Day 2 -- The Essence of VBScript




DAY 2
The Essence of VBScript




CONTENTS


What Is VBScript?
What Can VBScript Do?
Some Examples of VBScript in Action

Example #1: The DiscoTec Web Page
Example #2: The Pace Pal
Example #3: The Bird Feeder

Learning VBScript
Security and VBScript
VBScript Versus Visual Basic and Visual Basic for Applications
Summary
Q&A
Workshop
Quiz



You've probably seen and heard a lot of excitement surrounding
Microsoft's new Internet development platform and suite of Internet
tools. This new technology is indeed very exciting to almost everyone
in the computer industry today. When any new technology emerges,
it takes time for the technology to "settle down." The
creators of the technology first fill the airwaves with hype and
send out beta copies of what they're working on. Finally, a solid
release of the product emerges, and builders can actually start
making full use of the technology that has been discussed for
so long. After that, it takes a certain amount of time for the
intended users of that technology to adjust to how it works and
how to use it.

If you've heard a lot about VBScript and what it can do but you've
been bombarded with so much new information that it's hard to
absorb it all, you're not alone. Today's lesson was written for
you! It will clearly and methodically explain to you the essence
of VBScript-that is, what it's all about. Rather than drop a load
of technical bombs that only a rocket scientist can understand,
I explain in plain English why VBScript is exciting and what it
can do for you. Here is a list of some of the questions I will
answer today:

What is VBScript?
What can it do?
Is VBScript easy to learn?
What do I have to know to use VBScript?
What software or tools do I need to use it?
How secure is VBScript?
How does it compare to Visual Basic and Visual Basic for Applications?


You will also find several examples of Web pages that use VBScript
so that you can see just how powerful and revolutionary VBScript
really is. Think of today as a friendly introduction to the world
of Internet programming with VBScript. You won't get hit with
a lot of techno-jargon in this lesson, but you will see just what
you can do with this new and exciting language.
What Is
VBScript?

When the World Wide Web first became popular, HTML was the only
language programmers could use to create Web pages. They soon
learned that HTML was quite limited in what it could do. It presented
the user with a "page" of information, but the Web page
and the user had a limited amount of interaction; it was like
reading the front page of a newspaper on a computer monitor. Now
most computer users, whether they use Windows, Macintosh, UNIX,
or a combination of the three, are accustomed to graphical applications
that provide interaction. They're used to clicking buttons, entering
values into text boxes, and choosing from menus. The only way
to get useful work done with a computer is to interact with it.
The first generation of Web pages provided information to the
users, but the users could not interact with the Web the way they
could with their word processors. The interaction available to
them required that they send the data to the server, where all
the "smarts" were provided. The results were then sent
back to the Web page. This interaction required a great deal of
extra time, effort, and overhead, and the interface presented
to the user was very constrained compared to the applications
they were accustomed to using.

Fortunately, the builders of the Internet and the World Wide Web
could see these limitations. They soon realized that if the user
was denied the capability to interact with the Web page, it would
become little more than a collection of information, much like
a library of books. Although that collection is very useful, users
demand more from their computers than what they could get elsewhere.
The capabilities of HTML began to grow and become more powerful.
Soon, designers began to realize that they needed more than just
HTML to make the Internet accessible and useful to the masses.
Corporations who wanted to develop enterprise solutions or make
money off the Internet also began to put pressure on designers
to give them something more.

These demands have resulted in a continued improvement of HTML,
the emergence of browsers such as Internet Explorer that tap into
the power of HTML, and the advent of scripting languages such
as VBScript. To understand what a scripting language is,
think of HTML as an airport runway. You can get where you need
to go on the ground, but you have an entire sky to travel through
above you. Scripting languages are like the airplanes that make
it possible for you to lift off the ground. They extend the capabilities
of the Web much like an airplane extends the capabilities of man
so he can travel through the sky. A script lets the page become
an active, dynamic piece of software rather than a static piece
of content.

A scripting language is a type of programming language
used to provide control in another host environment. It is interpreted
rather than compiled. This means that a program built with a scripting
language must be run in the environment that contains the scripting
language's interpreter and cannot be run as a stand-alone application.

HTML can't interpret a scripting language itself, but it knows
enough to call the interpreter of the scripting language to carry
out the interpretation. This enables you to go above and beyond
HTML, using any browser-supported scripting language you want
to extend the Web page. With scripting languages such as VBScript,
the limitations of HTML disappear; the opportunities are now limited
only by the scripting language itself! Although other scripting
languages are bound to emerge, two widely used scripting languages
in existence today are JavaScript and VBScript. Both of these
languages can be embedded in a Web page, and if the browser supports
them, they provide the path to smart, active programs that are
part of that page.

With HTML, you can place controls such as buttons and text boxes
on a Web page. Without a scripting language such as VBScript,
any actions the user takes on the controls of a Web page must
be sent back to the Web page server. They cannot be handled at
the user's computer. Furthermore, the amount of control and flexibility
available without a scripting language is very limited. With VBScript,
you not only can link up to controls on the Web page, but you
can also write code to respond to what the user does with those
controls. If, for example, a Web page contains a command button,
you can write VBScript code that gets executed immediately when
the user clicks that button. An example of such a code segment
might look like the following:

Sub Button_OnClick
   ' The message below will be displayed when the
user clicks on the button
   Msgbox "This button was clicked"
End Sub


Button is the name of the
button, and OnClick is the
event that the user causes to occur when he or she clicks the
button. You can supply code, such as the message statement shown
here, to be executed every time the user clicks the button. The
MsgBox statement, which will
be covered in more detail on Day 14, "Working
with Documents and User Interface Functions," simply presents
a message box to the user. This example is simple, but it shows
how VBScript code can give a page the capability to respond immediately
to user actions. Rather than present the user with a lifeless
Web page, VBScript breathes life into Web pages, making them dynamic,
responsive, intelligent, and interactive.
What
Can VBScript Do?

