Manual VB 6.0

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Object Oriented Programming 1: Using Microsoft Visual Basic 6.0 Lecture and Laboratory Exercises

A Brief Description of Visual Basic

VISUAL BASIC

Is a high level programming language evolved from the earlier DOS version called BASIC. BASIC means Beginners' All-purpose Symbolic Instruction Code. It is a fairly easy programming language to learn. The codes look a bit like English Language. Different software companies produced different version of BASIC, such as Microsoft QBASIC, QUICKBASIC, GWBASIC, IBM BASICA and so on.

What is Visual Basic?

Visual Basic is a tool that allows you to develop Windows (Graphical 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.

Some features of Visual Basic

• Full set of objects – you draw the application• Lots of icons and pictures for your use• Response to mouse and keyboard actions• Clipboard and printer access• Full array of mathematical, string handling and graphics functions.• Can handle fixed and dynamic variable and control arrays• Sequential and random access file support• Useful debugger and error-handling facilities• Powerful database access tools• ActiveX support• Package & Deployment Wizard makes distributing your applications simple

Structure of Visual Basic Application

PLP – College of Computer Studies - rct- 6/‘06

Event?

Basic Code Basic Code Basic Code

Event processor

Event procedure

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Object Oriented Programming 1: Using Microsoft Visual Basic 6.0 Lecture and Laboratory ExercisesProject (.VBP, .MAK)

Visual Basic Start-up Dialog Box

On start up, Visual Basic 6.0 will display the following dialog box as shown in figure 1.1. You can choose to:

Start a new project Open an existing project Select a list of recently opened programs.

Project A project is a collection of files that make up your application. There are various types of

applications we could create; however, we shall concentrate on creating Standard EXE programs (EXE means executable program).

Note: By clicking on the Standard EXE icon to go into the actual VB programming

environment.

Figure 1: The Visual Basic Start-up Dialog Box


Form 1 (.FRM)

Control 1

Control 2

Control 3

Form 2 (.FRM)

Control 1

Control 2

Control 3

Form 3 (.FRM)

Control 1

Control 2

Control 3

Module 1 (.BAS)

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The Visual Basic Environment

Figure 2: The Visual Basic Environment

The Visual Basic Environment consists of the:

• A Blank Form for you to design your application's interface. • The Project window which displays the files that are created in your application. • The Properties window which displays the properties of various controls and objects that are

created in your applications.

Application (Project) is making up of:

• Forms – Windows that you create for user interface.• Controls – Graphical features drawn on Forms to allows user interaction (text boxes, labels,

scroll bars, command button, etc.) (Forms and Controls are objects).• Properties – Every characteristics 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 events occurs.• General Procedure – Code not related to objects. This code must be invoked by the application.


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• Modules – Collection of general procedures, variable declarations and constant definitions used by application.

Steps in Developing ApplicationThere are three primary steps involved in building a Visual Basic application:• Draw the user interface• Assign properties to controls• Attach code to controls

Drawing the User interface and Setting PropertiesVisual 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.

Six windows appear when you start Visual Basic.

The Main Window consists of the title bar, menu bar, and toolbar. The Title bar indicates the project name, the current Visual Basic operating mode, and the current Form. The menu bar has drop-down menus from which you control the operation of the Visual Basic environment. The toolbar has buttons that provide shortcuts to some of the menus options. The main window also shows the location of the current Form relative to the upper left corner of the screen (measured in twips) and the width and length of the current Form.

The Form Window is central to developing Visual Basic applications. It is where you draw your application. (see figure 3)

Figure 3: Visual Basic Form Window

Note:

The most prominent element of the Visual Basic program development environment is the blank Form that is displayed in the middle of the screen. A Visual Basic Form Window is a window in which you design the user interface for your application


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Adding controls to a Form:There are two ways to place a control on a Form:• Double – clicking• Drawing

The Toolbox is the selection menu for controls used in your application

Figure 4: Toolbox Form Controls


Pointer

Label

Frame

Check Box

Combo Box

Horizontal Scroll Bar

Timer

Directory List Box

Shapes

Image Box

Object Linking Embedding

Picture Box

Text Box

Command Button

Option Button

List Box

Vertical Scroll Bar

Drive List Box

File List Box

Lines

Data Control

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Object Oriented Programming 1: Using Microsoft Visual Basic 6.0 Lecture and Laboratory ExercisesCommon Object/Controls and Their Naming Conventions:

Object Type Prefix Example DescriptionForm frm frmCalculatorProgra

mA window or dialog box that makes up part of an applications user interface

Picture Box pic picHappyFace A container that can display graphicsLabel lbl lblEnterName Displays text that the user cannot directly

modify at Run time.Text Box txt txtEnterName Displays text that the user can modify at Run

TimeFrame fra frmPickOptions A container that groups other controls such as

radio buttons or check boxes.Command Button

cmd cmdEndProgram Responds to a user click to trigger an event

Check Box chk chkPickFeatures Displays a check mark or an x to indicate the current state of a True/False option and responds to a user click to toggle the choice.

Option Button

opt optPaymentChoice An option button can be turned off or on by clicking the option button with the mouse. This control is typically used to enable the user to select from mutually exclusive options.

Combo Box cbo cboColorChoice Combines the features of a text box and list box. The user can specify data by typing it or by selecting a value from a list.

List Box lst lstTravelDestination Displays a list of values from which the user can select

Horizontal Scroll Bar

hsb hsbVolumeControl Provides a visual mechanism for a user to easily navigate through large amount of inFormation. Can also provide an analog representation of a current position

Vertical Scroll Bar

vsb vsbTrebleControl Same as a horizontal scroll bar, only it is displayed vertically.

Timer tmr tmrDelay Triggers an event when a specified time period elapses.

Drive List Box

drv drvHardDiskContent Provides a list of available disk drives and enables the user to select one.

Directory List Box

dir dirTree Provides a list drive paths and directories, enabling the user to select one

File List Box fil filProgramFiles Provides a list of files, enabling the user to select one.

Shape shp shpCircle A two-dimensional tool for drawing shapes.Line lin linBorder A two-dimensional tool for drawing straight

lines.Image img imgClouds Similar to the Picture Box, but easier to use, it

can display graphic images.Data dat datEmployeeRecords Support database compatibility with programs

such as Microsoft Access.OLE ole oleSpreadsheet Provides a data link with an Object Linking and

Embedding compliant application


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Handling some of the common controls

The Text Box

The text box is the standard control that is used to receive input from the user as well as to display the output.

Note: It can handle string (text) and numeric data but not images or pictures. String in a text box can be converted to a numeric data by using the function Val(text).

Example:

In this program, two text boxes are inserted into the form together with a few labels. The two text boxes are used to accept inputs from the user and one of the labels will be used to display the sum of two numbers that are entered into the two text boxes. Besides, a command button is also programmed to calculate the sum of the two numbers using the plus operator. The program use creates a variable sum to accept the summation of values from text box 1 and text box 2.The procedure to calculate and to display the output on the label is shown below.

Figure 5: Sample Form Layout/Interface

`Program Listing 1: Example of Text Box Controls

Private Sub Command1_Click()‘To add the values in text box 1 and text box 2Sum = Val(Text1.Text) + Val(Text2.Text)‘To display the answer on label 1Label1.Caption = Sum

End Sub


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The Label

The label is a very useful control for Visual Basic, as it is not only used to provide instructions and guides to the users, it can also be used to display outputs. One of its most important properties is Caption. Using the syntax label.Caption, it can display text and numeric data.

