Imagine that the form contains a button called Button1 and that we want to give a "Hello" greeting when the button is clicked by the user. Double-clicking the button opens up the code window and we see that several lines of code have been automatically generated for us already:

Public Class Form1

Private Sub Button1_Click(BLAH BLAH) Handles Button1.Click

End Sub

End Class

The first and last lines are always needed but I won't try to explain them here nor will I bother showing them in all my code examples. Just remember: those lines are always needed.

Visual Basic also puts a lot of hard-to-understand stuff into the line beginning 'Private Sub' but fortunately you don't need to understand this either at this time so I have just replaced it with 'BLAH BLAH' above.

These two lines 'Private Sub' and 'End Sub' are called 'wrappers' - they mark the beginning and end of the subroutine and therefore the code we write must be inserted between these wrappers. Note the word 'sub' in the first line - this is short for subroutine, of course. At the end of the first line we see that this subroutine will be activated when Button1 is clicked. The parentheses are empty here but sometimes they will contain variables called 'parameters' that are used to pass information to the subroutine.

Add a line of code and the subroutine will be complete:

Private Sub Button1_Click(BLAH BLAH) Handles Button1.Click
MsgBox ("Hello")
End Sub

MsgBox is short for 'messagebox' and will display your message on the screen. Your program is now complete! Click the Run icon (or press the F5 key) and test your program by clicking the button. Stop the program by hitting the stop icon or by clicking the X in the top-right corner of the form (don't close VB itself!).

Now let's extend the code to add an 'input' instruction - we will make the computer ask the user for his or her name. Modify the code so it looks like this:

Private Sub Button1_Click(BLAH BLAH) Handles Button1.Click
    UserName = InputBox("Enter your name")
    MsgBox ("Hello, " & UserName)
End Sub

The second line displays an 'inputbox' that asks the user to enter his or her name, and then stores the answer in a variable called UserName. A variable is like a container - it can contain numbers or text, and the contents of the variable can change while the program is running - hence the name variable! You've met variables before in your math classes, hopefully. Note that variable names can't contain spaces - this variable could not be called 'User Name'. Interestingly, the name 'Name' is also not allowed, for it is one a few dozen 'keywords' that are reserved by Visual Basic.

Look again at the second line. Note how the equals sign is being used in a way here that is very different to its use in your math class. In VB, the equals sign is usually used to modify the contents of a variable, or to change the properties of a control. When used in this way, the equals sign is called the 'assignment operator'. Notice that the variable on the LEFT of the operator is assigned the value given on the RIGHT of the operator.

Imagine that your program uses a variable called x. What would the following line do?

x = x + 1

This line (which would make no sense in a math class!) works out the value of the expression on the right by adding one to the existing value of x and then stores the result back into the variable called x. In other words, this line has the effect of adding one to x.

Sometimes the equals sign is used as in your math class, as in the following line:

If (x = y) then MsgBox ("X and y are the same.")

This line checks to see whether the variables x and y have the same value and if they do then the computer displays a message.

So by now you should have understood that the line

            UserName = InputBox("Enter your name")

will display an inputbox into which you can type your name and then will take your name and store it in the variable called UserName. The following line then displays a messagebox containing the word "Hello, " followed by the name that was stored in the UserName container (variable). the ampersand character '&' is used to join the name to the word "hello" to form a 'text string' (a string of characters) that the messagebox can display.

There is one further complication: Visual Basic normally does not allow us to use variables that have not previously been 'declared'. However, by including a special statement 'Option Explicit Off' at the beginning of our code we can do away with the need to declare variables. Declaring variables is a good idea, however, since it protects your program from errors, so you will learn how to do that later.

Thus the full code (but still with BLAH BLAH) that we have developed on this page looks like this:

Option Explicit Off

Public Class Form1

Private Sub Button1_Click(BLAH BLAH) Handles Button1.Click
UserName = InputBox("Enter your name")
MsgBox ("Hello, " & UserName)
End Sub

End Class

You will notice that there are some minus signs in small boxes at the left side of the Code Window - clicking these allows you to temporarily hide procedures so that they do not distract you while you are trying to work on other procedures. You can unhide hidden procedures by clicking on the plus signs.

VB is very fussy about grammar (called 'syntax' in computer programming). If the syntax is not correct then your program may not run at all! VB tries to help you avoid syntax errors - it will report errors in the Error List window if the program still has errors when you try to run ('build') the program by choosing Debug>Start Debugging or pressing F5.