VBScript lets the user interact with a Web page rather than simply
view it. There are many possible scenarios for this interaction.
For instance, this capability to interact makes it possible for
Web pages to ask questions and respond to how the user answers
them. VBScript can then take input from the user and check the
data to make sure it is valid or meets certain criteria. Then,
it can put an Internet server to work either by actually storing
the data or causing some action to take place on the server based
on the information given. For example, VBScript could respond
to a user's request for an airline reservation. It could read
in the data, check to make sure all fields have been filled out
and that the phone number and zip code are in a valid format,
inform the user of the estimated price, and then notify the server
of the reservation. All these tasks could be carried out by the
code in the Web page that was downloaded across the Internet as
it sits on the user's client pc. The server in turn would make
sure there is an open slot for the customer for when he wants
a ticket and then book the flight and get tickets out in the mail
to the customer.

Interaction can also be helpful in advertising services or products
to a user. Through an interactive survey, you can target exactly
what the potential customer is looking for. Imagine, for example,
a series of Web pages that ask you all kinds of questions about
your dream car, along with what you want to spend, and then give
you a series of vehicles that match your criteria. Rather than
dealing with a pushy salesperson, you can take your time on the
Internet and carefully research the facts. When you go to the
dealer, you can be specific and avoid having to wrestle with a
salesperson.

In this type of example, VBScript can play an important role in
many ways, including validating data, pricing, providing impressive
multimedia feedback, and initiating data storage. You can use
VBScript to sequence the questions based on responses. For example,
if a user indicates he wants a van, VBScript can generate an input
box asking him how many seats he wants. Throughout the data entry
process, VBScript can make sure the user enters a valid order,
address, and method of payment, and it can even present him with
a pie chart of how much of the cost goes toward the base price
and how much goes toward extras. The generation of the bar graph
can be accompanied by the sound of a trumpet fanfare. The possibilities
are endless.

VBScript can also perform calculations on data, such as computing
the cost of an item after taking into account the sales tax. Often,
calculations on a Web page are useful in providing the user a
way of figuring out what he wants to do, or perhaps giving the
user some sort of result he is seeking. In this way, your Web
page enables the user to walk away with more than a mere presentation
of fixed information. You could, for example, allow the user to
choose what luxury items he wants on a car and, as the luxury
items are selected, keep adjusting the overall cost. The user
could spend as much time as he wants and choose as many combinations
as he likes until the perfect combination of features versus price
is calculated. How often can you do that at a car dealership?

By utilizing other technologies such as CGI, VBScript code can
even initiate order placement for that item in the computer of
the company that is selling the item. If the script determines
all criteria for a valid order are met, it can place the order.
Otherwise, it can generate an error message. Using script logic,
it could even place the order on a different server, depending
on which type of car was requested, and provide an estimated time
frame for delivery based on a rules-of-thumb calculation for that
type of order. VBScript can carry out virtually anything you can
think of that a traditional application could carry out. Even
in areas where VBScript can't directly cause some action such
as writing to the server database or playing a sound file, it
can achieve these results indirectly by making use of CGI scripts
or sound controls, for example. VBScript becomes the application
behind the Web page that the user views and interacts with.

Another important aspect of this programming model is that you
can also use the intrinsic HTML form controls and Microsoft's
ActiveX controls with VBScript to give Web pages an attractive
look and feel. Intrinsic HTML form controls, which are discussed
in Days 8, "Intrinsic HTML Form Controls,"
and 9, "More Intrinsic HTML Form Controls,"
provide the Web page developer with a standard set of controls
similar to those used in the Windows environment. ActiveX controls,
which are discussed in Days 10, "An
Introduction to Objects and ActiveX Controls," and 11,
"More ActiveX Controls," consist of useful controls
such as graphs and charts, labels that can be rotated 360 degrees,
a timer control that enables you to time events on Web pages,
a pre-load control that lets you load bitmaps and other time-consuming
parts of a Web page before it gets displayed, and so on. These
controls further enhance Web pages to give them a professional,
polished look. They also provide pages with smarter interactive
response because the control characteristics can be controlled
dynamically by a VBScript program. For example, your code can
generate a new graph based on the user's input on a page.

Designers can now place ActiveX custom controls directly on Web
pages in the Windows environment. OCXs, the forerunner of ActiveX
controls, have made languages such as Visual Basic incredibly
powerful because programmers can take an OCX that performs some
task for them, such as displaying a calendar on the screen, and
"glue" that component into the application. They don't
have to create code to put a calendar on the screen; the OCX already
does that for them. Likewise, programmers can now put an ActiveX
control on a Web page and access the control through VBScript.
The goal is to make Web pages capable of what a regular Windows
application can do. There are some restrictions on what can be
achieved due to security (addressed in Day 21,
"Security, Stability, and Distributed Source Control Issues"),
but the technology is rapidly moving in that direction. The Internet
might someday be the "platform" that all our applications
rest upon and work within.

