INTRODUCTION TO VISUAL BASIC PART-2

THE VISUAL BASIC ENVIRONMENT

The visual Basic environment is where you create and run your project

One of the most significant changes in Visual Basic 6.0 is the Integrated Development Environment (IDE). IDE is a term commonly used in the programming world to describe the interface and environment that we use to create our applications. It is called integrated because we can access virtually all of the development tools that we need from one screen called an interface. The IDE is also commonly referred to as the design environment, or the program.

The Visual Basic IDE is made up of a number of components

• Menu Bar
• Tool Bar
• Project Explorer window
• Properties window
• Form Layout Window
• Toolbox
• Form Designer
• Object Browser

In previous versions of Visual Basic, the IDE was designed as a Single Document Interface (SDI). In a Single Document Interface, each window is a free-floating window that is contained within a main window and can move anywhere on the screen as long as Visual Basic is the current application. But, in Visual Basic 6.0, the IDE is in a Multiple Document Interface (MDI) format. In this format, the windows associated with the project will stay within a single container known as the parent. Code and form-based windows will stay within the main container form.

The Form Window

The form window is where you design form that make up your user interface.  When you begin a new project the visual basic gives your new form the default name Form1. As soon as you save the file you give a new meaningful name.

The Project Explorer Window

This holds the filenames for the files included in the project. The windows title bar holds the name of your project (.vbp) file which is project1 by default until you save it with a new name. The Project Window displays a list of all forms and modules making up your application. You can also obtain a view of the Form or Code windows (window containing the actual Basic coding) from the Project window.

Properties  Window

This is used to set properties for the objects in your project. The Properties Window is used to establish initial property values for objects. The drop-down box at the top of the window lists all objects in the current form. Two views are available: Alphabetic and Categorized. Under this box are the available properties for the currently selected object.

Menu Bar

This Menu Bar displays the commands that are required to build an application. The main menu items have sub menu items that can be chosen when needed. The toolbars in the menu bar provide quick access to the commonly used commands and a button in the toolbar is clicked once to carry out the action represented by it.

Toolbox

The Toolbox contains a set of controls that are used to place on a Form at design time thereby creating the user interface area. Additional controls can be included in the toolbox by using the Components menu item on the Project menu. A Toolbox is represented in figure 2 shown below.

Toolbox window with its commonly available controls

Control	Description
Pointer	Provides a way to move and resize the controls form
PictureBox	Displays icons/bitmaps and metafiles. It displays text or acts as a visual container for other controls.
TextBox	Used to display message and enter text.
Frame	Serves as a visual and functional container for controls
CommandButton	Used to carry out the specified action when the user chooses it.
CheckBox	Displays a True/False or Yes/No option.
OptionButton	OptionButton control which is a part of an option group allows the user to select only one option even if it displays mulitiple choices.
ListBox	Displays a list of items from which a user can select one.
ComboBox	Contains a TextBox and a ListBox. This allows the user to select an ietm from the dropdown ListBox, or to type in a selection in the TextBox.
HScrollBar and VScrollBar	These controls allow the user to select a value within the specified range of values
Timer	Executes the timer events at specified intervals of time
DriveListBox	Displays the valid disk drives and allows the user to select one of them.
DirListBox	Allows the user to select the directories and paths, which are displayed.
FileListBox	Displays a set of files from which a user can select the desired one.
Shape	Used to add shape (rectangle, square or circle) to a Form
Line	Used to draw straight line to the Form
Image	used to display images such as icons, bitmaps and metafiles. But less capability than the PictureBox
Data	Enables the use to connect to an existing database and display information from it.
OLE	Used to link or embed an object, display and manipulate data from other windows based applications.
Label	Displays a text that the user cannot modify or interact with.

 NAMIMG RULES AND CONVENTIONS FOR OBJECTS, PROCEDURES AND VARIABLES

Using good meaningful and consistent names for objects makes projects easier to read and understand as well as easier to debug.

 NAMING RULES FOR AN OBJECT

·         Must select a name for an object

·         The name must begin with letter

·         Can be up to 40 characters in length

·         Can contain letters digits and underscore

·         An object name should not include a space or punctuation mark

	Main Visual Basic Window
		Tool Box

OBJECT NAMING CONVENTION

A convention has been established for naming Visual Basic objects. This convention is to use a three letter prefix (depending on the object) followed by a name you assign. A few of the prefixes are (we’ll see more as we progress in the class):

Object                                                 Prefix                          Example

Form                                                    frm                              frmWatch

Command Button                               cmd                             cmdExit

Label                                                   lbl                                lblStart, lblEnd

Text Box                                             txt                                txtTime, txtName

Menu                                                   mnu                             mnuExit, mnuSave

Check box                                           chk                              chkChoice

Prefix              Control                                               Prefix                          Control

Cbo                 combo box                             chk                              check box

cmd                 command button                                 dir                                directory list box

drv                   drive list box                                      fil                                 file list box

fil                     file list box                                          fra                                frame

frm                  form                                                    grd                              grid

hsb                   horizontal scrollbar                              img                             image

lbl                    label                                                    lin                               line

lst                    list box                                               mnu                             menu

ole                   OLE client                                          opt                               option button

pic                   picture box                                         shp                              shape

tmr                   timer                                                   txt                               text box

vsb                   vertical scrollbar

   NAMING RULES AND CONVENTIONS FOR VARIABLES AND CONSTANTS

·         Names must not be more than 255 characters

·         May consist of letter, digits and underscore

·         Must not contain any space or period

·         Must not be a reserved word (aka keywords)

·         Give meaningful names to your variables and constants, do not use short names such as x or y

·         Precede each variable with a lower case prefix that specifies its data type

·         Capitalize each word of the name, always use mixed case, never use upper case all through

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