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what do mean by Hide and Show form methods ? Give the syntax

By Dinesh Thakur

You can display a form with show method and Cancel a form with hide method use the hide method .When you want to make sure when form disappears.

 

 

Syntax:

 

<formname>.Show (Style)

 

Formname is name of form you which to display the optional style determines whether form will display model or modeless.value for style are of or modelless and for model default is 0.You can also use the VB intrinsic constants: vbModal and vbModeless.

 

When you display a form as model user must response to form in some way usually by clicking command button number other program code can execute until modal form has been reponsed for hidden.However, if you display modeless user may switch to another form without respond to form.

 

Example

 

 

frmSombody.show

frmSombody.show vdModal

frmSombody.show vdModeless

The hide method is similar to show method but it is used to remove from form screen

<formname>.hide

 

 

Difference Between Hide and Unload Form Methods

By Dinesh Thakur

i. hide method is used to remove the form from the screen.

ii.it does not get removed the memory location.

 

iii. Syntax:

<fromname>.hide

iv.Example:

frmSomebody.hide

v.unload method is used to unload the form.

vi.unload method remove the form from the memory.

vii.Syntax:

Unload.<Formname>

viii.Example:

Unload Me

 

 

Subroutines and Functions

By Dinesh Thakur

The code you write won’t be a monolithic listing. It will be made up of small segments called procedures and you will work on one procedure at a time. This is called modularized approach of programming.

 

It permeates the Visual Basic language even the longest applications are written by breaking them into small, well defined tasks. Each task is performed by a separate procedure that is written and tested separately from the others. Procedures are useful for implementing repeated tasks.

The two types of procedures are subroutines and functions—the building blocks of your application.

Subroutines : A subroutine is a block of statements that carries out a well-defined task. The subroutine begins with Sub and name of subroutine and its execution stops when EndSub statement is reached, and control returns to the calling program. It is possible to exit a Subroutine prematurely with the Exit statement.

 

Functions : A function is similar to a subroutine, but a function returns a result. Subroutines perform a task and don’t report anything to the calling program; functions commonly carry out calculations and report the result. The statements that make up a function are placed in a pair of Function/End Function statements. Because the function must report the result to the calling program, it must have a return type.

 

Give the Steps Required to Convert a Project into an .exe File

By Dinesh Thakur

You can create .exe file of your project which a executable file. In windows after clicking on the .exe file project starts running. The simple steps for creating .exe file are as follows:

 

1. After completing project save it.

 

2. Then click on file menu.

 

3. In file menu there is an sub menu ‘Make Project’.

 

4. After clicking on Make Project sub menu it will open a save dialog box to locate the path where .exe file will be created.  Select the location and click on Ok then your project will be converted into .exe file at specified location.

 

Difference Between ByRef and ByVal. When would each be used

By Dinesh Thakur

When you pass a value to procedure you may pass it ByVal of ByRef

The ByVal sends a copy of the argument’s value to the procedure cannot alter the original value. ByRef sends a reference indicating where the value is stored in memory, allowing the called procedure to actually change the argument’s original value.  

 

You can specify how you want to pass the argument by using the ByVal or ByRef keyword before the arguments. Arguments are passed by reference by default.

What is return value? How it can be used

By Dinesh Thakur

While writing a Function procedure you must set up a return value. This return value is placed in the a variable that Visual Basic names the with the procedure name as function name.

 

You can also specify the data type of return value by adding as clause after the function name. If return type of Procedure is Currency the procedure should be named as curCommission()

 

The return value can be used as follows:

 

Private Function curCommission(ByVal curSalesAmount as Currency) as Currency

 

‘Calculate the sales commission

If curSalesAmount < 1000 Then

curCommission = 0

Else

curCommission = 1.5 * curSalesAmount

End If

End Function

 

Difference Between Sub Procedure and Function Procedure

By Dinesh Thakur


Sub Procedure

Function Procedures

 

Sub Procedure is procedure that performs some action.

