Unit 2 - Variables 2.1
Introduction
We are definitely becoming a society of vast amounts of information. However this
information needs to be stored where it can be used and accessed. Our mail gets stored
in a mailbox, our E-mail gets stored in our in boxes and our personal items hopefully get
stored neatly in our rooms.
Programming requires information to be stored. The information is stored in what are
called variables. Variables are like the mailboxes of our computers. Each variable
contains information, just as a mailbox contains envelopes/letters. Each variable has an
address, just as each mailbox is assigned a street address. Each variable will have a
specific name, similarly each mailbox is labeled with the name of a family or business.
A variable in programming is
information or a value that is expected
to change. Days of the year change,
the temperature in our Canadian
climate changes and whether we like
it or not our age changes. In
programming we use variables to
store information or values that are
expected to change during the course
of the program.
Variables in Visual Basic hold
information or values. When a variable is used or declared the Visual Basic sets up a
storage space, such as a named memory box, in the computers memory. When needed
in a program visual basic can access this variable and its value as long as it has been
declared.
Definition
Declared means when a variable is given a name.
Required Skills
1. From design.
2. Command controls, text boxes and label boxes.
3. Comments
New Skills
1.
2.
3.
4.
5.
Variables and Variable Data Types
Constants
Message Box
Color
Multiple Forms
Outcomes
In order to work through this unit you should be able to:
9.
10.
11.
12.
13.
1. Declare a variable using a data type.
2. Declare a variable using all eleven data
types.
3. Declare a variable and assign the variable
to an object.
4. Know where to declare a variable (local,
global or modular).
5. Declare more than one variable of the
same data type.
6. Know the scope of variables.
7. Know the difference between a variable
and a constant.
8. Declare a constant and use it in a program.
Know the order of operations (PEDMAS/BEDMAS).
Use mathematical operations in a program.
Use the message box where appropriate in a program.
Use of multiple forms in a project.
Know how to refer to object values or information from form to form.
Key Words
For the explanations and definitions of the key words see Appendix B
Variable Description
A variables is a named storage place in a computers memory. Variables are used in a
code statements to store temporary values used by other code statements. Code
statements are lines of programming code inside an object. For the most part variables
are declared as Option Explicit in the General Declarations area of the program (see
frmVariableDeclaration) . Variables in Visual Basic all have a name, that the programmer
creates, and a data type that Visual Basic pre-defines.
of
The
contents
a variable
determine what data type a variable will be. A data type is whether the contents of a
variable is numbers, letters or special numbers. Data types will be discussed below.
The following is an example of a variable declaration using Option Explicit in the General
Declarations section of a program. Notice that the Object is General and the Proc is
declarations.
Variable Data Types
The contents of a variable is a determining factor as to what data type the variable will
be. Visual Basic holds 11 standard data types for variables. It is also possible to define
your own variable types. For our purposes we will be using the standard data types. The
most often used data types include string and integer.
For example: Dim Num1 as Integer
Variable
Type
Storage
Size (in
bytes)
Range
String
length
1 to 65,535 characters
1


of string
Byte
Description
0 to 255


Boolean
2
True or False


Integer
2
-32,768 to 32,767


Long
Integers
4
-2,147,483,647 to
2,147,483,647



Single
Precision
4
-3.402823E38 to


string variables hold
characters.
one of the most common uses
of strings variables is to pick
up the information contained
in a text box.
hold relatively small integer
values.
it is a no type-declaration
characters
are no type_ declaration
characters.
used when there are logical
tests to be performed.
hold relatively small integer
values.
used when integers require no
decimal point.
it is a no type-declaration
character
use whenever a number is
larger than an integer.
eg. the cost of a new house,
$150,000
hold relatively small integer
values.
it is a no type-declaration
-1.401298E-45

for negative numbers

-1.401298E-45 to
character.
usually numbers that contain
decimal places.
use when you do not want
integers to be rounded off. eg.
23.45
-3.402823E38
for positive numbers
Double
Precision
Currency
8
8
-1.79769313486232E308
to 4.94065645841247E324 for negative numbers

4.94065645841247E-324
to 1.79769313486232E308
for positive numbers


-922,337,203,685,477.
5808 to
2,337,203,685,477.5807




hold relatively small integer
values.
it is a no type-declaration
character.
needs greater storage.
use when you need very small
or very large numbers that
require great precision.
hold relatively small integer
values.
it is a no type-declaration
character.
used when accuracy is
important.
Date
8
Jan. 1, 100 to Dec. 31,
9999

used to find days between two
dates.
Variant
16 for
negative
numbers
Any numeric value up to
the range of a Double

hold relatively small integer
values.
it is a no type-declaration
character
22 + string
length

