Visual Basic for Kids
2. The Visual Basic Environment
Review and Preview
In Class 1, we learned the important
parts of a Visual Basic project. We saw that a project is built on a form using controls. By interacting
with the controls using events, we
get the computer to do assigned tasks via instructions we provide. In this second class, we will learn the
beginning steps of building our own Visual Basic projects by looking at the
different parts of the project and where they fit in the Visual Basic
environment. Like Class 1, there are
also a lot of new terms and skills to learn.
Parts of a Visual Basic Project
In Class 1, we saw that there are
three major components in a Visual Basic project: the project itself, the form, and the
controls. Project is the word used to encompass everything in a Visual Basic
project. Other words used to describe a
project are application or program. The Form
is the window where you create the interface between the user and the
computer. Controls are graphical features or tools that are placed on forms
to allow user interaction (text boxes, labels, scroll bars, command
buttons). Recall the form itself is a
control. Controls are also referred to
as objects. Pictorially, a project is:
So,
a project consists of a form containing several controls. In looking around your computer’s file
directory, you may find some files associated with a Visual Basic project. Two primary files are used to save a Visual
Basic project. The project file will
have an extension of vbp (in
addition, there is sometimes a file with a vbw extension). The form file has an extension of frm (in addition, there is sometimes a
form file with a frx extension). Look in
your project folder (VB4Projects, VB5Projects, or VB6Projects) and see if you can find Sample.vbp and Sample.frm
- those are the files for the project you opened in Class 1. You need to know these extensions for proper
opening and saving of your projects.
An important concept concerning a
Visual Basic project is that of a property. Every characteristic of a control (including
the form itself) is specified by a property. Example properties include names, captions, sizes, colors, position on
the form, and contents. For each control
studied in this class, we will spend a lot of time talking about properties.
Also, in Class 1, we discovered that
Visual Basic is an event-driven
language. Visual Basic is governed by an
event processor. That means that
nothing happens in a Visual Basic project until some event occurs. Once an event is detected, the project finds
a series of instructions related to that event, called an event procedure. That procedure is executed, then program
control is returned to the event:
Event
procedures are where we do the actual computer programming and are saved with
the form in the file with the frm
extension. These procedures are where we
write BASIC language statements. You
will learn a lot of programming and BASIC language in this class. The BASIC you will learn is very similar to
the original BASIC used by Bill Gates and Paul Allen when starting Microsoft.
Parts of the Visual Basic Program
Visual Basic is more than just a
computer language. It is a project
building environment. Within this one
environment, we can begin and build our project, run and test our project,
eliminate errors (if any) in our project, and save our project for future
use. With other computer languages, many
times you need a separate text editor to write your program, something called a
compiler to create the program, and then a different area to test your
program. Visual Basic integrates each
step of the project building process into one environment. Let’s look at the parts of the Visual Basic
environment.
Main Window
Start Visual Basic using the
procedure learned in Class 1. Notice
that several windows appear. The Main Window is used to control most
aspects of the Visual Basic project building and running process.
VB4:
VB5:
VB6:
The main window consists of the title bar, menu bar, and toolbar. The title bar indicates the project name and
the current Visual Basic operating mode (design, break, run). The menu bar has drop-down menus from which
you control the operation of the Visual Basic environment. The toolbar has buttons that provide
shortcuts to some of the menu options. Look for the buttons we used in Class 1 to open a project, start a
project, and stop a project.
Form Window
The Form Window is central to developing Visual Basic
applications. It is where you develop
your application.
If
the form window is not present on the screen:
VB4 Click
View on the main menu, then Form.
VB5, VB6 Click
View on the main menu, then Object.
As
an alternate, if the window does not show up, press the F7 function key while holding down <Shift>.
Toolbox Window
The Toolbox Window is the selection menu for controls used in your
application. Many times, controls are
also referred to as tools. So, three words are used to describe
controls: objects, tools, and, most
commonly, controls.
VB4:
VB5, VB6:
If
the toolbox window is not present on the screen, click View on the main menu, then Toolbox. See if you can identify controls we used in
Class 1 with our Sample project.
Properties Window
The Properties Window is used to establish initial property values for
controls. The drop-down box at the top
of the window lists all controls on the current form. Under this box are the available properties
for the currently selected object.
VB4:
VB5, VB6: Two
views are available: Alphabetic and Categorized. We will always
used the Alphabetic view.
If
the properties window is not present on the screen:
VB4: Click View on the main menu, then Properties.
VB5, VB6: Click View
on the main menu, then Properties Window.
As
an alternate, if the window does not show up, press the F4 function key. The
properties window will only display when the form and its controls is also
displayed.
Project Window
The Project Window shows which form makes up your project. As you become a more proficient Visual Basic
programmer, you will learn to develop projects with more than one form. In that case, all forms in your project are
listed in this window. You can also
obtain a view of the Form or Code windows (window containing the
actual BASIC coding) from the Project window by clicking one of the displayed
buttons. We will look at the code window
in the next section.
VB4:
VB5, VB6:
If
the project window is not present on the screen:
VB4: Click View on the main menu, then Project.
VB5, VB6 Click
View on the main menu, then Project Explorer.