Function Procedure also perform some action but also returns some value to point from which it was called

 

Syntax for Sub Procedure is as follows:

Private Sub <procedure name>

‘ Actions to performed

End Sub

Syntax for Function Procedure is as follows:

Private Function Commission()

‘ Action to performed

Commission = <value that to be return>

End Function

 

Example:

Form_Load()

Example:

Val(), FormatPercentage()

What does the common dialog box means? Explain types of common dialog boxes

By Dinesh Thakur

1. You can use set of predefined standard dialog boxes in your projects for such tasks as specifying colors and fonts, printing, opening and saving. The common dialog boxes control, which is a custom control, allows your project to use the dialog boxes that are  provided as a part of the Windows environment.

2. To use the common dialog control, you first place a control, and its location doesn’t matter, you can not change size of the control, since it will be invisible when your program will run.

3. In code when you wish to display one of the standard dialog boxes, you refer the properties and methods of the control.

4. You don’t need more than one dialog control on your form.

In Visual Basic common dialog box provides commonly used dialog boxes as given below:

1. Color Dialog Box:

Visual Basic common dialog box provides Color dialog box which can be used for user to select color from the common dialog box. You can assign the values selected by user to controls in your project. This dialog box can be used by writing a code as follows:

dlgCommon.ShowColor

2. Font Dialog Box:

Font Dialog Box allows user to select his custom font setting like, font name, font size, font color, font style, strike through etc. To display the font dialog on screen use ShowFont method of the common dialog object.

But before using the ShowFont method you first initiate the flag property for font that is cdlScreenFont.

3. Save Dialog Box:

Visual Basic even provides save file dialog box which displays a save file dialog box to get the path for file to save.

What is Separator Bar and How it is Created

By Dinesh Thakur

1. When you create menus in the menu bar, you should group the commands according to their purpose. You can create a separator bar in a menu, which draws a bar across the entire menu.

 

2. To define a separator bar, type a single hyphen(-) for the caption and give it a name. Even though you can never refer to separator bar in code and it does not have click event, you must still give it a unique name. Call your separator bar mnuSep1.

 

Difference Between Menus and Submenus

By Dinesh Thakur

1. Menus:

 

a. Menus consist of a menu bar with menu names, each of which drops down to display a list of menu commands.

b. You can use menu commands in place of or addition to command buttons to active procedures.

c. Menu commands are actually controls; they have properties and events. Each event has name property and click event, similar to action command buttons.

 

2. Sub menus:

 

d. The drop down list of commands below a menu name is called a menu. When a command on the menu has another list of commands that pops up, the new list is called submenu.

e. The filled triangle to the right of the command indicates the a menu command has a sub menu.

 

Different Looping Constructs in VB

By Dinesh Thakur

Loop statements allow you to execute one or more lines of code repetitively. Visual Basic supports the following loop statements:

Do……Loop : The Do……Loop executes a block of statements for as long as a condition is True. Visual Basic evaluates an expression, and if it’s True, the statements are executed. If the expression is False, the program continues and the statement following the loop is executed.

 

There are two variations of the Do……Loop statement. A loop can be executed either while the condition is True or until the condition becomes True. These two variations use the keywords While and Until to specify how long the statements are executed. To execute a block of statements while a condition is true, use the following syntax :

 

Do While condition

statement block

Loop

 

To execute a block of statements until the condition becomes True, use the following syntax :

 

Do Until condition

statement block

Loop

 

Another variation of the Do loop executes the statements first and evaluates the condition after each execution. This Do…Loop has the following syntax :

 

Do

statements

Loop While condition

Or

Do

statements

Loop Until condition

 

For…..Next : The For…….Next loop is one of the oldest loop structures in programming languages. Unlike the Do….loop, the For …..Next loop requires that you know how many times the statements in the loop will be executed. The For…Next loop uses a variable(it’s called the loop’s counter) that increases or decreases in value during each repetition of the loop. The

 

For…..Next loop has the following syntax :

 

For counter=start to end[Step increment]

statements

Next[counter]

 

The keywords in the square brackets are optional. The arguments counter, start, end and increment are all numeric. The loop is executed as many times as required for the counter to reach the end value.

While ………Wend : The while……wend loop executes a block of statements while a condition is True. The while…..wend loop has the following syntax :

 

While condition

statement – block

Wend

 

If condition is true, all statements are executed and when the Wend statement is reached, control is returned to the While statement which evaluates condition again. If condition is still True, the process is repeated. If condition is False, the program resumes with the statement following the Wend statement.

