Programming Visual Basic .NET, Second Edition

Variables and Constants

A variable is a storage location with a type. The type will be one of the intrinsic types (variables of user-defined types are called objects, and are explained in Chapter 5). In the examples in Section 3.2.3, both myInteger and myDouble are variables. Variables can have values assigned to them, and those values can be changed programmatically.

WriteLine( )

The .NET Framework provides a useful method for writing output to the screen. The details of this method, System.Console.WriteLine( ), will become clearer as we progress through the book, but the fundamentals are straightforward. You call WriteLine( ) in Example 3-1, passing in a String that you want printed to the console (the screen) and, optionally, parameters that will be substituted. In the following example:

System.Console.WriteLine("After assignment, myInteger: {0}", myInteger)

the String “After assignment, myInteger:” is printed as-is, followed by the value in the variable myInteger. The location of the substitution parameter {0} specifies where the value of the first output variable, myInteger, will be displayed, in this case at the end of the String. We’ll see a great deal more about WriteLine( ) in later chapters.

You create a variable by declaring its type and then giving it a name. You can initialize the variable when you declare it, and you can assign a new value to that variable at any time, changing the value held in the variable. Example 3-1 initializes the variable myInteger with the value ...