Variable Declaration 2.2
Variable Names
Variable names are given depending on the information the variable will store. For
example the variable name
FirstName
will be given to a variable that will hold a persons first name. Again The variable name is
declared or named in the general declarations area of a program as show in the Variable
Description section.
Rules for Declaring Variables
There are certain standards that we must follow when declaring variables. They include:
1. The variable name must begin with a character. For variables that are declared in
an event the first character must be a letter. The first character for variables
declared in the form or module the first letter must indicate whether the variable
is declared in the form's (f_) or module's (m_) general declarations area followed
by an underscore and the variable name.
eg. f_Age as Integer
The concepts of declaring variables in events, forms or modules will be discussed in the
Scope of Variables section.
NOTE: for smaller programs we will be declaring variables in forms or in objects
programs. For larger programs with multiple forms we will declare variables in modules.
1. All memory variables will be declared in the most appropriate location and
appear in lower case.
2. The name cannot be more than 40 characters long.
3. The name cannot contain punctuations or blank spaces
4. All variables must have a data type that is suitable to the variable use in the
program.
5. The name cannot be a reserved word (such as Print, Name, Hour), because
reserved words have special meaning in Visual Basic.
See Appendix A for a list of Reserved Words.
Examples of Proper Variable Declarations
Valid
Invalid
Reason for Invalidity
Variable Name
Variable Name
f_Hourswkd
Hours
hours is a reserved word
f_Salary97
97Salary
name must not begin with a
number
c_Discount_Price
Discount Price
name cannot contain a space
c_FirstName
Name
reserved word
m_FireDepartment
Fire.Department
name cannot contain punctuation
The Dim Statement for Data Types
Before a variables is declared programmers must include the Dim syntax. This indicates
to the program that the variables value could change as the program runs.
Syntax
Variable Declaration in an Event:
Dim <NameYouCreate> as Data Type
Variable Declaration in a form's General Declarations:
Dim <f_NameYouCreate> as Data Type
Variable Declaration in a module's General Declarations:
Dim <m_NameYouCreate> as Data Type
Examples
Dim CanadianDollar as Currency
Dim f_ Year as Integer
Dim m_FirstName as String
Dim CorrectAnswer as Boolean
Dim f_Temperature as Long
Dim m_FractionCalc as Single
Dim f_TheCalculation ' this makes f_TheCalculation have the variant data type.
The variant data type takes up a lot of space in memory. It is not good programming
practice to declare variables with the variant data type.
You can also declare variables on the same line. It is good programming practice to keep
all the same variables of the same data type on the same line.
Dim NumberofDays as Integer, HoursWorked as Integer
Dim m_FirstName as String, m_MiddleName as String, m_LastName as String
Dim f_TaxRate as Integer, f_Subtotal as Integer, f_Total As Integer
The Scope of Variables
Variables may be declared in the following levels in Visual Basic:
Variable Type
variable name = expression
Event
Dim Fname as Type
ReDim Fname as Type
Description



Static Fname as Type


Form
Dim f_Fname as Type



Module
Public m_Fname as Type
(for VB 4.0)
Global m_Fname as Type
(for VB 3.0)
Variable Assignment Statements