In addition to using ActiveX controls, the current beta version
of VBScript can also tie other applications into a Web page through
OLE automation technology. For example, with the appropriate object
declarations, you could tie an Excel spreadsheet into your Web
page so that when the user clicks on the spreadsheet, Microsoft
Excel runs and loads the spreadsheet for you to edit. Now, not
only can you work within a Web page, but you can bring other applications
into the Web page that can be activated at the click of a mouse
button. This capability to tie other applications to a Web page
lets you show virtually anything on a Web page; the only requirement
is that the applications you want to link to a page support the
OLE automation standard.

With VBScript and the right controls, you can even create 3-D
animation effects, making your Web page come alive with moving
objects in response to certain events. You can use animation to
make cars careen across the screen, butterflies fly across your
Web page, or arrows move and point to where you want the user
to interact with the Web page. Although this might seem quite
esoteric, animation does help attract the users' attention and
makes them feel like they're working with a living, breathing
entity. They're more likely to explore your Web page and stay
tuned in to it when a lot of neat animated effects grab their
attention.

The component incorporation capabilities of VBScript introduce
some special considerations and trade-offs in page design. A Web
page that includes VBScript code that interacts with Excel and
Microsoft Word, as well as the currently Windows-specific ActiveX
controls, is not one that can be fully distributed over the Internet
with all the support software. It also might not run easily on
any platform and operating system that could use it. On the other
hand, such a page would be very powerful for Internet or intranet
users who fit the target user profile. At the other end of the
spectrum, a page that incorporates VBScript to carry out a series
of calculations can be a perfect Internet citizen, fully downloadable
over the Internet and running on a variety of platforms and operating
systems. In this respect, the flavor and tone of your VBScript
Web pages depends largely on how you want to leverage it. This
is an important theme that we discuss throughout the remaining
days' lessons.


Note


Microsoft may support ActiveX controls on other environments such as the PowerMac in the future, but they are currently supported only in the Windows environment.





In order to gain a more complete understanding of how VBScript
works with browsers, controls, and objects, consider the simple
model shown in Figure 2.1.

Figure 2.1 : A simple diagram of the VBScript-host model.

In this model, the innermost box is where the core language of
the scripting language resides (in this case VBScript). Other
languages such as JavaScript could be placed in this box as well.
This core language cannot be run alone-it must be provided with
a host that supports it. This leads to the second, larger box
in the figure.

The second, larger box represents the host program that runs the
scripting language. At the time of this printing, VBScript could
be used with Microsoft Internet Explorer 3.0, which in this case
would be the host. While the host may vary, the core VBScript
language stays the same. In other words, the VBScript language
is the same regardless of the host, whether it be Internet Explorer
or any other product. The host may contain a set of internal objects
and controls, such as the case with Internet Explorer 3.0. For
example, you can access Internet Explorer's document object
from VBScript, which will be discussed further on Day 14.
You can also access Internet Explorer's intrinsic HTML controls
through VBScript (this is discussed on Day 8).
Any scripting language, such as JavaScript, has the same type
and level of access to these browser objects and controls as does
VBScript.

The third box represents components external to the browser but
available in the Windows environment, such as ActiveX controls,
OLE controls, and objects such as OLE automation servers. VBScript
can access these controls and objects through the browser, as
illustrated by Figure 2.1. In order for VBScript to access a control
at this level, it must be linked through the host. Each link of
the chain must be complete before VBScript can access any objects
or controls throughout the chain. Since the browser is a secure
environment, the user will be presented with appropriate warnings
before a control is used by a script if default browser options
are in place.

It's important to remember that any scripting language operates
using this model. JavaScript, another powerful scripting language,
would occupy the same position in the figure as VBScript does.
This means that any scripting language has access to the browser's
controls and objects as well as the system's controls and objects
if supported by the browser.

The variety of controls and technologies that surround the World
Wide Web is likely to increase dramatically over the next several
years. Although it can be quite dizzying to keep up with the changes
and new controls on the market, it's an exciting time to be a
part of the Internet revolution. Now that you have a glimpse of
the power of VBScript and the technologies that surround it, take
a look at the examples in the next section. They will help you
see some of what VBScript is capable of!
Some
Examples of VBScript in Action

To help you appreciate and understand the power that VBScript
gives you, I provide three simple examples in this lesson. Each
example is on the CD-ROM that accompanies this book. You might
want to load them into your browser and take a look at them for
yourself. All of the examples presented here are very simple,
but they help give you a taste of what lies ahead for you in building
your own Web pages.


Note


You can run samples in this book over the Internet as well as from the CD-ROM provided with the book. Refer to Appendix B, "Information Resources," for details on where to find the samples on the World Wide Web.




Example #1: The DiscoTec
Web Page

Imagine, for the moment, that you're the proud owner of a music
store, and business is booming. You're always interested in more
business, and you see tremendous potential in the Internet to
help you sell your product. In fact, you want to do more than
simply advertise; you want your customers to be able to figure
the cost of the music they want to order over the Internet! This
first example shows what you can do to make that possible. Take
a look at the Web page shown in Figure 2.2, where you see a "costing
form" page that lets the user calculate the cost of an order
of music.

Figure 2.2 : The Disco Tec Web page.

This page appears to the user after you have presented him or
her with one or more pages showing the selection of music you
offer. You could even get fancy and show a picture of each album
cover and, when the user clicks on the cover, play a sample of
the music contained on the album. You will see more about the
concepts of using controls for such purposes on Days 10
and 11.

As you can see, the user enters his home state along with the
number of cassettes or compact discs he wants. Then he clicks
the What's the Cost? button. When the user clicks this button,
the Web browser initiates VBScript code that calculates the cost
for shipping and handling, adds in the sales tax, and presents
the user with the total cost.


Note
This Web page, named discotec.htm, can be found on the CD-ROM that accompanies this book.




