Visual Basic Programming Starting Visual Basicteachers2.tulpehocken.org/knoecker/VisBasNotes.pdf ·...

Visual Basic Programming 1

Starting Visual Basic

1. Normally, you will have created a shortcut on your desktop to access Visual Basic.

If not, access it by using the Start – Programs – Microsoft Visual Basic series of

clicks.

2. Upon opening the software, you will see the New Project window.

To open a new project, left click the New tab and choose the Standard EXE

option.

To open an existing project, left click on the Existing tab and browse to choose

the project from its storage location (hard drive, diskette, etc.).

3. Left Click the Open button.

3. At this point, the project design window will become visible with the first form

already visible.

New Tab

Existing Tab

Standard EXE

option

Open button


Standard Toolbar

Toolbox

Project Name Form Name Menu Bar Standard

Toolbar

Project Container Window

Form Window

Toolbox

Window

Project

Explorer

Window

Properties

Window

Form Layout Window

Property

Description

Window

Add a

Project

Add a

Form

Menu

Editor

Open a

Project

Save a

Project

Paste

Start

Program

Break

Program

Stop

Program

Highlight Project Explorer,

Properties, Form Layout, Object

Browser, and Toolbox,

respectively


Project Window

Pointer

Label

Frame

Checkbox

Combo Box

H.Scroll Bar

Timer

Dir. List Box

Shape

Image

Picture Box

Text Box

Command Button

Option Button

List Box

V.Scroll Bar

Drive List Box

File List Box

Line

Data

View Code Button

View Object Button

Toggle (Show/Don‟t show) folders button

Project Name and Icon

Form Name and Icon


Programming Prefixes

Prefix Control Prefix Control

ani Animation button hsb Horizontal scroll bar

cbo Combo box img Image

ch3 3D Check box ils Image list

chk Check box lbl Label

clp Picture clip lin Line

cm3 3D Command button lst List box

cmd Command button mci Multimedia MCI

ctr Control (specific type

unknown)

mnu Menu

dat Data opt Option button

dir Directory list box pic Picture box

dlg Common dialog box prg Progress bar

drv Drive list box shp Shape

fil File list box sli Slider

fr3 3D frame spn Spin button

fra Frame tlb Toolbar

frm Form tmr Timer

gpb Group push button tre Tree view

gra Grid txt Text box

grd vtb Vertical scroll bar

File Extensions

.frm = Forms

.vbp = Visual Basic Project

.bas = Module


Forms, Labels, Text Boxes, and Buttons

The form is the vehicle in which all of the tools (Labels, Text Boxes, and Buttons)

reside. It is the master container for a portion of an application and is the application‟s

interface with the user.

Setting the Form’s Name and Caption Properties Example: We will build a form in which the user will be allowed to enter his/her name in

a text box. We will call this program MyName.

1. Open Visual Basic and choose New – Standard EXE application.

2. Name the form by

Left Clicking and dragging in the data side (the right side) of the Name property

in the Property Window to highlight the default entry.

Using the “frm” prefix, name the form “frmName” by typing it in this area

3. Change the caption property to reflect the name “MyName”

Left click and drag to

highlight the right side of

the Name property and

type frmName

Change the Caption property to

MyName. (Notice it appears at

the top of the form.)

Caption appears at the

top of the form.


Adding a Label to the Form 1. Add a label to the form by

Left Clicking on the Label tool

Place the mouse pointer on the form in the location where you would like to place

the upper left hand corner of the label

Left Click and drag the label onto the form

2. Change the label‟s Name property to “lblMessage”

3. Change the label‟s Caption property to “Please type your name”

Notice how this caption appears inside the label

4. Change the label‟s visible property to False. (This will cause the label to disappear.)

Note: Any tool or object inserted in a form can be moved by dragging it anywhere on the

form. Also, any object can also be resized by dragging on an edit handle in a

highlighted object just as an object in a Word Document or Excel spreadsheet.

Change the

Name option

Change the

Caption option

Caption appears in the

label


Adding a Text Box to the Form 1. Left Click the Text Box tool in the tool window

2. Drag a text box near the bottom of the form

3. Change the Name property of the text box to “txtName”

4. Change the Text property of the text box to a blank (Note that you will have to scroll

down in the properties window to see the text property.

Left click and drag over the default text entry

Press the backspace key or the delete key on the keyboard to remove the default

text

Text

box

tool Delete the default text

property to make the text

box blank No text in the text box

New name appears

in the title window


Adding Command Buttons to the Form 1. Left Click the Command Button tool in the tools window and drag two buttons on

the form.

2. Change the name properties of these buttons to “cmdOK” and “cmdCancel”.

3. Change the caption properties of these buttons to “OK” and “Cancel” respectively.

OK and Cancel

command buttons


Adding Code to Objects

We want our program to do the following things:

1. When the user clicks anywhere on the form the label “Please type your name”

should appear.

2. The user should then type his/her name in the text box.

3. The user should then click the OK button and the message “Hello _____” should

appear in the text box with the name the user typed inserted in the line.

4. The user can then click on the Cancel button to leave the program.

Follow these steps to create the application code:

Make the lblMessage Label Visible When the Form is Clicked 1. Left click on the View Code button located at the top of the project window.

2. When the Program Code view appears, click on the down arrow next to the Object

window. (Will probably have the word General there.)

3. When the drop-down menu appears, choose the Form object.

4. Click on the down arrow next to the Procedure window and choose the Click

procedure.

Object Window

Procedure Window


5. When the procedure code for Private Sub Form_Click( ) appears, left click below

this line and indent (space) a couple of spaces and type the text “lblMessage.”

6. As soon as you type the period (.), a drop-down menu of properties will appear.

Scroll to the Visible property and double click to place this property in the code you

are typing.

7. After the Visible property is added to the code, type an equal sign (=). Immediately,

a drop-down list of available values (True or False) appears. Double click on True

to make the text “Please type your name.” appear when the form is clicked on at

run time.

Drop-down list

of values

Completed Code


Code the OK Button to Show the Desired Message in txtName Text Box

1. In the Program Code view, choose the OK command button (cmdOK) from the

Object Window list.

2. Choose the Click procedure from the Procedure drop-down list.

3. The Private sub cmdOK_Click( ) procedure is now ready to code.

4. Type the following code inside the procedure :

txtName.text = “Hello “ & txtName.txt

Code Hints:

“ “ = Whatever is placed inside of quotation marks will be printed

& = Will append a string to another string

5. The code is saying “the Text property of the txtName text box is equal to the

string “Hello “ and its current text.”

6. Run the application by clicking the Run button

7. Exit the application by clicking the close button in the application

window.

X


An Alternate Method

1. Inside the Private sub cmdOK_Click( ) procedure, place the following code:

Dim strName As String

strName = "Hello " & txtName.Text

txtName.Text = strName

Code Hints:

To declare a variable (such as strName), the syntax is as follows:

Dim <Correct Prefix><Name of the Variable> As <Choose type from drop-down list>

Prefixes:

Data

Type

Prefix Example

Boolean bln blnBooleanVariable

Byte byt bytVar

Collection object col colThisObject

Currency cur curMyCost

Date(Time) dtm dtmBirthDate

Double dbl dblThisVar

Error err errThis Err

Integer int intCounter

Long lng lngThisVar

Object obj objCircleOne

Single sng sngThisVar

String str strNameOne

User-defined type udt udtMyUDT

Variant vnt vntThisVar

Example: To declare an integer variable Dim intCounter as Integer

To declare a single precision variable Dim sngValOne as Single

1. Define the variable strName as a string

2. Assign it the value of the contents of

txtName preceded by the string “Hello “

3. Reassign the contents of txtName the

value of strName


Code the Cancel Button to Close the Application 1. In the Program Code view, choose the down arrow in the Objects window.

2. Left Click the cmdCancel object.

3. The Click procedure should appear by default. If not, click the down arrow and

choose Click.

4. Insert the code “Unload Me” in the procedure‟s code section.

Note: The automatic help guide appears telling you to enter an object after the word

“Unload”. The word “Me” refers to the form currently active.

5. Now, when the application is run, it will end by either of two actions:

Left Click the Close Window button at the top right corner of the form

Left Click the Cancel button

Saving a Project

1. When saving a project (program) for the first time, you will be prompted to name

both the project and the form.

2. Name the form the same name as that used in the Name property and use a

recognizable name for the project

First click the File

menu option

Second, choose either the Save Project option (if saving

to the default location) or Save Project As (if saving to

a different location such as the diskette).


Exercise 1

1. Create an application that does the following things:

Have the user enter two numbers in two separate text boxes

If the user clicks on an Add button, the sum of these two numbers will be

displayed in another text box labeled Result

If the user clicks on a Mult button, the product of these two numbers will be

displayed in the Result window

If the user clicks on the Done button, the application will end

Note: The following parameters should be included:

1. Both the Add and Mult buttons should be coded, including single precision

numeric variables, to complete the calculation required and place the result

in the Result text box. (Hint: Don‟t forget that since the contents of a text

box are considered to be text, it will be necessary to use the Val function

[from BASIC] to change these contents to numeric values.)

2. All buttons as well as the Result label should be set to size 14 – bold font and

the “Please enter _ number” labels should be set for size 12 – bold font.

3. Follow all good programming conventions discussed in class.

An example of the form appears below:

An example of the results appears below:

After pressing

the Add button


Using Assignment to Change Property Values

In exercise #1, we have created an application to either add or multiply two numbers

entered in two separate text boxes. You may want to be certain that numbers have been

entered in both boxes before allowing a calculation to occur. Therefore, it may be

necessary to default the Enabled property for both the add and multiply command

buttons to False until both text boxes have entries. Then, when both text boxes contain

entries, change the enabled property to True. (Please note that the object names referred

to may not be the same as yours, but they will be easy enough to discern).

1. In the project's View Object view, choose the Add command button (cmdAdd) and

change its Enabled property to False.

2. Do the same for the cmdMult command button.

3. This will ensure that both buttons will not be enabled at the project's load time.

4. Return to the Code View and choose the txtNum1 text box object.

5. Choose the Change event and add the following code:

Private Sub txtNum1_Change()

If txtNum2.Text <> "" Then

cmdAdd.Enabled = True

cmdMult.Enabled = True

End If End Sub

6. Do the same with the Change event for the txtNum2 object

Private Sub txtNum2_Change()

If txtNum1.Text <> "" Then

cmdAdd.Enabled = True

cmdMult.Enabled = True

End If End Sub

Note that here, we are checking the

contents of the txtNum2 text box.

Note that here, we are checking the

contents of the txtNum1 text box.


7. The completed code appears below. Note that, every time the text property in either

text box is changed, the other box is checked to be sure that it has an entry in it before

the command buttons are enabled to do the calculations.

8. When this application is loaded, both command buttons are not enabled. But if one

of the text boxes is changed by highlighting its contents and deleting it, the buttons

remain enabled because we are only checking the contents of the other text box, not

the selected one. (Try this by running your application. You could click a calculation

button without re-entering a value in the text box.) Therefor, we need to also check

the contents of the text box in which the editing is taking place.

9. Change the code to appear as it does below.

10. Now, any time one of the text boxes is changed, both command buttons are disabled

and both text boxes are checked for contents.

11. It is now impossible to perform a calculation with one of the text boxes being empty.


Including Image Objects

In our example, we will add a picture between the two text boxes holding the numbers we

have entered. If we choose to add, we will display a plus sign between the numbers. If

we choose to multiply, we will show a multiplication sign between the two numbers.

These pictures can be created using Microsoft Paint and saving each (to your diskette or

personal folder) as a bitmap image. We will call the addition sign Plus.Bmp and we

will call the multiplication sign Mult.Bmp. After creating and saving these pictures,

begin the following procedure.

1. Choose the Image object from the toolbar.

2. Drag a box to the appropriate size and place it between the text boxes.

3. Name the image imgPlus in the properties window.

4. Change the Visible property for the image to False so it will not appear when the

form is loaded.

Image Object

New Image

Object

Name the image


5. Set the Stretch property for the image to True. This will ensure that the image

loaded into the image object will be sized to fit the size of the image object. If this

property were set to false, the image may be cut off if the image object were sized too

small.

6. Set the Picture property for the image box by

Left clicking in the right side of the Picture property row.

Left clicking on the three-dot button that appears.

Choose the Plus.Bmp file from the resulting window.

7. After all this is done, create the imgMult image object and place it directly over top

of the imgPlus image object.

8. Set the properties exactly as those of the imgPlus image object with the exception of

the Picture property. (Choose the Mult.Bmp file instead.)


9. Add the following code to the cmdAdd button click event. This code will cause the

multiplication sign, if it is visible, to be removed and the plus sign to become visible.

Programming Hint: Note the remarks added to the right of the code. These remarks can be added by

preceding each remark with an apostrophe ( ' ).

10. Do the same thing with the cmdMult command button's click event.

11. Add the following code to both the txtNum1 and the txtNum2 text box change event

to remove either sign if any changes are made to the numbers entered.


Review

Object Procedure Property Effect

Form Load Code takes effect when the form is loaded

Click Code executes when form is clicked on

Name Name of the form – frm----

Caption Title in upper left corner of form

Command

Button

Click Code executes when button is clicked

Name Name of command button – cmd----

Caption Text that appears on the face of the button

Enabled Is button available ? True / False

Font Size and style of the caption text

Visible Is button visible when the form loads?

