vb 6.0 tutorial

7/30/2019 Vb 6.0 Tutorial

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Meaning

of

Visual Basic


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VB as Programming Language

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Visual Basic is a Programming tool that allows user to developWindows or

GUI ( Graphical User Interface ) applications. It means that rather

than writing numerous line for code to describe the appearance and

location for interface elements like C , C + + or Basic. User can simply

drag and drop pre-built objects into the form window on computer screen.

VB is a much enhanced version of BASIC programming language

( BASIC is Predecessor of VB ). The main difference is that the VB can

create windows programs by just Drag & Drop where as BASIC could onlycreate DOS programs or work only in CUI (Command User Interface ).


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Features of Visual Basic ( VB )

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VB introduces the concept of Event Driven programming Model.

It has built in Database Handling Features of VB.

It incorporated the concepts of objects.

It has useful Error

Handling Features.

It has Front End Application Developer.

It also known as RAD ( Rapid Application Development )


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Event & Event Procedure

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An event is an actionrecognized by an object, such

as clicking a mouse or pressinga key. User can write code torespond to that event. Eachobject has different eventsthat it recognizes.

An event procedure is a sectionof code that is executed when an

event (like clicking a commandbutton) takes place. Eventprocedures can be added to yourproject in the code editorwindow.


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Program Development Process

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It is a process in which an ordered sequence of steps is defined to

develop an application. It includes :-

How the Program should Work

Plan about User Interface

Implement it

Test it


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6

Starting

Visual Basic


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STARTING VB APPLICATION

Opening a Project : -

To open a VB project , invoke VB6

shortcut on the Desktop or going throughthe pull-up menu select VB program .

Start Program Microsoft Visual

Basic 6.0 .

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Visual Basic I D E

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When user choose any application platform, like any other window

application, VB consists of multiple window, which appear at start up. The

windows that are display when user start VB are collectively Known as

Visual basic Integrated Development Environment ( IDE ).


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Visual Basic I D E

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ProjectWindow

PropertiesWindow

FormLayoutWindow

FormWindow

Toolbox

Toolbar

Title bar Menu bar

Visual Basic Integrated Development Environment


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Properties Window

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The Properties window let user tochange the characteristics, or

property settings, of the form itselfand of visual interface elements on

the form. The Properties windowconsists of two columns: the first isthe name of the property, which usercannot change; the second column,which is the property setting thatuser can change. Any Change in the

property of the object will affectthe object on the form.


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Tool Box

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The toolbox consists ofthe various objects thatuser will use to design theapplication. These objects,called controls, are objectsthat user see in allstandard Win applications,such as textboxes,command buttons, option

(radio) buttons,checkboxes, etc.


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Form Window

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The Form window is thecentral area where usercan draw application. The

forms are windows whichholds control like Button ,Checkbox etc which makeuser application. The largearea of form is calledclient area for working

with different controls.


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Source Code Window

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The Source Code window iswhere user type the codewhich VB execute. It has

two parts Control Box ,Event Box . The Heading ofwindow indicate whichevent the code isassociated . It is a windowwhere user write most of

the code .


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Source Code Window

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It shows the control Boxwhich contains two controls( Command 1 & Form ).


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Source Code Window

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It shows the Event Boxthat Selected Control canperform these event.


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Saving a VB program

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Saving a Project : - After creating a Project , user need to save it . For

this click File menu and select save project. Then system asks : -

1. Provide a name for Form File ( . frm )

2. After that Provide a name for Project file ( .vbp )


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Running a program

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Running a Project : - After saving the project , the next step is to

execute the program. Following are different ways to execute a

project.

1. Press F5 Key

2. On Menu Bar Click Run - Start

3. On VB Toolbar , Click Run Icon.


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Opening a vb program

After you created and saved a file , you

can open it at any time.

Click fileopenselect your vb program

from the open dialogok

Then you can get your saved vbapplivation.

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Steps in DevelopingApplication

1. Draw the user interface

2. Assign properties to controls3. Attach code to controls


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Draw the User Interface

Visual Basic operates in three modes.

Design mode - used to build application

Run mode - used to run the application Break mode - application halted and

debugger is available


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Getting Started


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7 Windows

1. Main Window

2. Form Window

3. Toolbox4. Properties Window

5. Form Layout Window

6. Project Window7. Code Editor Window


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Main Window

consists of the title bar, menu bar, and

toolbar.


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Form Window

is central to developing Visual Basic

applications. It is where you draw your

application.


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Toolbox

is theselection

menu for

controlsused in your

application.


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Properties Window

is used to

establish initial

property values

for objects.


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Form Layout Window

shows where (upon program

execution) your form will be

displayed relative to your

monitors screen.


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Project Window

displays a list of all forms

and modules making up

your application.


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Code Editor Window

Contains the actual Basic coding.