Listing 2.1 shows the Web page source code, which includes the
VBScript code that gets executed when the user clicks the What's
the Cost? button.


Listing 2.1. The HTML source code for the DiscoTec Web page.




<HTML>

<HEAD>
<TITLE>The DiscoTec Example</TITLE>
</HEAD>

<BODY>

<H1>
<A HREF="http://www.mcp.com"><IMG  ALIGN=BOTTOM

SRC="../shared/jpg/samsnet.jpg" BORDER=2></A>

<EM>The DiscoTec Music Company</EM></H1>
<HR>

<H2>What's It Gonna Cost Me?</H2>
<P>To determine the cost of an album, enter the order number
of the album
you're interested in followed by the quantity desired. Cassettes
cost
$15.00 each, and compact disks cost $25.00 each. Residents of
California must
pay an additional sales tax of 6%.

<PRE>
     The State you live in: <INPUT NAME="txtState"
SIZE=2>
       Number of Cassettes: <INPUT
NAME="txtCassettes" SIZE=5>
   Number of Compact Disks: <INPUT NAME="txtDisks"
SIZE=5>

</PRE>

<CENTER><B><INPUT TYPE=BUTTON VALUE="What's
the cost?" NAME="cmdCost">
</B></CENTER>

<PRE>
    Cost                    $<INPUT
NAME="txtCost" SIZE=10>
    Sales Tax (6% CA only)  $<INPUT
NAME="txtTax" SIZE=10>
    Shipping (12% of cost)  $<INPUT
NAME="txtShipping" SIZE=10>
<BR>
    Total Cost              $<INPUT
NAME="txtTotal" SIZE=10>
</PRE>

<HR>

<center>
From <em>Teach Yourself VBScript in 21 Days</em> by

<A HREF="../shared/info/keith.htm">Keith Brophy</A>
and
<A HREF="../shared/info/tim.htm">Tim Koets</A><br>

Return to <a href="..\default.htm">Content Overview</A><br>

Copyright 1996 by SamsNet<br>
</center>

<SCRIPT LANGUAGE="VBScript">
<!-- Option Explicit

   Sub cmdCost_OnClick()

      Dim State
      Dim Cassettes
      Dim Disks
      Dim Cost
      Dim Tax
      Dim Shipping
      Dim Total

      Cassettes = txtCassettes.Value

      Disks = txtDisks.Value
      State = txtState.Value

      If Cassettes = ""
Then
         Cassettes
= 0
      Else
         Cassettes
= CInt(Cassettes)
      End If

      If Disks = "" Then

         Disks =
0
      Else
         Disks =
CInt(Disks)
      End If

      If Cassettes + Disks = 0 Then

         MsgBox "You
must enter at least one cassette or disk."
         Exit Sub

     End If

     Cost = 15.00 * Cassettes + 25.00 * Disks


     If State = "CA" Then
        Tax = Cost * 0.06

     Else
        Tax = 0
     End If

     Shipping = Cost * 0.12

     Total = Cost + Tax + Shipping

     txtCost.Value = Cost
     txtTax.Value = Tax
     txtShipping.Value = Shipping
     txtTotal.Value = Total

   End Sub

-->
</SCRIPT>

</BODY>
</HTML>



If the code doesn't make any sense to you, don't worry-it doesn't
have to yet. You can see, however, that a fairly small amount
of code is needed to do the calculations for the total cost of
the items, and it's all accomplished on the user's computer. Without
a scripting language, this kind of application would be impossible
on the user's computer; the data would have to be transmitted
back to the server, calculated there, and sent back. That would
take considerably more time because of all the delay in getting
the information back and forth, not to mention the overhead required
to carry out the transaction.

One of the powerful benefits of VBScript is its capability to
ensure the validity of the data the user enters. Suppose, for
example, that the user enters a negative number for the quantity
of an item. Obviously, this is an invalid amount. Fortunately,
VBScript can validate the data the user enters. If, for example,
the user doesn't enter a quantity either for cassettes or CDs,
the message shown in Figure 2.3 appears when the user tries to
calculate the cost.

Figure 2.3 : What hapens when the user forgets to enter the quantity.

This example shows you how you can make a Web page intelligent
with VBScript. In addition to presenting a Web page that shows
simple text and graphics, you can also truly interact with the
Web page. Not only can you retrieve and process data entered by
the user, but you can also perform checks to make sure the information
he enters is valid, and if it isn't valid, you can take the steps
necessary to make sure he enters the information correctly.
Example #2: The Pace Pal


This next example of VBScript is very useful to a runner, jogger,
or walker. You can use the Web page in this example to calculate
your pace from a running, jogging, or walking workout. All the
user has to do is enter the distance traveled and the time it
took to travel that distance. Then, VBScript code calculates the
pace and displays it back to the user. Figure 2.4 shows the Web
page.

Figure 2.4 : The Pace-Pal Web page.

Figure 2.4 shows a text box where the user enters the distance
traveled. He must choose the units of travel as either miles or
kilometers. Notice the two special controls to the right of the
text box. You use these special controls, called radio buttons,
to limit the user to selecting one of the choices. VBScript can
interact fully with controls such as these. You are not merely
limited to text boxes and buttons as in the first example. Radio
buttons, along with other important controls, will be discussed
on Day 8.

Having entered the distance, the user then enters the time in
the designated text box. Once the data is entered correctly, the
user clicks the Display Pace button, which starts the calculation
of the runner's pace. The result is displayed in miles and kilometers
as shown on the page. This example once again shows you the benefits
of VBScript. The pace calculation can be done entirely on the
user's computer with no Internet involvement. Once the page is
loaded into the browser, VBScript does the rest. You could, in
fact, even disconnect from the Internet and use this page offline.