Note: You can change its caption in the properties window and also at runtime. Please refer to

Program Listing 1 and Figure 5 for the usage of label.

The Command Button

The command button is a very important control as it is used to execute commands. It displays an illusion that the button is pressed when the user click on it. The most common event associated with the command button is the Click event, and the syntax for the procedure is

Private Sub Command1_Click () StatementsEnd Sub

The Picture Box

The Picture Box is one of the controls that used to handle graphics. You can load a picture at design phase by clicking on the picture item in the properties window and select the picture from the selected folder. You can also load the picture at runtime using the LoadPicture method.

Example: the statement will load the picture grape.gif into the picture box.

Picture1.Picture=LoadPicture ("C:\VB program\Images\grape.gif")

Note: The image in the picture box is not resizable.

The Image Box

The Image Box is another control that handles images and pictures. It functions almost identically to the picture box. However, there is one major difference, the image in an Image Box is stretchable, which means it can be resized. This feature is not available in the Picture Box. Similar to the Picture Box, it can also use the LoadPicture method to load the picture.

Example: the statement loads the picture grape.gif into the image box.

Image1.Picture=LoadPicture ("C:\VB program\Images\grape.gif")


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The List Box

The function of the List Box is to present a list of items where the user can click and select the items from the list. In order to add items to the list, we can use the AddItem method. For example, if you wish to add a number of items to list box 1, you can key in the following statements

Example:Private Sub Form_Load ( )

List1.AddItem “Lesson1”List1.AddItem “Lesson2”List1.AddItem “Lesson3”List1.AddItem “Lesson4”

End Sub

Note: The items in the list box can be identified by the ListIndex property, the value of

the ListIndex for the first item is 0, the second item has a ListIndex 1, and the second item has a ListIndex 2 and so on

The Combo Box

The function of the Combo Box is also to present a list of items where the user can click and select the items from the list. However, the user needs to click on the small arrowhead on the right of the combo box to see the items which are presented in a drop-down list. In order to add items to the list, you can also use the AddItem method. For example, if you wish to add a number of items to Combo box 1, you can key in the following statements

Example:Private Sub Form_Load ( )

Combo1.AddItem “Item1”Combo1.AddItem “Item2”Combo1.AddItem “Item3”Combo1.AddItem “Item4”

End Sub

The Check Box

The Check Box control lets the user to select or unselect an option. When the Check Box is checked, its value is set to 1 and when it is unchecked, the value is set to 0. You can include the statements Check1.Value=1 to mark the Check Box and Check1.Value=0 unmark the Check Box, and use them to initiate certain actions. For example, the program will change the background color of the form to red when the check box is unchecked and it will change to blue when the check box is checked.

Note:


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You will learn about the conditional statement If….Then….Elesif in later lesson. VbRed and vbBlue are color constants and BackColor is the background color property of the form.

Example:

Private Sub Check1_Click ()If Check1.Value = 0 Then Form1.BackColor = vbRedElseIf Check1.Value = 1 Then Form1.BackColor = vbBlueEnd If

End Sub

The Option Box

The Option Box control also lets the user selects one of the choices. However, two or more Option Boxes must work together because as one of the Option Boxes is selected, the other Option Boxes will be unselected. In fact, only one Option Box can be selected at one time. When an option box is selected, its value is set to “True” and when it is unselected; its value is set to “False”. In the following example, the shape control is placed in the form together with six Option Boxes. When the user clicks on different option boxes, different shapes will appear. The values of the shape control are 0, 1, and 2,3,4 which will make it appear as a rectangle, a square, an oval shape, and a rounded square respectively.

Example:Private Sub Option1_Click ( ) Shape1.Shape = 0End Sub

Private Sub Option2_Click() Shape1.Shape = 1End Sub




The Drive List Box


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The Drive ListBox is used to display a list of drives available in your computer. When you place this control into the form and run the program, you will be able to select different drives from your computer as shown in Figure 6.

Figure 6: The Drive List Box

The Directory List Box

The Directory List Box is used to display the list of directories or folders in a selected drive. When you place this control into the form and run the program, you will be able to select different directories from a selected drive in your computer as shown in Figure 7.

Figure 7: The Directory List Box 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;


Object Box

Properties List

Setting Box

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Alphabetic and Categorized. Under this box are the available properties for the currently selected object.

Figure 8: Properties Window

The Form Layout Window shows where (upon program execution) your Form will be displayed relative to your monitor’s screen.

Figure 9: Form Layout Window

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.

Figure 10: Project Window

Building a Visual Basic ApplicationPLP – College of Computer Studies - rct- 6/‘06

Properties Window Title Bar

View Object

View Code Toggle Folders

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Creating Your First Application

Figure 11: Source Code Window

Figure 12: List of Objects

Figure 13: List of ProceduresWriting Visual Basic Code


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Code Window• Visual Basic Window that you open when you want to type VB code into your program or

view the program statements already in your program. It is also known as the Code Editor Window. It contains an:o Object box – performs the same function as the Object box in the Properties window;

both allow you to choose either the Form or one of the controls on the Form. You can also use the Object Box to verify the name of a control while you are writing instruction in the Code Window

o Procedure box – list the event procedures to which the selected object is capable of responding Input box

Saving Project and Form/s

To save the Project & Form:1. Click <File> <Save Project> OR

Click <File> <Save Project As> ORClick Save Button

2. Then, displayed Save File As dialog box

3. Type the Form name(follow the Form filename format )ex: PEFRM01RICHARDGWAPO

Note: Before typing the Form name

makes sure that the Save File As dialog box (as shown besides) is displayed in your screen.

4. Click Save button5. Then, displayed Save Project As dialog box6. Type the project name (follow the project Format filename) ex:

PEPJT01RICHARDGWAPO

Note: Before typing the project name

makes sure that the Save Project As dialog box (as shown besides) is displayed in your screen.

7. Click Save button

Note: To RUN/EXECUTE the program/application Click on Run menu then, click Start - OR - Press F5 function key -

OR - Click Start button


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To TERMINATE execution mode (to go back to Form Window) Click on End button


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Object Oriented Programming 1: Using Microsoft Visual Basic 6.0 Lecture and Laboratory ExercisesName : ____________________________ Rating: Date Finished : _____________ Section: _________ Time: ________Instructor : ____________________________

Practice Exercise #1: Adding several controls to Form WindowProject Name : PEPJT01<FirstNameLastName> Example: PEPJT01RichardGwapoForm Name : PE01FRM01<FirstNameLastName> Example: PE01FRM01RichardGwapo

Steps:1. Launch Visual Basic application/program;

Displays New Project as shown (see figure 1)

Be sure that Standard EXE is being selected2. Click Open button

Then, displays Form Window as shown below (see figure 2)

3. Add the following controls as shown (see figure 3) Labels Text Box Combo Box List Box Frame (Course & Subjects

enrolled) Command Button

4. Click Save button or File Save Project or File Save Project As Follow the project name and

Form name Format

5. Apply necessary enhancement:Font, Font Size, Font Color,Changing Caption etc.


Figure 1: New Project Window

Figure 2: Form Window

Figure 3: Sample Form Interface

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Name : ____________________________ Rating: Date Finished : _____________ Section: _________ Time: ________Instructor : ____________________________