As
an alternate, if the window does not show up, press the R key while holding down <Ctrl>.
You should be familiar with each of
these windows and know where they are and how to locate them, if they are not
displayed. Next, we’ll revisit the
project we used in Class 1 to illustrate some of the points we’ve covered here.
Moving Around in Visual Basic
Project Window
Open the project named Sample that we used in Class 1. Find and examine the Project window:
VB4:
VB5, VB6:
The
project window indicates we have a project file saved as Sample.vbp which includes a single form saved as Sample.frm. Note, too, that the form is referred to by a
name frmSample. Remember the Properties window? One of
the most important properties we assign to a control is its Name - frmSample is the name property of our form. We always refer to controls by their name
property, so it is critical that we are careful in how we name them (we will
talk a lot about this in the next class). The name is so important here that it is listed in the project window.
Properties Window
Now, find the Properties window. Remember
it can only be shown when the form is displayed. So, you may have to make sure the form is
displayed first. Review the steps that
get the desired windows on your screen.
VB4:
VB5, VB6:
The
drop-down box at the top of the properties window is called the control list. It displays the name
(the name property) of each control used in the project, as well as the type of
control it is. Notice, as displayed, the
current control is the Form and it
is named frmSample. The properties list is directly below this
box. In this list, you can scroll (using
the scroll bar) through the properties for the selected control. The property name is on the left side of the
list and the current property value is on the right side. Scroll through the properties for the form. Do you see how many properties there
are? You’ll learn about many of these as
you continue through the course. Don’t
worry about them for now, though.
Click on the down arrow in the
control list (remember that’s the drop-down box at the top of the properties
window).
VB4:
VB5, VB6:
Scroll
through the displayed list of all the controls on the form. There are a lot of them. Notice the assigned names and control
types. Notice it’s pretty easy to
identify which control the name refers too. For example, imgTrike is
obviously the image control holding
a picture of a trike. That’s the idea of
proper control naming - making it easy to identify a control just by it’s
name. As we said, we’ll spend time
talking about control naming in the later classes.
Select a control and scroll through
the properties for that control. Look at
the properties for several controls. Notice every control has many properties. Most properties are assigned by default, that
is the values are given to it by Visual Basic. We will change some properties from their default values to customize
them for our use. We will look at how to
change properties in Class 3.
Code Window
Let’s look at a new window. Recall Visual Basic is event-driven - when an
event is detected, the project goes to the correct event procedure. Event procedures are used to tell the
computer what to do in response to an event. They are where the actual computer programming (using the BASIC
language) occurs. We view the event
procedures in the Code Window. There are many ways to display the code window. One way is to use the appropriate button
found in the project window. Another is
to click View on the main menu, then
Code. Or, as an alternate, press the F7 function key. Find the code window for the Sample project.
VB4:
VB5, VB6:
At
the top of the code window are two boxes, the object (or control) list
and the procedure list. The object list is similar to the control list in the properties
window. It lists all objects on the form
by name. Once an object, or control,
name is selected in that list, the procedure list shows all possible event
procedures for that control. As shown,
the code window is displaying the Load
event procedure for the Form
control. (If the Form control is not
selected in the object list, click the drop-down arrow, scroll until you find
the word Form and select it). The Load event occurs when a project is first
loaded into your computer. Under the
object and procedure list boxes is the actual BASIC code for that event procedure. This code probably looks like a foreign
language right now and don’t worry - it should! In subsequent classes, you will start to learn BASIC and such code will
become easy to read. Click on the
drop-down arrow in the procedures list box. Notice all the other possible event procedures for the Form
control. Fortunately, we don’t have to
write BASIC code for all of these procedures. We only write code for events we expect will happen when our project is
running.
Click on the drop-down arrow in the
objects list. Select optBlue as the object.
VB4:
VB5, VB6:
This
is the Click event procedure for the
control name optBlue. And even though you may not know any BASIC right now, you should be able
for figure out what is going on here. Since we are careful in how we name controls, you should recognize this
control to be the option button (one with a little circle) with the word Blue next to it (the word next to an
option button is its Caption
property). So, this event procedure is
called whenever we click on the Blue option button. Notice the procedure has a single line of
instruction (ignore the first and last line for now):
frmSample.BackColor
= vbBlue
What
this line of BASIC code says is set the BackColor
property of the control named frmSample
to Blue (represented by the word vbBlue). Pretty easy, huh?
Actually, most BASIC code is pretty
easy to understand. So, don’t be too
worried. Select other objects in the
object list and look at the corresponding event procedures. Look at the BASIC code. Start at the top line of code (again, ignore
the top header line) and work down. Can
you figure out what’s going on even though you don’t know any BASIC? I think you’ll find you can in most cases. Writing BASIC code is primarily paying
attention to lots of details. For the
most part, it’s very logical and obvious. And, you’re about to start writing your own code!
Summary
In this second class, we’ve learned
the parts of the Visual Basic environment and how to move around in that
environment. We’ve also learned some
important new terms like properties and
event procedures. You’re now ready
to build your first Visual Basic project. In the next class, you’ll learn how to place controls on a form, move
them around, and make them appear just like you want. And, you will learn the all-important step of
how to put BASIC code in the event procedures.