True / False

Label Click Code executes when the label is clicked

on

Change Code executes when the text of the label is

changed

Name Name of the label – lbl-----

Caption Text within the label

Enabled Is label dark (True) or “gray out”(False) ?

Visible Is label visible? True / False

Text Box Change Code executes when contents is changed

Click Code executes when text box is clicked

Name Name of the text box – txt-----

Alignment Position of text – Left, Right, or Centered

Enabled Is text box dark (True) or gray (False)?

Text Text contents of the text box

Visible Is text box visible at run time? True /

False

Image Box Click Code executes when clicked on

Name Name of the image box – img---

Enabled Is box dark (True) or gray (False)?

Picture Picture file to appear in the image box

Stretch Does image shrink or expand to fit the size

of the image box? True / False

Visible Is the box visible at run time? True / False


Exercises

1. Create an application that will print your first name, middle name, and last name in

separate text boxes, depending upon which text box you click on.

2. Create an application that does the following things:

Enter two numbers

Provide command buttons to add the numbers, subtract the second number from

the first number, multiply the numbers, divide the second number into the first

number

Provide a text box to display the result

Provide a “Done” command button to exit the application

3. Create an application that does the following

Provide a command button labeled “Hello”

Provide a command button labeled “Goodbye”

When the “Hello” command button is clicked, have a smiley face (You may have

to create it in MS Paint.) appear and the word “Hello!” appear in a text box on the

form

When the “Goodbye” command button is clicked, have a frowning face appear on

the form and the word “Goodbye!” appear in the text box created above

4. Create an application that does the following

Create three text boxes with three different questions

Create three “answer” text boxes (one for each question)

Provide an “Answer” command button

Show the question in a given text box only when it is clicked on

Show the answer in its answer text box when the “answer” command button is

clicked


Variable Assignments

When creating applications, you will want to manipulate numeric values and store them

in variables. Variables must be dimensioned when created. That is, they must be

assigned a type as well as a name (See page 12 for naming conventions.).

1. At the beginning of the object‟s event code, type the word Dim to start dimensioning

a variable.

2. Next, name the variable according to its correct prefix (i.e. a string variable should

start with the str prefix and an integer variable should start with a int prefix.).

3. Then, add the name.

4. Next, type the word as.

5. Finally, enter the type of variable you are creating.

Example: To create an integer variable named Num1, you would type the following

code – Dim intNum1 as Integer

6. The variable is now ready to receive an integer value within the code.

7. The variable is only recognizable within the subroutine in which it was created.

8. The same variable can be created within a different subroutine without values

crossing over between the subroutines.

9. Variables can be used before being created, but their values at that point are equal to

zero.

In order to not allow a variable to be used before it is

dimensioned, add the Option Explicit command to the general section of the

form module.

Choose the General object from the drop down list

Type the Option Explicit command

Example

Returning to our “Addition and Multiplication” exercise, let‟s assign the values found in

the two text boxes to variables and then, perform the calculation requested.

1. Add the Option Explicit statement to the General portion of the module. (See

above)

General object chosen


2. Change the code for the cmdAdd button‟s click action to the following:

Private Sub cmdAdd_Click()

Dim intNum1 As Integer ' Dimension the intNum1 variable

imgPlus.Visible = True

imgMult.Visible = False

If txtNum1.Text <> "" And txtNum2.Text <> "" Then

intNum1 = Val(txtNum1.Text) + Val(txtNum2.Text)

txtResult.Text = intNum1

End If

End Sub

3. Make a similar change to the cmdMult command button „s click action. (See below)

Private Sub cmdMult_Click()

Dim intNum1 As Integer

imgPlus.Visible = True

imgMult.Visible = False

If txtNum1.Text <> "" And txtNum2.Text <> "" Then

intNum1 = Val(txtNum1) * Val(txtNum2)

txtResult.Text = intNum1

End If

End Sub

4. Notice that, in both the cmdAdd and cmdMult click events, we used the same variable

(intNum1). Because dimensioned variables are local to the event in which they are

created, this will cause no problem.

Note the change to a

multiplication sign


Debugging Using the Immediate Window

As an application is developed, the results of calculations or assignments may not be

exactly what the programmer had in mind. In these cases, it is important for the

programmer to be able to view the results of calculations or assignments as they are

executed within the code. that is the purpose of the Immediate Window.

1. To make the immediate window visible, either press Ctrl + G on the keyboard

simultaneously, or click on View from the main menu and choose Immediate

Window from the drop down list.

2. The Immediate Window will now appear on the Visual Basic Programming Screen

Immediate Window


3. In order to use the immediate window, the term Debug.Print must be inserted next to

the result that it is desired to view.

Example: In our addition / multiplication application, if we wanted to view the

calculation as it occurs in the code for the cmdAdd and cmdMult buttons, we would

add the following code to these events.

4. When the application is run, any time the code inside the cmdAdd or cmdMult click

events is run, the result of the calculation being performed along with its text

description will appear in the Immediate Window.

5. If we run the application and click the Add button followed by the Multiply button,

the results will appear as depicted on the next page.

The Debug.Print code

is followed by a

descriptive string

(optional) to

differentiate between

the addition and

multiplication

calculations. Next, is a

semicolon ( ; ), followed

by the variable

representing the result

of the calculation.


First, the Add button is clicked

Then, the Multiply button is clicked

Results in the Immediate Window

Results in the Immediate Window


Data Types

Visual Basic includes many built-in data types. A listing of these data types and a brief

explanation of each appears below.

Data Type Will Represent

Single Numbers with a value up to 3.438

that could contain a decimal point

Double Numbers with a value up to 1.8308

that could contain a decimal point

Integer Whole numbers up to 32,767

Long Whole numbers greater than 32,767

Currency Numbers that represent money

String A group of characters

Boolean Only two valid values … True or False

The value limits discussed in the table above extend an equal distance to the negative

If a decimal value is assigned to an integer or long data type, the value is rounded to

the nearest integer.

In order to assign a string literal to a string variable, it must be enclosed in quotes.

Data Type Naming Conventions

A table of prefixes for all data types is presented on page 12. Proper programming style

dictates the use of these prefixes.

Multiple Variable Declarations

More than one variable can be assigned with one DIM statement. Since the DIM

statement is used to assign variable type as well, all variables in a single DIM statement

must be of the same type.

Example

To assign variables X and Y to be integers, the DIM statement would look like the

one appearing below.

DIM intX, intY as Integer

Option Explicit

This command causes the program to generate an error message if a variable is used

without first being dimensioned. If option explicit is not used, a variable referenced

inside a program is assigned a value of zero.

Place it in the General section of the Form module


To make it mandatory that all variables throughout the project must be dimensioned

before being used, set this option as follows:

Choose the Options item from the Tools menu

Then, place a check in the Require Variable Declaration option

Then, click OK

Automatic Type Conversion

If an Integer variable is assigned a value with a decimal point, the value is

automatically rounded to the nearest integer.

If a text box contains a number for its text and that number is used in a calculation,

Visual Basic will automatically change the text version of the number to a

numeric value.

Require Variable Declaration

Option


Modulus Division

Modulus Division returns the remainder of a division. Suppose we want to find out if

273 is divisible by 3.

We perform modulus division (273 mod 3)

If the result is equal to zero, then we know that there is no remainder from that

division. Hence, 273 is divisible by 3.

The code may look like the following:

intremainder = 273 mod 3

If intremainder = 0 then

txtResult.text = “273 is divisible by 3”

Endif

Option Buttons

Option buttons (or Radio buttons) are designed to provide a group of possible responses

from the user, only one of which is permitted at a time. For instance, suppose we want

the user to decide whether to add or multiply the two numbers in our Example 1

calculator project:

The Caption Property assigns the text that labels the option designated by that

particular option button

When the program is run, the option button that is clicked will contain the highlight

and any other option button that was formerly highlighted will lose the highlight.

After setting the code as it appears below, the application will display either the sum

or product of the two numbers, depending upon which control button is highlighted.

Option Button Tool

Name Property

Caption Property


Option Explicit

Private Sub optAdd_Click()

txtAnswer.Text = Val(txtFirst.Text) + Val(txtSecond.Text)

End Sub

Private Sub optMult_Click()

txtAnswer.Text = Val(txtFirst.Text) * Val(txtSecond.Text)

End Sub

Private Sub txtFirst_Change()

optAdd.Enabled = False

optMult.Enabled = False

If txtFirst.Text <> "" And txtSecond.Text <> "" Then

optAdd.Enabled = True

optMult.Enabled = True

End If

End Sub

Private Sub txtSecond_Change()

optAdd.Enabled = False

optMult.Enabled = False

If txtFirst.Text <> "" And txtSecond.Text <> "" Then

optAdd.Enabled = True

optMult.Enabled = True

End If

End Sub

The application will appear as below:

The Value property can be set to true (chosen) or false (not chosen)

The Alignment property can be set to left or right to align the caption on that side

of the option button.


Frames

Frames are used to group option buttons related to the same choice. The application

appears below complete with a frame around the option buttons.

The Caption Property assigns the text to appear at the top of the frame. In this case,

the caption is “Choose an Operation”.

Constants

Values that will not change can be assigned so that they can be used without constantly

having to write the value.

For instance, if we wanted to use the value of Pi as 3.14, we could assign this value to

a constant (PI for example) and use it instead.

The code would look like that below:

Const dblPi As Double = 3.14

Now, whenever the value for Pi is used, we need not type 3.14, we simply need to use

dblPi.

Frame Tool

Caption Property

C


If … Then Statements

The If … Then statement is used when a condition must be tested in order to either

execute or skip a section of code. For instance, suppose the value of the variable intX

must be greater than 10 in order to place the text “Greater Than 10” in the “txtResponse”

text box. The code would appear as below:

If intX > 10 Then

txtResponse.Text = “Greater Than 10”

End If

Note the following aspects of the statement:

The If … Then statement is always ended with the End If section.

The condition tested must be between the If and the Then portion of the statement.

If the condition is True, the code between the If and the End If portion of the

statement will be executed.

If the condition is False, the code between the If and the End If portion of the

statement will not be executed.

Boolean Relational Operators

Operator Meaning

= Equal to < Less than

<= Less than or Equal to

> Greater than

>= Greater than or Equal to

<> Not equal to

Roundoff Errors

Care must be taken when testing equalities involving floating point numbers because the

rounding of these numbers. For instance, rounding off .8 results in a binary form of

0.1100110011 … . Since this number never reaches an end, it must be rounded and will,

therefore not be equal to any finite number unless this math has been done and that

particular number has been used to conduct the test in the IF portion.

If … Then… Else Statements

The “Else” portion of this statement provides a logical alternative to the condition in the

“If” statement, other than simply moving on to the next area of the code. Simply stated,

if the If criteria is true, the Then portion of the statement will execute. Otherwise, the

Else portion will execute.

As with all “If … Then” statements, it is good programming style to indent the code

inside of the If, Then, and Else portions of the code.


Nested If … Then … Else Loops

Additional criteria can be included within a given loop using the Else … If option. For

instance, suppose we wanted to do the following:

1. Have the user place a number in a text box

2. Have a different label appear saying “Large” if the number is greater than 75,

“Medium” if the number is greater than 25 and less than 76, or “Small” if the number

is 25 or less.

3. The above would occur after a command button was clicked

4. We use an “If … Then … Else” statement in the text box‟s change procedure to

either enable or disable the “Calculate” button:

If txtNumber.Text <> “” Then

cmdCalculate.Enabled = True

Else

cmdCalculate.Enabled = False

End If

5. Then, in the cmdCommand button‟s click procedure, we need to use nested “If …

Then … Else” statements to decide which label (Small, Medium, or Large) should

appear: Private Sub cmdCalculate_Click()

If txtNumber.Text > 75 Then

lblSmall.Visible = False

lblMedium.Visible = False

lblLarge.Visible = True

Else



lblMedium.Visible = True

lblLarge.Visible = False

Else

lblSmall.Visible = True



End If

End If

End Sub

Main If/Then

Nested If/Then


If … Then … ElseIf

This option is usually used to decide between three or more options. It eliminates the

creation of many separate nested If/Then loops.

Changing the application referred to previously, the code would appear as below:

Private Sub cmdCalculate_Click()




lblLarge.Visible = True

ElseIf txtNumber.Text > 25 Then


lblMedium.Visible = True


Else lblSmall.Visible = True



End If

End Sub

Generating Random Numbers

Random numbers are extremely useful when designing games or computerized study

programs.

The random number generator function is called Rnd.

It will generate a random number within the range 0 through 1

In order to generate numbers within a range of integers, use the following

formula:

(High number – Low number + 1) * Rnd + Low number

For instance, to generate a random number between 5 and 10, the formula

would be (10 –5 +1) * Rnd + 5

= 6 * Rnd + 5

The random numbers generated by the formula above will be real numbers

and not necessarily integers

To be certain that the numbers generated are integers, utilize the Int or Fix

functions.

Int Function The Int function returns an integer less than or equal to its argument.

The integer returned by Int(3.7) is 3

The integer returned by Int(-15.23) is –16

Fix Function The Fix function will truncate or cut off the numbers to the right of the decimal point

The integer returned by Fix(3.7) is 3

The integer returned by Fix(-15.23) is –15

Only one

If/Then

statement

needed Last option usually

only needs “Else”


Randomize Random numbers are generated by seeding the generator with the time from the system

clock in the computer. Running a program to randomly generate numbers will generate

the same random numbers each time until the generator is re-seeded.