declared in any procedure.
available only in the procedure
or object in which it is called.
ReDim is used to change the
size of an array, only in a
procedure.
Static is when the programmer
wishes to have a procedure
retain a variable's values for the
duration of the application.
also known as local to the
event, local to the object or
control or procedure
in any procedure.
in the declaration section of a
form.
available to all procedures in
that module, but not to any
other form or code module.
in declaration section of a
module, cannot be declared
anywhere.
available in every procedure in
all forms and code modules in
the application.
The easiest way to create a
variable is to assign a value to the
variable's name in a code
statement.
An assignment statement assigns a
value to the property of an control/object. After the period is the property of the object
followed by the equal sign and the value. The value could be a variable or a piece of
information.
<Object.Property> = <value property >
EXAMPLE
CHANGES THE...
txtLname.Text = "Jones"
the text displayed in the text box to Jones
HourlyIncome = 10.55
f_FirstName = "John"
g_PresentAge = 16
Variables can either hold numbers called numeric data or characters called string data.
String data must be placed in quotation marks. Numeric data need not be in quotation
marks.
Variables can also be assigned to the value of another variable, the value of an
object/control or the value of a mathematical expression.
txtHourlyIncome.Text = f_HourlyIncome
If you prefer output to be tested you can print any output on the form. All you need to do
is separate the variables or anything as text with a semi-colon. Remember that variables
need not have quotes around them, but the programmers setup must.
For example:
print "The "; f_Chlorine ; "is too high and the"; f_AlgaeCount ; "is normal."
Visual Basic Variable Declaration Exercises
Activity 2.2.1
1. Complete the following table. PLEASE DO NOT WRITE ON THIS HANDOUT.
Variable Declaration
Explanation
Or Assignments
Why Correct or
Incorrect?
Correction or Better
Choice
Dim Name as Integer
Dim m_FirstName as Integer
Dim m_Money Earned as Integer
Dim f_Currency as String
Dim f_ Person as String
Dim m_Name as String
Dim GoldbachNo as Integer
Dim m_PizzaOrder
Dim !Factorial as Double
Dim m_Chemicalppms as Double
Dim x, y, z as Integer
Dim m_Num1 as Integer, m_Num2 as
Integer
txtCarPayment.txt = m_CarPayment
TextOrderNum.Text = m_OrderNum
txtCarPayment.txt = m_CarPayment
Distance = txtDistance
print "Show me the $ "; m_Money "!!!"
m_FibonacciNum = "45"
Activity 2.2.2
TOPICS: Variable Text Boxes, Label Boxes, Command Boxes and the Message Box.
PART A
You need to create the following:
1. 5 Label Objects
2. 4 Text Boxes
3. 3 Command Boxes
1. Change the form NAME to THE PERSONAL INFORMATION PROGRAM.
Your form should appear similar to the following form:
The following will help you
create your program:
Label1
CHANGE THE NAME TO:
lblTPersonal
CHANGE THE CAPTION
TO: MY PERSONAL
INFORMATION
Change the FontSize to 18
point.
Label2
CHANGE THE NAME TO:lblFirst
CHANGE THE CAPTION TO: First Name
Label3
CHANGE THE NAME TO: lblLast
CHANGE THE CAPTION TO: Last Name
Label4
CHANGE THE NAME TO: lblHeight
CHANGE THE CAPTION TO: Height
Label5
CHANGE THE NAME TO: lblHair
Please use American spelling of color, since this is American software.
CHANGE THE CAPTION TO: Hair Colour
Text1 Diagram #1
CHANGE THE NAME TO: txtFirstName
CHANGE THE TEXT TO: null, delete text1
As see in Diagram #1
Text2
CHANGE THE NAME TO: txtLastName
CHANGE THE TEXT TO: delete Text2
Text3
CHANGE THE NAME TO: txtHeight
CHANGE THE TEXT TO: delete Text3
Text4
CHANGE THE NAME TO: txtHairColor
CHANGE THE TEXT TO: delete Text4
Command1
CHANGE THE NAME TO: cmdDisplay
CHANGE THE TEXT TO: DISPLAY
Double Click on Command2
CHANGE THE NAME TO: cmdClear
CHANGE THE TEXT TO: CLEAR
Double Click on Command3
CHANGE THE NAME TO: cmdExit
CHANGE THE TEXT TO: E&XIT
Double click on the command button, type in End between the sub and end sub.
1. Assignment Statements
2. In the general declarations area declare the following variables.
REMEMBER!!!
Accessing the general declarations area: double click on the form, beside Object click on
the arrow down choose (General), beside Proc click on the arrow down choose
(Declarations). You are using f_ because your variables are declared at the form level.
This will allow you to use the variables anywhere else in the program.
f_FirstName - string
f_LastName - string
f_Height - integer
1. Double Click on cmdDisplay.
2. Assign the 3 text boxes to the 3 appropriate variables
f_FirstName = txtFirstName.Text
f_LastName = txtLastName.Text
f_Height = txtHeight.Text
1. Using the MSGBOX Statement
The MessageBox displays one of Visual Basic's predefined dialog boxes.
Example #1
MsgBox txtFirstName.Text
or
MsgBox f_FirstName
This will display your first name in the message box.
For string expressions, you must enclose them in quotations
Example #2
MsgBox "Hello"
Syntax
<ReturnValue> = MsgBox (prompt [,buttons][,title][helpfile][,context]
You can also omit the return value and the equal sign.
If you want to display more than one item in the message box it is possible using the
ampersand sign (&) . You can use quotes to type in text and for blank spaces between
you name.
Example #3
MsgBox f_FirstName & " " & f_LastName & ". " & "Your height is " & f_Height
1. Add in a text box for hair colour and declare a variable for hair colour.
2. Double Click on cmdDisplay. Type in the following code below your assignment
statements:
