Compsci 82, Fall 2009, November 16

By entering your name/net-id below you indicate you are in class on November 16 to answer these questions and that you have answered them. As many as four can claim credit for answers on one sheet.

Name: ___________________    Net id: _______ ||| Name: ___________________    Net id: _______

Name: ___________________    Net id: _______ ||| Name: ___________________    Net id: _______

  1. Suppose Moore's law holds for the speed of computing, and we use the "doubles every two years" version of the law. If computers execute one billion instructions a second today, how many instructions per second will be executed in 2019? Why?
  2. In 1998 Jakob Nielsen said bandwidth grows by 50% a year (measured in downloading bits-per-second). The Duke wireless network uses 802.11n, which is about 100 Mbit/s or 100 Megabits/second. This is about 100 million bits/second. I can download a bootleg/illegal copy of Harry Potter and the Half-Blood Prince that is roughly 1.4 Gigabytes in size. That's 1.4 billion bytes and a byte is 8 bits. How long will it take to download via the 802.11n network. How long will it take in 2019 if Nielsen's law holds?
  3. The url is valid. If every URL with the same length is valid, and any digit as well as upper/lower case letters can be used, how many possible URLs/videos are there?


    Google log anonymizing paper

  4. In the article you can find the following phrase, "Since each octet (the numbers between each period of an IP) can contain values from 1-255, ...". Explain why the numbers are between 1 and 255.
  5. If you remove cookies every few months will some of the author's concerns by eliminated (e.g., on the second page when the author talks about a "9-month-old search log ... because the cookie values remain".