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Assign Properties to Controls

Naming Convention of Controls

Object Prefix Example

Form frm frmHello

Command Button cmd, btn cmdExit, btnStart

Label lbl lblStart, lblEnd

TextBox txt txtTime, txtName

Menu mnu mnuExit, mnuSave

Check box chk chkChoice


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Attach Code to Controls

Code in a Visual Basic application is

divided into smaller blocks called

procedures.

Event procedure syntax:

object name_event()

Ex. Command1_Click ()


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Private Sub object name_event()

End Sub

___________________________________

____Private Sub Command1_Click ()

End Sub


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Private Sub Command1_Click ()

object name.property= value

End Sub

_______________________________________

Private Sub Command1_Click ()

Text1.Text = "Hello, world!"

End Sub


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Variables

Variable is a data name that is used to

strore a value.

Syntax :

Dim variablename as datatype

Example :

Dim a as IntegerDim b as Integer,c as Double,d as Date

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R l d i i i bl


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Rules used in naming variables

Variable name cannot exceed 255 characters.

They may include letters, numbers, and

underscore (_).

The first character must be a letter.

You cannot use a reserved word like

Dim,If,Else etc. Vb is not case sensitive.


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Data Types

VB supports all common data types such

as Bytes,Boolean,Date,Integer,String,

Double and variant etc.

Integer To store a integer value

String To strore a String (group of

characters).

DoubleTo store decimal value.

Visual Basic Controls


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Visual Basic Controls

Controls are the elements of the User Interface

with which the user can interact and

control the application. Form is the first and mainelement of the user interface which acts

as container for other elements. The basic

controls are displayed as icons on the toolboxwhich is a part of the interface during the design

time.

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TOOL BOX

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PICTURE BOX & IMAGE BOX

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Displays a graphic image. Itcan also serve as acontainer for other controls

Displays a graphic image.Similar in appearance to thepicture control but with

different functionality.Main property:Strutch =true


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LABEL ,TEXT BOX & BUTTON

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Displays text that the usercan edit.Main Properties :Multiline to enter multiple lines in text box.Password char to enter password format.Scollbar To make vertical or horisontal

Scrollbars.

Enables the user to initiate aprogram action.

To pass information to the user throughtext.


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FRAME & TIMER

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Serves as a container for other controls.Provides a method for groupingcontrols. (To group controls in a frame, selectthe frame with a single-click first,

then draw a control in it.)

Provides a means for an action to be takenafter passage of a certain amount of time.

Main Property :Interval property integer value ranges from0 to 65535.A zero value disables thetimer.Positive value represents the number ofmilliseconds between timed events.


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CHECK BOX & OPTION BUTTON

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Displays or enables input ofa two-part choice, such asYes/No or True/False.At a time more thanone check box can be selected.

Value 1=checked and 0=unchecked.

Displays or enables achoice among multipleitems. (Also known as a

radio button.).Only one option can be select at a time.True=option selected and False=Optiondeselected.


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OLE & DATA CONTROL

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OLE=Object linking and embedding which is usedto place other files such as word,poerpoint,exceletc with the vb form.

Provides a link to database files.It act as amediator between front end (vb) and back end(database=access).That means it connects vb and access.


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COMBO BOX & LIST BOX

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Enables the user to select anentry from a list or enter anew value.It is a combination of text box and list box.Value can to added to it through coding or by

using list property in pro.pert box

Displays a list of itemsfrom which the user can

select one or more entries.Value can to added to it through coding or byusing list property in pro.pert box


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HscrollBar & VscrollBar

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Produces a numerical value

based on the scroll bar'svertical position.

Produces a numerical valuebased on the scroll bar'shorisontal position.

DriveListBox & Dir ListBox &


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DriveListBox & Dir ListBox &

FileListBox

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Displays and enables a user to choose fromavailable disk drives on the computer.

Displays and enables a userto choose from availablesubdirectories on a drive.

Displays and enables a userto choose from availablefiles in a directory.


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LINES & SHAPES

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Displays lines on the form

Displays geometric shapeson the form such as circle,rectangle,oval

etc.


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OPERATORS

VB contains the following operators.

Arithmetic operator

Assignment operator

Relational operator

Logical Operator

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ARITHMETIC OPERATOR

SYMBOL MEANING

+ Addition

- Subtration

* Multiplication

/ Common division operator that gives result

in real number (decimal number).

\ Used for integer division that gives result in

integer.^ Exponential (To get the power value.).

Mod To get the remainder.

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ASSIGNMENT OPERATOR

The = sign is used to assign a value to a

variable.

Example :

Dim a as Integer

a=10

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RELATIONAL OPERATOR

SUMBOL MEANING

= Equal Not Equal

< Less than

> Greater than

< Less than or equal to

> Greater than or equal to

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Logical Operator

The logical operators are

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SYAMBOL MEANING

AND Both conditions must be true.