Note


This Web page, named pacepal.htm, is also on the CD-ROM that comes with the book.






This example shows you how you can design Web pages to assist
the user in some way. In a sense, a Web page can become an application
delivered over the Internet. Before the Web page phenomenon grew
so popular, you would probably write such an application using
C++ or Visual Basic. Then, you might distribute the application
as shareware. With the World Wide Web and VBScript, however, anyone
who uses the Internet has instant access to your application,
and it appears very attractively on a Web page. If you want to
share your application with friends across the country, it's much
easier for you to point them all to your Web page rather than
send each of them a copy of it.
Example #3: The Bird Feeder


The last example today is a simple Web page that provides assistance
to the user and helps advertise a product at the same time. This
Web page is targeted to your average cockatiel owner. It determines
just how much bird seed you need to feed your cockatiel each day
over the next month. By the way, this example is purely fictitious,
so please don't base your own cockatiel's diet on the results!
Figure 2.5 shows the Web page.

Figure 2.5 : The Bird Feeder Web page.

This simple Web page asks the user for the age, sex, activity
level, and weight of your cockatiel. Notice that when you enter
the sex of the bird, you can only choose Male or Female through
the use of the special radio button controls. When you enter the
activity level of the bird, you can choose from a variety of selections
that are contained in a special control called a list box.
The list box gives you the ability to select one of several choices,
but you cannot enter a new choice like you can in a text box.
On Day 8, you will learn more about list
box controls and how to use them.

When you click the Calculate button, VBScript performs some simple
calculations to determine the amount of bird seed required. The
formula used to calculate this amount is in no way scientific
and should not be considered valid if you want to use this on
your own bird. It's just a fictitious example to show you what
you can do with VBScript. Still, it shows you the potential of
providing this service to the public. If you were selling bird
seed, this Web page might be just enough of a convenience for
the user to click the handy little Order Seed button at the bottom
of the Web page!


Note


This Web page, named birdfeed.htm, is also on the CD-ROM that comes with the book.






These examples show only a fraction of what you can do with VBScript.
All these examples involve taking input from the user, processing
that input, and providing the results back to the user on the
Web page. As you progress through the book, you will see how to
use ActiveX controls, OLE, Java applets, CGI, animation, sound,
and other useful features to make Web pages even more powerful.
If you've used the Internet for a while, you can begin to appreciate
just how useful VBScript really is. We've come a long way from
the static text-and-graphic Web pages, and the journey has only
begun.
Learning
VBScript

VBScript is much easier to learn than programming languages such
as C/C++ and other scripting languages such as JavaScript. Derived
from the Visual Basic language, VBScript should not be difficult
for anyone who has done computer programming before. If you have
done no programming whatsoever, it might take you a bit more time
to come up to speed, but rest assured-you will. The most effective
way to learn VBScript is to read this book and practice creating
your own Web pages with VBScript. Reading a book is never enough
unless it is accompanied with experience and practice. Fortunately,
this book doesn't just tell you how to use VBScript; it shows
you how and gives you exercises to try on your own. You can count
on the fact that you will get knowledge and experience as a result
of working through this book.

You need to know how to do two things before you begin to write
VBScript code. First, you need to know how to use a browser and
navigate through the World Wide Web. Second, you should be somewhat
familiar with the Microsoft Windows environment and how to navigate
your way through a Windows application, or have equivalent experience
in another graphical user interface (GUI) environment. If you
want to use VBScript to design Web pages, chances are you already
have a browser and are quite capable of using it. You are probably
very familiar with GUI applications as well. If so, the only remaining
obstacle is learning how to program with VBScript. The more programming
you have done in the past, the better you'll pick up on VBScript,
especially if you've written programs using Visual Basic or Visual
Basic for Applications. If you've never written a computer program,
don't worry: You don't need a programming background to use this
book.

To start working with VBScript, you need several things: a browser
that supports VBScript, the VBScript run-time interpreter, access
to required controls, and an editor or other tool to help you
assemble Web pages or edit HTML documents. The first step is to
obtain a browser that includes VBScript run-time support if you
do not already have one. Microsoft's Internet Explorer 3.0 was
the first publicly available browser that provided support for
VBScript. This browser is available free of charge from Microsoft.
At the time this was written, you could obtain Internet Explorer
3.0 from http://www.microsoft.com/ie.

The VBScript run-time interpreter will usually be included with
any browser that supports VBScript. This is the case with Internet
Explorer 3.0. If you obtain the browser and install it, you have
everything you need to run VBScript, including the run-time interpreter.
No separate installation is required to provide run-time capabilities.
You don't need to obtain any other pieces. However, you might
want to refer to the location http://www.microsoft.com/vbscript
if you want a general description of run-time capabilities beyond
that provided in this book. The run-time interpreter for VBScript
is license free, just like Internet Explorer. Even if other browsers
incorporate the VBScript run-time interpreter, Microsoft does
not charge a licensing fee to the end user or the company that
produces the browser. Therefore, it is a safe bet that the VBScript
interpreter will be widely distributed with most browsers in the
future.