NOTE: Make sure that you type the line below in one line. The ampersand (&) sign does
not need to be bold and large.
MsgBox f_FirstName & " "& f_LastName & " your height is " & f_Height & " and your hair
color is " & f_HairColor & ". "
THE KEY FOR UNDERSTANDING:
" " = a space
". " = a period and a space
" and your hair color is" = a space and your hair color is
Double Click on the cmdClear.
Assign all the variables to a null string to clear the text boxes.
txtFirstName.Text = " "
txtLastName.Text = " "
txtHeight.Text = " "
Remember to add in your hair colour text box.
Run the program use F5.
Save the Form File as: vars1.frm
Save the project as: vars1.vbp
1. Enter in your first name, last name, height in centimeters and your hair color.
2. Click on Display.
What is the output? Note the output word for word and space for space.
If you have syntax errors check cmdDisplay. Make sure you have all the quotes and
ampersand signs. Ask a friend in the class for help.
Here is what your output could look like:
Activity 2.2.3
Part B
ENHANCEMENTS:
Add some color to your form by changing the properties of the objects. Change the color
of the text boxes and label boxes as well as the text.
See is you can add a label box and a text box for your favorite food. Don't forget to
declare the variable for your favorite food and assign it to the text box.
Label6
NAME: lblFood
CAPTION: Favorite Food
Text5
NAME: txtFood
TEXT: delete Text5
Assign the food text box to the variable f_Food. Using the ampersand sign add in f_Food
to the code in cmdDisplay. For example:
MsgBox f_FirstName & " "& f_LastName & " your height is " & f_Height & " and your hair
color is " & f_HairColor & ". " & "Your favorite food is " & f_Food " ."
Note the output in your computer science binders.
Constants 2.3
Constants are useful when the programmer declares a variable and it's value never
changes. It is best to declare constants in the general declarations area.
Constants are declared because it is easier to change a constant's value in one area. It is
time consuming to search for a variable and change its value in the locations where the
variable has been used.
The same rules for declaring variables also applies for constants.
(See the Variable Declaration section above.)
Syntax
Const <areadeclared_ConstantName> = <Value>
Example
Const f_CdnTax = 0.15
Const f_UserName = "Grade 11 Students"
Visual Basic also declare constants for your file properties in a module. eg. Global Const
Left_Justify = 0
The tax constant could be used in many of your programs dealing with currency.
Activity 2.3.1
Name and 5 instances where constants are necessary.
Use the proper syntax to declare the constants.
The Format Function 2.4
Functions in Visual Basic are predefined procedures that perform a specific task.
The Format Function
The format is used to improve the appearance of numbers in your application. The
Format Function formats any expression according to a set of string instructions you
specify. If your application included using currency for millions of dollars you could
specify how the dollar value should appear or you could use the predefined format
function to display the dollar value.
When using the format function it is not necessary to code with the format function until
the formatted expressions are displayed.
Note: # is a place holder for a digit.
Pre-defined Formats
Format
Explanation
Currency
Displays a number with a dollar sign and two decimal places; if
appropriate displays a number with a thousand separator; negative
numbers are enclosed in parenthesis
Fixed
Displays a number with at least one digit to the left and two digits to the
right of the decimal point.
Standard
Displays a number with two decimal places; if appropriate, displays a
number with a thousand separator; negative numbers are enclosed in
parenthesis
Percent
Multiplies a number by 100 and displays the number with a percent
sign(%); displays two digits to the right of the decimal point.
Scientific
Displays a value as a decimal number between 0 and 10 time the
appropriate power of 10.
Syntax
Format$(NumericExpression, FormatString$)
The $ sign is to distinguish that the format output will become a string. When a variable is
a variant the $ is not needed.
Note: the date function will be discussed below.
Examples
1.
2.
3.
4.
5.
6.
Format$(99, "Percent")
Format$(123000, "Currency")
txtNetPay.Text = Format$(m_NetPay, "Currency")
txtPlanetMass.Text = Format$(Mass, "Scientific")
txtTermMark.Text = Format$(FinalMark, "Percent")
lblPrice.Caption = Format(lblTotalPrice.Caption *100 *1.05, "Currency")
Activity 2.4.1
Write the code in a program for the examples above and note their output.
For example:
On a blank form create a label box and Name it cmdDisplay with a caption Display. Type
in:
Print Format$(99, "Percent")
Run the program and click on Display.
Activity 2.4.2
The expressions below are manually/user defined. For the following expressions note the
output in your computer science binders.
What is the output????
Print Format$(987.654321, "###.##")
Print "The interest rate is " ; Format$(Payment, "####.##).
Assume:
Dim Payment as Integer
Payment = 4532.1
Print Format$(543.210, "###.###")
Print Format$(543.210, "000.000")
Print Format$(123456789.91, "#.#.##")
Print Format$(500000000, "#00,,"):"million yen"
Print Format$(81.234, "###.##%")
Print Format$(Amount, "$###.##").
Assume:
Dim f_Amount as Integer
Amount =12.3
Print Format$(456.120,"###.###")
Print Format$(1000000000000,"#.#.#.##")
Calendar Functions 2.5
A. The Date Function
Date$ returns a string for the Month-Day-Year (mm-dd-yyyy). The month and day always
