Visusual basic

Contend
1.Introduction
2.Definition
3.Features
4.Variables Declaration
2/21/2016

Introduction to Visual Basic
Visual Basic is a programming language
and development environment created
by Microsoft.
Visual Basic provides a graphical user
interface GUI that allows the developer
drag and drop objects into the program
as well as manually write program code.
Visual Basic, also referred to as "VB," is
designed to make software development
easy and efficient
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Visual Basic 6.0
—1. Visual Basic is a programming
language and integrated
development environment.
—2. It derives from the much older
BASIC programming language, and
so is considered useful and easy
programming language for the
beginner to learn.
—3. Visual Basic 6.0 was the final
edition of Visual Basic.
2/21/2016

VISUAL BASIC: - GUI (Graphical User Interface)
•Easy to use / Interact
•Easy to understand and process
•Nearly every action can be implemented with click of the
mouse cursor.
Visual Basic is referred as event driven programming
language because each and every execution of the instruction
is executed on the occurrence of any event. These events are
always related with controls and components of the Visual
Basic package. The event can be related to button, text boxes
etc. where it can be a click event of the mouse cursor, change
event of the text box and so many which relates the entire
package to a GUI package with all the advantages of GUI
based applications.
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Feature Of visual basic 6.0
1. Learning Consists of all necessary tools required to
build main stream Windows Applications
2. Professional Includes advanced features such as tools
to develop ActiveX and Internet controls.
3. Enterprise In addition to all Professional features, it
also includes tools such as Visual
GUI Interface
Modularization
Object Oriented
Debugging
Macros IDE
Data access feature
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Guo Interface: - VB is a Graphical User
Interface language. This means that a VB
program will always show something on the
screen that the user can interact with to get a
job done.
Modularization: - It is considered good
programming practice to modularize your
programs. Small modules where it is clearly
indicated what comes into the module and
what goes out makes a program easy to
understand.
Object Oriented: - Object Oriented
Programming is a concept where the
programmer thinks of the program in
"objects" that interact with each other. Visual
Basic forces this good programming practice.
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The Major advantages of GUI based
applications are: -
•User Friendly: - It is very easy to use by the user who is not highly
computer literate.
•Easy to Understand: - The applications developed from Visual Basic
package can redirect the information to the users so that their
interaction with the system can be made very easy.
•Processing is Simple: - The user can interact with the application by
just using the mouse cursor and performing the click events which
allows to execute the instructions internally.
•Easy to Developer: - The development of any application in the Visual
Basic environment is very simple because there are inbuilt controls and
components which are ready to use in drag and drop mode. The
interfaces can be easily designed and instructions can be placed for
different processing under different actions.
The only major disadvantage in respect to the restriction on the
programmer or developer regarding the limitation in number of controls
attributes for the controls and events for the control. The developer is
2/21/2016

Variable Declaration: - In Visual Basic
environment, the variables are declared for
accepting the values from the controls in the
application. There are three categories in which
declaration of variable is performed. They are
mention below: -
Syntax: -
Dim <variable/object> as <data type/class>
Example: - Dim a as integer
Dim a, b, c as integer
•Local Variable: - Whenever any variable is
declared within an event or method of an interface
is referred as local variable. They are not
accessible outside the event or method.
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•Semi-Global: - This declaration of variable acts partially
like semi-global and as well as global. This declaration is
performed under general declaration of the code window
and are supposed to be accessible in all the events or
methods define for the interface. If there is only one
interface then it acts like global variable but when there is
more than one form in the application, it acts like semi-
global variable.
•Global Variable: - The concept of global variable in the
Visual Basic application is related with accessing the
variable in all the forms or interfaces in the application. The
global variables or methods are declared in a “module”
which can be placed in the application from the project
menu. The important aspect in declaring global variable is
in the use of “public” keyword. The variables and methods
in modules are defined as public.
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Option Explicit: - The variable declaration in
Visual Basic environment can be forced by the
compiler and as well as can be ignored by the
compiler. When it is necessary to declare the variable
and the compiler also validates the declaration of
variable then option explicit is placed as the first line
of code in the code window. When the declaration is
not mandatory then option explicit is removed from the
code window. It’s a standard practice to declare all
types of variables in the application. So that accurate
values can be stored in the respective variables.
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Code Window
• Private Sub Command1_Click ( )
....................................................
....................................................
End Sub
This is the most generic set of code visible in the code
window which allows the user to identify the type of action to
be performed in the application. The very first word “Private”
denotes that the scope of the action is limited to the interface
or form where it belongs. It can't be accessed outside the
form.
The second word “Sub” represents subroutine which
instructs the compiler regarding the set of instructions
provided by the user for execution and it doesn't return any
value.
The next word is combination of control and action for the
user interface. It describes the specific control with events so
that the execution of instructions can be performed when that
specific action occurs.
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The concluding combination i.e. “End Sub”
represents the termination of the particular subroutine. It is
essential because there is no curly brace to represent the
termination of the event or subroutine.
•Private/Public Function <function name> (...........)
<return type>
.............................................................................................
.............................................................................................
End Function
The above block represents the declaration of a function in
the Visual Basic environment. The first word is similar with
respect to subroutine but when the scope of the function is to
be declared as global accessibility then the access specifier
public is used otherwise for a single form or user interface
private access specifier is used.
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The next word function is also a keyword in the
Visual Basic environment which suggests the
compiler that a set of instructions will be executed
and at the same time when the execution will
complete it returns the value to the calling function,
subroutine or event. It also accepts argument
which can be supplied from user interface control
or variables. As the function returns a value it is
necessary to declare the return type of the function.
The return type is mention after the parameter list.
It is obvious that the function should be terminated
and for that “End Function” is used.
2/21/2016

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