INTRODUCTION
There
are literally hundreds of programming languages. Each was developed to solve a
particular type of problem. Most traditional languages such as BASIC, C, COBOL,
FORTRAN, PL/1 and Pascal are considered as procedural languages. In procedural
languages the program specifies the exact sequence of all operations. Program
logic determines the next instruction to execute in response to conditions and
users request.
Newer
programming languages such as C++, and Visual BASIC use a different approach
known as Object-Oriented programming and event driving programming. Visual
Basic is an event driven programming language used to write application
programs that runs in windows operating environment. It has many but not
all the elements of an object oriented language such as java. In the event
driven model, programs are no longer procedural i.e. don’t follow a sequential
logic.
OBJECTIVES
·
Understand the benefits of using
Microsoft Visual Basic 6.0 for Windows
as an application tool
·
Understand the Visual Basic event-driven
programming concepts, terminology, and available tools
·
Learn the fundamentals of designing,
implementing, and distributing a Visual
Basic application
·
Learn to use the Visual Basic toolbox
·
Learn to modify object properties
·
Learn object methods
·
Use the menu design window
·
Understand proper debugging and
error-handling procedures
·
Gain a basic understanding of database
access and management using data bound
controls
·
Obtain an introduction to ActiveX
controls and the Windows Application Programming Interface (API)
VISUAL BASIC’S VISUAL NATURE
Visual
Basic 6 is more than just a programming language. The secret to Visual Basic is
in its name: visual. With today’s Windows operating systems, a program
must be able to interact with the screen, keyboard, mouse, and printer
graphically. Older programming
Languages
such as BASIC, worked well in a text-only computing environment, but such
languages do not support the graphical interface needed for today’s computers.
In Visual Basic we will work with objects which have properties and methods.
Objects:
è a thing or noun
eg forms and controls
Properties:
è describes the
objects such as name, color, size, location, behavior etc
Methods:
è actions
associated with the objects such as move, print, clear etc.
Visual
Basic is a tool that allows you to develop Windows
(Graphic User Interface - GUI) applications. The applications have a
familiar appearance to the user. Visual Basic is event-driven, meaning
code remains idle until called upon to respond to some event (button pressing,
menu selection, ...). Visual Basic is governed by an event processor. Nothing
happens until an event is detected. Once an event is detected, the code
corresponding to that event (event procedure) is executed. Program control is
then returned to the event processor.
Visual
Basic comes in several varieties including the following:
•
Visual Basic Enterprise Edition: Created for team
programming environments and client/server computing where applications
distribute processing and data among several computers.
•
Visual Basic Professional Edition: Geared toward
professional programmers who want to get the most from the Visual Basic
programming environment. This edition includes a full set of tools and wizards
that help you package and distribute applications.
•
Visual Basic Learning Edition: The essentials with the
standard complement of programming tools and everything one needs to get
started programming. A multimedia CD-ROM called Learn VB Now comes with
the package as well as a full set of Microsoft Developer Network documentation so
that you will have the help that you require to learn and use Visual Basic.
Note:
A special edition of Visual Basic comes with a package called Visual Studio.
Visual Studio is a programming environment that supports several Microsoft
languages including Visual Basic, Visual C++, and Visual J++. When you use
Visual Basic, you use the same environment that users of these other languages
also use. Therefore, if you move to another programming language, you will not
have to master a new set of menus and dialog boxes.
STRUCTURE
OF VISUAL BASIC PROJECT
Application
(Project)
is made up of:
·
Forms -
Windows that you create for user interface
·
Controls -
Graphical features drawn on forms to allow user interaction (text boxes,
labels, scroll bars, command buttons, etc.) (Forms and Controls are objects.)
·
Properties -
Every characteristic of a form or control is specified by a property. Example
properties include names, captions, size, color, position, and contents. Visual
Basic applies default properties. You can change properties at design time or
run time.
·
Methods -
Built-in procedure that can be invoked to impart some action to a particular
object.
·
Event Procedures -
Code related to some object. This is the code that is executed when a certain event occurs.
·
General Procedures -
Code not related to objects. This code must be invoked by the application.
·
Modules -
Collection of general procedures, variable declarations, and constant
definitions used by application.
THE PROGRAMMING PROCESS
When
you write a Visual Basic project you follow three basic steps for planning and
also repeat the process in creating the project. The three steps involved:
·
Setting up the user interface
·
Defining the properties
·
Creating the codes
Design User Interface
When
you plan the user interface, you draw a sketch of the screen the user will see
when running your project. On the sketch show the forms and all the controls
that you plan to use, indicate the names that you want to give the form and
each of the objects on the form.
Defining the Properties
For
each object write down the properties that you plan to set or change during the
design of the form.
Designing the Code
This
step is where you write the procedures that will execute when your project is
being run. You will also determine which events require action to be taking and
make step by step plan for those actions.
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