Visual Basic.NET How to Program (PDF)

Chapter 3 Introduction to Visual Basic Programming 63
1 ' Fig. 3.1: Welcome1.vb
2 ' Simple Visual Basic program.
3
4 Module modFirstWelcome
5
6 Sub Main()
7 Console.WriteLine("Welcome to Visual Basic!")
8 End Sub ' Main
9
10 End Module ' modFirstWelcome
Welcome to Visual Basic!
Fig. Fig. 3.1 3.1 Simple Visual Basic program .
“end-of-line comments”). The Visual Basic compiler ignores comments, which means that
comments do not cause the computer to perform any actions when the program is run. The
comment in line 1 simply indicates the figure number and file name for this program. Line
2 provides a brief description of the program. By convention, every program in this book
begins in this manner—you can write anything you want in a comment. In this case, the file
is named Welcome1.vb. Recall that .vb is the file extension for Visual Basic files.
Good Programming Practice 3.1
Every program should begin with one or more comments describing the program’s purpose. 3.1
Good Programming Practice 3.2
Comments written at the end of a line should be preceded by one or more spaces to enhance
program readability. 3.2
Lines 4–10 define our first module (these lines collectively are called a module definition).
Visual Basic console applications consist of pieces called modules, which are logical
groupings of procedures that simplify program organization. Procedures perform tasks and
can return information when the tasks are completed. Every console application in Visual
Basic consists of at least one module definition and one procedure. In Chapter 6, Procedures,
we discuss modules and procedures in detail.
The word Module is an example of a keyword (or reserved word). Keywords are
reserved for use by Visual Basic (a complete list of Visual Basic keywords is presented in
the next chapter). The name of the Module (i.e., modFirstWelcome) is known as an
identifier, which is a series of characters consisting of letters, digits, and underscores ( _ ).
Identifiers cannot begin with a digit and cannot contain spaces. Examples of valid identifiers
are value1, xy_coordinate, __total and cmdExit. The name 7Welcome
is not a valid identifier because it begins with a digit, and the name input field is not
a valid identifier because it contains a space.
Good Programming Practice 3.3
Begin each module identifier with mod to make modules easier to identify. 3.3