ICS 1C: Quiz 1 Answers

Here are some notes on Quiz 1. -- Dan.

General note on scoring: on several questions, a check mark means full credit (2 points), a "1" means 1 point, and an "X" means no credit.

You can see a histogram of the scores on Quiz 1.

Compare and contrast "As We May Think" and "The Word Wide Web".

Of the concepts and mechanisms V. Bush presents in "As We May Think," state two which are also found in the World Wide Web as described in the article by T. Berners-Lee. et al.

Some good answers would be:

Multimedia.
Records knowledge - boundless information world.
Associatative indexing - concept of hypertext.
Dissemination of knowledge.
Scaling up - ability to access efficiently large quantities of data.
Distributed, non-hierarchical.
Computer-assisted collaboration.
Easy to use interface, accessible to non-specialists.

State two fundamental characteristics of the World Wide Web as described by T. Berners-Lee et al. which are not present in V. Bush's "As We May Think".

How about:

Consistent user interface.
HTML.
HTTP.
Existence of a variety of browsers (specific browsers don't count, as they are not fundamental).
World-wideness, Internet-based, global network.

Note that I used incomplete sentences in several of my answers. This practice, however, was penalized on the quiz.

What the heck are "name space," "address space," "hierarchical space" and "information space"?

The shared meaning of space here is "range of possibilities." For instance, consider "7-digit phone number space." This space does not include "000-0000," as that is not a valid phone number. Berners-Lee et al. write "The prefix 'http' . . . indicates the address space," which means that the possibilities and syntax following "http" may be different than what might follow another prefix. Now make sure you completely understand the following very important sentence in the Berners-Lee article, from the top of the middle column on p. 78: "The fact that it is easy to address an object anywhere on the Internet is essential . . . for the information space to be independent of the network and server topology." (Look up topology if you're not 100% clear on its meaning!) Based on your experience so far, would you say that this sentence is correct?

No one got this question right. My favorite valiant attempt was "Space is used in an almost virtual way." Be prepared for challenging vocabulary questions on future quizzes -- did someone say extensible? idempotent? metainformation? bit-map? wysiwyg? virtual?

What did you do in lab?

How do you save a copy of an e-mail into a file in a subdirectory?

The magic word here is "export".

How do you interpret ^G or ^C?

For full credit, you had to say "hold down the control key and C or G." Half credit for writing merely "Control C" or "Control G".

Fun with binary numbers.

How many bits do you need to represent 120 or 140 distinct values?

Each (decimal) digit gives you 10 times as many distinct values. Thus there are 10 x 10 x 10 x 10 x 10 x 10 x 10 possible seven digit phone number, minus a few illegal ones such as 000-0000. Each additional bit (binary digit) gives 2 times as many possibilities:

Number   Distinct
of bits  values     List of those distinct values
-------  --------   -----------------------------------------------------
  1         2       0, 1
  2         4       00, 01, 10, 11
  3         8       000, 001, 010, 011, 100, 101, 110, 111
  4        16       0000, 0001, 0010, 0011, 0100, 0101, 0110, 0111, ... 1111
  5        32       00000, 00001, 00010, 00011, ... 11100, 11101, 11110, 11111
  6        64       000000, 000001, 000010, 000011, ... 111101, 111110, 111111
  7       128       0000000, 0000001, 0000010, 0000011, ... 1111110, 1111111
  8       256       00000000, 00000001, 00000010, ... 11111110, 11111111

So, 120 values requires 7 bits (6 won't do), and 7 bits gives 128 distinct values. 140 values requires 8 bits (7 won't do), and 8 bits gives 256 distinct values.

Baby, won't you drive my car?

There were two versions of this question. Most people correctly know what the units meant, but a lot of people messed up on the math.

2 micro-miles in 400 nano-hours is (2/1,000,000)/(400/1,000,000,000) mph, or 5 mph, which isn't even worth a kilo-nickel.

On the other hand, 70 milli-miles in 100 micro-hours is (70/1,000)/(100/1,000,000) mph, or 700 mph, which is a pretty good deal.

Describe "WWW client-waitperson architecture."

Here are a couple of ways of handling the question, both of which are much more detailed than I (SDF) would expect student answers to be:

An individual or organization wishing to provide information or services via the Web do so via programs called "servers" which run at all times. When a person wants to access such information or services, s/he does so by running a "client" program on her/his "own" computer system. This "client" program requests services from various "servers" by contacting the server programs on whatever system each server happens to be running.

In general, a server provides a service to another program called a "client" which (typically) is receiving commands from a person. A client is a program which asks for service. Generally it does so because a human being tells it, "Do this or do that" but in order to do this or do that the client program has to contact another program, called a server, which delivers a service to the client program which in turn uses what it gets from the server to meet the request/command issued by the human being.

In both cases, the key fact about a browser is that a browser is a web client. Based on direct/interactive control by a person wanting to access information/services via the Web, the browser contacts Web servers, makes requests in keeping with the user's commands, and displays the results to the user in an appropriate format.