Visual Basic - Fundamentals of VB and IDE

Since ages, Visual Basic (VB) has been the choice of programmers and there are many attributes supporting this.  The first and foremost being the ease with which one can build large sized user-friendly application.  The second being, no much of formal training required to start programming in VB.

In this series, we aim at understanding programming from a programmers point of view. Initially called by as a programming language for hobbyist, Visual Basic has now captured the corporate world too.  Applications written in Visual Basic can run on any platform with minimum Windows 95. 

Let’s embark our journey to Visual Basic Programming.  As we proceed through the series, we shall explore the various dimensions in VB.

Objects & Variables

As in real world, person is an object (a real time entity), so does VB have objects.  These objects represent some characteristics which we technically call Properties of objects. These properties can be assigned values (using ‘=’ operator) when required.   The properties can be referred to by using a dot ‘.’ operator as:

ObjectName.PropertyName = ValueAssigned

The objects can perform specific tasks, which we call as Methods. There are special types of actions, which we call as Functions. These functions accept piece of information called Arguments.

The objects also have special events to be captured that are referred by an underscore separator ‘_’as:

ObjectName_Click

Here, Click is known as an Event of ObjectName

Besides Objects, there are some global definitions of variables, which can be used in any of the Events of Objects. There are different types of variables which are as follows:

Table 1: Variable Types

Type	Bytes	Suffix	Range
Boolean	2	N/A	True/False
Byte	1	N/A	0 to 255
Currency	8	@	-922,337,203,685,477.5808 to 922,337,203,685,477.5807
Date	8	#...#	1 Jan 100 to 31st Dec 9999 and times from 0:00:00 to 23:59:59
Decimal	12	N/A	-79,228,162,514,264,337,593,543,950,335 to 79,228,162,514,264,337,593,543,950,335
Double	8	#	-1.79769313486232E308 to -4.94065645841247E-324 for negative values
			4.94065645841247E-324 to 1.79769313486232E308  for positive values
Integer	2	%	-32,768 to 32,767
Long	4	&	-2,147,483,648 to 2,147,483,647
Single	4	!	-3.402823e38 to -1.401298E-45 for negative values
			1.401298E-45 to 3.402823e38 for positive values
String	N/A	$	2 Billion characters
Variant	N/A	N/A	N/A

These Variables can be declared using some keywords that decide the scope of the same. They are as follows:

           

Table 2: Variables Scope

Keyword	Interpretation
Dim	Used to create variables along with keyword ‘As’ to specify variable type
ReDim	Reallocates the memory location to the previously defined or dynamic array variables
Static	The variable retains its value during procedural calls
Private	The scope of this variable is in the current form or module
Public	These are global variables

Variable Declaration

There are three commonly used methods to define variables:

Dim name As String

Dim age As Integer

Dim address

The first declaration declares name as a string variable and age as an integer variable. The second declaration defines address as a variant, which can assume any value during run-time.

Dim Grad1, Grad2, Grad3 As Integer

As shown in the third method of declaration we can separate the variable names using comma ‘,’.  But this method can be used only if the variables belong to a common type. 

Integrated Development Environment

Let us begin our first project as a beginner. We select Standard EXE when the first window pops up.

Figure 1: New Project Window

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A new form appears in front of us with some graphic controls to create GUI. Many such forms can be created for different modules and then integrated or interlinked to be called as a project. This project is saved with an extension .vbp and the form is stored with an extension .frm.

Project Explorer Window

<![if !vml]=> Figure 2: Project Explorer

In this window, the Project Forms and Modules are visible.  On clicking on the name of form/module we can design the form or write code in the same. The three buttons in the window are to view the code, design the form or see various forms and modules in the project.Â

Toolbox Window

<![if !vml]=><![endif]>Â Figure 3: Toolbox Window

The toolbox appears as shown in Figure 3. This toolbox consists of various tools and controls that can be used.  These controls are also called as objects.  Sometimes, this toolbox is not visible.  In that case, we need to select Toolbox Option from the View Menu.  Other than those visible on the screen, we can add few more controls (.OCX) through Project Menu > Components.

Properties Window

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Figure 4: Properties Window

The property window deals with object properties that we had earlier talked of.  Several properties are displayed in this window along with their values.  The values can be altered as required. 

