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Abhinav KamraComputer Science, Columbia University
1.1Operating System ConceptsSilberschatz, Galvin and Gagne 2002
COMS 4118Operating Systems
Spring 2005
Abhinav [email protected]
http://www.cs.columbia.edu/~kamra/teaching/
Abhinav KamraComputer Science, Columbia University
1.2Operating System ConceptsSilberschatz, Galvin and Gagne 2002
Course Contents
Processes 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
Abhinav KamraComputer Science, Columbia University
1.3Operating System ConceptsSilberschatz, Galvin and Gagne 2002
Logistics
Lectures Tuesdays and Thursdays
9:30am – 10:45am Exams
No mid-term exam 4-5 “Quizzes” A Comprehensive Final Exam
Abhinav KamraComputer Science, Columbia University
1.4Operating System ConceptsSilberschatz, Galvin and Gagne 2002
Logistics (continued)
Homework Assignments None
Grading Quizzes: 25% Programming Assignments: 50% Final Exam: 25%
Abhinav KamraComputer Science, Columbia University
1.5Operating System ConceptsSilberschatz, Galvin and Gagne 2002
Logistics (continued)
Programming Assignments 2-3 small assignments One “big” assignment (A Real OS)
OSKit and VMWare An MP3 CD Player OS
Abhinav KamraComputer Science, Columbia University
1.6Operating System ConceptsSilberschatz, Galvin and Gagne 2002
Chapter 1: Introduction
What is an Operating System? Mainframe Systems Desktop Systems Multiprocessor Systems Distributed Systems Clustered System Real -Time Systems Handheld Systems
Abhinav KamraComputer Science, Columbia University
1.7Operating System ConceptsSilberschatz, Galvin and Gagne 2002
“I think that there is a world market for five computers”
- Thomas J. Watson (1945)
Abhinav KamraComputer Science, Columbia University
1.8Operating System ConceptsSilberschatz, Galvin and Gagne 2002
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.
Abhinav KamraComputer Science, Columbia University
1.9Operating System ConceptsSilberschatz, Galvin and Gagne 2002
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
Abhinav KamraComputer Science, Columbia University
1.10Operating System ConceptsSilberschatz, Galvin and Gagne 2002
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
Abhinav KamraComputer Science, Columbia University
1.11Operating System ConceptsSilberschatz, Galvin and Gagne 2002
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).
Abhinav KamraComputer Science, Columbia University
1.12Operating System ConceptsSilberschatz, Galvin and Gagne 2002
Abstract View of System Components
Abhinav KamraComputer Science, Columbia University
1.13Operating System ConceptsSilberschatz, Galvin and Gagne 2002
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).
Abhinav KamraComputer Science, Columbia University
1.14Operating System ConceptsSilberschatz, Galvin and Gagne 2002
Operating Systems Ease the Pain
Performs the interface task with the hardware (file operations, memory 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
Abhinav KamraComputer Science, Columbia University
1.15Operating System ConceptsSilberschatz, Galvin and Gagne 2002
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!)
Abhinav KamraComputer Science, Columbia University
1.16Operating System ConceptsSilberschatz, Galvin and Gagne 2002
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
Abhinav KamraComputer Science, Columbia University
1.17Operating System ConceptsSilberschatz, Galvin and Gagne 2002
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
Abhinav KamraComputer Science, Columbia University
1.18Operating System ConceptsSilberschatz, Galvin and Gagne 2002
Memory Layout for a Simple Batch System
Abhinav KamraComputer Science, Columbia University
1.19Operating System ConceptsSilberschatz, Galvin and Gagne 2002
Offline Processing
Allowed jobs to be read ahead of time onto tape
CardReader CPU Line
printer
CardReader CPU Line
printer
TapeDrive
TapeDrive
TapeDrive
TapeDrive
On-line processing
Off-line processing
Abhinav KamraComputer Science, Columbia University
1.20Operating System ConceptsSilberschatz, Galvin and Gagne 2002
History: Spooling
Allowed jobs to be read ahead onto disk Spool (Simultaneous Peripheral Operation On-Line)
CardReader CPU
Lineprinter
disk
Abhinav KamraComputer Science, Columbia University
1.21Operating System ConceptsSilberschatz, Galvin and Gagne 2002
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
Abhinav KamraComputer Science, Columbia University
1.22Operating System ConceptsSilberschatz, Galvin and Gagne 2002
Multiprogrammed Batch Systems
Several jobs are kept in main memory at the same time, and the CPU is multiplexed among them.
Abhinav KamraComputer Science, Columbia University
1.23Operating System ConceptsSilberschatz, Galvin and Gagne 2002
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
Abhinav KamraComputer Science, Columbia University
1.24Operating System ConceptsSilberschatz, Galvin and Gagne 2002
Desktop Systems
Personal computers – computer system dedicated to a 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)
Abhinav KamraComputer Science, Columbia University
1.25Operating System ConceptsSilberschatz, Galvin and Gagne 2002
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)
Abhinav KamraComputer Science, Columbia University
1.26Operating System ConceptsSilberschatz, Galvin and Gagne 2002
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
Abhinav KamraComputer Science, Columbia University
1.27Operating System ConceptsSilberschatz, Galvin and Gagne 2002
Symmetric Multiprocessing Architecture
Abhinav KamraComputer Science, Columbia University
1.28Operating System ConceptsSilberschatz, Galvin and Gagne 2002
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 high-speed buses or telephone lines.
Advantages of distributed systems. Resources Sharing Computation speed up – load sharing Reliability Communications
Abhinav KamraComputer Science, Columbia University
1.29Operating System ConceptsSilberschatz, Galvin and Gagne 2002
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.
Abhinav KamraComputer Science, Columbia University
1.30Operating System ConceptsSilberschatz, Galvin and Gagne 2002
General Structure of Client-Server
Abhinav KamraComputer Science, Columbia University
1.31Operating System ConceptsSilberschatz, Galvin and Gagne 2002
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.
Abhinav KamraComputer Science, Columbia University
1.32Operating System ConceptsSilberschatz, Galvin and Gagne 2002
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.
Abhinav KamraComputer Science, Columbia University
1.33Operating System ConceptsSilberschatz, Galvin and Gagne 2002
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.
Abhinav KamraComputer Science, Columbia University
1.34Operating System ConceptsSilberschatz, Galvin and Gagne 2002
Handheld Systems
Personal Digital Assistants (PDAs) Cellular telephones Issues:
Limited memory Slow processors Small display screens.