OR Either one condition is true.

NOT True changes to false case and vice versa


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VB Control Structures

In a program, statements may be executedsequentially, selectively or iteratively. Every

programming language provides constructs tosupport sequence, selection or iteration. Sothere are three types of programmingconstructs :

Sequential Constructs Selection Constructs

Iterative Constructs

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CONTROL FLOW


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Sequential Construct

The sequential construct means the

statements are being executed

sequentially. This represents the default

flow of statements.

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Stament 1

Stament 2

Stament 3


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Selection Construct

The selection construct means the

execution of statement(s) depending

upon the condition-test. If a condition

evaluates to true, a course-of-action (aset of statements) is followed otherwise

another course-of-action is followed. This

construct is also called decisionconstruct as it helps in decision making.

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Selection Construct

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Condition? Statement 1 Statement 2

Statement 2

Statement 1

One course-of-action

Anothercourse-

of-action

true

false


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Iterative Constructs

The iterative or repetitive constructs

means repetition of a set-of-statements

depending upon a condition-test. A set-

of-statements are repeated again andagain till the condition or Boolean

Expression evaluates to true. The

iteration constructs are also called aslooping constructs.

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Iterative Construct

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Condition?

Statement 2

Statement 1 The loopbody

false

The exitcondition True


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Selection Constructs

VB provides two types of selection construct :

1) If statement

2) Select Case statement

The If Statement : If statement of VB comes invarious forms & are given below:

1) If..Then Statement

2) If..Then..Else Statement

3) If..Then..ElseIf Statement

4) Nested Ifs

f S


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If..Then Statement

Def. : An If..Then statement tests a

particular condition; if the condition

evaluates to true, a course-of-action is

followed otherwise it is ignored. Syntax :

If (condition) Then

statements

End If

If Th S


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If..Then Statement

Example 1. :If (Num>0) Then

Print It is a positive number

End if

Example 2 :

If txtAge.Text>=18 ThenPrint You are eligible to vote

End if

If Th El St t t


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If..Then..Else Statement

If..Then..Else statement provides an alternatechoice to the user i.e. if the condition is truethen a set of statements are executedotherwise another set of statements are

executed. Syntax :

If (condition) Then

VB Statement(s)Else

VB Statement(s)

End If

f f


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Examples of If..Then..Else

Example 1 :

If txtAge.Text>=18 ThenPrint You are eligible to vote

Else

Print Sorry, You are not eligible to vote

End If

Example 2 :

If Num Mod 2=0 Then

Print It is an Even Number

Else

Print It is an Odd Number

End If

If Th El If S


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If..Then..ElseIf Statement

If..Then..ElseIf statement is used to test a number of mutuallyexclusive cases and only executes one set of statements for thecase that is true first.

Syntax :

If (condition 1) Then

Statement(s)ElseIf (condition 2) Then

Statement(s)

ElseIf (condition 2) Then

Statement(s)

:Else

Statement(s)

End If

E l f If Th El If


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Example of If..Then..ElseIf

If (Age


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Nested Ifs

A nested If is an if that has another If in its ifsbody or in its elses body. The nested if can haveone of the following three forms :

1. If (expresssion 1) Then

If (expression 2 ) Then

Statement 1[Else

Statement 2

End If

Else

body-of-else]

End If

N t d If


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Nested Ifs

2. If (expression 1) Then

body-of-if

Else

:

If (expression 2) Then

Statement-1

[Else

Statement-2]

End If

Nested Ifs


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Nested If s

3) If (expression 1) Then

:


Statement-1

[Else

Statement-2]

End IfElse


Statement-3

[Else

Statement-4]:

End If

End If

E l f N t d If


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Example of Nested Ifs

If Num>0 Then

Print It is a positive number

Else

If Num


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Select-Case Statement

Select-Case is a multiple branchingstatement and is used to executed a set of

statements depending upon the value of

the expression. It is better to use Select-Case statement in comparison to

If..Then..ElseIf Statement when the

number of checks are more. There are 3

different forms of using Select-Case

statements and are given below :

Diff t f f S l t C


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Different forms of Select-Case

1. Select Case : Simplest Form [Exact match]

Select Case Expression

Case Value

one or more visual basic statements

Case Value


Case Else :one or more visual basic statements

End Select

E l f F 1


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Example of Form 1

Select Case byMonth

Case 1,3,5,7,8,10,12

number_of_days=31

Case 2

number_of_days=28

Case 4,6,9,11

number_of_days=30

End Select

Syntax of Form 2


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Syntax of Form 2

Select Case : Second Form [Relational Test]


Case is relation :


Case is relation :


[Case Else :


End Select

Example of Form 2


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Example of Form 2

Select Case marksCase Is < 50

Result = Fail

Case Is < 60Result = Grade B

Case Is < 75

Result = Grade A

Case Else

Result = Grade A+

End Select

Third Form of Select Case


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Third Form of Select Case

Select Case : Third Format [Range Check]


Case exp1 To exp2:


Case exp1 To exp2:


[Case Else:


End Select

Example of Form 3


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Example of Form 3

Select Case Age

Case 2 to 4 : Print PreNursery

Case 4 to 6 : Print Kindergarden

Case 6 to 10 : Print Primary

Case Else : Print OthersEnd Select

Iterative Constructs (Looping


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( p g

Structures)

A loop is said to be the set of instructions

which are repeated again and again in aprogram.