The Randomize command should be placed in the Form_Load procedure of the

form in which the generator is run. In this way, new numbers will be generated

each time the form is loaded.

Scope

When a variable is created within a procedure, it is said to be “local” to that procedure.

That is, it cannot be accessed by any other procedure outside of the one in which it was

created. The same is true for constants. These are known as local declarations.

Therefore, the scope of the particular variable or constant is the procedure in which it has

been declared. Since the scope is local, another procedure within the same form module

can use the exact same variable or constant without any problems.

If, on the other hand, the programmer wishes a variable or constant to be recognized

throughout the entire form module, it can be declared as a global declaration. Global

variables and constants are declared in the general section of the form module. They

are declared in the same way as any other variable or constant except that the key word

Private should be used instead of dim when declaring a variable. In the case of a

constant, the key word Private should be used before the keyword Const.

It is always best to avoid using global declarations and stick with local ones. This is

because the programmer runs the risk of using a global variable locally. Dimensioning a

local variable that is the same as a global variable will change the value of the variable

or constant within that procedure.

The following code shows how to declare a global variable and constant


The application will execute as follows:

When the Global button is clicked When the Local button is clicked

Logical Operators

Logical operators are the boolean operators And; Or; Not. They return a value of either

True or False.

Example

If we wanted to enable a command button called cmdCalculate if and only if the

number entered in text box txtNumber is within the range 10 through 30

If Val(txtNumber.Text) > 9 AND Val(txtNumber.Text) < 31 Then

cmdCalculate.Enabled = True

End if

Operator Function

And All conditions must be true in order for the expression to be true

Or Any condition can be true in order for the expression to be true

Not The opposite must be true in order for the expression to be true

Logical operators are most often used in If … Then statements

Message Box

Message boxes provide information to the user as to what he/she may have done wrong

while running an application. They require the user to click an OK button in order to

continue.

For example, the following code:


Will result in the following application when the number is out of range

Password Applications

To password protect your application, you need to make the first form of the application a

password form. It must be coded so that, if the password entered is correct, the next form

will appear and the password form is unloaded.

For example the following code

Results in the following application if the password is incorrect

Note the asterisks as the

user types the password.

This is done by setting the

password textbox

PasswordChar property

to “*”. Any other

character could be used as

well.


Or the following application if the password is correct

Counters

Counters keep track of the number of times an action takes place. For instance, you may

only want to give a user three chances to correctly enter the correct password and then

unload the application. An example of this appears below. Variables are updated by

placing them on both sides of the equal sign (=) and adding or subtracting some value

from the right side. ( For example : intX = intX + 1)

It is important to remember that, if a variable is to be updated in more than one procedure

within the module, it must be declared as a global variable. Also, if the variable‟s value

is used throughout the entire module and it is dimensioned locally, every time the local

procedure is executed the variable is re-dimensioned which will set its value back to

zero.

Global counter variable declaration

Increment the counter variable each time the user

enters the wrong password. Then, check how

many incorrect entries were made.


Check Boxes

Check boxes work exactly the same way as option buttons except for the fact that more

than one can be checked at a time. The important properties are:

Property Definition Options

Name The name by which it is called Use the “chk” prefix

Caption The label next to the individual box Up to the user

Value Its possible settings Set to either checked,

unchecked, or grayed during

design. Changed to

vbChecked, vbUnchecked,

or vbGrayed during runtime.

Alignment Where the box is with respect to the

caption

Left or right of the caption

The Click event is usually coded for each box.

For example, if we wanted a caption to be any combination of bold, underlined, or

italics, we would use the following application:

Here are some of the various results


Printing a Form

Objects have properties and methods. One such method is the PrintForm method which

allows a form to be printed by the printer. Using dot notation, the syntax for this method

is <Name of the form>.PrintForm. In our example, by adding a print button called

cmdPrint, and adding the following code, we can print the form at the printer.

Note the reference to the current form as

“me”. This is the easiest way to refer to

a current form. Alternatively, we could

have said “frmStyles.PrintForm” since

frmStyles is the name of the form to

print.


Do Loops

Do loops execute instructions repeatedly while a given set of criteria is true. The criteria

are acted upon inside the loop so that, eventually, it becomes false. At that time, control

of the code passes from the loop and continues with the code immediately following it.

Do – Loop While This loop will execute at least one time. When the end of the loop is reached (Loop

While) the criteria are analyzed and the decision is made whether or not to execute the

code within the loop again.

For example, the following loop will continue adding one to the value of the text box

txtNum until the total exceeds 25. Then, the label lblGotIt will appear.

intTotal = Val(txtNum.Text)

Do

intTotal = intTotal + 1

Loop While intTotal <= 25

lblGotIt.Visible = True

Do While – Loop

This loop analyzes the criteria first and then enters the loop if the criteria is true. The

loop continues if the criteria remain true. If not the code continues after the Loop

statement.

intTotal = Val(txtNum.Text)

Do While intTotal <= 25

intTotal = intTotal + 1

Loop

lblGotIt.Visible = True

Infinite Loops If a program enters a loop and the criteria do not become false, it will continue

indefinitely. If this happens, the program can be halted by pressing the key combination

Ctrl / Break.

Input Box

Input boxes provide a method for the user to add data to the program. The box appears

when signaled within the code. It contains a text box for the user to enter data along with

The loop begins at the Do statement

The loop will re-execute as long as

intTotal does not exceed 25

This loop will

execute at least

one time

because the

criteria are not

analyzed until

the end of the

loop

This loop may not

execute at all because the criteria

are checked before

the loop executes


an OK button. When the OK button is clicked, the data is assimilated into the program as

if it were coded.

Syntax InputBox(“Prompt”,”Title”)

Example To use an input box to assign a value for the caption property of a label called

lblData

lblData.Caption = InputBox(“Please enter the value”,”Input Box for the Label”)

When the OK button is clicked, the caption is assigned the value in the input box


Accumulators

An accumulator tracks a changing value through the course of the program

Example A variable is created to store a value

We use an input box to add to the value after the Start button is clicked

Each time we add to the value, we calculate its sum and display it on the form

We will use a Do Loop to monitor the value until it exceeds 100

Then, we will display a message box saying that we have reached the limit

The code appears below

Here, we add value to the accumulator


String Conversion Functions

String conversion functions are use to change strings to a string of a different form.

LCase Used to convert all of the letters in a string to lower case

Syntax

LCase(String)

Example

strTest = “COMPUTER”

strLCase = LCase(strTest)

The strLCase variable would contain the string “computer”

UCase Changes all lower case letters in a string to upper case

Syntax

UCase(String)

Example

strTest = “Computer”

strUCase = UCase(strTest)

The variable strUCase would contain the string “COMPUTER”

StrConv Converts strings to either upper case (vbUpperCase), lower case (vbLowerCase), or

proper case (first letter of each word is capitalized)(vbProperCase).

Syntax

StrConv(String,Conversion)

Example

strTest = “happy valley”

strNew = StrConv(strTest,vbProperCase)

The string strNew contains the string “Happy Valley”.

Note: The string variable “strTest” could be replaced with the string literal.

strNew = StrConv(“happy valley”,vbProperCase)


Manipulating Strings

Left

Returns a given number of characters in a string starting from the left and reading to the

right.

Syntax

Left(String, Length)

Example


strTest2 = Left(strTest,4)

Here, the variable strTest2 would contain the string ”Comp”.

Note: The string variable strTest could be replaced with the string literal “Computer”

strTest2 = Left(“Computer”,4)

Right

Returns a given number of characters in a string starting from the given number of

characters in from the right and reading to the right.

Syntax

Right(String, Length)

Example


strTest2 = Right(strTest,4)

Here, the variable strTest2 would contain the string ”uter”.

Note: The string variable strTest could be replaced with the string literal “Computer”

strTest2 = Right(“Computer”,4)

Mid Function

Returns a string of a number of characters within a main string, starting at a position a

given number of characters from the left, and reading left to right.

Syntax

Mid(String, Start, Length)

Example


strTest2 = Mid(strTest,4,3)

Here, the variable strTest2 would contain the string ”put”.


Mid Statement

Whereas the Mid function returns a sub-string from the main string. The Mid Statement

is used to replace a portion of a string with another string and is placed to the left of the

equals sign.

Syntax

Mid(String1, Start, Length) = String2

Example


Mid(strTest,4,2) = “Science”

Here, the variable strTest would contain the string ”CompScter”. The string

strTest was changed by replacing the 2 characters starting at the 4th

character with

the same number of characters (starting at the left) from the string “Science”.

Note: As with all of these functions and statements, any string variable can be

replaced with a string literal or vice versa.

Len Function

Returns a number reflecting the number of characters in a string.

Syntax

Len(String)

Example


intNumChar = Len(strTest)

Here, the numeric variable intNumChar assumes a value of 8 because the string

“Computer” contains 8 characters.

InStr Function

Compares a portion of a string with a sub-string starting at a given character, to see if

the string contains that sub-string. It will return the number of the character where

the match begins. If the sub-string is not contained in the string, it will return a 0.

Syntax

InStr(Start, String, Sub-string)

Example

strString = “Computer”

strSub = “put”

intNumChar = InStr(3,strString,strSub)

Here, intNumChar equals 4 because “put” occurs at the 4th

character in “Computer”.

If a starting point is

omitted, the search will

begin at the first character

in the string.


For … Next Loop

This loop will allow the program to execute a series of commands for a given number of

times. It can also be used to perform calculations on a series of numbers that have the

same values between each (i.e. All even numbers have one number between them).

Syntax

For <Variable> = <Start> to <Limit> Step <Number>

Example

To calculate the average of the numbers 1 through 10:

For intX = 1 to 10

intTotal = intTotal + intX

Next intX

sngAverage = intTotal / 10

To calculate the average of all of the even numbers from 30 through 40:

For intX = 30 to 40 Step 2

intTotal = intTotal + intX

Next intX

sngAverage = intTotal / 6

Note: Any number in a For … Next loop can be replaced with a numeric variable as well.

For intX = intStart to intLimit Step intStep

The Step Clause can also be a negative number to decrement the variable in the

For statement.

For intX = 15 to 5 Step –5

Generating Strings

String

Generates a series of a given length of a particular character or string.

Syntax

String(Integer, Character)

Example

strExample = String(10,”+”)

If the step clause is

omitted, the variable

will increment by 1.

The step clause 2,

causes the variable to

increment by 2.

Assigns a string consisting of 10 “+”

signs to the variable strExample.


Space

Inserts a given number of spaces inside a string.

Syntax

Space(Integer)

Example 1

strSpace = Space(20)

lblText.Caption = strSpace

Example 2

lblText.Caption = Space(20)

&

Used to concatenate one string onto another.

Syntax

String = String1 & String2

Example 1

strFirstName = “John”

strLastName = “Smith”

strName = strFirstName & strLastName

Example 2

strName = “John” & “Smith”

vbTab

Places eight(8) spaces in a string. Most often used in conjunction with the

“&”

Example

strName = “John” & vbTab & “Smith”

vbCrLf

Used to execute a carriage return (place the next text at the leftmost position) and a line

feed (move the cursor to the next line below the current line).

Example

strName = “John” & vbCrLf & “Smith”

Both examples insert a string of 20

spaces in the lblText label.

The variable strName is set

equal to “JohnSmith”.


equal to “John Smith”


equal to “John

Smith”


Comparing Strings

Strings can be evaluated with regard to value via each character‟s ASCII code value.

Since the capital letters have a lower value than the lower case letters, the statement

“Zebra” < “apple” is actually true. However, the statement “apple” < “Apple” is false.

The statement “Apple” = “Apple” is true because each character in both strings has the

same ASCII number.

StrComp

Uses the constant vbTextCompare to evaluate if two strings are textually equal. That is,

do they contain the same characters without regard to case. It will return one of the

following values:

0 = textually equal

-1 = String1 < String2

1 = String1 > String2

Syntax

StrComp(String1,String2,vbTextCompare)

Example

strString1 = “Computer”

strString2 = “Monitor”

strString3 = “computer”

txtAnswer1.Text = StrComp(strString1, strString2, vbTextCompare)



Like

Used to detect matching patterns between strings. The Like operator returns a boolean

value of either True (if a matching pattern is detected) or False (if a matching pattern is

not detected).

Syntax

Result = String Like Pattern

Possible global characters

1. ? = Used to signify any one character “Run” Like “?un” True

2. * = Used to signify any of many characters “Hit” Like “H*” True

3. # = Used to signify any one number “SN532” Like “SN53#” True

4. [ ] = Used to enclose a list of characters “K” Like [A,C,K,N] True

5. - = Used to indicate a range of char. in a list “K” Like [H-N] True

6. , = Used to separate characters in a list “K” Like [I,J,K,L] True

Example lblResult.Caption = “Hit” Like “H*” The label would read True.

Text boxes contain the following:

txtAnswer1 = -1

txtAnswer2 = 0

txtAnswer3 = 1


Sub Procedures

Procedures are blocks of code performing a specific task. Event procedures such as

cmdDone_click are referred to as sub procedures. There are two types of sub

procedures.

General Procedures

General procedures are created by the user and break up the code into smaller portions.

Many times, they are used for repetitive operations where the same calculations or

events are programmed to occur throughout a module.