 

Branching Statements in Visual Basic

By Dinesh Thakur

An application needs a built-in capability to test conditions and take a different course of action depending on the outcome of the test. Visual Basic provides three control flow, or decision, structures :

 

If……Then : The If….Then structure tests the condition specified, and if it’s True, executes the statement(s) that follow. The If structure can have a single-line or a multiple-line syntax.

 

The general form is : If condition Then statement

 

If……Then……Else : A variation of the If……Then statement is the If……Then……Else statement, which executes one block of statements if the condition is True and another if the condition is False. The syntax of the If… Then….Else statement is as follows:

 

If condition Then

statement block-1

Else

statement block-2

End If

 

Select Case : The Select Case structure compares one expression to different values. The advantage of the Select Case statement over multiple If…..Then…..Else statements is that it makes the code easier to read and maintain.

 

The Select Case structure tests a single expression, which is evaluated once at the top of the structure. The result of the test is then compared with several values, and if it matches one of them, the corresponding block of statements is executed.

 

The syntax is :

Select Case expression

Case value1

Statement block-1

Case value2

Statement block-2

.

.

.

Case Else

Statement block

End Select

 

difference between step into and step over

By Dinesh Thakur

Step into: Most likely you will use step into command more than you will use step over command.

When you choose step into, the next line of the code is executed and the program pauses again in break time. If line of code is call to another procedure will be displayed. To continue stepping through your program execution, continue choosing the step into command.

Step over: The step over also executes one line of code at a time. The difference between Step Over and Step Into occurs when your code calls to other procedure. Step over displays only one line of code in the current procedure.

 

Define the term Validation. When is it appropriate to do validation

By Dinesh Thakur

Validation is a form of self protecting; it is better to reject bad data then spend hours trying to find out an error only to discover that the problem was caused by a “user error”.

 

Checking to verify that appropriate values have been entered for the text box is called validation. The validation may include making sure that data is numeric, checking for specific values, checking a range of values, making sure that required data is entered.

What is a message box? Type Of message box

By Dinesh Thakur

A message box is special type of Visual Basic window in which you can display a message to the user. You can display message, an optional icon, a title bar caption, and command buttons in a message box.

 

You may want to display a message when the user has entered some invalid data or neglected to enter some required data value.

 

Message box constant:

 

vbQuestion : This constant sets a Question marked icon for the message box. It can be used as follows: MsgBox “Lets this be warning”, vbQuestion, “Error”

 

vbOkOnly: This constant makes message box to appear with only one ok button. Example: MsgBox “Welcome”, vbOkOnly “ Greeting”.

 

vbInformation: Shows information icon on the message box. Example: MsgBox “Welcome”, vbInformation “ Greeting”.

 

Variable’s Scope and Lifetime of a Variable

By Dinesh Thakur

A Variable’s Scope : The scope of a variable is the section of the application that can see and manipulate the variable. If a variable is declared within a procedure, only the code in the specific procedure has access to that variable. When the variable’s scope is limited to a procedure it’s called local.

 

e.g.

Private Sub Command1_Click()

Dim i as Integer

Dim Sum as Integer

For i=0 to 100 Step 2

Sum = Sum +i

Next

MsgBox “ The Sum is “& Sum

End Sub

A variable whose value is available to all procedures within the same Form or Module are called Form-wide or Module-wide and can be accessed from within all procedures in a component.  In some situations the entire application must access a certain variable. Such variable must be declared as Public.

Lifetime of a Variable : It is the period for which they retain their value. Variables declared as Public exist for the lifetime of the application. Local variables, declared within procedures with the Dim or Private statement, live as long as the procedure.

You can force a local variable to preserve its value between procedure calls with the Static keyword. The advantage of using static variables is that they help you minimize the number of total variables in the application.

Variables declared in a Form outside any procedure take effect when the Form is loaded and cease to exist when the Form is unloaded. If the Form is loaded again, its variables are initialized, as if it’s being loaded for the first time.

