 Transfers control from one job to the next
Operating System Concepts
Silberschatz, Galvin and Gagne 2002
1.17
Abhinav Kamra
Computer Science, Columbia University
Memory Layout for a Simple Batch System
Operating System Concepts
Silberschatz, Galvin and Gagne 2002
1.18
Abhinav Kamra
Computer Science, Columbia University
Offline Processing
Allowed jobs to be read ahead of time onto tape
Card
Reader
Line
printer
CPU
On-line processing
Card
Reader
Tape
Drive
Operating System Concepts
Silberschatz, Galvin and Gagne 2002
Tape
Drive
Tape
Drive
CPU
Off-line processing
1.19
Line
printer
Tape
Drive
Abhinav Kamra
Computer Science, Columbia University
History: Spooling
 Allowed jobs to be read ahead onto disk
 Spool (Simultaneous Peripheral Operation On-Line)
disk
Card
Reader
Operating System Concepts
Silberschatz, Galvin and Gagne 2002
CPU
1.20
Line
printer
Abhinav Kamra
Computer Science, Columbia University
Multiprogrammed Systems
 Multiprogrammed batch systems provided increased utilization
 Keeps several jobs in memory simultaneously
 I/O processing of one job overlaps with computation of another
 Analogy: Lawyer working on several cases; while waiting to go to trial
on one, can work on another
 Needs CPU scheduling
Operating System Concepts
Silberschatz, Galvin and Gagne 2002
1.21
Abhinav Kamra
Computer Science, Columbia University
Multiprogrammed Batch Systems
Several jobs are kept in main memory at the same time, and the
CPU is multiplexed among them.
Operating System Concepts
Silberschatz, Galvin and Gagne 2002
1.22
Abhinav Kamra
Computer Science, Columbia University
Timesharing/Multitasking Systems
 Timesharing supported interactive
use
 Each user feels as if he/she has
the entire machine
 Tries to optimize response time
 Based on time-slicing; divide CPU
equally among others
Operating System Concepts
Silberschatz, Galvin and Gagne 2002
1.23
Abhinav Kamra
Computer Science, Columbia University
Desktop Systems
 Personal computers – computer system dedicated to a
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single user.
I/O devices – keyboards, mice, display screens, small
printers.
User convenience and responsiveness.
Can adopt technology developed for larger operating
system. Often individuals have sole use of computer and
do not need advanced CPU utilization of protection
features.
May run several different types of operating systems
(Windows, MacOS, UNIX, Linux)
Operating System Concepts
Silberschatz, Galvin and Gagne 2002
1.24
Abhinav Kamra
Computer Science, Columbia University
Parallel Systems
 Multiprocessor systems with more than one CPU in close
communication.
 Tightly coupled system – processors share memory and a
clock; communication usually takes place through the
shared memory.
 Advantages of parallel system:
 Increased throughput
 Economical
 Increased reliability
 graceful degradation
 fail-soft systems (shut down non-essential components)
Operating System Concepts
Silberschatz, Galvin and Gagne 2002
1.25
Abhinav Kamra
Computer Science, Columbia University
Parallel Systems (Cont.)
 Symmetric multiprocessing (SMP)
 Each processor runs and identical copy of the operating
system.
 Many processes can run at once without performance
deterioration.
 Most modern operating systems support SMP
 Asymmetric multiprocessing
 Each processor is assigned a specific task; master
processor schedules and allocated work to slave
processors.
 More common in extremely large systems
Operating System Concepts
Silberschatz, Galvin and Gagne 2002
1.26
Abhinav Kamra
Computer Science, Columbia University
Symmetric Multiprocessing Architecture
Operating System Concepts
Silberschatz, Galvin and Gagne 2002
1.27
Abhinav Kamra
Computer Science, Columbia University
Distributed Systems
 Distribute the computation among several physical
processors.
 Loosely coupled system – each processor has its own
local memory; processors communicate with one another
through various communications lines, such as highspeed buses or telephone lines.
 Advantages of distributed systems.
 Resources Sharing
 Computation speed up – load sharing
 Reliability
 Communications
Operating System Concepts
Silberschatz, Galvin and Gagne 2002
1.28
Abhinav Kamra
Computer Science, Columbia University
Distributed Systems (cont)
 Requires networking infrastructure.
 Local area networks (LAN) or Wide area networks (WAN)
 May be either client-server or peer-to-peer systems.
Operating System Concepts
Silberschatz, Galvin and Gagne 2002
1.29
Abhinav Kamra
Computer Science, Columbia University
General Structure of Client-Server
Operating System Concepts
Silberschatz, Galvin and Gagne 2002
1.30
Abhinav Kamra
Computer Science, Columbia University
Clustered Systems
 Clustering allows two or more systems to share storage.
 Provides high reliability.
 Asymmetric clustering: one server runs the application
while other servers standby.
 Symmetric clustering: all N hosts are running the
application.
Operating System Concepts
Silberschatz, Galvin and Gagne 2002
1.31
Abhinav Kamra
Computer Science, Columbia University
Real-Time Systems
 Often used as a control device in a dedicated application
such as controlling scientific experiments, medical
imaging systems, industrial control systems, and some
display systems.
 Well-defined fixed-time constraints.
 Real-Time systems may be either hard or soft real-time.
Operating System Concepts
Silberschatz, Galvin and Gagne 2002
1.32
Abhinav Kamra
Computer Science, Columbia University
Real-Time Systems (Cont.)
 Hard real-time:
 Secondary storage limited or absent, data stored in short
term memory, or read-only memory (ROM)
 Conflicts with time-sharing systems, not supported by
general-purpose operating systems.
 Soft real-time
 Limited utility in industrial control of robotics
 Useful in applications (multimedia, virtual reality) requiring
advanced operating-system features.
Operating System Concepts
Silberschatz, Galvin and Gagne 2002
1.33
Abhinav Kamra
Computer Science, Columbia University
Handheld Systems
 Personal Digital Assistants (PDAs)
 Cellular telephones
 Issues:
 Limited memory
 Slow processors
 Small display screens.
Operating System Concepts
Silberschatz, Galvin and Gagne 2002
1.34
Abhinav Kamra
Computer Science, Columbia University
Migration of Operating-System Concepts and Features
Operating System Concepts
Silberschatz, Galvin and Gagne 2002
1.35
Abhinav Kamra
Computer Science, Columbia University