Unidad VII
Parte “a”
Lectocomprensión y análisis
de textos varios
Dear students from First Level of English for
Information Technology:
This is the last reading comprehension exercise of the
current year. I wish you good luck at your final exams; and I hope you have
fully profitted from our lessons this year...
I wish you a Merry Christmas and Happy New Year!
How
the Web Works
The "Internet" and the "World
Wide Web" are not synonymous.
Although the two terms are often used interchangeably, they actually
describe two discrete functions. While
the Internet acts as a facilitator for the exchange of information, the web
itself contains merely one type of information which can be transported over
the Net.
The web is a collection of interlinked
documents written in a common format known as hypertext markup language, or
HTML. Individuals can use personal
computers to gain access to the web via the Internet, by using clients known as
web browsers. The most common web
browsers in use today are Netscape's Navigator and Microsoft's Internet
Explorer. A user can locate a
particular HTML document, or web page, by entering its address, or URL, into
the web browser.
A Uniform Resource Locator, or URL, consists of
an Internet Protocol prefix, generally HTTP, and an Internet domain name, as
well as any file or folder names which refer to a specific document
location. Take a moment to look at the
URL for the current page. The URL tells
you that this page is in the "eon.law.harvard.edu" domain, in the
directory "property," in the folder "introtech," and that
the name of the document itself is "webworks.html."
When an individual "calls up" a URL
through his web browser, the web browser first has to resolve the address it
has been given. In this case, your web
browser will first look for the computer which stores information on the
".edu" domain. The domain
name system is structured as a hierarchy of names, and .edu is what is referred
to as a gTLD, a generic top level domain name.
A second level domain name consists of a top level domain name, with
another name preceding it, separated by a dot.
For example, "harvard.edu" is a second level domain name. The more "dots" which precede the
top level domain name, the further the hierarchy is stretched. In the case of the fourth level domain name
"eon.law.harvard.edu", your browser will first "ask" the
computer containing the ".edu" registry where "harvard" can
be found. Having located "harvard,"
the browser will ask the directory at "harvard" where "law"
can be found, and so on, until it reaches the location you have requested. The browser then requests this information
from the computer on which it is stored, and the information is sent back to
the web browser, which displays it on your screen.
In addition to entering a URL directly into a
web browser, search engines and directories are available to assist individuals
in sorting through the millions of web pages accessible from the web. The very popular Yahoo! is an example of a
web directory. Common search engines
include AltaVista, Excite, and WebCrawler, among others. There are also search engines designed to
search for information on specific topics, such as GOVBOT which searches for
government documents, and there are search engines designed to search multiple
search engines at once, sometimes called "meta-searchers".
Search engines use several methods for
obtaining information on particular sites on the web. One of the most common tools is the use of a spider which
"crawls" across the web recording incidences of search terms
occurring in documents. This
information, in turn, assists search engine administrators in classifying
documents. No two search engines are
likely to produce identical results for the same search query because of the
differing methods employed by administrators in gathering and classifying
information about specific web sites.
(Second Reading Comprehension Exercise)
COBOL is a rigid language,
and you must comply exactly with the layout and syntax rules for your programs
to compile cleanly, and run properly. The structure may seem lengthy or wordy
at times, but when you have worked in COBOL a few years you will find this is a
virtue, not a fault.
Every COBOL program has four division names
that always appear in the same order. They must be spelled exactly as shown and
followed by a period. The divisions (in order) are:
IDENTIFICATION DIVISION.
ENVIRONMENT DIVISION.
DATA DIVISION.
PROCEDURE DIVISION.
The IDENTIFICATION DIVISION includes
information about the program, what it is called, who wrote it, and when it was
written. None of these entries is mandantory, but I recommend you use them
along with a statement telling what the program does. (See the example below)
The ENVIRONMENT DIVISION includes information
about the computer you are running on, where to find the files, and special
information that may be needed for this program. We will look at each of these
features as we need them, for now just put the division header. (See the
example below)
The DATA DIVISION is a repository of
information about the data your program uses. This is the real power of COBOL,
the ability to explicitly define and describe the data. We will get into the
structure later, for now just use the division header. (See the example below)
The PROCEDURE DIVISION is where the work gets
done. The COBOL verbs are used here to tell the computer how to manipulate the
data you have described. In the example I have included a paragraph name, a
DISPLAY statement to print a message on the screen, and the mandandory STOP RUN
statement to end the program. Please note, the paragraph ends with a period.
Rules for defining a COBOL word.
The selection of variable names and paragraph
names is left to the programmer. You may use any names you wish, as long as
they comply with the rules for COBOL words:
Up to 30 characters long
Any letter of the alphabet, and the numeric
digits may be used
Hyphens may be used with the word for clarity,
but not on either end
Words reserved for use by COBOL may not be used
Paragraph names may be all numeric digits,
other names should contain at least one letter.
Compilers vary somewhat on how critical it is
to use certain columns when writing your programs. All COBOL compilers will
accept programs that use the stardard sections on each line, that is:
Section A is columns 8 through 11,
Section B is columns 12 through 72.
Columns 1 through 6 are used for line numbers,
and column 7 is reserved for special use. For now, put an astrisk in column 7
to include a comment line.
All Divisions, Sections, and Paragraphs,
including File Descriptions and Record Names, must begin in Section A.
Everything else must be in section B. Do not go past column 72, everthing past
column 72 is usually considered to be comments for program identification and
ignored by the compiler.