Datasheet

Chapter 1: A Quick Introduction to Programming
6
Line 4 is another comment. Line 5 is more code. Now that you’ve initialized this variable, you’re going to
do something useful with it.
MsgBox is another built-in VBScript function that you will probably use a lot
during the course of your VBScript programming. Using the
MsgBox function is a good way to introduce
the programming concept of passing function parameters, also known as arguments . Some functions
don’t require you to pass parameters to them while others do. This is because some functions (take the
Date function as an example — this returns the current date based on the system time) do not need any
additional information from you in order to do their job. The
MsgBox function, on the other hand, dis-
plays a piece of information to the user in the form of a dialog box, such as the one shown in Figure 1-2 .
Figure 1-2
You have to pass
MsgBox a parameter because on its own it doesn’t have anything useful to display (in
fact, it will just bring up a blank pop-up box). The
MsgBox function actually has several parameters, but
for now you’re just going to look at one. All of the other parameters are optional parameters.
Understanding Syntax Issues
Take another look at line 5 and you’ll probably notice the ampersand ( & ). The ampersand is a VBScript
operator, and is used to concatenate (join) pieces of text together. To concatenate simply means to “string
together.” This text can take the form of either a literal or a variable. A literal is the opposite of a variable.
A variable is so named because it is exactly that — a variable — and can change throughout the lifetime
of the script (a script’s lifetime is the time from when it starts executing, to the time it stops). Unlike a
variable, a literal cannot change during the lifetime of the script. Here is line 5 of the script again.
MsgBox “Hello “& YourName & “! Pleased to meet you.”
An operator is a symbol or a word that you use within your code that is usually used to change or test a
value. Other operators include the standard mathematical operators (
+ , - , / , * ), and the equals sign ( = ),
which can actually be used in either a comparison or an assignment. So far, you’ve used the equals sign
as an assignment operator. Later in this chapter you’ll find out more about operators.
Now take a closer look at variables. Remember how we said that a variable is a piece of reserved
memory? One question you might have is, How does the computer know how large to make that piece
of memory? Well, again, in VBScript this isn’t something that you need to worry about and it is all
handled automatically by the VBScript engine. You don’t have to worry in advance about how big or
small you need to make a variable. You can even change your mind and the VBScript engine will
dynamically change and reallocate the actual memory addresses that are used up by a variable. For
example, take a quick look at this VBScript program.
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