Syntax

Sub ProcedureName( )

Lines of Code

End Sub

Example

Sub ClearLabel ( )

lblName.Caption = “”

End Sub

Call The call command is used to execute a previously created sub procedure.

Syntax

Call SubProcedureName

Example

Private Sub cmdClearLabel_Click( )

Call ClearLabel

End Sub

Note: Sub procedures can call other sub procedures.

Line Continuation Sometimes, a typed line of code may become too long to fit in the code window. To

continue a line of code on the next line without generating an error message, use the

line continuation ( _ ) character.

Example

lblText.Caption = “lblText.Caption & _

“In addition, the previously mentioned item may be taxed at 6%.”


Value Parameters Value parameters are used to pass data from the call statement to the sub procedure.

Syntax

Call SubProcedureName(value parameter, value parameter)

Example

Call AddNumbers(intNum1, intNum2)

Sub AddNumbers(ByVal intVal1, intVal2 as integer)

lblSum.Caption = intVal1 + intVal2

End Sub

The application looks like the form to

the left. It runs like the following:

The user enters a number in each

text box

The user clicks the Calculate button

The sum of the two numbers entered

in the text boxes appears in the label

at the bottom

In the code, the sub procedure Sum

is called in the calculate command

button click procedure.

The values assigned to the int1 and

int2 variables are passes as

arguments to the Sum sub procedure.

The arguments are accepted by the

Sum sub procedure and assigned by

value to the parameters intX and intY

Value parameters

passed to a sub

procedure are

called arguments.

The sub procedure AddNumbers is called

and the values stored in the variables

intNum1 and intNum2 are passed to the

sub procedure.

The sub procedure receives the

values passed by the call

statement and stores them in

intVal1 and intVal2. These two

containers are called parameters.

The parameters containing the values passed are used to

calculate the sum of the values passed and place this data

in the lblSum label.

The ByVal statement means that the

parameter(s) created are value parameters.

Note: Since the Int1 and Int2

arguments have been dimensioned as

integers, the parameters intX and

intY are created by value as integers.


Reference Parameters Reference parameters are created in the same way as value parameters except that,

instead of ByVal, the term used is ByRef. When a parameter is created by value, its

value is stored in a new memory location. When a parameter is created by reference,

the value is stored in the memory location of the argument passed. Reference

parameters cannot accept constants as arguments. Values must be passes as variables.

As with all argument / parameter sets, they are assigned in the same order as they are

received.

It must be remembered, if an argument is passed by reference, its value can be changed

during the course of the sub procedure. This is because the value is accessed via the

argument’s memory location.

We have added a label to list the

value of the int1 variable that is now

created as a global in the general

section

As a value is typed in the first text

box, it is echoed in the new label.

After the Calculate button is clicked,

the value of the parameter intX that

has received the value of int1 in the

Sum sub procedure by reference, is

decreased by 5

The value of int1 is then printed in

the bottom label and its value has

decreased by 5 because its reference

parameter intX has been decreased by

5

We reduce the value of intX by 5

We print the value of int1

The value

of int1 is

reflected in

the change

in intX

because

int1‟s value

was passed

by

reference

Value passed by reference


Documenting Procedures As procedures are created, it is good to document what the job of the procedure is as well

as what will happen after the procedure is run. As with all remarks, each line of

documentation is preceded by an apostrophe („). Below is an example of the Sum

Procedure as created above.

„*********************************************************

„Receives two values from the calling statement and adds them

„

„post : Prints the sum of the two numbers

„*********************************************************

When coded, normally remarks will appear in green text

Static Variables Not only do variables have a scope (Local variables are accessible to only the procedure

in which it is created. Global variables are accessible to every procedure in the module.)

but variables have a lifetime as well. A variable‟s lifetime is the length of time it

remains in memory.

Local variables remain in memory only for the duration of the procedure. Global

variables remain in memory for the duration of the program. A static variable’s scope is

limited to the procedure in which it is created but its lifetime is for the entire program.

It is preferred to use static variables instead of global variables because they will not

interfere with other procedures.

Syntax

Static variable name as variable type


Example

Static intSum as integer

In the program above, a static variable has been created to store the grand total of all

of the sums

It will then print this sum in the new label at the bottom of the form

Static variables are initialized to zero when they are created

A picture of the above application appears below. The calculate button was clicked

for first number values of 10 and then 20.

Note how the intSum variable displayed in the Grand Total label does not zero out

each time the Calculate button is clicked. This is because it was created as a Static

Variable.

If this variable were to be created

as a local variable, the grand

total would be “zeroed out” each

time the Calculate button was

clicked because its life was only

as long as the click procedure.

As a static variable, its life is as

long as the program runs. So, it

will not be recreated each time

the button is clicked.


Function Procedures A function procedure performs a task and returns a value. Visual Basic functions like

Left ( ), Right ( ), and MID ( ) are examples.

Syntax

Function procedure name (ByVal parameter1 as type) As Return type

Statements

End Function

Functions parameters should always be ByVal

The Return Type is the type of a value returned by the function

Functions usually require at least one parameter

Example

In this example, we add a label to

display the running sum multiplied by

10

Each time the Calculate button is

clicked, the Grand Total is multiplied

and displayed in the bottom label

This was accomplished by creating a

function called Times

The code is displayed below

The Times

function is called

to assign a value

to the caption

property

Here is the

Times function


Creating a Function

Choose the Add Procedure option from the Tools

menu

Choose the Function option (Note that

sub procedures can be created this way

too)

Name the function (or sub procedure)

Click OK

Most functions and procedures are public

in scope since they are designed to be called

from any procedure.

Object Parameters Objects can be passed as parameters as well. In our example, we can add another label to

display the sum multiplied by 10. This time, we will call a sub procedure to add the text

to the label caption by passing the label and the value to print to the sub procedure

called Times10.

Example

The new label is located below the Done

button and includes the text “Times 10 Sub

=”

This data is printed to the label lbl10 via a

sub program called Times10 rather than a

function

The code appears below

Here is the code for the sub procedure

The name of the

label is passed

The value to be

printed is passed


Built-in Mathematical Functions

ABS

Returns the absolute value of a number.

Example:

dim intAbVal as integer

intAbVal = 7 – 10

txtAbVal.text = ABS(intAbVal)

In this case, the text box txtAbVal contains a 3

SQR

Returns the square root of a number.

Example:

dim intSqrRoot as integer

intSqrRoot = SQR(25)

txtSqrRoot.text = intSqrRoot

In this case, the text box txtSqrRoot contains a 5

SGN

Returns a 1, -1, or 0 depending upon whether a number or the value of a numeric

variable is positive, negative, or zero respectively.

Example:

dim intSign as integer

intSign = SGN(-7)

txtSign.text = intSign

In this case, the text box txtSign contains a –1

IsNumeric

Evaluates an entity or a variable to see if it is or can be changed to a numeric value.


Example:

dim strVal1, strVal2, strVal3 as string

strVal1 = “5”

strVal2 = “378”

strVal3 = “3+4”

txtVal1.text = isNumeric(strVal1)



In this case, the text properties of txtVal1, txtVal2, and txtVal3 would contain “True”,

“True”, and ”False” respectively. This is because the neither of the strings “5” nor

“378” contain any characters that cannot be changed to numeric values. TxtVal3, on the

other hand, contains a “+” sign which cannot be changed to a numeric value.

Round Rounds a number to a specified number of decimal places.

Example:

dim dblNum1, dblNum2 as double

dblNum1 = 5.7689372

dblNum2 = 1745.97753

txtRound1.text = ROUND(dblNum1,3)

txtRound2.text = ROUND(dblNum2, -3)

In this case, text box txtRound1 would contain 5.769.

Text Box txtRound2 would contain 1.8. This is because rounding to a negative moves

the decimal point to the left.

Formatting Numeric Output

There are nine different formats that Visual BASIC provides. They are as follows:

Format Example Result

General Number FORMAT(8789,”General Number”) „8789

Currency FORMAT(8789,”Currency”) „$8789.00

Fixed FORMAT(8789,”Fixed”) „8789.00

Standard FORMAT(8789,”Standard”) „8,789.00

Percent FORMAT(89,”Percent”) „8900.00%

Scientific FORMAT(8789,”Scientific”) „8.79E+3

Yes/No FORMAT(1,”Yes/No”) „Yes

True/False FORMAT(0,”True/False”) „False

On/Off FORMAT(1.”On/Off”) „On

The FORMAT function only changes the way a value is displayed, not its value.


Built-in Business Functions

PMT

Returns the periodic payment for an installment loan. An example would be to calculate

the monthly payment for a mortgage loan or a car loan.

Syntax

Pmt(rate, term, principal)

Let‟s say you want to calculate the monthly payment for a car loan with these

characteristics:

Interest rate = 5%

Term = 4 years (48 months)

Principal = $20,000.00

The code for this application can be

found on the next page. It explains how

to configure the code and why it must be

done this way.

The interest

rate is

obtained by

taking the

.05 (5%)

annual

interest rate

and dividing

it by 12 because the payments are monthly and the annual interest rate

covers 12 months.

The term is entered in months because the payments being calculated will be by

the month.

The principal must be multiplied by –1 because it is a loan taken out.


PV

Returns the present value of an investment.

Syntax

PV(rate, term, payment)

Let‟s say that you would like to calculate the total cost of financing a car over a period of

48 months at a 5% annual interest rate for a total of $20,000.00. That is, you would

like to know how much of your payments will go toward interest payments.

The application on the left illustrates the

fact that, if you were to take out a car

loan at 5% interest for a period of 4

years in the amount of $20,000.00, your

payments on interest would be a total

of $2,108.12. The code appears at the

top of the next page.


Note that, at the bottom of the code, the calculations were made in the following way:

1. The total amount paid was calculated by multiplying the monthly payments by the

number of months of the loan.

2. The PV function was then used to calculate the total value of the loan without the

interest.

3. The amount of the loan going to interest was then calculated by subtracting the value

of the loan (#2) from the total amount paid during the term of the loan (#1).

FV

The FV function returns the value of a series of payments invested at a fixed interest rate

over a period of time.

Syntax

FV(rate, term, investment)

Let‟s say that we would like to see how much those monthly payments of $460.59 that

we are paying for our car would earn if we invested them in a Certificate of Deposit at

7% interest instead.

The application and code appears on the next page.


Here, we have discovered that a loan

of $20,000.00 over a 48 month

period at an annual interest rate of

5%, would require payments of

$460.59 per month. We also know

that we will be paying $2,108.12 on

interest alone. Further, if we were to

take our $460.59 and invest it in a

certificate of deposit every month at

an annual interest rate of 7%, we

would, at the end of the 48 months,

realize an investment of $25,428.59.

The code appears below.

The bottom three lines of code create the information regarding the return on the monthly

payments if they would be invested at 7% instead of paid out at 5% annual interest rate.

The sngInvest variable is given a value based upon the interest rate entered in the text

box next to the label “Investment Interest Rate”. The variable sngReturn is calculated

using the FV function and plugging in the rate of investment from the previously

mentioned text box, the term of the loan gotten from the text box next to the “Term of

Loan” label, and the amount of the monthly investment (multiplied by –1).


List Box

List boxes are used to choose a selection from a list of options. It is created using the

List Box tool.

Below is a list of pertinent properties that are used often in conjunction

with this object.

Property Function

Name Uses the prefix “LST” and gives the object a name

List Stores the items contained in the list

Sorted Displays the list contents in alphabetical order

ListCount Used only at run-time, it returns the number of items in the list

Let‟s assume we are creating an application where :

A list box contains a list of names

When one of the names is clicked, it appears in a label saying “Hello ______ “

with the name clicked appearing in the blank line.

1. Create the form and add the list box along with the label.

2. Add the names to the list box at

design time, by using the “List”

property. (See the next page)

Highlight the “List” property

Click the down arrow

Type in the desired names

Events and Methods

Event or Method Function

Click Event When a list item is clicked on

AddItem Adds an item to the list of a list box

Clear Clears the item list of a list box


Below is the code, using the click event, that causes the name clicked on in the list to

appear in the label.

Note that the item in the

list box that was clicked

on is referenced simply as

“lstName”, which is the

name of the list box itself.

Running the application results in the example below:


Now, let‟s give the user the options of adding items to the list or clearing the list by :

1. Adding a command button making a text box appear to enter the name and a

command button to add it to the list.

2. Adding a command button to clear the list.

Now, the application will look like this:

To add a name to the list, click

on “Add a Name” and the

label, textbox, and “Add

Now” command button will

appear. The name can be

entered in the textbox and

when the “Add Now” button

is clicked, the new name is

added to the list. (See below)

Note that when the “Add

Now” button is clicked, the

contents of the text box are

cleared and the three objects that appeared for the purpose of entering a name disappear.

The “Add a Name” button has

been clicked, causing the

label, textbox, and “Add

Now” button to appear.

The name “Barb Wire” has

been typed into the textbox.

When the “Add Now” button

is clicked, the name “Barb

Wire” will be added to the list

in the list box.


Note that, after the “Add

Now” button is clicked, the

name “Barb Wire” appears in

the list and the textbox

contents are cleared. Then,

the label, textbox, and

command button disappear.

The code appears below:

When the “Add a Name”

command button is clicked,

the label, textbox, and “Add

Now” command button

appear.