What are Constants

By Dinesh Thakur

Some variables don’t change value during the execution of program. These are constants that appear many times in your code. The constants are preferred for two reasons :

 

• Constants don’t change value

• Constants are processed faster than variables

The general form to declare a constant is as follows :

Const constantname [As type] =value

The As type part of the declaration is optional. If you omit it, the constant’s type is determined by the value you assign to it. Constants also have a scope and can be Public or Private.

e.g. Public Const pi as Double =3.14159265358979

Visual Basic uses constants extensively to define the various arguments of its methods and the settings of the various control properties.

How variables are declared in Visual Basic

By Dinesh Thakur

Variables are used to store values during a program’s execution. So, variables are place values in which you can leave values and recall them at will.

 

Declaring Variables : In most programming languages, variables must be declared in advance for the compiler.

Explicit Declarations : To declare a variable, use the Dim statement followed by the variable’s   name and type as follows :

 

o Dim Meters as Integer

 

o Dim Names as String Implicit Declarations : When Visual Basic meets an undeclared variable name, it creates a new variable on the spot and uses it. The new variable’s type is variant, the generic data type that can accommodate all other data types.

The reserved word Dim is really short for dimension, which means ‘Size’. When you declare a variable, the amount of memory reserved depends on its data type. In the Dim statement [as data type] is optional. If you omit that statement the default data type is applied to the variable.

 

Dim var1, var2

var1=”Thank you”

var2=43.23

 

The var1 variable is a string variable, and var2 is a numeric one.

 

Types of Variables 

Integer:

Integer data type can store any whole numbers with in the range -32,768 to 32,767.

 

String:

String is also the most commonly used data type which can store Alphabetical data like letters, digits, other characters.

 

Variant:

Variant data type is default data type which can store the any kind of data like Integer, String, Object etc.

 

Currency:

Currency stores Decimal fractions, such as dollars and cents.

 

Date:

The date is also a data type which stores eight-character date.

 

Double:

Double-precision floating-point numbers with 14 digits of accuracy.

 

Long:

Larger whole number.

 

Object : An object variable refers to one of Visual Basic’s many objects, and you can use an object variable to access the actual object.

 

Variant : This is the most flexible data type because it can accommodate all other types.

 

 

What effect does the location of a Dim statement has on the variables is declares

By Dinesh Thakur

1. There are several ways of declaring the variable, the most commonly used statement is Dim statement to declare the variable. The syntax for declaring the variable using Dim is as follows:

 

Dim Identifier [As Data type]

 

2. The reserved word Dim is really short for dimension, which means ‘Size’. When you declare a variable, the amount of memory reserved depends on its data type.

 

3. In the Dim statement [as data type] is optional. If you omit that statement the default data type is applied to the variable.

 

4. Example for using Dim statement:

 

Dim strName as String                       ‘Declared the String variable

Dim intCounter as Integer                   ‘Declared an Integer variable

Dim curDiscount as Currency            ‘Declared a currency variable

Dim vntChanging                                ‘Default variant data type

 

What is Purpose of the Val Function

By Dinesh Thakur

1. Visual Basic provides number of built in functions. The Val function is one of it. Val function converts the text data into a numeric value.

 

The general form of Val function is as follows:

Val(Expression to Convert)

 

2. The expression you wish to convert can be the property of control, a variable, or a constant.

 

3. A function can not stand by itself. It returns (produces) a value that can be used a part of a statement, such as the assignment statements in the following examples.

 

4. When the Val function converts as argument to numeric, it begins at argument’s left most character. If that character is a number digit, decimal point, or sign, Val converts the character to numeric and moves to the next character. As soon as a nonnumeric character is found, the operation stops.

 

5. Example: Val(123.45) will return = 123.45 and Val(123A5) will return 123 only.

 

Explain Order of Precedence of Operators for Calculations

By Dinesh Thakur

1. The order in which operator are performed determines the result. Consider the expressions 3 + 4 * 2. Over here if addition is done first, the result is 14. However, if multiplication is done first then result is 11.

 2. The hierarchy of operations, or order of operations, or order of precedence, in arithmetic expressions from highest to lowest is:

 

a. Exponentiation

b. Multiplication and Division

c. Addition and Subtraction

 

3. In the previous example, the multiplication is done before addition, and the result is 11. to change the order of evolution, use parenthesis:

(3 + 4) * 2 will yield 14 as the result. One set of parenthesis can be used inside another set. In the case, parenthesis are said to be nested.