If you've obtained Internet Explorer 3.0, you're nearly all set
to run VBScript programs. You also will need ActiveX controls
from Microsoft for many of the samples in this book. Pages can
be set up with control definitions to automatically download required
controls from across the Internet. For best results we recommend
downloading the entire ActiveX control collection from Microsoft
before proceeding with the samples in the book. This also allows
you to work with the samples from the book's CD-ROM without being
connected to the Internet. The requirements page on the CD-ROM
will download the controls the samples require. Be sure to check
the book update sites, www.mcp.com
and www.DoubleBlaze.com,
to ensure you're using the latest version of the requirements
page. At the time of this printing, you could also go to www.microsoft.com/intdev
and do a search on ActiveX controls to find information about
ActiveX controls.

Once you get set up, you can directly load the book VBScript pages
from the CD-ROM or visit the Microsoft samples over the Internet
(at www.microsoft.com/vbscript),
or from any other site for that matter, and the VBScript capabilities
will work right in front of you. If you're merely an end user
of the Web, that's all you need to enjoy the power of VBScript
programs. If you are a VBScript programmer-in other words, you
want to edit VBScript programs or create your own from scratch-then
you need one more tool, a Web page editing tool. Such a tool should
not only let you generate Web pages, but it should also enable
you to embed VBScript code into those pages. Fortunately, most
tools provide this capability. As long as you can enter text insertion
mode and type text directly into your page as you create it, you
can insert VBScript statements. You can use many different tools
to accomplish this. They range from the Windows Notepad, a simple
text editor, to more sophisticated tools such as Internet Assistant,
a utility that incorporates itself into Microsoft Word and enables
you to quickly and easily build Web pages.

Another available tool for use in Web page design with VBScript
is Microsoft's ActiveX Control Pad. This tool is an HTML text
editor that allows you to insert HTML and ActiveX controls automatically
into your HTML documents with the help of a wizard. Figure 2.6
shows the ActiveX Control Pad in action.

Figure 2.6 : Microsoft's ActiveX Control Pad.

The Control Pad has a great deal of additional features that aid
in editing Web pages and incorporating ActiveX contols, VBScript,
and JavaScript into them. You will learn more about ActiveX controls
in general starting on Day 10.

Another useful capability from Microsoft is the Layout Control
forms interface. This, together with Internet Explorer's incorporation
of 2-D layout for HTML, makes it possible to position elements
and controls anywhere on a page in a form-like fashion much like
in Visual Basic. The layout takes place in a separate file that
the layout control incorporates into your main page when that
page is loaded. This approach is discussed in more detail on Day 18,
"Advanced User Interface and Browser Object Techniques."
Security
and VBScript

One of the many questions people have when learning about VBScript
is, "How secure is it?" VBScript was designed as a subset
of the Visual Basic language. When you look at the language and
compare it to VBScript, you essentially see a stripped-down version
of Visual Basic. The designers took any part of Visual Basic that
could cause VBScript to be unsafe and unsecure and eliminated
it. The end result of their work is a language that is safe and
"lighter" than its parent, Visual Basic.

When people think about security and the Internet, their concerns
are often valid. The Internet has just recently become popular
to the masses, and companies are starting to think of ways to
make money on the Internet. This brings to mind images of users
entering credit card numbers, making banking and shopping transactions,
and paying for other services. Obviously, before such activities
can take place, the Internet must be secure. Otherwise, people
simply won't want to take the chance of their credit card numbers
being intercepted or some secure password being used to access
their accounts. The World Wide Web and Internet consortia are
working very hard to establish security mechanisms for the Internet.
Rest assured; this will be an area of intense interest in the
short term until security issues can be firmly resolved.

Those who use VBScript are also likely to be concerned about safety.
They want to make sure that VBScript does not open the door for
a devious Web page to do damage to their computer systems in any
way. The most common type of computer damage most users fear is
viruses that are transmitted to computers when files are downloaded
from an Internet server and modified on the user's computer. Other
possible damage includes a Web page that, for some reason, causes
the loss of data on the client's computer system or otherwise
causes the computer to crash. Nothing is more frustrating to the
user than to have five applications open and lose all the data
because of a computer crash. Although multitasking systems such
as Windows 95, Windows NT, and UNIX make that less likely to occur
than the Windows operating system did, it is still an unfortunate
possibility in some cases.

VBScript prevents these and other potential security and safety
problems by eliminating the cause of such problems entirely. First
of all, it is not possible to read and write files or databases
in the normal fashion in VBScript. This might seem like quite
a limitation, and it is indeed limiting, but this stops up a very
large security leak. Damage could come to a user's computer through
a Web page that opens and modifies a file or perhaps deletes a
file on the user's computer. As a result, it is not possible for
VBScript to modify files on the user's computer using conventional
methods.

The second area of safety is making sure VBScript will not cause
the computer to crash. If there is an important exchange of information
happening in a Web page, the user would certainly not want the
computer to crash due to an ill-formed script. It's a safe assumption
that the designers of VBScript made this less likely by avoiding
any code that could potentially cause a crash. It's impossible
to state outright that a VBScript program cannot crash because
absolutes in the world of computers are rare. It certainly is
possible, however, to say that VBScript is very safe and robust
and not likely to crash in and of itself.

The design of VBScript properly reflects the goal to prevent security
leaks and ensure safety with VBScript, but the story does not
end there. VBScript works together with ActiveX controls, intrinsic
HTML controls, OCXs, and OLE objects within a Web page. VBScript
has no control over what goes on when the code that composes such
controls executes. All VBScript "sees" when working
with a control or object is the interface that control provides.
It is conceivable that a control could, for example, modify a
file. VBScript doesn't modify the file-the control does. Although
VBScript can't be faulted for causing damage to a user's system,
it cannot be responsible for any controls or OLE objects it works
with. This is true of security issues as well as stability.