use two digits. The year uses four eg. 01-01-1992 for 1 January 1992
Syntax
Date$= "mm-dd-yyyy"
Date$="mm/dd/yyyy"
mm = numbers between 01 and 12
dd = days between 01 and 31
yyyy= are years between 1980 and 2099
Remember that if your computer has a built-in clock calendar to permanently reset the
clock you may have to use to setup program that came with the computer.
Example
lblDate.Caption = Date$
What will happen to computers in the year 2000?
B. The Time Function
The time function runs on a 24-clock. The eight character string is returned as hh:mm:ss.
You can also set the time to show only the hours, hours and minutes or the full string.
Syntax
Time$(string)
Example
lblTime.Caption = Format(Time$, "Medium Time")
C. The DateValue Function
The DateValue(string) function accepts any date entered in by the user mm-dd-yyyy
The returned valued of a numeric calendar function is represented as a serial-number.
For example December 31, 1599 would be 1.000000 and January 1, 1600 would be
2.000000. The digits to the left of the decimal point is the date and to the right is the time.
This is called a double-precision number.
Syntax
DateValue$("Month-Day-Year")
DateValue$("Day-Month-Year")
The user can enter in the date the following ways:
DateValue $("12-30-1599")
DateValue$("December 30, 1599")
DateValue$("Dec 30, 1599")
DateValue$("30 December 1599")
DateValue$("30-Dec-1599")
Before using the DateValue function, you need to know the current serial date or the date
NOW.
Visual Basic uses a pre-defined function, Now to determine the current date.
Syntax
txtDateNow = Now
Example
txtDateNow = "Today's date is"; Format$(Now, "hh:mm:ss AM/PM mm/dd/yy")
txtDateNow = "Today's date is"; Format$(Now, Medium Date")
You can also have different types of formats to display the dates. Instead of having the
user define the dates with hh:mm etc... By using medium date, general date, long date or
short date. Medium date will be discussed in Activity 2.5.1 .
For
Other Numeric Calendar
Functions see Appendix C
Activity 2.5.1
Time Zones, Dates and
Introduction to Functions
Save as: Zone
In this project you will be
determining the time of day in
various international locations
around the world.
You will need
1.
2.
3.
4.
4 label boxes
2 text boxes
11 command boxes
1 picture (for now)
The text boxes are titled txtDate and txtTime.
Coding
The following code below will provide you with enough code to complete the rest of the
program. Make sure you use comments for each command button and you assign all
variables appropriately to the text boxes. You will be getting practice using the now and
date function.
Declare the variables f_Time and f_Date as strings in the general declarations area under
the word Option Explicit. Assign them to the appropriate text boxes in their respective
command boxes.
Example for the Mississauga Time Zone
Private Sub cmdMississauga_Click()
' the present time is now in Mississauga where we are located.
txtTime = f_Time
f_Time = Format(Time$, "Medium Time")
End Sub
Example for the Iceland Time Zone
Private Sub cmdIceland
' the time in Iceland is determined by the time now and 4 hours away.
txtTime = f_TIme
f_TIme = Format$(TimeSerial(Hour(Now)+ 4, Minute(Now), Second(Now)), "Medium
Time")
End Sub
You will now have to determine the time difference in hours for the other locations. Use
the same code as you have for cmdIceland but make sure you change the + 4 to the
appropriate number of hours away Auckland, France etc... are __ number of hours away.
The Date Function
Double click on the Date command button. Type in the following code:
Private Sub cmdDate_Click()
txtDate.Text = f_Date
f_Date.Caption = Date$
End Sub
How does the TimeSerial, Hour, Minute and Now function operate in this example?
See if you can add In flags for each location. Place the picture beside the name of
the city. Perhaps you can copy the code from the command box into the picture
and make it a click event.
Activity 2.5.4
Enhancement
The date function must be modified so that the date appears properly for each time zone.
Expressions 2.6
Expressions are used to calculate values. To create expression you need variables
and the operators.
The operators in Visual Basic include:
Addition +
Subtraction Multiplication *
Division /
Exponents ^
Mathematical Operations
Mathematical expressions many times involve multiple uses of different operators.
When an equation includes many operators the order of operations supercedes
any order in the expression. The order of operations works in Visual Basic the
same way as it does in your math class. The order of operations is also known as
the order of precedence. This means that certain mathematical functions will
always be calculated before any other calculation.
The Order of Operations/Precedence could be best remembered by PEDMAS or
BEDMAS.
Activity 2.5
Name the 6 orders of operation for arithmetics.
If there are two of the same operators in an expression/equation the all have equal
precedence, however they are evaluated from left to right in which they appear.
f_Calculation = Num1*Num2*Num3*Num4+Num6
Therefore Num1*Num2 would be calculated first.
In programming many times there are comparison or logical operators used along
with the in the arithmetic expressions. The order in this case is arithmetic,
comparison and then logical operators.
Comparison operators all have equal precedence; that is, they are evaluated in the
left to right order in which they appear. (VB help file) Arithmetic and logical
operators are evaluated in the following order of precedence:
Arithmetic
Comparison
Logical