Practice Exercise #2: Inserting/Adding Form in the existing project & using MsgBox Project Name : PEPJT01<FirstNameLastName> Example: PEPJT01RichardGwapoForm Name : PE02FRM02<FirstNameLastName> Example: PE02FRM02RichardGwapo

Steps:1. Retrieve/Open your PEPJT01 (Practice

Exercise project 1) 2. Click <Project> menu then select <Add

Form> New Form will be added in your existing project (see Figure 1)

3. Add 2 controls/objects in your new Form as shown (see Figure 2)

4. Change Properties:Form = Caption: Using MsgBox Label1 = Name: lblMsg

Caption: Message goes hereCommand1 = Name: cmdTest

Caption: Test (see Figure 3)

5. Apply codes to you’re application: Click <View> menu then <Code> OR select View Code button from

project explorer window OR double click the Test Button Then, displayed the Code Window (see Figure 4)

6. In the Event combo box (General) select cmdTest and in the Procedure combo box (Declarations) select click (see Figure 5) Note: The default event for a CommandButton Object is Click (see Figure 6)

7. Inside the procedure Type the source code as shown: (see Figure 7)


Figure 1: New Form in Project Explorer Window

Figure 2: Form2 with Label1 & Command1 controls

Figure 3: Modified Form2

Figure 4: Code Window of Form2

Object Procedure

Figure 5: Object cmdTest

Figure 6: Code Window for cmdTest Object with Procedure click

Figure 7: Sample procedure/code/command/message of cmdTest Object

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lblMsg is the object where you want to place the message and Caption is its property that holds the text to be displayed.

Note: - In object programming, the access to method and properties is done by joining the name of the object and the property (or method) with a dot.

- The message is enclosed with double quotation marks (“ “) because the text is a string constant.

Note: Before running the program you need to change the project properties to run Form2 otherwise, Form1 will always be the Form to be executed.o Click <Project> menu then click <Project Properties> then, displays the Project Properties dialog

box/window (see Figure 8)o Select Form2 (or the Form that you

wants to run/execute) from the Startup objects. Then, click OK button

8. Try to run the program and see the output : (see Figure 9)

9. Creating event/procedure for the object Form. Click the View Code button or simply Double click the Form to work on with the code window (see

Figure 10)

Notice that the default event for Form is not Click but Load. Select Click and type the procedure/code as shown (see Figure 11)

10. Save and Run the program to test the output.

11. To add Message Box command: Modify cmdTest procedure

and add this line of command (see Figure 12)


Figure 9: Output of Form2

Figure10: Code Window for Form object

Figure 11: Event for Form object

Figure 8: Project Properties Window

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Object Oriented Programming 1: Using Microsoft Visual Basic 6.0 Lecture and Laboratory ExercisesMsgBox – Text Message To be displayed.

12. Save and run the program/application to test the output

Try to enhance the Form by changing some object properties.


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Operators in Visual Basic

In order to compute inputs from users and to generate results, we need to use various mathematical operators. In Visual Basic, except for + and -, the symbols for the operators are different from normal mathematical operators.

Arithmetic Operators:

Operator Mathematical function Example^ Exponential 2^4=16* Multiplication 4*3=12/ Division 12/4=3

Mod Modulus(return the remainder from an integer division)

15 Mod 4=3

\ Integer Division(discards the decimal places)

19\4=4

+ or & String concatenation "Visual"&"Basic"="Visual Basic"

Program Listing 2: Example of Mathematical/Arithmetic Operators 1Dim firstName As StringDim secondName As StringDim yourName As String Private Sub Command1_Click() firstName = Text1.Text

secondName = Text2.TextyourName = secondName + " " + firstName

Label1.Caption = yourNameEnd Sub

In this example Program Listing 3, three variables are declared as string. For variables firstName

and secondName will receive their data from the user’s input into textbox1 and textbox2, and the variable yourName will be assigned the data by combining the first two variables. Finally, yourName is displayed on Label1.

Type Conversions

Values are classified as either String or Numeric. Both values can be manipulated separately. For example, we can concatenate two strings or add two numbers but we cannot add or concatenate a string and a number.

In many occasions, we need to convert a string format to numeric format for computation and a numeric format to string format for manipulation. To do this, we can use the STR( ) and VAL( ) functions.

STR( ) – converts a number to stringVAL( ) – converts a string to number


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Object Oriented Programming 1: Using Microsoft Visual Basic 6.0 Lecture and Laboratory ExercisesExamples:

Let X = “Hello! ” A = 5 C = “20”Y = “How old are you ” B = 10 AGE = 25

Z = X + “How are you” SUM = A + B

Output of Z Output of SUM

Z= Y + STR(AGE) D = A + B + VAL(C)

Output of Z Output of D

Program Listing 3: Example of Mathematical/Arithmetic Operators 2Dim number1, number2, number3 as IntegerDim total, average as variantPrivate sub Form_Click( )

number1=val(Text1.Text) number2=val(Text2.Text) number3= val(Text3.Text)

Total=number1+number2+number3Average=Total/5 Label1.Caption=TotalLabel2.Caption=Average

End Sub

In the Program Listing 4, three variables are declared as integer and two variables are declared as variant. Variant means the variable can hold any numeric data type. The program computes the total and average of the three numbers that are entered into three text boxes.


Hello! How are you

How old are you 25

15

35

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Practice Exercise #3: Using VAL( ) and Mathematical OperatorsProject Name : PEPJT01<FirstNameLastName> Example: PEPJT01RichardGwapoForm Name : PE03FRM03<FirstNameLastName> Example: PE03FRM03RichardGwapo

Steps:1. Retrieve/Open your PEPJT01 (Practice Exercise Project 1) 2. Click <Project> menu then select <Add Form>3. Sample Form Layout/Interface: (see Figure 1)4. Add the following objects/controls as shown5. Change properties:

Form = Caption: Mathematical Operations Text1 = Name: txtMyName Text2 = Name: txtYourName Text3 = Name: txtMyAge Text4 = Name: txtYourAge Label1 = Name: lblOurName Label2 = Name: lblSumAge Command1 = Name: cmdOurName Command2 = Name: cmdSumAge

Note: Please type the given names as it is to avoid errors in program codes.

6. Double Click NAME button then, type the following line of codes.

cmdOurName Event:

Private Sub cmdOurName_Click()' Displaying "Welcome MyName and YourName value"lblOurName.Caption = "Welcome! " + txtMyName.Text + " " + txtYourName.Text

End Sub

7. Double Click SUM button then, type the following line of codes.

cmdSumAge Event:

Private Sub cmdSumAge_Click()' Displaying MyAge and YourAge

lblSumAge.Caption = Val(txtMyAge.Text) + Val(txtYourAge.Text)

End Sub

8. Save and run the program to test the output (see Figure 2)9. Apply necessary enhancement to your Form (optional)

Single Quotation ( ‘ )


Figure 1: Sample Layout/Interface

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Single Quotation ( ‘) serves as a comment or remark


Figure 2: Sample Run

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Name : _______________________ Date Finished: ________ Rating: Course/Section: _________ Time: ________ Program Design (30%): _____Instructor : _______________________ Program Logic (70%): _____

100%

Machine Problem #1: Project Name : MPPJT01<FirstNameLastName> Example: MPPJT01RichardGwapoForm Name : MP01FRM01<FirstNameLastName> Example: MP01FRM01RichardGwapo

PROJECT #1q:FORM #1: SAMPLE FORM LAYOUT/INTERFACE: SAMPLE OUTPUT:

Objects/Controls Properties:

Form: Caption: Using Mathematical Operators]

Label: Text Box: Argument 1 1. Name: txtArg1 Alignment: Right Argument 2 2. Name: txtArg2 Alignment: Right Sum (+) 3. Name: txtSum Alignment: Right Enabled: False Difference (–) 4. Name: txtDiff Alignment: Right Enabled: False Product (*) 5. Name: txtProd Alignment: Right Enabled: False Quotient (/) 6. Name: txtQuo Alignment: Right Enabled: False

Command Button: Caption: Result Name: cmdResult


1) 2)

3) 4) 5) 6)

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100%


PROJECT #1:FORM #2: SAMPLE FORM LAYOUT

Form: Caption: SIMPLE CALCULATOR ContolBox: False

Note: If ControlBox is set to False the contol menu box will be removed along with the minimize, maximize and close button (see the sample output below)

Text Box:1. Name: txtArg12. Name: txtArg23. Name: txtResult Enabled: False

Command Buttons:

#’s Name Caption Description4 cmdClear &Clear To clear all entries (text box)5 cmdAdd &Add To add two numbers6 cmdSubract &Subtract To subtract two numbers7 cmdMultiply &Multiply To multiply two numbers8 cmdDivide &Divide To divide two numbers9 cmdExit E&xit To end/close the program

SAMPLE OUTPUT:Note: You can also use the following keys

Alt + C – Clear Alt + A – AddAlt + M – MultiplyAlt + S – SubtractAlt + D – DivideAlt + X – Exit

***** The effect of & symbol is to have a short-cut key for the following command button objects stated above.

Example: You type Effect: &Clear

Clear


1)

2)

3)

5)

6)

4)

9)7)

8)

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E&xit Exit


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Visual Basic Data Types

There are many types of data we come across in our daily life. For example, we need to handle data such as names, addresses, money, date, stock quotes, statistics and etc everyday. Similarly in Visual Basic, we are also going to deal with these kinds of data. However, to be more systematic,

VB divides data into different types.

Numeric Data Numeric data are data that consists of numbers, which can be computed mathematically

with various standard operators such as add, minus, multiply, divide and so on. In Visual Basic, the numeric data are divided into 7 types.

Numeric Data Types

Type Storage Range of ValuesByte 1 byte 0 to 255Integer 2 bytes -32,768 to 32,767Long 4 bytes -2,147,483,648 to 2,147,483,648Single 4 bytes -3.402823E+38 to -1.401298E-45 for negative values

1.401298E-45 to 3.402823E+38 for positive values.Double 8 bytes -1.79769313486232e+308 to -4.94065645841247E-324 for negative values

4.94065645841247E-324 to 1.79769313486232e+308 for positive values.Currency 8 bytes -922,337,203,685,477.5808 to 922,337,203,685,477.5807Decimal 12 bytes +/- 79,228,162,514,264,337,593,543,950,335 if no decimal is use

+/- 7.9228162514264337593543950335 (28 decimal places).

Non-numeric Data Types

Data Type Storage RangeString(fixed length) Length of string 1 to 65,400 charactersString(variable length) Length + 10 bytes 0 to 2 billion charactersDate 8 bytes January 1, 100 to December 31, 9999Boolean 2 bytes True or FalseObject 4 bytes Any embedded objectVariant(numeric) 16 bytes Any value as large as DoubleVariant(text) Length+22 bytes Same as variable-length string

Suffixes for Literals

Literals are values that you assign to a data. In some cases, we need to add a suffix behind a literal so that VB can handle the calculation more accurately. For example, we can use num=1.3089# for a Double type data.


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Suffix Data Type& Long! Single# Double@ Currency

In addition, we need to enclose string literals within two quotations and date and time literals within two # sign. Strings can contain any characters, including numbers.

Examples: memberName="Turban, John." TelNumber="1800-900-888-777" LastDay=#31-Dec-00# ExpTime=#12:00 am#

Declaring Variables and Constant

Variables are used by Visual Basic to hold information needed by your application. Variable is a temporary repository of information. Usually, these information are stored because they expect to be processed or be used as an element in a process.

Two classifications of variable name: Numeric String

Rules used in naming variables: Not more than 40 characters The first character must be a letter followed by either another letters, numbers and underscore

( _ ) They are not case sensitive which makes a lowercase variable the same as that written in its

uppercase Format. You cannot use a reserve word (word needed by Visual Basic)

Scoping of variables:

Variables can be Local to the procedure or Local to the whole Form. Local variables to a procedure are declared at the start of a procedure and can be used only in that procedure. Local variables to the whole Form, on the other hand, can be defined at the Declaration section of the General object found in the code window. See figure below.

Variables that are Local to the procedure are declared after DIM reserve word while variables that are Local to the Form are declared either by using DIM or PRIVATE reserve words. See figure 12.


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Figure 12: Variable Declaration

Managing Variables

Variables are like mail boxes in the post office. The contents of the variables changes every now and then, just like the mail boxes. In term of VB, variables are areas allocated by the computer memory to hold data. Like the mail boxes, each variable must be given a name. To name a variable in Visual Basic, you have to follow a set of rules.

Constant

Refers to fixed values. Like variable, constants can be Local for a specific procedure, Local for the entire Form, Private for a Module, and Public for the whole project.

The reserve word Const is use to declare a constant see Figure 13.

Figure 13: Constant Variable Declarations

Examples: Valid and Invalid Variable Names

Valid Name Invalid NameMy_Variable My.VariableThisDate 7DayLong_Name_Can_beUSE Mine&Yours *& is not acceptable


Loc al Variables

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Visual Basic Symbolic Constants

Many times Visual Basic, functions and objects require data arguments that affect their operation and return values you want to read and interpret. These arguments and values are constant numerical data and difficult to interpret based on just the numerical value. To make these constants more understandable, Visual Basic assigns names to the most widely used values – these are called symbolic constants.

Example: frmExample.BackColor = 0XFF0000frmExample.BackColor = vbBlue

Declaring Variables

In Visual Basic, one needs to declare the variables before using them by assigning names and data types. They are normally declared in the general section of the codes' windows using the Dim statement.

Format: Dim variableNmae as DataType

Example:Dim password As String Dim yourName As String Dim firstnum As Integer Dim secondnum As Integer Dim total As Integer Dim doDate As Date

Note:

You may also combine them in one line , separating each variable with a comma, as follows:

Example:Dim password As String, yourName As String, firstnum As Integer,.............

If data type is not specified, VB will automatically declare the variable as a Variant. For string declaration, there are two possible formats, one for the variable-length string and another for the fixed-length string. For the variable-length string, just use the same format as example 5.1 above. However, for the fixed-length string, you have to use the

Format: Dim VariableName as String * n,

(where n defines the number of characters the string can hold.)Example:

Dim yourName as String * 10 ‘yourName can holds no more than 10 Characters.


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Working with Variables

Assigning Values to Variables

After declaring various variables using the Dim statements, we can assign values to those variables. The general format of an assignment is

Variable=Expression

The variable can be a declared variable or a control property value. The expression could be a mathematical expression, a number, a string, a Boolean value (true or false) and etc.

