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Internet Applications

Ahmed M. Zeki

Sem – 2

2000/2001

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Chapter 1

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Programming Languages

Data Information

Hardware

Software = Programs

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Types of Programming Languages

1. Machine Languages Machine languages are machine

dependent. Machine languages are not people oriented. Machine languages generally consist of

strings of numbers (ultimately reduced to 1s and 0s) that instruct computers to perform their most elementary operations one at a time.

Example: +1300043774 +1200348372

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2. Assembly Languages English-like language. An assembler converts it to machine

language. Still difficult. Example: LOAD ACC ADD 5

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3. High-Level Languages Single statement could be written to

accomplish substantial tasks. The translator programs that convert

high-level language programs into machine language are called compilers.

Instructions look almost like everyday English.

Example: Total = Account1 + Account2

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History of the Internet The Internet has it roots in a networking

project started by the Pentagon’s Advanced Research Projects Agency (ARPA), which is an agency of the US Department of Defense.

ARPA’s goal was to build a network that: Would allow scientists at different locations to

share information and collaborate on military and scientific projects.

Could function even if part of the network were disabled or destroyed by a disaster such as a nuclear war.

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That network called ARPANET, became functional in 1969, effectively linking together scientific and academic researchers in the US.

The original ARPANET was a wide area network consisting of four main computer. Each one is located in one big university and served as the network’s host nodes*.

* In a network, a host node or host is any computer directly connected to the network. A host often stores and transfers data and messages on high speed communications lines and provides network connections for other computers.

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As researchers and other realized the great benefit of using ARPANET’s electronic mail to share information and notes, ARPANET underwent phenomenal growth.

By 1984, ARPANET had more than 1000 individual computers linked as hosts.

Today, more than 35 million hosts are connected to the Internet.

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To take further advantage of the high-speed communications offered by ARPANET, some organizations decided to connect entire networks to ARPANET.

In 1986, the National Science Foundation NSF connected its huge network of five supercomputer centers, called NSFnet, to ARPANET. This configuration of complex networks and hosts became known as the Internet.

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Because of its advanced technology, NSFnet served as the major backbone * network on the Internet until 1995.

* A backbone is a high-speed network that connects regional and local networks to the Internet; other computers then connect to these regional and local networks to access the Internet. A backbone thus handles the bulk of the communications activity or traffic on the Internet.

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In 1995, NSFnet terminated its backbone network on the Internet to return its status to a research network. Since then a variety of corporations, commercial firms, and other companies run backbone networks that provide access to the Internet.

These backbone networks, along with telephone companies, cable and satellite companies, and the government all contribute toward the internal structure of the Internet.

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Many donate resources, such as servers, communication lines and technical specialists making the internet truly collaborative.

The Internet remains a public, cooperative and independent network. Although no single person, company, institution or government agency controls or owns the Internet, several organizations contribute toward its success by advising, defining standards and addressing other issues.

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Browsers A browser is a program that enables you

to view pages on the Internet. The two most popular browsers are

Microsoft’s Internet Explorer and Netscape’s Communicator.

Portable Language: Programs written in portable languages can run on many different computers.

Browser Portability: (Many browsers, versions and platforms) --> Using portable languages such as: HTML, JScript and SQL.

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To connect to the Internet, you will need a computer, a modem and Internet software.

The first step to getting onto the Internet is registering with an Internet Service Provider (ISP). Once you have signed up for your account (with your ISP), you should start the Internet Connection Wizard.

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You will get the best browsing performance when viewing the Web if you have as few programs as possible open on your system. Why?

To maximize the amount of memory available for your browser and its extensions to use.

The URL (Uniform or Universal Resource Locator) describes the location of the file your browser is displaying or loading.

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The URLs of the files viewed on the Web normally begin with http:// (hypertext transfer protocol).

A hyperlink is a visual element on a Web page that, when clicked, loads a specified URL into the browser window.

IE5 has built-in controls that record the sites that your browser has loaded, called the history.

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The simplest way to use the history is to use Back and Forward buttons.

On pages that are frequently updated, you may want to click the Refresh button. This action will cause your browser to reload the current URL.

Clicking an email address will load your default email program and open a message addressed to the specified recipient email address.

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If a URL addresses a file that the browser is incapable of loading, then you will be given the option to download the file (which means making a copy of it on your computer).

You save an image on the page by right clicking it and choosing from the options box that pops up Save Picture As….