Exponents ^
Equality =
Not
Negation -
Inequality <>
And
Multiplication
Less than <
Or
Integer Division \
Greater than >
Xor
Modular arithmetic Mod
Less than or Equal to <=
Eqv
Addition and subtraction +,-
Greater than or Equal to >=
Imp
String concatenation &
Like
and Division *, /
Is
The string concatenation operator (&) is not an arithmetic operator, but in
precedence it does fall after all arithmetic operators and before all comparison
operators (see Unit 6). Similarly, the Like operator, while equal in precedence to all
comparison operators, is actually a pattern-matching operator. The Is operator is
an object reference comparison operator. It does not compare objects or their
values; it checks only to
determine if two object
references refer to the same
object.
Activity 2.6.1
Using Mathematical
Functions
You will now create a small
program that allows a user to enter in their name and income. Allow the program to
display taxes once the user clicks on the command button. The taxes are
multiplied by 40% since that is the average amount that most people working full
time would pay to the government.
Change the form's Caption to The Tax Man.
You will need the following
1. 4 labels
2. 3 text boxes
3. 3 command boxes
Label1
CAPTION: "Visual Basic is Fun"
NAME: lblTitle
Command1
Double click on command1
CAPTION: EXIT
NAME: cmdExit
Label2
Change the following:
CAPTION: Name
NAME: lblName
Text1
Change the following:
CAPTION: not available in for the text tool
NAME: txtName
TEXT: none
Label3
Change the following:
CAPTION: Income
NAME: lblIncome
Text2
Change the following:
CAPTION: not available in for the text tool
NAME: txtIncome
TEXT: none
Label4
Change the following:
CAPTION: Taxes
NAME:lblTaxes
Text3
Change the following:
CAPTION: not available for the text tool
NAME: txtTaxes
TEXT: none
Command2
Change the following:
CAPTION: "CALCULATE YOUR TAXES"
NAME: cmdCalcTaxes
Double Click on the command button and type in the following code.
Private Sub cmdCalcTax_Click()
' these variables are control variables
Dim Income As Integer, Taxes As Integer
Income = txtIncome.Text
Taxes = Int(Income *0.4)
txtTaxes.Text = taxes
End Sub
Int is a common mathematical function used in visual basic. Int() will return an
integer value of the number entered as the argument. With a negative number it
returns the first integer less than or equal to the number.
Command3
Change the following:
CAPTION: CLEAR
NAME: cmdClear
Sub cmdClear_Click()
txtTaxes.Text=""
txtIncome.Text = ""
EndSub
Activity 2.6.2
ADDING IN COLOUR
See appendix E for Lesson on Colour
Create a new label and place it anywhere on the form.
Change the following:
CAPTION: "Click Here for Fun"
NAME: lblResponse
Type in the following code:
Private Sub lblResponse_Click
Sample1.BackColor = QBColor(2)
lblReponse.BackColor=QBColor(13)
lblResponse.Caption = "Very Much Fun!"
End Sub
Run the program and click on CLICK HERE FOR FUN
Note what happens.
Sample1 is the name of the form and BackColor is one of its properties.
Try using QBColor(10) and then QBColor(7) in place of Sample1.BackColor in
lblResponse.
Describe what happens in your computer science binders.
1.
2.
3.
4.
What does QBColor change?
What does Sample1.BackColor change?
What does lblResponse.BackColor change?
For Commonly Used Mathematical Functions See Appendix D
Review and New Code Statements
Code Statement
Explanation
m_TicketCost = 10.50
numeric data
Movie = "Batman"
string data
f_TipTotal = m_SubTotal
value of another variable
m_FinalCost = m_Price * m_Tax
value of an expression
Interest = m_Principal * 4.25 * Time
value of an expression
Val 2.7
The Val Funciton tells Visual Basic to treat the a character or string as a numeric
function. Val is used when the user enters in information, such as a number, into a
text box that will be used in a mathematical expression. The string expression is to
be interpreted by Visual Basic as a numeric value thus a dollar sign, comma or
percent sign cannot be used in the expression.
Val is executed from left to right. If it encounters any alphabetical characters it
returns a value of 0. For example: Val(2001Olympics), the output would be 2001.
It is good practice to use val when creating large mathematical expressions.
Syntax
Val(String Expression)
Examples
Val("2001")
The output would be 2001 as numeric.
m_PresentAge = Val(txtEnteredAge.Text)
Length = Val(txtLength.Text)
f_Area = Val(txtLength.Text) * Val(txtWidth.Text) * Val(txtHeight.Text)
lblTotalAmount.Caption = Val(txtTotal.Text) + Val(txtTax.Text) + Val(txtTip.Text)
Val will be used in the preceding Units as well as the exercises.
Using Multiple Forms 2.8
Before starting this activity you need to write a short action adventure story. Make
sure the story has at least two story lines at the beginning and two for each
subsequent story. The story you will see below is an example how to create an
action adventure story using multiple forms. It is by no means creative so it does
need your talents.
HANDLING MULTIPLE FORMS AT RUN TIME:
Project Options - what form to start on right away.
Start up form - specify what form begins the program.
The Action Adventure Story
Action adventure stories include many different plots and story directions. When
reading you start with one story line and then you are given a choice of two story
lines. From this story line you are given two more choices and so on. Visual Basic
does not restrict you to one form. As your programs become more complicated
you will need to use multiple forms. You can include many forms in your program
provided you use the proper syntax and coding. .