When the “Add Now”

command button is clicked,

the contents of the textbox

are added to the list box list.

Then, the text box is cleared

and the objects disappear.

(Don‟t forget to code so that

an empty textbox results in a

disabled “Add Now” button.

When the “Clear” command

button is clicked, the list is

cleared.


Combo Box

Combo boxes serve much the same purpose as list boxes except that, depending upon the

style of the combo box, the user can add his/her own entry to the list. Both objects share

the same properties such as Name, List, Sorted, and ListCount. Two additional

properties are available with the combo box:

Property Description

Style Options include dropdown combo, which includes both an item list

and a text box to add items; simple combo, which includes a list that

does not drop down and a text box; and dropdown combo, which

includes a drop-down list only with no text box for user additions.

Text The text that appears in the combo box before any lists are opened.

All of the event methods are similar to the list box with one addition. The change event

is executed when the user changes the contents of the text box.

Example

In this example, we will use a combo box to choose from a list of numbers to multiply by

10. The product will then be added to the label when the list item is clicked.

The text “Choose a #” is the

value of the TEXT

property.

The numbers 0 through 5

have been added to the

LIST property.


When the down arrow is clicked, the list appears.

The user can now choose one of the

numbers from the dropdown list.

When a number is clicked, it

becomes the contents of the text

property. In this case, let‟s click on

the “3” in the dropdown list.

The math is done when the number

is clicked and the caption is added to

the label below.

The code appears below:

The item clicked becomes the combo box‟s TEXT property. Note that the proper prefix

for a combo box is cbo.

Underscore

Also note the underscore after the cboNumbers.Text. It is used to continue a line of

code text in the next line in order to be able to see all of the text without scrolling right.


Application Properties

Focus

Focus is the state of an object when it is chosen to perform some operation from the

keyboard. This can mean that pressing ENTER can perform a click (as in the case of a

command button). It could also mean that a text box has the cursor in it so something

can be typed into it. Focus can be changed by pressing the TAB key.

Below is an example of an application with three text boxes. At this point, there is no

code for any object. Notice how the cursor moves from textbox to textbox with each

press of the TAB key.

Access Key

Perhaps, you would like the user to be able to press a hot key along with the Ctrl key to

accomplish a task. We will add a command button to quit the above application. Its

caption property is “Done” and we want it to work if we press Ctrl/D.


Notice, in the Caption property we have preceded the word “Done” with a “&”. This

character designates the next letter, in this case a “D”, as the hot key to be used along

with the Ctrl key.

Tab Order

As was mentioned above, focus can be changed from one object on a form to another by

pressing the TAB key. The focus shifts, by default, in the order of the objects’

creation. To change the order of the movement of the focus, you need to establish a

TAB ORDER.

In order for an object to be able to receive the focus from a TAB, its TAB STOP

property must be set to True.

Then, the TAB INDEX property can be set. By default, the first object created has a tab

index of 0 and it moves up from there. Below, we will change the tab order of our three

text boxes so that the first text box to receive the focus is the middle one, followed by the

bottom one, and finally, the top one.

Above, the middle text box TabStop property has been set to True and the TabIndex

property has been set to 0.

On the next page, the settings for the other two boxes can be found.


Above, are the settings for the bottom text box.

Below, are the settings for the top text box.


Built-In Trigonometric Functions

SIN Returns the sine of an angle with the angle expressed in radians.

COS Returns the cosine of an angle with the angle expressed in radians.

TAN Returns the tangent of an angle with the angle expressed in radians.

Converting Degrees to Radians In most cases, angles are expressed in degrees. In order to use the trigonometric

functions listed, we first need to convert the degrees of the angle to radians. The formula

is:

Radians = ( / 180 ) * Degrees

So, if we wanted to create an application that generated the sine of a given angle, it would

look like this:

The code for this application appears below.

Note that the calculation for the sine could

not be done until the angle was converted

from degrees to radians.

Constant Pi created

Degrees to radians

Sine of angle calculated

Converting Radians to Degrees

The formula to convert from radians to degrees is:

Degrees = Radians * (180 / )


Note that, in the example on the previous page, was designated as a constant 3.14.

Inverse Trigonometric Functions

ATN Returns the angle in radians that has a given tangent.

Syntax:

ATN(Number)

Here, “Number” is the tangent of a given angle. ATN will return the angle corresponding

to that tangent number.

To use ATN to calculate the ARCSINE of an Angle in Radians Returns the angle in radians that has a given sine. The formula to calculate an angle in

radians that has a sine of dblSine is:

ATN(dblSine / Sqr(-dblSine * dblSine + 1))

To use ATN to calculate the ARCCOSINE of an Angle in Radians Returns the angle in radians that has a given cosine. The formula to calculate an angle

in radians that has a cosine of dblCos is:

ATN(-dblCos * dblCos + 1)) + 2 * ATN(1)

In our previous example, we could add the option to calculate the angle that corresponds

to a given sine.

Logarithmic and Exponential Functions

LOG The LOG function returns the natural logarithm of a number. This is the logarithm of a

number with the base e where e = 2.718282.


Syntax

LOG(number)

Using LOG to Calculate the Logarithm of a Number to A Base The formula to calculate the logarithm of a number to a different base than e is as

follows:

LOG(number) / LOG(base)

The code for this application appears

below. It can be seen that the number 25

with a base of 5 has a logarithm of 2

because 52 is equal to 25.

EXP Returns the natural exponential of a value, or e

x. For instance, EXP(2) = 7.389 which is

e2.


Variable Arrays

The programmer can store more than one value in the same variable through the use of

arrays. For instance, the programmer may want have five employee names he/she may

want to store. Instead of creating a series of variables (i.e. strEmp1, strEmp2, strEmp3,

strEmp4, and strEmp5), it is possible to store the names of all five employees in one

variable array (i.e. strEmp(1), strEmp(2), strEmp(3), strEmp(4), and strEmp(5)).

Array Declaration Variable arrays are created much the same way as normal variables using Dim, Private,

or Static. The only exception is that the number of elements included in the array must

be added to the declaration.

Dim strEmp(5) as String

Upper Bound The upper bound of the array is the highest element number in the array.

Lower Bound The lower bound of the array is the lowest element number in the array. By default, the

lower bound will be zero.

Option Base The lower bound of an array can be set to either 0 or 1 by using the Option Base

statement in the General Section of the form‟s code.

Option Base 1 or Option Base 0

Array Declaration Using Upper and Lower Bounds The array can be declared using both the upper an lower bounds within the element

parenthesis. This eliminates the need to use the Option Base statement.

Dim strEmp(1 to 5) as String

Constants can also be used to declare the upper and lower bounds of an array if they are

of the type Long.

Const lngLowBound as Long = 1

Const lngUpBound as Long = 5

Dim strEmp(lngLowBound to lngUpBound) as String

Array Initialization All numeric array elements are initialized to zero and all string array elements are

initialized to “” or empty.

Array Index Arrays elements are accessed via each element number, also called an index. For

instance, if we wanted to assign the fourth element of the strEmp array to the label

lblEmp, we would do the following:


lblEmp.Caption = strEmp(4)

Array elements can be assigned via the index as well. If we want to assign the second

element of the strEmp array the name “John Jones”, we would do the following:

strEmp(2) = “John Jones”

LBound and UBound Functions These functions return the numeric value of the lower and upper bounds of the array,

respectively.

intLow = LBound(strEmp)

intHigh = HBound(strEmp)

Run-Time Error If a program refers to an array index outside of the lower bound to upper bound range,

you will receive an error message saying: “Subscript out of range.” Subscript is

another word for index.

For … Next

This loop runs a section of code between the FOR and the NEXT statements a given

number of times. For instance, if we wanted to use a For…Next loop to assign names to

each of the five strEmp elements, we would do the following (assuming the lower and

upper bounds are 1 and 5 respectively):

Dim lngIndex as Long

Dim strEmp(1 to 5) as String

For lngIndex = 1 to 5

strEmp(lngIndex) = inputBox(“Please enter the employee’s name”,”Employees”)

Next lngIndex

Array Parameters

Arrays can be passed to functions and sub-procedures by using the array name followed

by an empty set of parenthesis. Arrays must be passed by reference. A single array

element can be passed by reference or by value. If we wanted to pass the strEmp array

to a function that adds the total number of characters in all of the five names:

Function AddChar(ByRef strEmp() As String) As Integer

Dim intIndex, intSum as Integer

For intIndex = 1 to UBound(strEmp)

intSum = intSum + Len(strEmp(intIndex))

Next IntIndex

AddChar = intSum

End Function


Or, to pass a single array element to a sub procedure by value – let‟s calculate the length

of the fifth element:

Sub OneChar(ByVal strName as String)

Dim intLen as Integer

intLen = Len(strName)

lblLength.Caption = “The length of the name is “ & intLen

End Sub

Call OneChar(strEmp(5))

Arrays With Meaningful Indexes

An array‟s index can carry some meaning. For instance, if we wanted to track the

number of times a roll of a die resulted in the numbers 1 through 6, we could create a

numeric array with six elements. Its lower bound would be 1 and its upper bound would

be 6. Each element of the array is initialized to zero. Each time a 3 would come up, we

could increment the element in index 3 by 1 and the same for each of the other 5

elements.

Searching an Array

Arrays can be checked for their contents, one element at a time from the lower bound

through the upper bound in succession (linear search), which is the most common way.

This would best be handled with a loop.

Dynamic Arrays

Dynamic arrays can change in size during the course of the program. For instance, let‟s

say we do not know how many employees names we will enter into our strEmp array.

When we run the program, we need to decide how many elements we will have. First

create the array using the empty parenthesis.

Dim strEmp() as String

ReDim The ReDim statement redimensions the array size during runtime. Before we enter our

first name, we need to redimension the array to accommodate the new elements. Let‟s

say we want to enter 3 names:

ReDim strEmp(1 to 3)

We can now begin entering names into each element.

Sub Procedure

Sub Procedure Call


Preserve

Arrays can be redimensioned as many times as needed. But each time it is

redimensioned, all data is lost.

Let‟s say we have entered three names and would like to enter another without losing

the first three we entered:

Dim lngUp as long

lngUp = UBound(strEmp)

lngUp = lngUp + 1

ReDim Preserve strEmp(1 to lngUp)

Control Arrays

Arrays can also be a collection of objects such as textboxes, labels, command buttons,

etc. Each individual object in the array has the same name but it has its own index.

Index Property The index property of a control array is dependent upon the order in which the object was

created. As with numeric arrays, the first index number is zero.

Example: We will create a form with three labels in it. The labels will be created as a control array.


Above, we create a label on the form named lblNum

Below, with the lblNum label selected, we choose the Edit – Copy options

Then, the copied label is pasted into the form by choosing the paste option

At this point, you will receive a message saying that “You already have a control

object named lblNum, do you want to create a control array?”

Choose Yes

The new object will appear in the upper left corner of the form. It can be dragged

into position from there.


Note that the Index property for the new label is set to 1. (The original label‟s index

property is zero).

The new label‟s name is lblNum(1)

The third label can be created the same way.

Add a command button to number each label according to its index property

The code to accomplish the

numbering of the labels appears

below.

Note that we use the intNum variable

in the index parenthesis to choose the

label that we wish to number.

LBound and UBound Properties

The LBound and UBound properties are associated with the lowest and highest index

numbers for all of the objects in the control array. Using these properties, we could

change the code for the previous example to that below:

Note that there is no need

to create a variable for the

For statement. Instead,

we are able to use the

Index property.

Count The count property is the total number of indexes in a control array. In our example, we

have a count property value of 3.


Example: Dim intCount as Integer

intCount = lblNum.Count

Control Arrays as Parameters

Control Arrays can be passed to functions or sub-procedures but must be passed ByRef.

It must also be of the type Object.

Removing an Object From a Control Array

To remove an object from a control array, you must:

1. Change the name of the object

2. Delete its index property

Two Dimensional Arrays

A Matrix is a two dimensional array whose elements can be displayed in a grid of

horizontal rows and vertical columns.

Example: A parking lot can be divided into rows (2) and columns (5). The upper left

space is row1, column 1 (or as computers go, row 0, column

0). It could be assigned to Bob. Therefore, Name(0,0) =

“Bob”. Maybe the middle space (column 2) in the second

row (row 1) is assigned to Mary. Therefore, Name(1,2) =

“Mary”.

Declaring a Matrix

Matrices are declared in the same way as a one dimensional variable array except for the

fact that two dimensions need to be declared. In the previous example, the matrix would

be declared as follows:

Dim strName(1,4) as String

This allows for two rows (0 and 1) and five columns (0 through 4).

Declaring a Matrix Using Upper and Lower Bounds

Another way of declaring the above matrix using its LBound and UBound properties is as

follows:

Dim strName(1 to 2,1 to 5) as String

In this way, we eliminate the somewhat confusing first element of zero.

(0,0)

(0,1)

(0,2)

(0,3)

(0,4)

(1,0)

(1,1)

(1,2)

(1,30

(1,4)


LBound and UBound Functions The LBound and UBound functions are utilized in this manner:

Dim intLowRow, intHighRow, intLowCol, intHighCol as Integer

intLowRow = LBound(strName,1)

intHighRow = UBound(strName,1)

intLowCol = LBound(strName,2)

intHighCol = UBound(strName,2)

Nested For…Next Loops

Data is best “loaded” into two dimensional arrays using a loop within a loop. Let‟s say

we want to use an input box to input names into each parking space:

Dim strName(1 to 2, 1 to 5) as String

Dim intRow, intCol as Integer

For intRow = 1 to 2

For intCol = 1 to 5

strName(intRow,intCol) = InputBox(“Please enter a name”, Input Name)

Next intCol

Next intRow

Note that the column For…Next loop is completely enclosed within the outer row

For…Next loop. A column value is generate for each row value with the row value not

incrementing until all five of the column values have been used.