Examples:firstNumber=100 secondNumber=firstNumber-99 userName="John Lyan" userpass.Text = password Label1.Visible = True Command1.Visible = false Label4.Caption = textbox1.Text ThirdNumber = Val(usernum1.Text) total = firstNumber + secondNumber+ThirdNumber

Visual Basic Functions

Visual Basic offers a rich assortment of built-in functions. The on-line help utility will give you information on any or all of these functions and their use:

Function Value ReturnedAbs Absolute value of a numberAsc ASCII or ANSI code of a characterChr Character corresponding to a given ASCII or ANSI codeCos Cosine of an angleDate Current date as a text stringFormat Date or number converted to a text stringLeft Selected left side of a text stringLen Number of characters in a text stringMid Selected portion of a text stringNow Current time and dateRight Selected right end a text stringRnd Random numberSin Sine of an angleSqr Square root of a numberStr Number converted to a text stringTime Current time as a text stringTimer Number of seconds elapsed since midnightVal Numeric value of a given text string.


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Rnd Function

In writing games and learning software, we use the Rnd funtion to introduce randomess. This ensures different results each time you try a program. The Visual Basic function Rnd returns a single precision, random numbers between 0 and 1 (actually greater than or equal to 0 and less than 1). To produce random integers (I) between Imin and Imax, use the formula:

I = Int(Imax – Imin + 1) * Rnd) + Imin

The random number generator in Visual Basic must be seeded. A seed value initializes the generator. The Randomize statement is used to do this:

Randomize Seed If you use the same Seed each time your run your application, the same sequence of random

numbers will be generated. To ensure you get different numbers everytime you use your application (preferred for games), use the Timer funtion to seed the generator:

Randomize Timer

Note:Place Randomize Timer statement in the Form_Load event procedure

Examples:

1. To roll a six-sided die, the number of spots would be computed using:

Answer:NumberSpots = Int(6 * Rnd) + 1

2. To randomly choose a number between 100 and 200, use:

Answer:Number = Int(100 * Rnd) + 100


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Practice Exercise #4: Stopwatch Application (Using several Visual Basic Functions)Project Name : PEPJT02<FirstNameLastName> Example: PEPJT02RichardGwapoForm Name : PE04FRM01<FirstNameLastName> Example: PE04FRM01RichardGwapo

Project 2 / Form 1Steps:

1. Create a New Project2. Add the following controls as shown (see Figure 1) (place

three command buttons and six labels on the form) 3. Set Properties of the form, three buttons and six labels:

Form1:BoarderStyle 1-Fixed SingleCaption Stopwatch ApplicationName frmStopWatch

Command1:Caption &Start TimingName cmdStart

Command2:Caption &Start TimingName cmdEnd

Command3:Caption E&xitName cmdExit

Label1:Caption Start Time

Label2:Caption End Time

Label3:Caption Elapsed Time

Label4:BoarderStyle 1-Fixed SingleCaption [Blank]Name lblStart

Label5:BoarderStyle 1-Fixed SingleCaption [Blank]Name lblEnd

Label6:BoarderStyle 1-Fixed SingleCaption [Blank]Name lblElapsed

(See Figure 2: Modified form properties)4. Stopwatch Application – Attaching Code5. Double click anywhere on the form to open the code window. Or select View Code from the project

window.6. Select specific object then type the following line of codes.


Figure 1: Sample Form Layout

Figure 2: Modified Form properties

Figure 3: Sample Run (Output)

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Object Oriented Programming 1: Using Microsoft Visual Basic 6.0 Lecture and Laboratory ExercisesGeneral Declaration

Option Explicit ‘This statement forces us to declare variables.‘Declaration of StartTime, EndTime & ElapsedTime as variables global within the form.Dim StartTime As VariantDim EndTime As VariantDim ElapsedTime As Variant

cmdStart EventPrivate Sub cmdStart_Click()

'Establish and print starting timeStartTime = NowlblStart.Caption = Format(StartTime, "hh:mm:ss")lblEnd.Caption = ""lblElapsed.Caption = ""

End Sub

cmdEnd EventPrivate Sub cmdEnd_Click()

'Find the ending time, compute the elapsed time'Put both values in label boxesEndTime = NowElapsedTime = EndTime - StartTimelblEnd.Caption = Format(EndTime, "hh:mm:ss")lblElapsed.Caption = Format(ElapsedTime, "hh:mm:ss")

End Sub

cmdExit EventPrivate Sub cmdExit_Click()

Unload MeEnd Sub

7. Save and run the program to test the output (see Figure 3)


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Practice Exercise #5: My Calendar Application Project Name : PEPJT02<FirstNameLastName> Example: PEPJT01RichardGwapoForm Name : PE05FRM02<FirstNameLastName> Example: PE05FRM02RichardGwapo


1. Retrieve/Open your PEPJT02 (Practice Exercise Project 2)

2. Add Form2 and add the following controls as shown (see Figure 1) (place 5 labels and 1 timer)

3. Set Properties: Form2:

Caption My CalendarBorderStyle 1-Fixed Single

Timer:Name timDisplayInterval 1000

Label1:Name lblDayCaption SundayFontName Times New RomanFontStyle BoldFontSize 24

Label2:Name lblTimeCaption 00:00:00 PMFontName Times New RomanFontStyle BoldFontSize 24

Label3:Name lblYearAlignment 2 – Center Caption 2004FontName Times New RomanFontStyle BoldFontSize 24

Label4:Name lblNumberAlignment 2 – CenterCaption 18FontName ArialFontStyle BoldFontSize 72FontSize 24


Figure 1: Sample Form Layout (Calendar)

Figure 2: Sample Run (Output)

Label5:Name lblMonthAlignment 2 – CenterCaption JulyFontName Time New RomanFontStyle Bold

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4. Source Codes:

General DeclarationOption Explicit

timDisplay Event Private Sub timDisplay_Timer() Dim Today As Variant Today = Now lblDay.Caption = Format(Today, "dddd") lblMonth.Caption = Format(Today, "mmmm") lblYear.Caption = Format(Today, "yyyy") lblNumber.Caption = Format(Today, "d") lblTime.Caption = Format(Today, "h:mm:ss ampm")End Sub

5. Run the program to test the output (see Figure 2)


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Controlling Program Flow

Six Comparison/Relational/Conditional Operators

To control the VB program flow, we can use various conditional operators. Basically, they resemble mathematical operators. Conditional operators are very powerful tools, they let the VB program compare data values and then decide what action to take, whether to execute a program or terminate the program and etc.

Operator Meaning= Equal to> More than< Less Than

>= More than and equal<= Less than and equal<> Not Equal to

Note: You can also compare strings with the above operators. However, there are certain rules

to follows: Upper case letters are less than lowercase letters, "A"<"B"<"C"<"D".......<"Z" and number are less than letters.

Logical Operators

In addition to conditional operators, there are a few logical operators which offer added power to the VB programs.

Operator MeaningAnd Both sides must be trueor One side or other must be true

Xor One side or other must be true but not bothNot Negates truth


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Conditional Statement / Selective Structure

If...Then...Else Statements

To effectively control the VB program flow, we shall use If...Then...Else statement together with the conditional operators and logical operators.

Format: if...then...else statement is :

If conditions Then VB expressions Else VB expressions End If

Note: any If..Then..Else statement must end with End If. Sometime it is not necessary to use

Else.