multiple forms add power and flexibility to your application.
you will always see the list of projects on the form.
make sure that you always name the properties of the form with something
meaningful.
Creating multiple forms is very simple process. On the menu bar choose insert and
then form. On the menu bar you can also click on
Activity 2.8.1
The Action Adventure Story
Your teacher will provide you with the a sample action adventure story.
MAIN STORY FORM
On the first form (the Main Story) you will need the following objects:





3 labels
2 text boxes
5 command boxes
1 oval shape
1 picture
Create a new program.
The form properties are as follows:
CAPTION: Main Story
TITLE : frmMainStory.
MAXIMIZING YOUR FORM DURING RUN TIME
To make the form appear on the entire screen you need to change the properties of
the form. Go the Properties, find WindowState and change the state from 0-Normal
to 2-Maximized. You form will appear as large as your computer screen.
Using the specifications in the table below create the frmMainStory.
Object
Name Property
Label for Title of the
Action Adventure
lblTitle
Text
Property
Caption Property
The Action
Adventure Story of ...
Variable Name
Label - prompt the
user to enter their
Name
lblEntireName
ENTER YOUR FULL
NAME:
Label for Choice of
Stories
lblAB
CLICK STORY A or
B
Shape around
Choice of Stories
shpAB
Text Box for Entire
Name
txtEntireName
Empty
Text Box for Story
txtPart1
Story type in
your own
story.
Command for
StoryA
cmdStoryA
STORY A
Command for Story
B
cmdStoryB
STORY B
Command for Help
and Hints
cmdHelpHints
HELP and HINTS
Command for Clear
cmdClear
CLEAR
Command for Exit
cmdExit
E&XIT
Click on the New Form icon twice. You should have two more forms appearing on
top of the MainStory form. On the menu bar click on View and then Projects. You
will see all the forms listed.
Click on form2.
Press F4 to show the properties.
CAPTION FOR FORM2: Story Line A
NAME: frmStoryA.
Click on form3.
Press F4 to show the properties.
CAPTION FOR FORM3: Story Line B
NAME: frmStoryB.
Create 4 more forms and change the properties as indicated. NOTE: You may
change the form Captions and Names as to the story lines of your stories. You may
want to keep the names of the forms to keep track of which forms are being used.
Form 4 - CAPTION: Story Line A1
NAME: frmStoryA1
Form 5 - CAPTION: Story Line
A2
NAME: frmStoryA2
Form 6 - CAPTION: Story Line
B1
NAME: frmStoryB1
Form 7 - CAPTION: Story Line
B2
NAME: frmStoryB2
You can add more forms as your story progresses.
1. Go to frmMainStory
2. Now you are going to program the first form so that subsequent story lines
can be accessed by the user of your action adventure story. The code that
you will be using to execute these functions include: Load, Show, Hide and
Unload.
Later on in the help section of the program you will be learning the properties of a
form.
Double Click on the command button STORY A. Type in the following code:
'Story Line A will display the next form and part of the action adventure story
Load frmStoryA
frmStoryA.Show
Double click on the command button STORY B. Type in the following code:
'Story Line B will display the next form and part of the action adventure story
Load frmStoryB
frmStoryB.Show
The meaning of the code....
Load - places the form into memory but it does now show the form. The properties
and controls in code also get loaded into the computers memory. Although load
uses up computer memory your program will respond faster to the user.
Syntax
Load <FormName>
Show - shows the form on the screen. Before the form can be shown Visual Basic must
check that the form is loaded into memory.
Syntax
<FormName>.Show
Hide
In this program you will also need to hide the forms when you are accessing help. You
will be using
<FormName>.Hide
For our purposes we will be needing the users Entire Name and possibly other
information throughout the program. Therefore we will not be using the command Unload.
Unload - removes the form from the computers memory. Any information that is in current
form being used is unloaded or lost.
Syntax
Unload <FormName>
Colouring the background of a form. Double Click on the command box (cmdStoryA)
"STORY A".
Add in the following code.
'This will change the background color of Story Line A
frmStoryA.BackColor = RGB(10, 20, 100)
If the programmer would like to change any properties of an object from form to form the
GENERAL SYNTAX is:
FormName.ControlName.Property = Value