Explain Boolean variable test for True and False. Give example

By Dinesh Thakur

In Visual Basic there are some controls properties that return you a Boolean value which can be as condition in the testing. For example, option buttons returns true when they are selected and returns you false when they are not.

 

These Boolean variables can be tested as follows:

 

If optFreshman.Value = True Then

mintFreshmanCount = mintFreshmanCount + 1

ElseIf optSophomore.Value = True Then

mintSophoreCount = mintSophoreCount + 1

End If

 

Explain purpose of relational operators and logical operator

By Dinesh Thakur

Relational operators: Relational operators are used for comparison of to variables of same data type. These operators are used in the conditions where two values are compared and true or false is returned according to test result.

Example: 3 > 5 returns you false and 3 < 5 returns you true, which can be used in if statement.

 

Logical operators: Logical operators are used write a compound condition. You can use compound conditions to test more than one condition. Create compound condition by joining two conditions with Logical Operators. The Logical Operators are Or, And and Not.

 

Example:

 

If optMale.Value = True And Val(txtAge.Text) < 21 Then

minMinorMaleCount = minMinorMaleCount + 1

End If

What is the general format of the statement used decisions in an application

By Dinesh Thakur

1. A power full asset of the computer is its ability to make decisions and to take alternate course of action based on the out come.

 

2. A decision made by the computer is formed as a question: is a given condition is true of false.

 

3. Decision can be taken using If statement which is used as follows:

 

If the sun is shining Then                    (Condition)

Go to beach                                        (Action to take)

Else

Go to Class                                         (Action if Condition is false)

End If

 

4. In If statement, when the condition is true, only Then clause is executed. When condition is false, only the Else clause, if present is executed.

 

If… Then statement general form is

 

If (Condition) Then

Statement(s)

Else

Statement(s)

End If

 

5. A block If … Then … Else must always include with End If. The word Then must appear on the same line as the If with nothing following Then. End If and Else clauses are indented for readability and clarity.

What is the Continuation operator ? When is it used

By Dinesh Thakur

When a Basic statement become too long for one line , use a line-Continuation

character.You can type a space and an underscore , press Enter, and continue the statement on the next line . It is OK to indent the continued lines.The only restriction is that the line-continuation character must appear between elements; you cannot place a continuation in the middle of a literal or split the name of an object or property.

 

Example:

 

lblGreetings.Caption = ” Greetings ” & txtName.Text & ” : ” & ” You have been selected to win a free prize.”

 

Explain Objects and Modules? What are the types of Modules in VB

By Dinesh Thakur

Objects : Objects are the real world entities. People, companies, employees, fan and ledger entries are all types of objects. In object-oriented terms, the word object is used to describe one specific thing like a car. Objects have an identity and this identity is defined with properties. A car has its name, model, cost and color.

 

Objects also do things. E.g. the car accelerates, races etc. The things an object can do are called its behaviours.

 

Objects can be anything that exists in real world. They can be conceptual things, such as engineering process or payroll. These conceptual things are not tangible but are conceptual. The same object-oriented concepts apply regardless of whether the object is based on the real world, on a concept, or on the implementation.

 

Modules: Modules are collection of code and data that function something like objects in objects oriented programming, but without defining OOP characteristics like inheritance, polymorphism etc. The concept behind modules is to enclose procedures and data in a way that hides them from the rest of the program.

 

The two main types of procedures used in VB :

 

Event and General : In VB event procedures are invoked in response to keyboard, mouse or system action. Your code can also explicitly invoke event procedures. The maximum number of events a control can have is fixed. Event procedures are stored in a form module and are private by default. A general procedure is not executed unless explicitly invoked. You can create a general procedure either by choosing the procedure from the insert menu or by typing the procedure heading Sub followed by the procedure name on a blank line.

 

Event and general procedures are further classified as : Sub & Function.

 

What are the common properties of the Controls

By Dinesh Thakur

The following properties apply to most of the objects :

• Name : It sets the name of the control, through which you can access the control’s properties and methods.

• Appearance : It can be 0 for a flat look or 1 for a 3-D look.

• Back Color : It sets the background color on which text is displayed or graphics are drawn.