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A nice new feature of IE5 is the address bar AutoComplete: when you start entering a URL stored in the history, a scrollable menu appears listing all URLs in the history that are potential matches for the URL you are entering.

This feature is also useful with forms (eg. entering usernames and passwords).

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The interactive history bar can be activated by clicking the button marked History in the row of buttons at the top of your browser window. This shows you your history over the past month chronologically and alphabetically.

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Search Engines Searching the Internet is usually

done through sites called search engines.

These search engines constantly explore Web pages all over the Internet through hyperlinks, recording characteristics of the sites they encounter.

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Solution for many problems you might encounter while using Internet Explorer are accessible through an online Tour and a built-in Help feature, each accessible through the Help menu.

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IE5 provides a mechanism called Favorites that allows you to save the URLs of sites, to give you easy access to those sites in the future.

When you visit a site that would you like to save as a favorite, select the Add Favorites … option in the Favorites menu. The site will be listed in the Favorites menu, identified its title.

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Through the Organize Favorites dialog box, you can rename favorites, create folders to organize favorites from these folders and delete favorites.

Downloading is typically initiated on a Web page by clicking a hyperlink targeted at a file on a Web or FTP site.

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FTP stands for File Transfer Protocol, a popular method for sending files over the Internet. The address of an FTP site begins with ftp://.

When you point your browser to the URL of an FTP sites, you will be presented with the contents of the specified directory.

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Many FTP sites on the Web have restricted access. This means that only people with specific user-names and passwords will be allowed to access the FTP site.

Sending a file to another location on the Internet is call uploading.

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Electronic mail, or email for short, is a method of sending formatted messages and files over the Internet to the other people.

When you sign up with an Internet Service Provider, you are given an email address in the form of username@domainname.

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Popular email programs include Microsoft Outlook, Netscape Messenger, and Eudora.

Outlook Express allows you to manage more than one email account. You can add new accounts by clicking the Accounts option in the tools menu.

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Outlook Express provides an easy interface for managing your accounts and messages. When you receive messages you have the option of saving them on your hard drive for later access. Outlook Express allows you to create folders for saving messages.

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Outlook Express checks for new messages several times per hour. When a new message arrives it is placed in your Inbox.

To set new entries for the address book, click on the Addresses button at the top of the window, or click on the Address Book….entry in the Tools menu.

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All entries in the Address Book are listed in the main dialog box. You can send a message to anyone in your list by highlighting that person’s entry, clicking the Action button, then clicking Send Mail.

The only mandatory property is the email address of the recipient, which is put into the To: field.

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When you have entered your message, click Send, and your message will be on its way to the designated recipient.

Using newsgroups, a person can post messages to online viewing areas. Other people can then view these messages, reply to them and post new messages.

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Outlook Express has a built-in capability to view Newsgroups. You must first register your newsgroup server settings with Outlook Express.

A subscribed newsgroup is comparable to a favorite site in IE5. The program will remember its location and give you easy access to its contents at the click of a button.

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To search through and subscribe to newsgroups, click the Newsgroups button on the top of the main screen. Outlook Express will then download a list of all available newsgroups.

To view the contents of a newsgroup, double-click on its entry.

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IE5 provides NetMeeting and Chat for communicating with people over the Internet via live written text and other media.

You can use NetMeeting to communicate with groups of people over via textual and visual aids.

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Microsoft Chat is similar to NetMeeting in its basic layout procedures, though it is simpler and offers a more casual atmosphere than NetMeeting.

Be cautious about revealing your true identity and contact information in NetMeeting and in Chat.

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IE5 is installed with a myriad of default settings, called Internet Options, that affect the way sites are displayed.

Toggling off the Load Pictures setting will stop the browser from loading images from a Web page and so save time.

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Under the Programs tab, you can specify the default programs you wan IE5 to use for such common Internet procedures as viewing newsgroups and sending email.

Under the Security tab, you can specify the level of cautious IE5 should exercise when browsing sites in general and also for specific sites.

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In the General options tab, you can specify a home page, which is the Web site that is loaded when IE5 starts.

The most recent version of RealPlayer plays live or prerecorded sound files and videos.

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The Adobe Acrobat reader is multiplatform software plug-in that is capable of showing documents online without changing the original format of the document.

Macromedia Shockwave is a plug-in that when installed and run with a site designed to take advantage of its capabilities, can produce breath-taking effects.