Program Listing 4: Example of Conditional StatementPrivate Sub OK_Click()

firstnum = Val(usernum1.Text) secondnum = Val(usernum2.Text) total = Val(sum.Text)

If total = firstnum + secondnum And Val(sum.Text) <> 0 Then correct.Visible = True wrong.Visible = False Else correct.Visible = False wrong.Visible = True End If

End Sub


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Select Case

If you have a lot of conditional statements, using If..Then..Else could be very messy. For multiple conditional statements, it is better to use Select Case

The format is :

Select Case expression Case value1 Block of one or more VB statements Case value2 Block of one or more VB Statements Case value3 Block of one or more VB statements Case value4 . . Case Else Block of one or more VB Statements

End Select

Note: The data type specified in expression must match that of Case values.

Program Listing 5: Example of Selective Structure 1'Examination Grades Dim grade As String Private Sub Compute_Click( )

grade=txtgrade.Text

Select Case grade Case "A"

result.Caption="High Distinction" Case "A-" result.Caption="Distinction" Case "B" result.Caption="Credit" Case "C" result.Caption="Pass" Case Else result.Caption="Fail" End Select

End sub

Note: Please note that grade is a string, so all the case values such as "A" are of String data type.


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Program Listing 6: Example of Selective Structure 2Dim mark As Single Private Sub Compute_Click() 'Examination Marks mark = mrk.Text

Select Case mark Case Is >= 85

comment.Caption = "Excellence" Case Is >= 70

comment.Caption = "Good" Case Is >= 60 comment.Caption = "Above Average" Case Is >= 50 comment.Caption = "Average" Case Else comment.Caption = "Need to work harder" End Select End Sub

Note we use the keyword Is here to impose the conditions. This is generally used for numeric data.

Program Listing 7: Example of Selective Structure 3

Dim mark As Single Private Sub Compute_Click() 'Examination Marks mark = mrk.Text Select Case mark Case 0 to 49 comment.Caption = "Need to work harder" Case 50 to 59 comment.Caption = "Average"

Case 60 to 69 comment.Caption = "Above Average"

Case 70 to 84 comment.Caption = "Good"

Case Else comment.Caption = "Excellence"

End Select End Sub


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Practice Exercise #6: Lucky Seven ProgramProject Name : PEPJT02<FirstNameLastName> Example: PEPJT02RichardGwapoForm Name : PE06FRM03<FirstNameLastName> Example: PE04FRM03RichardGwapo

Sample Form: Sample Output:

cmdSpic_Click Event:Private Sub cmdSpin_Click() Dim Num1 As Integer Dim Num2 As Integer Dim Num3 As Integer Num1 = Int(Rnd * 10) Num2 = Int(Rnd * 10) Num3 = Int(Rnd * 10) lblNum1.Caption = Format(Num1, "#0") lblNum2.Caption = Format(Num2, "#0") lblNum3.Caption = Format(Num3, "#0") If Num1 = 7 Or Num2 = 7 Or Num3 = 7 Then MsgBox "You win" Else MsgBox "Sorry " End IfEnd Sub

Form_Load Event Private Sub Form_Load() Randomize TimerEnd Sub


Specs:3 Labels: Name: lblNum1 Name: lblNum2 Name: lblNum3 FontSize: 201 CommandButton: Name: cmdSpin

7 7 7

Message: “You Win”

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Machine Problem #3:Project Name : MPPJT02<FirstNameLastName> Example: MPPJT02RichardGwapoForm Name : MP03FRM01<FirstNameLastName> Example: MP03FRM01RichardGwapo

PROJECT 2: FORM #1: 3 Digits Lotto Program

Instructions: 1. Your bet should not be less than 10 pesos, otherwise it will prompt you with “Enter minimum amount of

Php 10.00”2. Enter single digits for each of the text box3. If the content of the text box are all equal to the winning numbers (in order) it will prompt you with “You

have won 1 MILLION PESOS JACKPOT” (see sample Message box below), otherwise it will prompt you with “Sorry better luck next time”

4. But, if the content of the text box are equal to the winning numbers (but not in order) it will prompt you with “You have won a consolation prize of ____”. The consolation prizes will depend to the BET amount (Example: Bet is 100, multiply your bet to 1,000.00 to get the consolation amount.)


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Sample Output:

Formula: Semestral Grade = 25% of Prelim + 25% of Midterm + 50% of Final

Point Equivalent TableSem. Grade Equivalent Sem. Grade Equivalent98 – 100 1.00 83 – 85 2.2595 – 97 1.25 80 – 82 2.5092 – 94 1.50 77 – 79 2.7589 – 91 1.75 75 – 76 3.0086 – 88 2.00 74 & below 5.00 (FAILED)

Additional Logical Problems:

• For New Entry Button: Upon clicking displays this message box If “Yes” will clear all entries else nothing happen

• For Compute Button:Upon clicking displays this message boxIf “Yes” will display the results else nothing happen

• For Exit Button: Will close the program/application


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The Call Statement

To call another procedure, you can simply place the procedure name in code. You can also use the optional call statement.

Format: [Call] nmae [(argument list)] Example: Call cmdNext

Call An optional keyword used to signify the transfer of program control to another Procedure

Name The name of the procedure to pass control to.Argumentlist The variables or expression to pass to another procedure.

Introduction to VB Functions I

Functions are similar to normal procedures but the main purpose of the functions is to accept certain inputs and pass them on to the main program to finish the execution. They are two types of function, the built-in functions(or internal functions) and the functions created by the programmers.

The general format of a function is:functionName(arguments)

where arguments are values that are passed on to the functions. In this lesson, we are going to learn two very basic but useful internal functions, i.e. the

MsgBox( ) and InputBox ( ) functions.

The Message BoxMsgBox ( ) Function

The objective of MsgBox is to produce a pop-up message box and prompt the user to click on a command button before he /she can continues.

This message box format is as follows: yourMsg=MsgBox(Prompt, Style Value, Title)

The first argument, Prompt - will display the message in the message box. The Style Value will determine what type of command buttons appear on the message box. The Title argument will display the title of the message board.


46


Style Value Named Constant Buttons Displayed0 vbOkOnly Ok button1 vbOkCancel Ok and Cancel buttons2 vbAbortRetryIgnore Abort, Retry and Ignore buttons.3 vbYesNoCancel Yes, No and Cancel buttons4 vbYesNo Yes and No buttons5 vbRetryCancel Retry and Cancel buttons

Note: We can use named constant in place of integers for the second argument to make the programs

more readable. In fact, VB6 will automatically shows up a list of names constant where you can select one of them.

Example: yourMsg=MsgBox( "Click OK to Proceed", 1, "Startup Menu")

andyourMsg=Msg("Click OK to Proceed". vbOkCancel,"Startup Menu")

are the same.

yourMsg is a variable that holds values that are returned by the MsgBox ( ) function. The values are determined by the type of buttons being clicked by the users. It has to be declared as Integer data type in the procedure or in the general declaration section.

Return Values and Command ButtonsValue Named Constant Button Clicked

1 vbOk Ok button2 vbCancel Cancel button3 vbAbort Abort button4 vbRetry Retry button5 vbIgnore Ignore button6 vbYes Yes button7 vbNo No button

Example:

Figure 14: Sample Interface


47

Object Oriented Programming 1: Using Microsoft Visual Basic 6.0 Lecture and Laboratory ExercisesYou draw three command buttons and a label as shown in Figure 14.

Program Listing 8: The procedure for the test button: Private Sub Test_Click() Dim testmsg As Integer testmsg = MsgBox("Click to test", 1, "Test message")

If testmsg = 1 Then Display.Caption = "Testing Successful" Else Display.Caption = "Testing fail" End If End Sub

Note: When a user click on the test button, the image like the one shown in Figure 15 will appear. As

the user click on the OK button, the message "Testing successful" will be displayed and when he/she clicks on the Cancel button, the message "Testing fail" will be displayed.