• Fore Color : It sets the foreground color

• Font : It sets the face, attribute, and size of the font used for the text on the control.

• Caption : It sets the text that is displayed on many controls that don’t accept input, for example, the text on a Label control, the caption of a Command Button control.

• Text : It sets the text that is displayed on the controls that accept user input, for example, the TextBox control.

• Width & Height : These properties set the control’s dimensions.

• Left & Top : These properties set the coordinates of the control’s upper-left corner, expressed in the units of the container.

• Enabled : By default, this property’s value is True, which means that the control can get the focus.

 • Visible : Set this property to False to make a control invisible.

Explain the elements of the User Interface

By Dinesh Thakur

The user interface is what appears in the application’s window when it runs. It consists of various elements with which the user can interact and control the application. The first element of the user interface is the Form.

 

(i) Picture Box : This control is used to display images, and the images are set with Picture property

(ii) Label : This control displays text on a Form that the user can’t edit.

(iii) Text Box : It displays text that the user can edit.

(iv) Frame : It is used to draw boxes on the Form and to group other elements.

(v) Command Button : It is the most common element of the Windows interface. It represents an action that is carried out when the user clicks the button.

(vi) Check Box : It presents one or more choices that the user can select.

(vii) Option Button : Also called as radio buttons, appear in groups, and the user can choose only one of them.

(viii) Combo Box : It is similar to the List Box control, but it contains a text Edit field. The user can choose an item from the list or enter in the Edit field.

(ix) List Box : It contains a list of options from which the user can choose one or more. The user can scroll the list to locate an item.

(x) The Horizontal and Vertical Scroll Bars : The user specify a magnitude by scrolling the control’s button between its minimum and maximum value.

(xi) Timer : It is used to perform tasks at regular intervals.

(xii) File System Controls : These controls are used to add file-handling capabilities to your application

(xiii) Image : It is similar to the Picture Box control in that it can display images, but it supports only a few features of the Picture Box control and requires fewer resources.

(xiv) Data : It provides point and click access to data stored in data- bases.

(xv) OLE : It is a window you can place on your Form to host documents from other applications, such as Microsoft Word or Excel

What is an IDE

By Dinesh Thakur

Visual Basic is not only a language. It’s an Integrated Development Environment in which you can develop, run, test and debug your applications.

 The types of project that you can create in Visual Basic are as follows :

 

(i) Standard EXE : These are the typical applications that you develop with previous versions of Visual Basic.

(ii) ActiveX EXE, ActiveX DLL : These types of projects are available with the Professional edition. ActiveX components are OLE automation servers.

(iii) ActiveX Control : This type of project is also a feature of the Professional edition. We use it to develop your own ActiveX controls.

(iv) ActiveX Document EXE, ActiveX Document DLL : ActiveX documents are in essence Visual Basic applications that can run in the environment of the container that supports hyper-linking.

(v) VB Application Wizard, VB Wizard Manager : The Application Wizard takes you through the steps of setting up the skeleton of a new application. The Wizard Manager lets you build your own wizard.

(vi) Data Project : It’s identical to the Standard EXE project type, but it automatically adds the controls that are used in accessing databases to the Toolbox.

(vii) DHTML Application : VB6 allows you to build Dynamic HTML pages that can be displayed in the browser’s window on a client computer.

(viii) IIS Application : VB6 allows you to build applications that run on the Web server and interact with clients over the Internet with the Internet Information Server.

(ix) Addin : You can create your own add-ins for the VB IDE. These are special commands you can add to Visual Basic’s menus.

(x) VB Enterprise Edition Controls : It simply creates a new Standard EXE project and loads all the tools of the Enterprise Edition of Visual Basic.

What are objects and properties? How are they related to each other

By Dinesh Thakur

Objects:

 

Think of objects as a thing, or a noun. Examples of objects are forms and controls.  Forms are the windows and dialog boxes you place on the screen; controls are the elements that you place inside a form, such as text boxes, command buttons, and list boxes.

 

 Properties:

 

Properties tell something about an object, such as name, color, size, location, or how it will behave. You can think of properties as adjectives that describes objects.  When you refer to a property, you must first name the object, add a period, and then name the property. For example, refer to caption property of form called Form1 as Form1.Caption (say Form1.Caption).