you can use . periods or exclamation marks to separate the form names from the
control.
why? periods are generally used by older versions of VB .
!exclamations are generally used by newer versions of VB.
Other examples will be discussed later in this exercise.
It is now time to Run the program. Choose either STORY . If you choose STORY A you
should see the form Story Line A1 appear with a blue color.
STORY LINE A FORM
Re-create the Story Line A form as shown below.
Object
Name Property
Label for Welcome
Title
lblStoryA
Welcom.e...
Label for the Title
lblStoryAA
to Story Line A
Text Box for the
Story
txtStoryA
Label for Choice of
Stories
lblAB
CLICK STORY A1 or
A2
Shape around
Choice of Stories
shpAB
Make the shape oval
Label for the Entire
Name
lblTheName
*In properties
change the size of
the label box to
Autosize.
Picture of the Earth
picEarth
Command for
StoryA1
cmdStoryA1
STORY A1
Command for
StoryA2
cmdStoryA2
STORY A2
Command for Main
Screen
cmdMain
BACK TO THE MAIN
SCREEN
Command for Help
cmdHelpHints
HELP and HINTS
Command for Clear
cmdClear
CLEAR
Command for Exit
cmdExit
E&XIT
Referring to Objects in Other Forms
Text
Property
Caption Property
Type in
Story A
Variable Name
In the Main Story form a text box called txtEntireName allows the user to enter in their full
name. The idea is for the name to appear on the second form and throughout the
program in other forms. In order to do this you require the general syntax described
above. Double click on the Story Line A form. Type in the following code in the Sub Form
Load:
' the name entered in the Main Story
form will appear in the label box in
Story Line A
lblTheName.Caption =
frmMainStory.txtEntireName.Text
Explanation:
lblTheName.Caption - is a label on the
form of Story Line A where the name
will appear.
= - assigns the caption to the main form's textbox
frmMainStory.txtEntireName.Text - refers to the Main Story's text box where the name
was originally entered.
STORY LINE B
Created a form similar to Story Line A's form. See if you can design the form differently.
Don't forget to add color and pictures. The same coding can be used but make sure to
change the names of the story lines to B1 and B2.
THE HELP and HINTS FORM
The help file will assist the user in keeping track of the program.
Create a help form. Below is a simple example.
You can use any captions, labels or commands as needed.
SIZE OF THE FORM
Having the help form appear half the size of the screen during run time.
Go to the Main Form and double click on the help command. Type in the following code:
frmHelp.Height = Screen.Height / 2
Screen.Height/2 cuts the default height of the form in ½
The default for forms are as they appear when you run the program.
This allows the user to stay in the Action Adventure story and see part of the main form
while getting some help and hints about the story.
A help command could be added to each form.
With the code above you are now ready to complete the story with as many forms as
your story requires. Have fun and good luck!
EXERCISES
Save all programs as per your teachers instructions or use handbook convention and the
file names below.
or
Save the file (.frm and .vbp) as: The first three characters of the file name and then the
first five characters of your last name.
Programmers Last Name is: Golds
File Name: ArtPrices.
Save As: ArtGolds
My Favorite Month
Write a program that accepts what month of the year the user enjoys the most.
Have the user enter in their full name and display their favorite month.
Use the following Program Specifications:
1. Make a sketch of the interface before you begin the program. (5 points)
2. Complete the interface with the following properties table: (10 points)
Object
Name Property
Text
Property
Caption Property
Variable Name
First Name Label
lblFName
First Name
Middle Name Label
lblMName
Middle Name
Last Name Label
lblLName
Last Name
Title of the Program
lblTitle
Welcome to my first
Visual Basic
Program .....
First Name
txtFName
empty
Please Enter your
First Name
f_FName
Middle Name
txtMName
empty
Middle Name
f_MName
Last Name
txtLName
empty
Last Name
f_LName
Favorite Month
txtFMonth
empty
Favorite Month
f_Month
Process Display
Button
cmdDisplay
DISPLAY THE
MONTH
Clear Button
cmdClear
CLEAR
Exit Button
cmdExit
E&XIT
1. In order to display the information you should use the message box. Make sure
that when you display the users information that it has the proper spacing.
2. Change the form colour and title the form.
3. Change the text boxes to the same colour.
4. Declare the variables in general declarations.
5. Assign the text boxes to the proper variable names.
(2 points each = 10 points)
6. The program runs correctly (5 points)
TOTAL = 30 points
File Name: Month
the Pet Purchasing Program
INDEPENDANT RESEARCH: Find out the cost of your favorite pet, the vetrinary bills per
month, food costs and accessories. Make a list of at least 5 accessories and their costs.
Write a program that allows the user to enter in the type of pet, name of the pet, cost of a
pet, veterinary costs per month, food costs and accessory costs for the pet (minimum 5
accesories). The tax must be calculated on each item spent.
Sketch the interface of your pet purchasing program.
Program Specifications:Use val and constants, declare the appropriate variables and
assign them to any text boxes.
Use the format currency function to display the final cost a pet.
Properties Table
Object
Name Property
Text
Property
Caption Property
Variable Name
Title of the Program
lblTitle
THE PET ORDER
FORM
Type of Pet Label
lblPetType
Type of Pet
Name of Pet Label
lblPetName
Pet Name
Enter Information
Label
lblName
Enter the information
below.
Type of Pet Text
Box
txtPetType
empty
Pet Type
f_PetType
Name of Pet Text
Box
txtPetName
empty
Pet Name
f_PetName
Price of Pet Text
Box
txtPrice
empty
Price of Pet
f_Price
Veterinary Cost
Text Box
txtVetCost
empty
Veterinary Cost
f_VetCost
Food Cost Text Box
txtFoodCost
empty
Food Cost Per
Month
f_FoodCost
Accessory 1 Text
Box
txtAccess1
empty
Accesory Group 1
f_Access1
Accessory 2 Text
Box
txtAccess2
empty
Acessory Group 2
f_Access2
Accessory 3 or
more
programmers
decision
Text Boxes
Subtotal Text Box
txtSubTotal
empty
SubTotal
f_SubTotal
Tax Text Box
txtTax
empty
Tax
f_Tax
Total Text Box
txtTotal
empty
Total
f_Total
Process Display
Button
cmdDisplay
THE GRAND TOTAL
Clear Button
cmdClear
CLEAR
Exit Button
cmdExit
E&XIT
Happy Birthday
Write a program that asks for a person's Birthdat as month-day-year. Your program
should output the number of days that they have been alive. The current year
represents the year that you are writing this program in.
Program Specifications: variable declaration, calculations and correct age output.
File Name: Birthday
I Love Mathematics
Most of us enjoy a good challenge from calculations in math. Write a program that
accepts 4 numbers from a user and performs calculations written below.
Make a Sketch of the interface.
Complete the program using the Properties Table below.
Object
Name Property
Text
Property
Caption Property
Variable Name
First Number Label
lblNum1
First Number
Second Number
Label
lblNum2
Second Number
Third Number Label
lblNum3
Third Number
Fourth Number
Label
lblNum4
Fourth Number
Answer Label
lblAnswer
Answer
First Number Text
Box
txtNum1
empty
f_Num1
Second Number
Text Box
txtNum2
empty
f_Num2
Third Number Text
Box
txtNum3
empty
f_Num3
Fourth Number Text
Box
txtNum34
empty
f_Num4
Answer Text Box
txtAnswer
empty
f_Answer
Display Button
cmdProcess
PROCESS THE
EQUATION
Clear Button
cmdClear
CLEAR
Exit Button
cmdExit
E&XIT
The code to sum all four numbers entered in the text boxes would be attached to the
PROCESS THE EQUATION button. The code would appear as follows.
Private Sub cmdProcess_Click()
Dim f_Num1 as Integer, f_Num2 as Integer, f_Num3 as Integer, f_Num4 as Integer
Dim f_Answer as Integer
f_num1 = Val(txtNum1.Text)
f_num2 = Val(txtNum2.Text)
f_num3 = Val(txtNum3.Text)
f_num4 = Val(txtNum4.Text)
txtAnswer.Text = f_Num1 + f_Num2 +f_Num3 + f_Num4
End Sub
Why is Val used in the assignment statements?
Write the expression in your notebooks for the following equations. Then write the code
for the following equations. You may need to have 9 more command buttons.
Description
Expressions
1
the sum of the first two numbers times the sum of the
last two numbers
(num1+num2) *(num3 +num4)
2
the product of all the numbers
3
the average of all the numbers
4
the sum of the squares of the numbers
5
four times the first number minus two times the last
number
6
the first number minus the second number then times
the third number
7
the sum of the halves of each number
8
the average of the cubes of each number
9
the sum of the square root of each number