Computer Programming Concepts and Visual Basic David I. Schneider

To access an initial Web page, you must specify an address called a Uniform Resource
Locator (URL). You can do this by typing in a URL (or Locator) text box found toward the
top of your browser or by typing in the dialog box that appears when selecting the Open command
from the File menu or clicking the Open button in the toolbar.
■ A WEB BROWSER WALKTHROUGH
1. Connect to the Internet either through your commercial service provider or by
using your school’s network computers.
2. Start up a Web browser such as Netscape, Mosaic, Lynx, or Internet Explorer.
3. In the Location or URL text box toward the top of the browser, type in
http://www.whitehouse.gov
4. Press Enter.
5. Click on one of the highlighted or underlined phrases (links) in the document.
The page associated with this link will load. For instance if you click on “The
President & Vice President:” you will see pictures of them and their wives along
with information on how to send e-mail to them.
6. Click on some other links to see what pages are brought up.
7. When you are through exploring the White House page, try other URL addresses
such as:
Microsoft’s Visual Basic Page http://www.microsoft.com/vbasic
Carl and Gary’s Visual Basic Page http://www.apexsc.com/vb
Prentice-Hall’s Home Page http://www.prenhall.com
The remainder of this section is devoted to using Visual Basic to create our own Web
browser. The requirements for this task are as follows:
1. A modem, or a direct internet connection.
2. A Windows TCP/IP stack, usually referred to as a Winsock. (If you are using an
Internet connection through your school, it almost certainly meets this requirement.
If you are using a dialup connection from home, the Microsoft hookup to
the network that comes with Windows will work.)
3. Microsoft Internet Explorer 4.0 (or higher) must be installed.
To Add the Web Browrser Control to Your Visual Basic Toolbox
1. Invoke Visual Basic.
2. Press Ctrl+T to invoke the Components dialog box.
3. Click the check box next to Microsoft Internet Controls.
4. Click the OK button.
The Web Browser icon should now appear in your toolbox.
EXAMPLE 1
The following program creates a simplified Web browser. (Before running the program, be sure you are
connected to the Internet as discussed above.) The primary task of the program, accessing the Web, is
accomplished with the single statement
WebBrowser1.Navigate(txtURL.Text)
Accessing the Internet with Visual Basic 393
The On Error Resume Next statement specifies that when a run-time error occurs, control goes to the
statement immediately following the statement where the error occurred where execution continues. This