Dynamic Matrix

As with one dimension arrays, a matrix can be declared as dynamic by using empty

parenthesis in the dimension statement at its creation. The ReDim and Preserve

functions work the same way as with a one dimension array. Thus, additional data space

can be created as more spaces are created.

Note that the row dimension is always

referred to as dimension number 1 and

the column dimension is always

referred to as dimension number 2.


Color

The following objects have color properties: text boxes; labels; option buttons; check

boxes; list boxes; combo boxes; frames; and command buttons. Color properties can be

changed either at run time or design time.

Color Properties at Design Time BackColor

The BackColor property is used to choose the background color of an object.

Note that, in order to change the BackColor property for a command button, you first

need to set its STYLE property to GRAPHICAL.

For example, if we wanted to change the background color of a command button to RED,

we would do the following:

Highlight the

desired

command

button.

Choose the

“STYLE”

property in

properties

window.

Click the down

arrow to the

right.

Choose

“GRAPHICAL”

Choose the

“BackColor”

property from the

properties window.

Click the down

arrow.

Choose the “Palette”

tab.

Choose a color from

the palette.

This color will now

become the button‟s

background color.


ForeColor

The ForeColor property is the color of the text displayed in an object. Note that there is

no ForeColor property for a command button. Below, we will change the ForeColor

of a label to white with its BackColor set to green:

Choose the

object.

Choose the

ForeColor

property from the

properties

window.

Click the down

arrow.

Choose the

palette tab.

Choose the

desired font color

from the palette.

Setting Colors at Run Time

If we were to add two command buttons to the above application so that, when one is

clicked, the BackColor of the label will be green and when the other is clicked, the

BackColor will be red, it would look something like the application below. The code

appears as well.


Built-In Visual Basic Colors Note that Visual Basic provides built-in colors for programming use. They all start with

the constant prefix “vb”. They are as follows:

vbBlack vbBlue vbCyan vbGreen vbMagenta vbRed vbWhite vbYellow

RGB Function

Colors can be “fine tuned” using the RGB function. In this function, the “R” stands for

Red, the “G” stands for green, and the “B” stands for Blue. Each of the three colors is

assigned a value from 0 through 255. The higher the value, the more dominant that color.

The function takes the form RGB(#,#,#) with each number sign having a value as

explained previously. So, to add a purple button to the application above, we would need

to add the following:

Practice Application Using Color

Create the application above and add three more command buttons to change the

BackColor of the label to three other colors. You decide which colors to add. Be sure to

use at least one RGB function. Adjust the RGB values to change hues etc. Become

comfortable with the concept.

Adding Lines to an Application

Lines can be added to an application to set portions of the application apart from other

portions or to embellish the application in other ways.

Additional code including the

RGB function assigning a

RED value of 50, a GREEN

value of 0, and a BLUE value

of 100. This combination

results in a dark purple.


Line Properties Name

The name is used as with all other objects, to designate the object as a definitive object on

the form. Line names should begin with the prefix “lin”. So, for example, if we were to

create a line in a form to separate the top from the bottom, we could name it “linTop”.

BorderColor

The BorderColor property changes the actual color of the line. Here again, the color can

be set at design time as below:

BorderStyle

The BorderStyle of a line is the way it appears on the application. The options available

are transparent (vbTransparent), solid (vbBSSolid), dash (vbBSDash), dot

(vbBSDot), dash-dot (vbBSDashDot), dash-dot-dot (vbBSDashDotDot), and inside

solid (vbBSInsideSolid). These Visual Basic constants are used the same way the color

constants are used except they apply to the BorderStyle property.

At design time, the BorderStyle can be chosen

utilizing the dropdown menu as with colors.

During run-time, the BorderStyle property must

be changed using the Visual Basic constants as

they are listed above.


BorderWidth

The BorderWidth property changes the thickness of the line. This is done via a numeric

value ranging from 1 through 8,192. The higher the number, the thicker the line. Below,

is an example of the choice of line thickness via the BorderWidth property at design time.

The BorderWidth was set at “5”.

Objects and Form BackColor Note that changing the BackColor property of the form will erase all graphics drawn on

the form. Therefore, the BackColor property of the form should be set prior to adding

graphic objects to it.

Adding Shapes to an Application

Shape Property There are a number of shapes that can be chosen as an addition to an application. They

are listed below along with their Visual Basic constant. The items in the Shape column

can be chosen from the Shape Property at design time. The shape can be changed at

run-time utilizing the items listed in the Visual Basic Constant column.

Shape Visual Basic Constant

Rectangle vbShapeRectangle

Oval vbShapeOval

Rounded Rectangle vbShapeRoundedRectangle

Square vbShapeSquare

Circle vbShapeCircle

Rounded Square vbShapeRoundedSquare


Name Property The name for a shape should begin with the prefix “shp”.

BackColor Property This property changes the background color of the shape as with other objects as

discussed previously. The BackColor property can be chosen at design time via the

properties window (see “Color Properties at Design Time”). They can also be changed at

run-time using the Visual Basic color constants or the RGB function.

Note that, when the FillStyle property is set to Solid, or the BackStyle property is set to

Transparent, the BackColor property is ignored.

BackStyle Property The BackStyle property can be set to either opaque or transparent at design time. As

discussed above, if the BackStyle property is set to transparent, the BackColor property is

ignored, basically leaving the shape with an outline only.

The BackStyle property can be changed at run-time by setting it to a value of 0 for

transparent, or 1 for opaque.

BorderColor Property This property sets the color of the outline of the shape. It can be set at design time via the

properties window or at run-time via the Visual Basic constants or the RGB function.

BorderStyle Property The BorderStyle property for a shape is set at design time and at run time as per a line

object. (See the BorderStyle Property in the Line object section)

BorderWidth Property As with the line BorderWidth property, the values range from 1 through 8,192. The

property can be set at design time in the properties window or at run-time. (See the Line

section above).

FillColor Property This property sets the color of the inside of the shape. Even if the FillStyle property is set

to “Solid”, the FillColor property will work. It can be set at design time via the

dropdown menu in the FillColor property section of the Properties window. It can also

be changed at run-time via the Visual Basic constants or RGB function.

FillStyle Property The FillStyle property creates a pattern inside an object. Below are the dropdown menu

options in the FillStyle section of the Properties window along with their Visual Basic

constant counterparts used at run-time.


Style Visual Basic Constant

Solid vbFSSolid

Horizontal Line vbHorizontalLine

Upward Diagonal vbUpwardDiagonal Cross vbCross

Transparent vbFSTransparent

Vertical Line vbVerticalLine

Downward Diagonal vbDownwardDiagonal

Diagonal Cross vbDiagonalCross

When the FillStyle is set to transparent the FillColor property is ignored.

Below is an example of some shapes with various property assignments:

Here is the code to have the user input via an input box, the desired width of the

border.

Private Sub cmdBWidth_Click()

Dim intWidth As Integer

intWidth = 0

Do While intWidth < 1 Or intWidth > 8192

intWidth = InputBox("Enter a width 1 - 8192", "Enter Width")

Loop

shpShape1.BorderWidth = intWidth

End Sub

Depending upon the

command button that

is clicked, the shape

will be either a

rectangle, square,

circle, or oval.

When the Border

Width button is

clicked an input box

allows the user to

choose a border width

(see above).

Option buttons are

provided to choose fill

colors for the object

(remember that the

FillColor property

will be ignored unless

the FillStyle property is set to something other than the default transparent).

The Border Style option buttons allow the user to choose a value for the

BorderStyle property. Note that any style other than solid will not work if the

BorderWidth property is set to anything other than 1.


The Fill Styles option buttons allow the user to choose a value for the FillStyle

property. When this property is set to transparent, the FillColor property is ignored.

The Border Color frame contains option buttons to choose a value for the

BorderColor property.

Below is a sample of how the code may appear:

Chooses a shape

Uses Visual Basic constant to

choose a value for FillColor

Uses the RGB function to

choose a value for

BorderColor

Picture Boxes

With a picture box, you can place graphics and images into your application. Unlike the

image object, the picture box can accommodate either an image or a graphic. The

picture box demands more system resources because it is more versatile.

Picture Property This property assigns an image or graphic file to the picture box. It can

be assigned using the picture property in the properties window at design time. It can

also be assigned at run-time using the following procedure:

Suppose we create a simple drawing and save it to a diskette as “SMILEY.BMP”. This

image was created as a 256-color bitmap image using Microsoft Paint.


To insert this drawing into a picture box at design time, we use the picture property as

below:

Click the triple dot button in the picture property to open the file window.

Browse to find the file

Click on Open

At this point, the picture will appear in the picture box.


It can also be assigned at run-time as follows:

picPicture1.Picture = LoadPicture(“A:\Smiley.BMP”)

BorderStyle Property This property has two options at design time, Fixed Single, or None. Fixed single

provides a somewhat indented appearance as in the picture above. The “None” option

creates a flat look as below:

To set the BorderStyle property at run-time,

the options are 0 for “None” or 1 for “Fixed

Single”.

The code is

picPicture1.BorderStyle = 1

AutoSize Property You will notice that the entire picture does not fit inside the picture box. If the AutoSize

property is set to “True”, the picture box will expand to accommodate the entire picture.

This property can be set to either True or False and can be set at design time or run-time.

Below is the result of setting the property to “True”:


Moving Shapes and Picture Boxes

Shapes and graphics are stored in containers. This container can be either a form or a

picture box. These objects can be moved within their container. Below is a list of the

location properties:

Property Explanation

Left Changes the distance between the left edge of the object and the left

edge of the container

Top Changes the distance between the top edge of the object and the top

edge of the container

Width Changes the width of the object

Height Changes the height of the object

Twips Twips are units of measure (1 inch = 1,440 twips and 1 cm. = 567 twips) that are used in

the Move Method.


Move Method The move method includes arguments to move an object left, top, width, and height in

that order. Moving and object a negative value will move it toward that particular edge

or decrease that particular distance.

Example:

We will animate the jet plane in the form below so that it flies toward the left edge of

the form:

Create the picture box and, using the picture property, insert the jet plane image

Change the picture box‟s BorderStyle property to “None” so it appears more

seamlessly in the form

Add the “Animate” command button and code it like this:

By subtracting the

value of intNum from

the Left property, we

get the effect of

acceleration as the

plane approaches the

left margin. This is

because the value of

intNum increases by

5 each time through the

loop.

By changing the code as

it appears at the left, we

create a more steady

movement. This is

because we subtract 5

twips each time through

the loop instead of

increasing the value as

above.


If we wanted to increase the altitude as we move toward the left, we simply add the

following code to the second example above:

Graphic Methods

Coordinate System Graphic images are positioned via a X and Y coordinate grid. The “X” coordinate is the

distance the object is from the left margin of the container. The “Y” coordinate is the

distance the object is from the top of the container.

Line Method The line method is as follows:

object.Line(x1,y1)-(x2,y2),color,BF

Parts of the Method

Part Explanation

(x1,y1) Indicates the starting point of the line in twips from the left and top

(x2,y2) Indicates the stop point of the line in twips from the left and top

color Indicates the color of the line with Visual Basic color constants

BF “B” indicates that a box should be formed from the coordinates

“F” indicates that the box should be filled in with color

Example:

Note that the line starts 10 twips right of the

left margin of the form and runs 1990 twips

to the right. The line is positioned 500 twips

from the top of the form.


Here, we draw a diagonal line. By adding the

“B” option to the method, we can form a box.

The “F” option will fill the box with blue

color.

Note: If you would like to add one of the

optional values such as a box, but would

not like to designate a color, the color

place must be saved using a comma.

frmMethods.Line(10,500)-(2000,1500),,BF

Circle Method

The Circle Method takes the form:

object.Circle(x,y),radius,color,start,end,aspect ratio

Circle Method

Part Explanation

(x,y) The center point of the circle in twips from the left and top

radius The size of the radius in twips

color Visual Basic color constant for the circle

start Starting point of the arc in Pi-radians (not used for complete circle)

stop ending point of the arc in Pi-radians (not used for complete circle)

aspect ratio Specifies a circle or ellipse

(x,y); radius; color; and aspect ratio are values. Start and stop are values within the range

0 through 2 .


Observe the code below. Each of the command buttons creates the shape above it.

The circle is farthest to the left (note the

“x,y” coordinates of each object).

Note that Visual Basic constants or the

RGB function can be used to designate

color.

The ellipse is created using the aspect

ratio portion. An aspect ratio greater

than 1 will produce a tall ellipse. An

aspect ratio less than 1, will produce a flat

ellipse.

When drawing an arc beginning at the left-

most point of the circle and ending at the right-most point, you would use a beginning

point of (3.14) and an end point of 0.

.

Pset Method The Pset method draws a dot at the prescribed position and included a color option:

Pset (2000,3000),vbGreen

The code above draws a green dot 2000 twips right of the left margin and 3000 twips

below the top margin of the container.

