Search Engines and Directories
According to Google, there are over three billion files stored on the World Wide Web, and thousands more are being added daily. With that many pages, your odds of locating a single Web page by chance are worse than hopeless.
Fortunately, the World Wide Web is filled with a large assortment of search engines and directoriesdesigned to help you locate the files you need.
A search engine, also known as a "spider" or "crawler," is a computer that continuously and rapidly explores the World Wide Web, scanning all the documents it can find as quickly as possible. The search engine then stores all the words on all the pages it has visited in a large database.
A directory is a comprehensive, categorical list of files on the World Wide Web. Unlike search engines, directories are created and maintained by humans. In order to be listed, the creator of a Web page must submit the address of his or her work to the directory's caretakers. If the people in charge of the directory consider the document worthy of listing, it will be assigned to an appropriate category within the directory. You can locate documents in the directory by choosing only the document categories that interest you.
So what is the difference between a search engine and a directory?
Well, search engines require little human intervention to do their work. They are fast and fully automated. Search engines typically contain information on millions of documents, and no judgment is made as to their suitability for inclusion in the search engine database. If the search engine finds the document, it will be listed.
Directories, on the other hand, are managed by people. The caretakers of the directory must painstakingly classify each document to be listed in the directory. The decision to include or exclude a document is often the subject of lengthy debate. Because of the time and labor involved in adding a new directory listing, directories typically hold far fewer documents than do search engines. However, the average document listed in a directory is often better-designed and more informative than the average document listed in a search engine.
A Few Search Engines and Directories:
| Rank | Name | URL | Type |
|---|---|---|---|
| 1 | http://www.google.com | Search Engine | |
| 2 | Yahoo! | http://www.yahoo.com | Both |
| 3 | Windows Live Search | http://search.msn.com | Both |
| 4 | Ask | http://www.teoma.com | Search Engine |
| 5 | Open Directory | http://www.dmoz.org | Directory |