Figure 15: Test Message

o To make the message box looks more sophisticated, you can add an icon besides the message. There are four types of icons available in VB as shown in the table below:

Value Named Constant Icon16 vbCritical

32 vbQuestion

48 vbExclamation

64 vbInformation


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Object Oriented Programming 1: Using Microsoft Visual Basic 6.0 Lecture and Laboratory ExercisesIn this example, the following message box will be displayed:

Figure 16: Modified Test Message

Note: You could draw the same Interface as in example program listing 8, but modify the codes

as follows:

Program Listing 9: Example of MsgBox with Yes, No & Cancel buttonPrivate Sub test2_Click()

Dim testMsg2 As Integer testMsg2 = MsgBox("Click to Test", vbYesNoCancel + vbExclamation, "Test Message")

If testMsg2 = 6 Then display2.Caption = "Testing successful" ElseIf testMsg2 = 7 Then display2.Caption = "Are you sure?" Else display2.Caption = "Testing fail" End If

End Sub

The InputBox( ) Function

An InputBox( ) function will display a message box where the user can enter a value or a message in the form of text.

Format:

myMessage=InputBox(Prompt, Title, default_text, x-position, y-position)

Where: myMessage - is a variant data type but typically it is declared as string, which accept the

message input by the users. The arguments are explained as follows:o Prompt - The message displayed normally as a question asked. o Title - The title of the Input Box. o default-text - The default text that appears in the input field where users can use

it as his intended input or he may change to the message he wish to key in. o x-position and y-position - the position or the coordinate of the input box.


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Figure 17: Sample Interface for InputBox function

Program Listing 10: Example of an InputBox function‘The procedure for the OK button Private Sub OK_Click()

Dim userMsg As String userMsg = InputBox("What is your message?", "Message Entry Form", "Enter your message

here", 500, 700)

If userMsg <> "" Then message.Caption = userMsg Else message.Caption = "No Message" End If

End Sub

Note: When a user click the OK button, the input box as shown in Figure 18 will appear. After user

entering the message and click OK, the message will be displayed on the caption, if he click Cancel, "No message" will be displayed.

Figure 18: InputBox for Message Entry Form


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Practice Exercise #7: Flash Card Addition Problems Project Name : PEPJT03<FirstNameLastName> Example: PEPJT03RichardGwapoForm Name : PE07FRM01<FirstNameLastName> Example: PE07FRM01RichardGwapo


1. Retrieve/Open your PEPJT02 (Practice Exercise Project 2)2. Add Form3 and add the following controls as shown (see Figure 1) (place 5 labels

and 1 timer)

3. Set Properties: Form3

BorderStyle 1 – Fixed SingleCaption Flash Card Addition

Command1Name cmdNextCaption &Next ProblemEnabled False

Command2Name cmdExitCaption E&xit

Text1Name txtAnswerFontName ArialFontSize 48MaxLenght 2

Label1Name lblNum1Alignment 2 – CenterFontName ArialFontSize 48


Label1

Label3

Label2

Label4

Label5

Label6

Text1

Label7

Command1

Command2

Figure 1: Sample Layout

Figure 2: Sample Run (Output)with correct answer

Note: After entering your answer press enter key to check if the answer is correct or not.

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Caption [blank] Label2:

Alignment 2 – CenterCaption +FontName ArialFontSize 48

Label3:Name lblNum2Alignment 2 – CenterCaption [blank]FontName ArialFontSize 48

Label4:Alignment 2 – CenterCaption ScoreFontName MS Sans SerifFontSize 18

Label5:Name lblScoreAlignment 2 – CenterBackColor &H0000FFFF& (Yellow)BorderStyle 1 – Fixed SingleCaption 0FontName Times New RomanFontStyle BoldFontSize 36

Label6:Alignment 2 – CenterCaption =FontName ArialFontSize 48

Label7:Name lblMessageAlignment 2 – CenterBackColor &H00FFFF00& (Cyan)BorderStyle 1 – Fixed SingleFontName MS Sans SerifFontStyle Bold & ItalicFontSize 24

4. Source Codes:

General DeclarationOption Explicit

Dim Sum As Integer Dim NumProb As Integer, NumRight As Integer

cmdExit Event:Private Sub cmdExit_Click() EndEnd Sub

cmdNext Event:Private Sub cmdNext_Click()


Figure 3: Sample Run (Output)with incorrect answer

*** Click Next Problem button to flash another sets of numbers*** Click Exit button to end the application

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'Generate next addition problem Dim Number1 As Integer Dim Number2 As Integer txtAnswer.Text = "" lblMessage.Caption = "" NumProb = NumProb + 1 'Generate random numbers for addends Number1 = Int(Rnd * 21) Number2 = Int(Rnd * 21) lblNum1.Caption = Format(Number1, "#0") lblNum2.Caption = Format(Number2, "#0") 'Find sum Sum = Number1 + Number2 cmdNext.Enabled = False txtAnswer.SetFocusEnd Sub

Form_Activate Event:Private Sub Form_Activate() Call cmdNext_ClickEnd Sub

Form_Load Event:Private Sub Form_Load() Randomize Timer NumProb = 0 NumRight = 0End Sub

txtAnswer Event:Private Sub txtAnswer_KeyPress(KeyAscii As Integer) Dim Ans As Integer 'Check for number only input and for return key If (KeyAscii >= vbKey0 And KeyAscii <= vbKey9) Or KeyAscii = vbKeyBack Then Exit Sub ElseIf KeyAscii = vbKeyReturn Then

'Check answer Ans = Val(txtAnswer.Text) If Ans = Sum Then NumRight = NumRight + 1 lblMessage.Caption = "That's correct!" Else lblMessage.Caption = "Answer is " + Format(Sum, "#0") End If lblScore.Caption = Format(100 * NumRight / NumProb, "##0") cmdNext.Enabled = True cmdNext.SetFocus Else KeyAscii = 0 End IfEnd Sub


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5. Save and run the program to test the output (see Figure 2 & 3)


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PRICES:Size: Small – Php 100.00 Medium – 150.00 Large – 200.00

Crust Type: Thin Crust – same as size prices Thick Crust – Plus 50% of size prices

Drinks: Soft Drinks – Php 20.00 Fruit Juice – 15.00 Coffee/Chocolate 25.00

Extra Toppings: Plus Php 10.00 per extra toppings

Build Pizza Button: will display message box Your Pizza (see sample above)Clear Toppings Button: will uncheck all check boxes.Compute Button: will display all values under Amount frameClear All Button: will clear all entriesExit Button: will close the program.


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Logical Problems & Formulas: Position Code Rate/Day Civil Status Rate Basic Pay SSS Rate A 500.00 Single 10% 10,000 & above 7%

B 400.00 Married 5% 5,000 – 9,999 5%C 300.00 Widowed 5% 1,000 – 4,999 3%

below 1,000 1%

Basic Pay = No. of Days Worked * Rate/DaySSS Contribution = Basic Pay * SSS Rate Withholding Tax = Basic Pay * Tax RateNet Pay = Basic Pay – (SSS Contribution + Withholding Tax)

• Upon choosing the desired Employee Number, it will automatically display the Employee Name.

• For Compute Button, will compute the Basic Pay, SSS Contribution, Withholding Tax and Net Pay


EMPLOYEE PAYROLL COMPUTATION

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• For Clear Button, will clear all entries• For Quit Button, will close the program/application.


