Lecture 1 Notes (9/30/13)

Created by Greg Mogavero

What's a system?

1. Oxford English Dictionary, 1928
   I. An organized or connected group of objects
   II. A set of principles, etc., a scheme, method
2. Greek -- Organized whole, government, constitution, musical interval, group of connected verses

What's an operating system?

1. American Heritage, 4th ed. -- Software designed to control the hardware of a specific data processing system in order to allow users and application programs to make use of it
2. Encarta 2007 -- Master control program in a computer
3. Wikipedia 574029146 (2013-09-22) -- A collection of software that manages computer hardware resources and provides common services for computer programs
4. Principles of Computer System Design, 2007, Section 1.A.2 -- A system is a set of interconnected components that has a specified behavior observed at the interface with its environment

Can you safely ignore other parts of a system?

Problems with Computer Systems

• Incommensurate scaling
• • Not everything scales at the same rate
  • • Diseconomies of scale (e.g. star network)
    • Economies of scale (e.g. pin factory)
• Emergent properties arise when you scale
• • Tacoma Narrows bridge (resonant frequency of winds)
  • Napster, etc.
• Propagation of effects
• • Internal details leak out (hummingbird in CA -> hurricane in Taiwan)
  • Chaotic systems
  • Japanese characters in file names (Shift-JIS)

• Solutions:

• 1. Propagate the effects, fix them
  2. Build better walls (scales better)
• Complexity
• • Where does complexity come from?
  • • We're building on previous work
    • • UNIVAC I (lots of error correction)
      • UNIVAC II (used UNIVAC I to simulate UNIVAC II and then removed unnecessary error correction)
      • Moore's Law -- complexity of our chips doubles every 18 months