Lecture Notes for Operating Systems

7 September 2004 - Introduction

What is an OS?

• It's a program; a big piece of software.

• The program that manages resources.

  • Manages: both exploit (maximize good use) and protect (minimize bad use).

  • Resources: practically everything, including programs, including itself.

OS Themes

• The three OS themes: economy, protection, and convenience.

• Economy: efficiently manage resources; expensive (user time) or limited (handheld power) or both (wireless transmission bandwidth).

• Protection: levels of protection, protection against various levels of malevolence.

• Convenience: define useful models.

• Pick any one.

OS Techniques

• An OS does its work by implementing abstractions.

• An abstraction is a high-level model defined in terms of low-level details.

  • The high-level model is more convenient to use than the low-level details.

  • However, it may not be as efficient, or as flexible.

OS History

• But aren't operating systems a done deal?

• Operating systems evolve in response to changing environments.

  • Hardware: networked machines, 64 bit address spaces, mobile and other low-resource environments.

  • Resources: information and rights management.

  • Requirements: security.

OS Choices

• Different environments and responses lead to different operating systems.

• 60s: Big, expensive machines; IBM 360.

  • Batch operating systems had to return investment and manage complexity.

• 70s: Big, expensive machines; PDP 10.
  

  • Timesharing operating systems provided the virtual machine abstraction.

OS Choices, Continued

• 80s: Small, expensive machines; PDP 11.

  • Specialized operating systems; RTOS.

• 90s: Small, cheap machines; IBM PC

  • Single-user operating systems; Windows; Oberon.

• 00s: A Cambrian explosion; networks, hand-helds.
  

  • Sensor-network operating systems.

Automotive Electronics

• Consider automotive electronics.

  • Chassis control, engine control, automatic transmission, ABS/ASR, cruise control.

  • Cabin comfort, air conditioning, dashboard, trip computer, display range, radio, telephone, navigation.

  • Intelligent switching, anti-finger traps, power seats, alarms.

Automotive CPUs

• These applications require dozens of CPUs.

  • 32-bit power train, 16-bit vehicle control, 8-bit body control and driver information, 4-bit dashboard.

• Now, network them together, multiplex them, link them up to the external environment.

This page last modified on 14 November 2004.