Exercise 1
A Note about Wild Cards in Searches
Some search engines will allow you to use various
characters as "wild cards" that match anything.
Perhaps the most common "wild card" character
is "*" which is allowed to match any set
of 1 or more characters. So, in theory, if you entered
only "*" in your search term, you would
get every page on the web! (In practice, most search
engines won't return anything.)
But this can allow you to leave part of the search
string open-ended. For example, if you are looking
for a computer that is at least 2.0 GHz, but could
be 2.4 or 2.7, you could enter "2.* GHz" AND
computer AND 256MB in Google's search engine, and
it will match a computer that runs at 2.53 GHz. But
it also found a match with a computer that was described
as "Generation 2, 1.133GHz" - obviously
not what we want! And some pages came up with references
to 2.4GHz cordless phones that just happened to be
listed on the same page as a computer with 256 MB
of memory.
As we said, some search engines will allow wild
cards of various types and some will not. But it
is interesting to note that while Google finds the
pages mentioned above using the * wild card, in its
help section, Google explicitly says that it will
not accept wild cards such as "*" or word
stems. Go figure!
On the other hand, AltaVista's help page lists the
* wild card character and explains its meaning, but
after several search attempts using "2.* GHz",
no pages came up that obviously matched it, and some
pages were found that did not contain the "2.*
GHz" string. Go figure that, too!
You've seen examples of all three Boolean operators: AND,
OR & NOT. Here are some exercises to try.
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Write the Boolean expression
that a search engine could use to find
each of the following topics.
- Lodging rooms in Atlanta, Georgia
(similar to the above), but excluding
the Sheraton and the Hilton. (Your
boss has a personal grudge against
those chains, but he's not concerned
about the price.)
- Digital cameras that have a resolution
of at least 2.0 megapixels. (2 million
picture elements - for example, a resolution
of 1600 by 1280)
- A laptop computer with a 2.0 gigahertz
processor and 256MB of RAM.
- Universities with colleges of engineering.
- Used Hondas or Toyotas for sale
in the Tuscaloosa area.
- Sources to supply concrete for the
building you're planning to build in
Gadsden.
- Sources to supply rebar and steel
beams for the same building.
- People named (pick your favorite
name: "John Brown" for example)
who live in Mobile.
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