Some of the properties are mentioned in Table 3:

Table 3: Some Commonly Used Properties of Objects

Property	Interpretation
Name	This is the name of object or form, which will be used whenever one calls the object events, methods, or changes its properties.  The nomenclature follows a specific rule as mentioned in Table 4.
Appearance	If set to Flat, it paints controls and forms without visual effect
	If set to 3D, it gives visual effects to controls and forms
Backcolor	This property enables us to choose the backcolor of object or form. It has two options as Palette – Range of all colors and their shades System – Shows colors commonly used in Windows The colors in System bar can be changed only through proper configuration of control panel
BorderStyle	Sets the border style for an object.
Enabled	When we need to put off the controls of objects, we disable the object.  When needed, one can put Enabled to ON and hence restrict the controls to the user.
Font	The default Font is MS Sans Serif.  It’s preferable to use the commonly available fonts so that installing our software on some other PC doesn’t disturb the appearance.
Height Width	This property is used to change the height and the width of the form or the control.  The controls are by default measured in twips and 1,440 twips make up to an inch. You can change the ScaleMode from Twips to Inch or any other measuring unit by changing the ScaleMode
Index	This is used to create an array of objects. The objects are then referred by their index numbers that are unique. This renders flexibility of using same code while programming.
Left Top	These properties define the top and left of the form.  These properties are also known as X and Y properties.
MousePointer	When mouse is dragged on the object, Mouse Pointer assumes different shapes as defined in this property.  The default value is 99 – Custom
TabIndex	This defines the sequence of focus when the user presses TAB key.  The first value assumes 0.  This can help us to define the sequence of operation if the user prefers to operate through keyboard.
ToolTip Text	This property is used to display some text when mouse is placed over the object.   The general appearance of the text is yellow as backcolor and black as forecolor.
Visible	This hides the control or the form, whichever is desired. This is different from Enable property.  The Enable property does keep the control visible but not accessible.

Table 4: Conventional Method of Naming Objects

Prefix	Objects	Example
prj	Project	prjCalculator
frm	Form	frmAddition
cmd	Command Button	cmdSaveAs
txt	TextBox	txtName
lbl	Label	lblName
lst	Listbox	lstTemperature
cbo	Combobox	cboChoice
opt	Option Button	optChoice
img	Image	imgCapture
fra	Frame	fraPersonal
tmr	Timer	tmrMain
dat	Data	datEmployeeRec

Building A Form

Before placing different objects on the form and writing code for them, lets first view the properties of form that make a difference in the appearance.  These properties are visible in the Property Window (see Figure 4)

Name of the form (in the Property Window, here Form1) should reflect the purpose of the form, normally preceded by a prefix frm (e.g. frmMath for mathematical calculations.)

The Caption Property helps us to title our form, which appears next to the icon.

A normal form appears with a blue screen with minimize, maximize and close button. With the help of BorderStyle property, we can change the appearance of the form

Table 5: BorderStyle Property

BorderStyle	Border	Sizable	Caption	Icon	Control Box
0- None	No	No	No	No	No
1- Fixed Single	Yes	No	Yes	Yes	Yes
2-Sizable	Yes	Yes	Yes	Yes	Yes
3-Fixed Dialog	Yes	No	Yes	No	No
4-Fixed ToolWindow	Yes	No	Yes, Slimmer	Yes	No
5-Sizable ToolWindow	Yes	Yes	Yes, Slimmer	Yes	No

Besides BorderStyle, how the form shall be displayed initially is also important. The WindowState property assumes either Normal, Minimised or Maximised as its value.In the minimized state, the form is seen in the windows task bar.

The position of the form also plays an important role, which is defined by StartUpPosition property.

Table 6: StartUpPosition Property

StartUpPosition	Position
0-Manual	The form position is as defined in the Left and the Top properties.
1-CenterOwner	The form is centered on the form that has called it.
2-CenterScreen	At the center of the screen.
3-WindowsDefault	Can place anywhere on the screen. This is selected by default.

With this information, let us view different objects and their properties so that we can create good real-time applications.

 

 

 

Note: This series was first published in DeveloperIQ and was co-authored by Puneet Ghanshani with Pranjali Bakeri in 2005-2006.