2 (0)

/ 2 (1.57)

(3.14)

3 / 2 (4.71)

(- /2)


PaintPicture Method The PaintPicture method allows a picture existing in one container to be painted into

another container. Below is an example where the picture in the “picPicture1” picture

box is painted into the “picPicture2” picture box.

Note the code below

In this case, the picture placed in the

picPicture1 picture box via its Picture

property is painted into the picPicture2

picture box to its left.

In this case, the picture is positioned 10

twips from the left margin of the picture

box and 10 twips below the top margin of

the picture box.

Cls Method This method clears any graphics inside a container. So to clear the picture in the

“picPicture2” picture box, we would add this code to an “Erase” command button.

picPicture2.Cls

Note the code in the cmdErase command

button. When it is clicked, it clears the

picture from the picPicture2 picture box.


Container Properties Affecting Graphics

AutoRedraw When set to True, the drawn object will appear in the container. When set to False, the

drawn object may not appear.

DrawStyle Changes the style of the outline of the object.

Constant Definition

vbSolid Solid Line

vbDash Dashed Line

vbDot Dotted Line

vbDashDot Combination of dashes and dots

vbDashDotDot One dash followed by two dots

vbInvisible The line is not seen

vbInsideSolid A form of double line

DrawWidth Sets the thickness of the line. The value is expressed in terms of a number ranging from

1 through 32,767. In order for the BorderStyle property to work, the DrawWidth

property must be set to 1 except for solid or inside solid styles.

FillColor Changes the fill color of the object. It is assigned via the Visual Basic constants or RGB

function. (Don‟t forget that the FillStyle must not be set to transparent in order for

FillColor to work).

FillStyle See the previous section on graphic object FillStyle. These options are identical.

ForeColor This property changes the color of the outline for the graphic contained within the

container. It can be assigned, again, using the Visual Basic constants or RGB.


Timer Object

A timer object is used to execute code at specific timed intervals. It is very handy for

animation effects.

Name Property The name of a timer object should begin with the prefix tmr. The Timer Object will

appear on the form in design mode but will not appear at run-time.

Interval Property The amount of time that passes before the Timer event procedure is executed. It is

expressed in milliseconds (1/1000 of a second). So an interval of 1 second would be

expressed as 1000. The acceptable range for this property is 0 through 64,767.

Enabled Property Can be set to either True or False. When the enabled property is set to False, the timer

event will not be called.

Timer Event The timer event occurs after the interval has expired. Following the event, the interval

countdown begins again. Remember that the interval is set in milliseconds.

Below is an example where the picture changes from a smile to a frown and vice versa

every second.

The code for the above application appears on the next page.


Create a global boolean

variable to track the

condition of either a

smile or frown

Set the boolean to false

when the form loads

Set up the timer object

so that, if the boolean

is false, clear the

picture object and draw

a smiling face. Then,

set the boolean to true.

If the boolean is not

false (therefore it is

true), clear the picture

object and draw a

frowning face. Then,

set the boolean to false.

Below is the creation of the timer object. Note that the interval was set to 1000 or 1

second. Also, note that the timer object appears in design mode but not at run-time.


Moving Line Objects

Line objects are created by designating their beginning (X1,Y1) and ending (X2,Y2)

coordinates. Therefore, by changing these coordinates, we can move the line.

Below is an example where a line was created using the line tool.

Create a global variable to keep track

of the number of movements that the

line will make.

When the “Enable” button is clicked,

the timer object is enabled (Its

enabled property was set to False at

design time.)

The timer object executes every ¼

second (its interval was set to 250).

Each time, it moves the X1, Y1, X2,

and Y2 coordinates of the line by 10

twips. It will execute 50 times since

the global variable, intX is

incremented by one each time the

timer executes.

The timer object is disabled after 50

movements.


Animation

Animation effects can be created by making alternating graphic objects‟ visible

properties from true to false. Below is an example of a bouncing ball animation.

The ball will appear to bounce up in the air,

following the path of the picture boxes

inserted in the application as it appears to the

left.

The code for this application appears below:

A global integer variable is created

When the “Bounce” button is clicked,

the timer object is enabled.

The series of ball pictures were

created as an array. The “picBall(0)”

object visible property was set to

“True” at design time. The timer

interval was set to 500 (1/2 second).

Every ½ second, the current picture

box array‟s visible property is set to

False unless it is the last picture

(picBall(6)). Then, the intX variable

is incremented by one and its

corresponding picture array object‟s

visible property is set to true, creating

the illusion of a bouncing ball.


Adding Sound

To add sound to an application, you will need to use the MMControl control. If this tool

is not available on your toolbar, you can add it by following this procedure:

Choose Project from the Menu Bar.

Choose Components from the Drop-down Menu.

Click on Microsoft

Multimedia Control 6.0 to

check it.

Click on OK.

The Multimedia Control

should now be in your

Visual Basic Toolbar.

Name Property

Multimedia objects should begin with the prefix “mmc”.

Device Type This property chooses the type of device that will be needed. Below are a couple of

possibilities regarding sound files:

Control Name Files used

WaveAudio .WAV Files

CDAudio Music From CD

Enabled Property When this property is set to True, the multimedia object can play sounds. When it‟s set

to False, it cannot play sounds.

FileName Property This property chooses the file to be played and can be set at design time or via dot

notation at run-time.

Visible Property This property hides the object if it is set to False and allows it to be seen if it is set to

True.


Using Wav Sounds

You can insert files with a “.WAV” extension by using the OLE object and choosing

“Wav Sound”.

As soon as the OLE object is inserted in the form, the “Insert Object” window opens

and a large number of options appear.

Scroll to Wave Sound

Decide if you want to create the file New (microphone is required) or create it from a

file. Then, click OK.

Creating the Wave File After you click OK, the sound recorder will appear.

Be sure a microphone is connected to

your sound card.

Click the Record Button

Record through the microphone

Close the sound recorder

When you run the application, the

recording will play when the object is

double clicked.

Applying the Wave Sound from a File

Instead of choosing Create New, choose Create From File. At that point, a window

will open allowing you to browse for the desired file.

Record Button


Browse to the folder

containing the sound file

you want

Click on the desired file

Click Insert

Now, when the

application is run and

the OLE object is

double clicked, the

inserted Wave file will

play.


Sequential Access Files

One of the advantages of using arrays to hold data for a program is that it is an extremely

fast way of accessing information that the program may need. The biggest disadvantage

is that, once the program is halted, all of the data in the array is lost. Thus, it is good to

be able to save data permanently on disk for later access and use during subsequent

application runs. This is accomplished via data files.

Most data files are sequential files; that is, data is stored in order from the first item

saved through the last. Access to individual pieces of data (known as records) is done by

moving from record 1 through the last record, using the data in the program, and

accessing the next record.

Opening a File Sequential data files can only be opened for one mode at a time. The possibilities are

Input, Output, or Append.

Mode Direction Code

Input Reads data into

a program

Open <path\file> for input as <file number>

i.e. Open C:\Data\file1 for input as #1

Output

Writes data to a

newly opened

file. If this file

existed before,

it is deleted and

a new, empty

file is created

Open<path\file> for output as<file number>

i.e. Open C:\Data\File1 for output as #1

Append

Writes data to

an existing file

without

deleting it and

re-creating it.

The new data is

added to the

existing data

Open<path\file> for append as<file number>

i.e. Open C:\Data\File1 for append as #1

FreeFile Function

Since it is possible to have more than one file open at a time, it is nice to know, upon

opening the next file, what the next available file number is. FreeFile returns this value.

So, for example, if we already have 2 files open, (numbers 1 and 2) FreeFile will return a

3.

intFNum = FreeFile

Open “C:\Data\thisFile” for input as #intFNum


Reading & Writing Text from a File In order to read data from a file, it must be opened for input. Then, the Line Input

command reads a complete line of text from the data file.

Line Input

File1

Record # Text

1 Tom Morrow

2 Willie Makeit

3 Betty Wont

intF = FreeFile

open “File1” for input as #intF

for x = 1 to 3

Line Input #intF,strTextLine

lstResult.additem strTextLine

next x

lstResult

EOF

Maybe you are not sure how many lines of text or records exist in the file. The EOF

function returns true if there are no more lines or records in the file. Changing the

code above to use the EOF function:

intF = FreeFile

open File1 for input as #intF

Do While not(EOF(intF))

Line Input #intF,strTextLine

lstResult.additem strTextLine

Loop

In the above example, the program will continue to read lines of text until it reaches the

end of the file. Using this method substantially lessens the possibility of trying to read

a line of text or a record after reaching the end of the file, which will result in an error

and will stop the program.

Assigns intF the value of the next

available file number

Opens the “File1” file for input

Reads each of the 3 lines of text into

the variable strTextLine

Places each line of text in the

lstResult text box

Tom Morrow

Willie Makeit

Betty Wont


vbCrLf

There may be times where the text may not be neatly entered in separate lines. Such may

be the case when pulling words out of a sentence. Instead of pressing enter, the vbCrLf

function may be used to add the end of line character in a text file.

In the following example, we:

Open the form with an input box to input a complete phrase

Check each character of the phrase, adding it to a long string unless the character is a

space. In which case, we insert a vbCrLf

After reading through the entire phrase, we write the new string (with the vbCrLf) to

a text file. We then close the file.

When we click the Generate List command button, we open the text file for input and

add the entire phrase to the list box

The resulting application appears on the next page…..

If the character is not a

space, we add it to

“strWord”. If it is a

space, we insert a

vbCrLf into “strWord”

Open “strF” for

Output and enter the

text for “strPhrase”

Place the string

created with the loop

into the file

Open “strF” for Input

Place each line of text into

the list box with the vbCrLf

designating a new line


Multi-Line Text Box

Above, we used a list box to show the results. A text box can also be used if its

MultiLine Property is set to true. Then, if multiple lines appear, scroll bars will

automatically appear.

Scroll Bar Properties

Scroll bar properties can be set only if the text box’s MultiLine property is set to true.

At runtime, the options are:

vbSBNone = Scroll bars will not appear

vbHorizontal = Horizontal scroll bar will appear

vbVertical = Vertical scroll bar will appear

As separate lines of text are read from a text file, they can be added to the text box using

the vbCrLf to start a new line

Do while not EOF(1)

Line Input #1,strData

lstListBox.Text = lstListBox.Text & strData & vbCrLf

Loop


Reading & Writing Records to a File Most times, data will need to be stored in various types such as numbers and writing it to

text files won‟t fit the bill. So, it is necessary to write data to files with varying data

types.

Suppose we want to keep inventory data for a grocery store. We need to keep track of

each item in inventory by its name, unit of measure, and amount. We open the form and

open a sequential data file (F:\Ch11Data) for output. We then use a series of input boxes

to enter the following data:

Item Name Amount in Stock Unit of Measure

Potatoes 100 pounds

Eggs 75 dozen

Beans 250 cans

Here, we write the three data

elements in the record to the data file.

(Note the comma delimiter)


Next, we enter the item searching for in the txtSearch text box and, go through the data

file until we find its name. If we encounter an end of file, we know that the item is not in

the data base.

Closing a Data File Always remember to close the data file before ending the program. Data is cached in

memory when sent to a file. It is only written when the buffer is full or when the file is

closed. So, ending a program without closing could result in lost data.

Here, we check to see if the item

searching for is in the data base.

Data is read from the file

one record at a time.

(Note the comma delimiter)


Appending Data to a File As mentioned before, a data file can be opened without losing all of its contents so that

additional data can be added to it by opening it for append.

Using the code from the previous example, we do this by simply replacing the mode from

output to append.

Open “Ch11Data” for append as #1

Updating and Deleting Records It is now clear that writing and reading data to and from files is pretty much a one-way

street. That is, a file can be opened for output/append or input only. So if we want to

change or delete a record in a file, we need to :

1. Open the original file for input

2. Open a second file for output

3. Read each record from the input file, checking for some key as to which record

we want to change or delete (In our grocery store example, we could look for the

item name.)

a. Write each record that we do not want to change or delete to the output

file

b. Change or delete the record(s) we want and write these new records to the

output file

4. Delete the original (input) file

5. Rename the new (output) file as the original file‟s name

To illustrate the procedure, we examine the following application that:

Opens the “Ch11Data” data file for input

Uses its contents to list all item names in a list box

Allows the user to choose an item from the list

Reads through each record, writing other records to a “temp” file

Places the data from that item‟s record in text boxes for editing

Replaces the edited data for the record into the “temp” file

Finishes reading all of the other data from the original file and writing it to the “temp”

file

Closes both files

Deletes the original file

Renames the “temp” file as the

original


We will change the amount from 75 to 77 and click “Change Record”. Running this

application again reveals the change made to the data.

Here is the code:

Open the “Ch11Data” file for

input and the “temp” file for

output.

Go through all of the records,

placing each record’s item

name in the list box.

The record pointer moves from record to record as it reads

data. Closing the file allows the record pointer to be replaced

at the beginning of the file upon re-opening it.


Reopening the file following the

previous close sets the record

pointer at the beginning of the

file.

Each record is read and, if it’s “strItem” value does not match

the “strTarget” from the list box, that record is written to the

“temp” file. When a match is found, the data from that record

is placed in the three text boxes in the form for editing.

After the changes are made to

the targeted record in the text

boxes and the “Change Record”

button is clicked, that record is

written to the “temp” file.