TYPES OF LOOP


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TYPES OF LOOP

1) Sentinel-controlled Loop Structures :repeat statements until a special valuecalled sentinel value (or the terminating

value) is reached.2) Counter-controlled Loop Structures :

repeat the set of statements until thevalue specified by the counter variable

is reached.

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Looping Structures


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Looping Structures

VB offers broadly following three types oflooping structures :

1. For..Next

2. Do Loopa) Do While..Loop

b) Do..Loop While

c) Do Until..Loopd) Do..Loop Until

3. While..Wend

F N t St t t


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For..Next Statement

This type of statement is used when theuser knows in advance how many times

the loop is going to be executed.

Syntax :

For = To

Step

One or more VB Statements

Next

Examples


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Examples

Example 1 : Generate natural nos from 1to 100

For I = 1 To 100

Print INext I

Example 2 : Generate first 20 even nos.

For E = 2 to 40 Step 2Print E

Next E

More Examples


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More Examples

Example 3 : Generate odd nos from 100to 30 in a list box.

For O = 99 to 31 Step -2

ListO.AddItem(O)Next O

Example 4 : Generate table of any number

N.For T = 1 To N

Print N; *; T; =; N*T

Next T

More Examples


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More Examples

Example 5 : Find factorial of a givennumber N.

:

Fact=1For I= 1 to N

Fact = Fact * I

Next IPrint Factorial of ; N; =; Fact

:

Do Loop Structures


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Do..Loop Structures Do While..Loop : Do While loop is an entry

controlled loop in which the condition isplaced at the entry point. This statementexecutes the statements specified in thebody of the loop till the condition evaluatesto true. The loop may not be executed atall the if the condition is initially false.

Syntax :

Do While


Loop

Examples of Do While Loop


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Examples of Do While..Loop

Example 1 : Never executes loop

Dim A as ByteA=10

Do While A>10

A=A-1

Loop

Example 2 : Executes loop

Dim P as Byte

P=20Do While P>5

P=P-2

Loop

Do Loop While


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Do..Loop While

Do Loop While is an exit controlled loop asthe condition is placed at exit point. Thebody of the loop is going to be executed at

least once whether the condition evaluatesto true or false. Loop is executed as longas the result of the condition remains true.

Syntax :

Do


Loop While

Examples


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Examples

Example 1 :Do

num = InputBox (Enter a number)

sum = sum + num

Loop While num < > 0

Here the statements inside the loop will be

executed once no matter what the

comparison test evaluates to.

Do Until Loop


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Do..Until Loop

Do Until loop is an entry controlled loop inwhich the condition is placed at the entry point.This statement executes the statementsspecified in the body of the loop till the

condition evaluates to false. The loop may notbe executed at all the if the condition is initiallytrue.

Syntax :

Do Until One or more VB Statements

Loop

Examples of Do Until Loop


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Examples of Do Until..Loop

Example 1 : Never executes loop

Dim A as ByteA=10

Do Until A


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Do..Loop Until

Do Loop Until is an exit controlled loop asthe condition is placed at exit point. Thebody of the loop is going to be executed at

least once whether the condition evaluatesto true or false. Loop is executed as longas the result of the condition remainsfalse.

Syntax :Do


Loop Until


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Examples

Example 1 :Do

num = InputBox (Enter a number)

sum = sum + num

Loop Until num = 0

Here the statements inside the loop will be

executed once no matter what the

comparison test evaluates to.

While Wend


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While..Wend

While..Wend loop is functionally equivalentto the Do While..Loop. It executes a set of

VB statements till the condition evaluates

to true.

Syntax :

While

one or more vb statements

Wend

Examples


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Examples

Example 1 : Generate the sum of first 10natural nos

I = 1

While I


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Nested Loops

A loop within another loop is called asNested Loop.

Example :

For I = 1 to 5For J = 1 To 3

Print J

Next JPrint

Next I

Inner Loop Outer Loop

Working of Nested Loops


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Working of Nested Loops

In nested loops the inner loop is executedcompletely for one time execution of the

outer loop. In the Previous example the

Inner Loop will be executed three times forevery execution of the outer loop.

Nested loops are very useful when there is

a requirement to generate different kind ofpatterns as output.

vb 6.0 tutorial

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