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PROJECT 4: FORM #1: Hotel Billing System

Sample Form and sample output:

Room Capacity

Room Type Rate/day Type of Payment

Additional Charge

Regular 100.00 Cash No add’l chargeSingle De Luxe 300.00 Check + 5%

Suite 500.00 Credit Card + 10%Regular 200.00

Double De Luxe 500.00Suite 800.00Regular 500.00

Family De Luxe 750.00Suite 1,000.00


Problem:• Compute for Total Amount based on the date of

check-in and check-out.• Select room capacity, room type and payment

type before clicking Compute button otherwise, will prompt you with “No selected room capacity” or “No selected room type” or “No selected type of payment”

58


Looping

Visual Basic allows a procedure to be repeated as many times as long as the processor could support. This is generally called looping .

Do Loop

Format:a) Do While condition

Block of one or more VB statements Loop

b) Do Block of one or more VB statements Loop While condition

c) Do Until condition Block of one or more VB statements Loop

d) Do Block of one or more VB statements

Loop Until condition

Example:Do while counter <=1000

num.Text=counter counter =counter+1 Loop

Note: The above example will keep on adding until counter >1000. The above example can be rewritten as

Do num.Text=counter counter=counter+1 Loop until counter>1000


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For....Next Loop

Format: For counter=startNumber to endNumber (Step increment)

One or more VB statements Next

Example: (a) For counter = 1 to 10 display.Text =counter Next

(b) For counter=1 to 1000 step 10 counter = counter + 1 Next

(c) For counter = 1000 to 5 step -5 counter = counter - 10 Next


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Introduction to VB Functions II

Creating Your Own Functions

Format: Public Function functionName (Arg As dataType,..........) As dataType or Function functionName (Arg As dataType,..........) As dataType

Note: Public indicates that the function is applicable to the whole program and Private indicates that the function is only applicable to a certain module or procedure.

Example: The following program will automatically compute examination grades based on the

marks that a student obtained.

Figure 11: Sample Interface

Program Listing 19: Example of Functions declaration‘Declaration of Function gradePublic Function grade(mark As Variant) As String

Select Case mark Case Is >= 80 grade = "A" Case Is >= 70 grade = "B" Case Is >= 60 grade = "C" Case Is >= 50


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grade = "D" Case Is >= 40 grade = "E" Case Else grade = "F" End Select

End Function

‘Procedure computePrivate Sub compute_Click() grading.Caption = grade(mark) End Sub

‘Procedure end – to close the applicationPrivate Sub End_Click() End End Sub


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Practice Exercise #8: Password EntryProject Name : PEPJT03<FirstNameLastName> Example: PEPJT03RichardGwapoForm Name : PE07FRM02<FirstNameLastName> Example: PE07FRM02RichardGwapo

Form 1: Password Entry

Specs:TextBox Name: txtPassword

CommandButton Name: cmdAccept

Display this message box if the password is incorrect:

Click Retry: to go back to Password Entry Form Click Cancel: to quits the application/program.

Display this message box if you failed to enter the password correctly (three (3) attempts only)

Click OK: to quits the application/program.


Then, will display Form 1 after clicking on OK button (Sample Program above)

Display this Message Box if the password is correct

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Object Oriented Programming 1: Using Microsoft Visual Basic 6.0 Lecture and Laboratory ExercisesSource Codes:

cmdAccept Event: Private Sub cmdAccept_Click()

Dim Ans As IntegerStatic Trial As Integer

If txtPassword.Text = "gwapo" Then MsgBox "Password Accepted...", vbInformation, "Password Entry" Unload Me Form3.Show Else Ans = MsgBox("Invalid Password....Try Again...", vbQuestion + vbRetryCancel, "Password Entry") If Ans = vbRetry Then txtPassword.Text = "" txtPassword.SetFocus If Trial = 2 Then MsgBox "Intruder!....", vbCritical + vbOKOnly, "Password Entry" End Else Trial = Trial + 1 End If Else End End If End If

End Sub

Form_Activate Event:Private Sub Form_Activate()

txtPassword.SetFocus End Sub


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PROJECT #5:FORMS: SAMPLE FORM LAYOUT

Upon running the program displays the 1st form, which is the PASSWORD ENTRY

FORM 1:

Note: No limit for password, if incorrect password will prompt the user to RETRY & CANCEL and user name should have an entered value otherwise will prompt the user to enter value for user name.

If the password is correct will display the 2nd form (MENU)

FORM 2: (with File & Help Menu)Main Menu: File HelpSub Menus: Transaction About

Exit

<File> <Transaction>, will display the Transaction Form:

For TRANSACTION Form:Initially; BUTTONS: New, Clear, Close & Compute are all in disabled layout (as shown below)

<File> <Exit>, will close the program If Transaction is clicked, displays 3rd Form: (as shown below)


Richard Gwapo

* * * * *

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Object Oriented Programming 1: Using Microsoft Visual Basic 6.0 Lecture and Laboratory ExercisesFORM 3:

Appliances/Items Unit Price Appliances/Items Unit PriceElectric Fan 500.00 Television 5,000.00Refrigerator 9,000.00 Air Conditioner 10,000.00Washing Machine 4,000.00 Rice Cooker 600.00Oven Toaster 550.00 Electric Stove 1,000.00Flat Iron 350.00 Electric Pot 800.00VCD Player 1,200.00 Karaoke 2,500.00Mini Component 3,500.00 Microwave Oven 3,000.00

Logical Problems: Double click Appliance item (List Box) then the selected item will be displayed to the Appliance Sold (List

Box) and UnitPrice (List Box) (see example below)Note: Be sure that you have enter value in the Quantity

If quantity is less than or equal to zero (0) it will prompt the user to input quantity. Amount Text Box will be based on the Appliance Unit Price * Quantity

Example: Appliance Sold: Electric Fan, Unit Price: 500, Quantity: 2 (see example below) Sub-total Text Box will be based on the total item sold.

Example: Appliance Sold: Air Conditioner 10,000.00 X 1 and Electric Fan 500.00 X 2(see example below);

Choose Type of Payment: Cash or Charge then, will enable Compute buttonIf Compute button is clicked; for CASH

Total Amount = Sub-total less 5% discount


3rd Form: (Transaction Form)

User Name: Railee Darrel <Insert Date & Time here>

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Object Oriented Programming 1: Using Microsoft Visual Basic 6.0 Lecture and Laboratory ExercisesOutput:For Cash Payment

Then, will enable buttons; New, Clear & Close

Enter value for Amount Tendered: Amount Tendered should be exact amount or should be greater than Total Amount otherwise, will prompt the user to enter valid amount.

Click Change button to display the amount change. For New button, will clear all entries For Clear button, will Quantity, Appliance Sold, Unit Price and Type of Payment only. If Compute button is clicked; for CHARGE

Total Amount = Sub-total + 5% additional charge For Close button, will close the transaction window only.

Output:For Charge Payment.


User Name: Richard Gwapo <Insert Date & Time here>

User Name: Richard Gwapo <Insert Date & Time here>

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Then, will hide all controls under Total Amount and displays 5% Additional to all Charge Payments (see example above)

FORM 4:

If Help then About is clicked, will display a Form “About the program”

If button OK is clicked will close the form window.

If button AUTHOR is clicked will display message group members/programmers.


Manual VB 6.0

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Transcript of Manual VB 6.0