If a control were written with some sort of a glitch or bug inside
of it, it could cause a computer to crash or, at the very least,
cause the Web page to not function properly. Again, the problem
does not lie in VBScript itself but in the control it interfaces
with. A Web page is only as stable as its least stable component.
If a buggy control is included on a Web page, the potential of
that Web page to become unstable is equal to the stability of
that control. Therefore, it is very important to choose controls
that will work as bug free as possible with any browser or any
platform the Web page is run on.

Microsoft's Internet Explorer 3.0 is a good example of the current
state of browser security. Internet Explorer contains a feature
called Safe Content that makes sure that no unknown programs or
components can be downloaded to the user's computer by a Web page
without the user's consent. See Figure 2.7 for Internet Explorer
3.0 beta's security dialog for programs you receive within Web
pages from the Internet.

Figure 2.7 : The Microsoft Internet Explorer 3.0 (beta) Program Security dialog.

As you can see, you have the option of choosing Expert, which
warns you about any security problems before a Web page is displayed;
Normal, which automatically prevents security problems by not
displaying content that causes security violations; and None,
which displays all contents without worrying about security violations.
With the current beta version of Internet Explorer 3.0, you should
use either Expert or None when working with VBScript Web pages
that contain ActiveX controls. This Expert setting will inform
you whenever an object is required by the Web page or if a scripting
language changes the properties of an existing control on a Web
page. These safeguards are an example of part of an evolving process
of making Web browsers more secure in an environment of rapidly
growing objects, controls, and scripting languages.

You may wish to set this setting to None while using the samples
in this book on the
CD-ROM. These samples only make use of Microsoft ActiveX controls.
Since your browser can run these locally from the CD-ROM, you
don't even have to be on the Internet to progress through the
samples and can be sure that you are working in a safe computing
environment. Once you go out on the real Internet, any page can
cause a control to be downloaded, and all bets are off! It is
recommended that you use Expert when visiting pages you are not
well acquainted with. Microsoft has provided a framework for certifying
and identifying trusted controls so you can only choose to work
with known commodity controls. This is discussed more fully on
Day 21.

Industry approaches are continuing to rapidly develop in the arena
of Web security, particularly in the area of component distribution
and security. These issues will be addressed later in considerably
more detail on Day 21. For now, it is
important to understand that security considerations have shaped
the capabilities inherent in the VBScript language.
VBScript
Versus Visual Basic and Visual Basic for Applications


Many programmers who are interested in VBScript have used either
Visual Basic or Visual Basic for Applications. If you are included
in that group, you most likely know that VBScript is a subset
of Visual Basic. You've probably also heard from Microsoft that
if you already know Visual Basic or Visual Basic for Applications,
you already know VBScript. Yes, well-sort of. You know what you
could do, but you might not be sure what you cannot do.

One of the first striking differences between VBScript and Visual
Basic is that Visual Basic has a design-time environment. When
you run Visual Basic, you get an attractive editing environment
where you can craft forms and write code using an interactive
shell. When you work with VBScript, on the other hand, you have
no such environment. VBScript code "lives" within an
HTML document, which is a plain text file. At the time of this
printing, neither Microsoft nor any other large commercial vendor
has a design environment that lets users create VBScript code
like Visual Basic does. This is due, in part, to the way in which
VBScript works. Visual Basic code creates Windows applications
that operate in and of themselves. On the other hand, VBScript
code works inside of HTML documents and runs along with HTML.
Even though VBScript is an interpreted language as is its parent,
you must create VBScript code manually. Some tools are already
emerging to overcome this limitation. Microsoft's ActiveX Control
Pad, for example, helps overcome the tedious work of inserting
controls and editing HTML code by providing a more sophisticated
editing tool than Notepad. This tool is currently available for
free and can be located by doing a search at www.microsoft.com/intdev.
The tool provides for automatic insertion of control object definitions,
and it provides a layout editor. The layout editor lets you lay
out pages interactively, much like Visual Basic 4.0, and stores
the results in a separate file for the layout control to integrate
on your page. The ActiveX Control Pad even provides a Script wizard
that lets you define scripts through an interactive high-level
interface rather than by entering source code statements. Since
the focus in this book is on helping you understand all the details
of VBScript, however, we steer clear of the higher-level tools,
which can shield you from some of the underlying details. We want
you to learn those details! Therefore, the samples here are presented
at the source code level and can be entered with a text editor
such as Notepad. After you gain a well-grounded knowledge of VBScript,
you might choose to progress to some of the higher-level tools.

The other primary difference between VBScript and Visual Basic
aside from development environments is the language itself. As
mentioned previously, many of the commands, keywords, and data
types that are supported in Visual Basic are not supported in
VBScript. Rather than provide a list of specifics in this lesson,
we summarize all the differences between VBScript and Visual Basic
in Appendix A, "VBScript Syntax Quick Reference." You'll
notice quite a number of differences. If you've used Visual Basic
in the past and you think you can use exactly the same code in
VBScript, you will probably be surprised. It's important to understand
how the languages differ. On Day 20, "Porting
Between Visual Basic and VBScript," you will see how to properly
port code from Visual Basic over to VBScript. Knowing what will
and will not port is essential to that process. Day 20
will give you the information you need to make the transition
as painless as possible.
Summary


Today you have been given a taste of what VBScript can do for
you. The lesson begins by telling you a bit more about VBScript
and what it does. You have learned that VBScript enables you to
accomplish tasks otherwise impossible in HTML, and you can often
do them with a small, simple amount of code. You have also been
introduced to many of the technologies that surround the World
Wide Web and VBScript, including CGI, ActiveX controls, intrinsic
HTML form controls, OLE objects, and so on. All these accompanying
technologies help make your Web pages even more powerful and useful
in ways never before possible. VBScript acts as a "glue"
that helps you integrate all these components together. VBScript
keeps the components together and working with each other, much
like cartilage helps keep our bones moving freely and cooperatively.

