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.