Emery Berger

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Operating SystemsCMPSCI 377Lecture 1

• Emery Berger
• University of Massachusetts, Amherst

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Information

• Course web page
• http//www.cs.umass.edu/emery/cmpsci377
• My contact info
• emery_at_cs.umass.edu
• Phone [phone]
• Office hours by appointment
• TAs
• Gene Novark, Louis Theran
• Discussion section
• W 1220 110, Hasbrouck 138

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Todays Class

• Administrivia
• Course organization outline
• Prerequisites course sign-up
• Introduction History of Operating Systems

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Course Organization

• Capacity is 50
• Class junior or senior-level
• Not for freshman or sophomores
• Enrollment policy
• If space becomes an issue,graduating seniors get
  preference

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Prerequisites

• CMPSCI 187 (Data Structures)
• CMPSCI 201 (Architecture)
• Textbook
• Operating Systems(Deitel, Deitel Choffnes)

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Course Requirements

• Class participation 10 (includes in-class
  quizzes)
• Homework 10
• Programming projects 40
• Exams (two in-class, one final) 40
• Programming assignments Java
• Strict late policy not accepted late
• Cheaters will be found and punished
• Will use sophisticated software to detect
  plagiarized programs

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Course Organization

• Accounts in EdLab 30 Linux PCs
• Discussion section to help you with lab
  assignments
• Office hours and location of TAs
• Gene Novark to be announced
• gnovark_at_gmail.com
• Louis Theran to be announced
• theran_at_cs.umass.edu

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Introduction to Operating Systems

• Whats an operating system? (OS)
• Why are OSs important?
• Historical perspective on operating systems

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Whats An Operating System?

• Definition has changed over years
• Originally, very bare bones
• Now, includes more and more
• Bill Gates Windows
• Everything in other operating systems
• Internet Explorer
• Media player
• even a ham sandwich (DOJ vs. Microsoft)

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OS More Traditional View

• Interface between user and architecture
• Hides architectural details
• Implements virtual machine
• Easier to program than raw hardware (hopefully)
• Provides services and coordinates machine
  activities

User-level Applications
virtual machine interface
Operating System
physical machine interface
Hardware
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Operating Systems Key Features

• Provides standard services (interface) that
  hardware implements
• File system, virtual memory, networking,
  scheduling, time-sharing
• Coordinates multiple applications and users to
  achieve safety, fairness and efficiency (high
  throughput)
• Concurrency, memory protection, networking,
  security
• OS design challenges convenient and efficient
• Software engineering systems engineering
  problems

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Introduction to Operating Systems

• Whats an operating system? (OS)
• Why are OSs important?
• Historical perspective on operating systems

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Importance of Operating Systems

• Key component of computer systems
• Meeting point of software hardware
• Understanding how computers work understanding
  operating systems
• OS provides key services required by all
  application programs
• Rich topic
• OS most complex software on your PC
• Windows XP kernel 40 million lines of code

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Why So Complex?

• Provides high-level of abstraction
• Illusion of
• Infinite memory
• Complete control of resources
• Requires sophisticated system design
• Tradeoffs
• Performance vs. convenience (OS abstractions)
• Performance vs. simplicity (OS design)
• Putting functionality in hardware vs. software
• As systems changes, OS must adapt (new hardware,
  software)

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New Developments in OS Design

• Operating systems very active field of research
• Demands on OSs growing
• New application spaces (Web, Grid)
• Rapidly evolving hardware
• Advent of open-source operating systems Linux
• You can contribute to and develop OSs!
• Excellent research platform

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Background You Need

• OS software that manages hardware
• Must understand both
• Hardware
• CPU instruction sets, memory hierarchies
• I/O systems
• Software
• Complex data structures
• Object-oriented programming (esp. for
  encapsulation)
• Java (although)

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Introduction to Operating Systems

• Whats an operating system? (OS)
• Why are OSs important?
• Historical perspective on operating systems

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The Dark Ages (1940s-1960s)

• Hardware expensive humans cheap
• Evolution of functionality
• One user
• Batch processing
• Overlap of I/O computation
• Multiprogramming

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1. Single-User Computers

• One user at a time on console
• Computer executes one function at a time
• No overlap computation I/O
• User must be at console to debug
• Multiple users inefficient use of machine

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2. Batch Processing

• Execute multiple jobs in batch
• Load program
• Run
• Print results, dump machine state
• Repeat
• Users submit jobs (on cards or tape)
• Human schedules jobs
• Operating system loads runs jobs
• More efficient use of machine, complicates
  debugging

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3. Overlap I/O and Computation

• Before machine waits for I/O
• New approach
• Allow CPU to execute while waiting
• Add buffering, interrupt handling
• More efficient use of machine, but still one job
  at a time

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4. Multiprogramming

• Allow several programs to run at same time
• Run one job until I/O
• Run another job, etc.
• OS manages interaction between programs
• Which jobs to start
• Protects programs memory from others
• Decides which to resume when CPU available

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OS Complexity

• Increased functionality complexity
• First OS failures
• Multics (GE MIT)announced 1963, released 1969
• OS/360 released with 1000 known bugs
• Need to treat OS design scientifically
• Managing complexity becomes key to

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The Renaissance (1970s)

• Hardware cheap humans expensive
• Users share system via terminals
• The UNIX era
• Multics
• army of programmers, six years
• UNIX
• three guys, two years
• Shell composable commands
• No distinction between programs data
• But response time thrashing

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The Industrial Revolution (1980s)

• Hardware very cheap
• humans expensive
• Widespread use of PCs
• IBM PC 1981, Macintosh 1984
• Simple OS (DOS, MacOS)
• No multiprogramming, concurrency, memory
  protection, virtual memory,
• Later networking, file-sharing, remote printing
• GUI added to OS (WIMP)

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The Modern Era (1990s-now)

• Hardware cheap Processing demands increasing
• Real operating systems on PCs
• NT (1991) Mac OS X Linux
• Different modalities
• Parallel Multiple processors, one machine
• Distributed Multiple networked processors
• Real-time Strict or loose deadlines
• Sensor networks Many small computers

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Moral of the Story

• The only constant Change
• In 50 years, almost every computer component
  now9 orders of magnitude faster, larger, cheaper
• Example

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Moral of the Story, II

• No counterpart in any other sphere of human
  existence!
• Transportation
• 200 years to go from horseback (10 mph) to
  Concorde (1000 mph) 2 orders of magnitude
• Communication is closest
• 100 years to go from Pony Express (10 mph) to
  nearly speed of light (600 million mph) 7
  orders of magnitude
• And operating systems must adapt

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Next Time

• Operating Systems Architecture
• Work on Lab 1!