You have seen several examples of VBScript in action. The purpose
of these examples is to show you some of the things VBScript can
do. The examples are by no means advanced nor even very sophisticated,
but they do help convey some of the exciting and powerful possibilities
at your fingertips. The examples today are centered around getting
information from the user, processing that information, and then
displaying the information back to the user. As you progress through
this book, you will learn how to manage this flow of information
and make your Web pages very useful to your users. You want them
to have a productive, fun, and exciting time working with your
Web pages, and you will learn the tools and techniques to accomplish
that.

After providing a taste of what VBScript can do, today's lesson
discusses some of the questions people have about this new language.
You have learned what tools and programs you need to get started
with VBScript. You must have a browser that includes VBScript
run-time support, such as Microsoft's Internet Explorer 3.0, to
use VBScript pages. Any text editor will suffice to create or
modify pages.

The lesson then discusses the safety and security of VBScript.
There has been a lot of discussion recently about Internet security
in the industry. VBScript is a very safe language because it prevents
a Web page from accessing any of the data on your computer. Furthermore,
the language itself is very safe. It is not easy to cause a VBScript
program to crash or otherwise interrupt the normal flow of a Web
page or its browser. Security is discussed in detail on Day 21.

Finally, today's lesson provides information for programmers who
have used VBScript's parent product, Visual Basic. The lesson
discusses the similarities and differences between the languages
and what the Visual Basic or Visual Basic for Applications programmer
should expect when working with VBScript. This subject is also
discussed in detail on Day 20. As the
lesson points out, those who have programmed in Visual Basic or
Visual Basic for Applications will realize that VBScript is a
subset of Visual Basic and Visual Basic for Applications. In other
words, many of the commands in Visual Basic and Visual Basic for
Applications do not exist in VBScript. This makes VBScript more
stable, safe, and efficient. Stripped of the weight of its parent,
VBScript can perform very efficiently and reliably in the browser.

Today's lesson gives you an overview of VBScript, its capabilities,
what you need to know to learn it and use it, how safe and secure
it is, and how it differs from its parent. Tomorrow, you will
learn more about where VBScript is supported and, in particular,
how it is supported. You will learn how VBScript is "connected"
to a browser, and you will also write your first VBScript program.
Q&A



QYou mentioned that VBScript acts like "glue" to bind components together on a Web page. What do you mean by the term "glue"?

AThe term "glue" is borrowed from VBScript's parent, Visual Basic. Controls and objects placed on a Web page can be linked together using VBScript. For example, you can use VBScript to
respond and execute code when a user clicks a command button that places text in a text box control. In this way, you can create a "fabric" that makes all the components work together the way you intend. This applies not only to simple intrinsic
controls, but also to more sophisticated objects such as Java applets, ActiveX controls, and other objects.

QWhen a user is working with a Web page, what's so important about having the Web page execute code on the user's computer? Why can't all the code execute on the server?

AThe most significant benefit of being able to execute code on the user's computer rather than the server is that first, it eliminates all the extra Internet traffic required between the client
and the server; second, it relieves the server from the burden of performing the processing that the client could do itself. To the user, this means the Web page will be more peppy and responsive. To Internet users as a whole, this means less traffic and
better response time. To the owners of the Internet servers, it means less work they have to handle on their servers and the more people they can serve at once who access those servers.

QI've never done any programming at all. I just want to be able to write Web pages without going through a lot of hassle and learning time. Will it take me a long time to learn VBScript?

AIf ever there was an easy language to learn, VBScript is it. Unlike more complicated scripting languages such as JavaScript, VBScript is derived from one of the easiest-to-learn languages used
for programming today. One could argue that the simplicity of VBScript comes at the expense of power and functionality. Power and simplicity have always been competing goals. VBScript gives the programmer a reasonable trade-off, however, because it is
sufficiently powerful for sophisticated Web page applications, yet it is safe enough and easy enough for the beginner to learn quickly.

QIf VBScript is secure, but other components within a Web page might not be, how can I be sure a Web page won't damage my system when I load it into my browser and work with it?

ASecurity is a concern that is foremost on the minds of Internet developers and solutions providers. The bottom line is that market and corporate pressures will force control vendors and solution
providers to make sure their controls do not contain security threats. Industry movements underway to clearly establish the identity of components (discussed further on Day 21) will further these efforts. At the very least, any
possibility of such threats should be fully documented to the programmer and the users of the Web page before they have a chance of doing any potential damage.



Workshop


Take each of the examples presented today, and knowing what you
know now about what VBScript can do, make a list of additional
ideas and suggestions for these pages. Are there other Web pages
you can create that will help make these examples more useful?
Is there anything you can add to the Web pages to make them more
powerful? When you've finished reading this book, take another
look at these examples and ask yourself these questions again.
Quiz





Note


Refer to Appendix C, "Answers to Quiz Questions," for the answers to these questions.





What major capability does a scripting language give to a
Web page?
Name a few of the surrounding technologies that can be "glued"
together using VBScript.
What aspects of VBScript make it safe so that a Web page using
VBScript cannot destroy or corrupt information on a user's computer?
Where did the VBScript language originate?
What do you need to write VBScript code or use Web pages that
contain VBScript code?