Then, the program continues through the rest of the

“Ch11Data” file reading each record and writing it to the

“temp” file.

Delete the “Ch11Data” file and

rename the “temp” file as

“Ch11Data” with its edited data.


Deleting and Renaming Files At the end of the code in the previous segment, there exists two lines of code – one that

deletes the original “Ch11Data” file followed by one that renames the “temp” file as

“Ch11Data”.

Kill

The Kill command simply deletes the file following it. In the code above, it is deleting

the “Ch11Data” file from the F: drive. The file to be deleted must be closed.

Name

The Name command follows this syntax:

Name <The old file name> As <Its new file name>

So, in the example above, it is renaming “temp” on the F: drive “Ch11Data” on that same

drive. The file to be renamed must be closed and there cannot be another file with the

new name in the same folder.


Starting Visual Basic ...................................................................................................................................... 1

Standard Toolbar ........................................................................................................................................ 2 Toolbox ...................................................................................................................................................... 2 Project Window .......................................................................................................................................... 3

Programming Prefixes .................................................................................................................................... 4 File Extensions ............................................................................................................................................... 4 Forms, Labels, Text Boxes, and Buttons ........................................................................................................ 5

Setting the Form‟s Name and Caption Properties ...................................................................................... 5 Adding a Label to the Form ........................................................................................................................ 6 Adding a Text Box to the Form .................................................................................................................. 7 Adding Command Buttons to the Form ...................................................................................................... 8

Adding Code to Objects ................................................................................................................................. 9 Make the lblMessage Label Visible When the Form is Clicked ................................................................. 9 Code the OK Button to Show the Desired Message in txtName Text Box ...............................................11

An Alternate Method .............................................................................................................................12 Code the Cancel Button to Close the Application .....................................................................................13

Saving a Project .............................................................................................................................................13 Using Assignment to Change Property Values..............................................................................................15 Including Image Objects ................................................................................................................................17 Review ...........................................................................................................................................................20 Variable Assignments ....................................................................................................................................22 Debugging Using the Immediate Window ....................................................................................................24 Data Types .....................................................................................................................................................27

Will Represent .......................................................................................................................................27 Data Type Naming Conventions ...............................................................................................................27 Multiple Variable Declarations..................................................................................................................27 Option Explicit ..........................................................................................................................................27

Automatic Type Conversion ..........................................................................................................................28 Modulus Division ..........................................................................................................................................29 Option Buttons ..............................................................................................................................................29 Frames ...........................................................................................................................................................31 Constants .......................................................................................................................................................31 If … Then Statements ....................................................................................................................................32

Boolean Relational Operators ....................................................................................................................32 Operator .................................................................................................................................................32

Equal to......................................................................................................................................................32 Roundoff Errors .........................................................................................................................................32

If … Then… Else Statements ........................................................................................................................32 Nested If … Then … Else Loops ..................................................................................................................33 If … Then … ElseIf .......................................................................................................................................34

Else ..........................................................................................................................................................34 Generating Random Numbers .......................................................................................................................34

Int Function ...............................................................................................................................................34 Fix Function ..............................................................................................................................................34 Randomize .................................................................................................................................................35

Scope .............................................................................................................................................................35 Logical Operators ..........................................................................................................................................36

Function .................................................................................................................................................36 Message Box .................................................................................................................................................36 Password Applications ..................................................................................................................................37 Counters ........................................................................................................................................................38 Check Boxes ..................................................................................................................................................39 Printing a Form ..............................................................................................................................................40 Do Loops .......................................................................................................................................................41


Do – Loop While .......................................................................................................................................41 intTotal = Val(txtNum.Text) .................................................................................................................41 Do ..........................................................................................................................................................41

Do While – Loop .......................................................................................................................................41 Infinite Loops ............................................................................................................................................41

Input Box .......................................................................................................................................................41 Syntax ........................................................................................................................................................42 Example .....................................................................................................................................................42

Accumulators .................................................................................................................................................43 Example .....................................................................................................................................................43

String Conversion Functions .........................................................................................................................44 LCase .........................................................................................................................................................44 UCase ........................................................................................................................................................44 StrConv ......................................................................................................................................................44 Manipulating Strings .................................................................................................................................45

Left ........................................................................................................................................................45 Right ......................................................................................................................................................45 Mid Function .........................................................................................................................................45 Mid Statement .......................................................................................................................................46 Len Function ..........................................................................................................................................46 InStr Function ........................................................................................................................................46

For … Next Loop ..........................................................................................................................................47 Generating Strings .........................................................................................................................................47

String .........................................................................................................................................................47 Space .........................................................................................................................................................48 & ................................................................................................................................................................48 vbTab .........................................................................................................................................................48 vbCrLf .......................................................................................................................................................48

Comparing Strings .........................................................................................................................................49 StrComp.....................................................................................................................................................49 Like ............................................................................................................................................................49

Sub Procedures ..............................................................................................................................................50 General Procedures ....................................................................................................................................50

Syntax ....................................................................................................................................................50 Example .................................................................................................................................................50

Call ............................................................................................................................................................50 Syntax ....................................................................................................................................................50 Example .................................................................................................................................................50

Line Continuation ......................................................................................................................................50 Example .................................................................................................................................................50

Value Parameters .......................................................................................................................................51 Syntax ....................................................................................................................................................51 Example .................................................................................................................................................51

Reference Parameters ................................................................................................................................52 Documenting Procedures ...........................................................................................................................53 Static Variables ..........................................................................................................................................53

Syntax ....................................................................................................................................................53 Example .................................................................................................................................................54

Function Procedures ..................................................................................................................................55 Syntax ....................................................................................................................................................55 Example .................................................................................................................................................55 Creating a Function ...............................................................................................................................56

Object Parameters ......................................................................................................................................56 Example .................................................................................................................................................56

Built-in Mathematical Functions ...................................................................................................................57 ABS ...........................................................................................................................................................57


SQR ...........................................................................................................................................................57 SGN ...........................................................................................................................................................57 IsNumeric ..................................................................................................................................................57 Round ........................................................................................................................................................58

Formatting Numeric Output ..........................................................................................................................58 Format ...................................................................................................................................................58

Built-in Business Functions ...........................................................................................................................59 PMT ...........................................................................................................................................................59

Syntax ....................................................................................................................................................59 PV ..............................................................................................................................................................60 FV ..............................................................................................................................................................61

List Box .........................................................................................................................................................63 Event or Method ....................................................................................................................................63

Combo Box....................................................................................................................................................67 Property .................................................................................................................................................67

Underscore.....................................................................................................................................................68 Application Properties ...................................................................................................................................69

Focus .........................................................................................................................................................69 Access Key ................................................................................................................................................69 Tab Order ..................................................................................................................................................70 Built-In Trigonometric Functions ..............................................................................................................72 SIN ............................................................................................................................................................72 COS ...........................................................................................................................................................72 TAN ...........................................................................................................................................................72 Converting Degrees to Radians .................................................................................................................72 Converting Radians to Degrees .................................................................................................................72

Inverse Trigonometric Functions ...................................................................................................................73 ATN ...........................................................................................................................................................73 To use ATN to calculate the ARCSINE of an Angle in Radians ..............................................................73 To use ATN to calculate the ARCCOSINE of an Angle in Radians .........................................................73

Logarithmic and Exponential Functions ........................................................................................................73 LOG ...........................................................................................................................................................73 Using LOG to Calculate the Logarithm of a Number to A Base ...............................................................74 EXP ...........................................................................................................................................................74

Variable Arrays .............................................................................................................................................75 Array Declaration ......................................................................................................................................75

Dim strEmp(5) as String ........................................................................................................................75 Upper Bound .............................................................................................................................................75 Lower Bound .............................................................................................................................................75 Option Base ...............................................................................................................................................75

Option Base 1 or Option Base 0 .........................................................................................................75 Array Declaration Using Upper and Lower Bounds..................................................................................75

Dim strEmp(1 to 5) as String .................................................................................................................75 Const lngLowBound as Long = 1 ..........................................................................................................75

Array Initialization ....................................................................................................................................75 Array Index ................................................................................................................................................75 LBound and UBound Functions ................................................................................................................76 Run-Time Error .........................................................................................................................................76

For … Next ....................................................................................................................................................76 Dim lngIndex as Long ...........................................................................................................................76

Array Parameters ...........................................................................................................................................76 Function AddChar(ByRef strEmp() As String) As Integer ...................................................................76

Arrays With Meaningful Indexes ..................................................................................................................77 Searching an Array ........................................................................................................................................77 Dynamic Arrays ............................................................................................................................................77

ReDim .......................................................................................................................................................77


Preserve .....................................................................................................................................................78 Control Arrays ...............................................................................................................................................78

Index Property ...........................................................................................................................................78 LBound and UBound Properties ................................................................................................................80 Count .........................................................................................................................................................80 Control Arrays as Parameters ....................................................................................................................81 Removing an Object From a Control Array ..............................................................................................81

Two Dimensional Arrays ..............................................................................................................................81 Declaring a Matrix .....................................................................................................................................81

Dim strName(1,4) as String ...................................................................................................................81 Declaring a Matrix Using Upper and Lower Bounds ............................................................................81 Dim strName(1 to 2,1 to 5) as String .....................................................................................................81

LBound and UBound Functions ................................................................................................................82 Dim intLowRow, intHighRow, intLowCol, intHighCol as Integer .......................................................82

Nested For…Next Loops ...........................................................................................................................82 Dim intRow, intCol as Integer ...............................................................................................................82

Dynamic Matrix.........................................................................................................................................82 Color ..............................................................................................................................................................83

Color Properties at Design Time ...............................................................................................................83 BackColor ..............................................................................................................................................83 ForeColor...............................................................................................................................................84

Setting Colors at Run Time .......................................................................................................................84 Built-In Visual Basic Colors ......................................................................................................................85 RGB Function ............................................................................................................................................85

Practice Application Using Color ..........................................................................................................85 Adding Lines to an Application.....................................................................................................................85

Line Properties...........................................................................................................................................86 Name .....................................................................................................................................................86 BorderColor ...........................................................................................................................................86 BorderStyle ............................................................................................................................................86 BorderWidth ..........................................................................................................................................87

Objects and Form BackColor ....................................................................................................................87 Adding Shapes to an Application ..................................................................................................................87

Shape Property ..........................................................................................................................................87 Name Property ...........................................................................................................................................88 BackColor Property ...................................................................................................................................88 BackStyle Property ....................................................................................................................................88 BorderColor Property ................................................................................................................................88 BorderStyle Property .................................................................................................................................88 BorderWidth Property ...............................................................................................................................88 FillColor Property ......................................................................................................................................88 FillStyle Property.......................................................................................................................................88

Picture Boxes .................................................................................................................................................90 Picture Property .........................................................................................................................................90 BorderStyle Property .................................................................................................................................92 AutoSize Property .....................................................................................................................................92

Moving Shapes and Picture Boxes ................................................................................................................93 Twips .........................................................................................................................................................93 Move Method ............................................................................................................................................94

Graphic Methods ...........................................................................................................................................95 Coordinate System.....................................................................................................................................95 Line Method ..............................................................................................................................................95 Circle Method ............................................................................................................................................96 Pset Method ...............................................................................................................................................97 PaintPicture Method ..................................................................................................................................98 Cls Method ................................................................................................................................................98


Container Properties Affecting Graphics .......................................................................................................99 AutoRedraw ...............................................................................................................................................99 DrawStyle ..................................................................................................................................................99 DrawWidth ................................................................................................................................................99 FillColor ....................................................................................................................................................99 FillStyle .....................................................................................................................................................99 ForeColor...................................................................................................................................................99

Timer Object................................................................................................................................................100 Name Property .........................................................................................................................................100 Interval Property ......................................................................................................................................100 Enabled Property .....................................................................................................................................100 Timer Event .............................................................................................................................................100

Moving Line Objects ...................................................................................................................................102 Animation ....................................................................................................................................................103 Adding Sound ..............................................................................................................................................104

Name Property .........................................................................................................................................104 Device Type ............................................................................................................................................104 Enabled Property .....................................................................................................................................104 FileName Property ...................................................................................................................................104 Visible Property .......................................................................................................................................104

Using Wav Sounds ......................................................................................................................................105 Creating the Wave File ............................................................................................................................105 Applying the Wave Sound from a File ....................................................................................................105

Sequential Access Files ...............................................................................................................................107 Opening a File .........................................................................................................................................107

FreeFile Function.................................................................................................................................107 Reading & Writing Text from a File .......................................................................................................108

Line Input ............................................................................................................................................108 EOF .....................................................................................................................................................108

vbCrLf .....................................................................................................................................................109 Multi-Line Text Box ................................................................................................................................110

Scroll Bar Properties ............................................................................................................................110 Reading & Writing Records to a File ......................................................................................................111 Closing a Data File ..................................................................................................................................112 Appending Data to a File .........................................................................................................................113 Updating and Deleting Records ...............................................................................................................113 Deleting and Renaming Files ..................................................................................................................116

Kill .......................................................................................................................................................116 Name ...................................................................................................................................................116

Visual Basic Programming Starting Visual Basicteachers2.tulpehocken.org/knoecker/VisBasNotes.pdf ·...

Documents

Transcript of Visual Basic Programming Starting Visual Basicteachers2.tulpehocken.org/knoecker/VisBasNotes.pdf ·...