3
Chapter 3
Programming
Fundamentals
Writing Code
By Carlotta Eaton
Exploring Microsoft Visual Basic 6.0
Copyright © 1999 Prentice-Hall, Inc.
Objectives...
1. Use the Sub command to create event
procedures and general procedures
2. Use variables and differentiate data types
3. Differentiate between a variable and a
constant
4. Differentiate between Dim and Static
statements
5. Use help to find appropriate predefined
function, and then utilize the function
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Objectives
6. Convert an algebraic formula to a Visual
Basic statement; Write a program that
calculates
7. Use the If...Then or Select Case
statements to write code that makes
decisions
8. Write code that repeats using Do...Loop,
For...Next, or For Each ...Next looping
statements
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Modules and Procedures
Code - the man behind the curtain
Modules - large units of code that
comprise a Visual Basic application
Form Modules - contains a form and
code for the form
Standard Modules - contains code that
is typically used by other modules
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Modules and Procedures
Procedures - smaller units that comprise a
module
Event procedure - automatically invoked by
an event
General procedure - explicitly invoked by
another procedure
Private procedure - accessible from within a
module
Public procedure - accessible from anywhere
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The Code Editor Window
View and edit code
Views
 Full
Module View
 Procedure View
Features
 Auto
List Members
 Auto Quick Info
 Auto Syntax Check
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The Code Editor Window
Object List Box
Procedure List Box
Full Module View
button
Auto List Members
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Basic 6
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The Code Editor Window
Help
window
Syntax error in Red
Procedure view button
Error message box
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Basic 6
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Syntax Boxes
Syntax for a Visual Basic statement is
shown in a syntax box
Reserved words are shown in bold
Programmer named words are shown in
italics
See next slide for an example
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The Sub Statement
Private Sub controlname_eventname( )
Statements
End Sub
Where
Private is the default procedure type
Sub indicates beginning of procedure
controlname is name of associated control
_ (underscore) required separator
eventname is name of corresponding event
( ) set of parentheses is required
End Sub indicates end of a procedure
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The Sub Statement
Example
Private Sub cmdCalcTriangle_Click
Dim Base As Single
Dim Height As Single
Dim Height As Single
Area = 1 / 2 * (Base * Height)
End Sub
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Declarations, Variables,
and Constants
Variable - a uniquely named storage
location that contains data that
changes during program execution
Constant - a uniquely named storage
locations that contains data that does
not change during program execution
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Declarations, Variables,
and Constants
Rules for Naming Variables
Must begin with an alphabetic character
 Can’t contain a period or type-declaration
characters such as
%, &, !, #, @ or $
 Must be unique with same scope
 Must be no longer than 255 characters
 Should not reserved word (See Appendix A)

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Declaring Variables
Declaration statement - nonexecutable
code that sets aside storage locations
for future use
Local variables - declared within a
procedure or function
Global variables - declared in the
general section of the application
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Declaring Variables
Declare variables using the Dim or
Static statements
Dim statement - value of variable
preserved only until procedure ends
Static statement - value of variable
preserved the entire time the
application is running
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The Dim Statement
Dim variablename As datatype
Where
Dim is required
variablename should be a descriptive name
As is required
datatype is one of the following types:
Boolean, Byte, Date, Integer, Long, Single,
Double, Currency, String, Object or Variant
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Declaring Variables
Data Types
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Boolean - True or false
Date - From Jan 1, 100 to Dec 31, 9999
Integer - Numbers without a decimal point
Long - Long integer
Single - Numbers with a decimal point
Double - Long Single
Currency - Dollar amounts
String - Character and alphanumeric data
Object - Any object reference such as Word document
Variant - default, can hold any data type
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Assigning Values to Variables
Variablename = value
Where
variablename is the descriptive name of the variable
= is the assignment operator
value is the value the variable will contain
Examples:
Number1 = 5
FirstName = “Steve”
LoanAmount = 67.38
Length = 17.8
Note: Order is important. Variable name always on the left, and value
on the right.
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Declaring Constants
Const constantname As datatype = value
Where
Const is required
constantname is the descriptive name of the constant
As is required
datatype is the type of data the constant will contain
= is the assignment operator
value is the value of the constant
Examples:
Const Pi As Single 3.14159265358979
Const MaxNumber As Integer = 100
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The Wind Chill Project
Write a program that calculates the
wind chill temperature
Find a formula UST Today Weather Web site
www.usatoday.com/weather/wchilform.htm
 Inputs: Wind Speed and Temperature
 Outputs: Wind Chill Temperature
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The Wind Chill Project
Orginal formula
 WC
= 0.0817(3.71(V **0.5) + 5.81 0.25V)(T - 91.4) + 91.4
Visual Basic statement
 WC
= 0.0817 * (3.71 * Sqr(V) + 5.81 (0.25 * V)) * (T - 91.4) + 91.4
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Functions
Function - unit of code that returns a
value
Build-in Functions
 Sqr
- square root
 Rnd - random number generator
 Int - returns integer portion of a
number
 Val - converts a string to a value
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Functions
Locating built-in functions
 Open
the Functions online reference
book or search for a function by name
Programmer-written functions
 Write
your own functions using the
Function statement
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Basic 6
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The Function Statement
Private Function function-name (argument1, argument2....)
statements
End Function
Where
Private or Public is required
Function indicates the beginning of a function
function-name is the name that will be used to call the function
( ) parentheses are required around the argument list
argument1, argument2 are optional variables needed to perform
the calculation or actions needed for the function
End Function indicates the end of the function
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WindChill Function
Private Function WindChill( )
‘Purpose: Calculate the Wind Chill
‘Reference: National Weather Service
Dim V As Integer ‘Wind Speed Velocity
Dim T AS Integer ‘Temperature
V = hsbSpeed.Value
T = hsbTemperature.Value
WindChill = 0.0817 * (3.71 * Sqr(V) _
+5.81 - (0.25*V)) * (T-91.4)+91.4
End Function
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WindChill Function
When the cmdCalculate button is clicked,
the WindChill function is executed
Private Sub cmdCalculate_Click()
WC = WindChill()
txtWindChill.Text = Cint(WC)
End Sub
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The Wind Chill Project using
Functions and Procedures
Hands-On Exercise 1
Create a New Project
 Create the Controls for Temperature Input
 Create the Controls for Wind Speed Input
 Create the Controls for Wind Chill Output
 Create the Image Control
 Add Banner Comments
 Add the Wind Chill Function
 Add Temperature and Speed Procedures
 Save, Run, Test your Project

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Basic 6
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Controlling your Application
 Sequence

Functions and Procedures
 Selection
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If...Then...Else statement
Select Case statement
 Repetition
For...Next Loop statement
 For Each...Next statement
 Do Loops

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Basic 6
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Learning to Add Project
Specification for the Game
purpose of the game is to practice addition
skills
 use numbers between 0 and 9
 user is a pre-school age child, in kindergarten,
or in first grade
 user may not yet know how to read
 game should give visual feedback indicating
correct or incorrect answer

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Learning to Add Game
Reward
for
correct
answer
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Basic 6
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Learning to Add Game
Image for
incorrect
answer
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Basic 6
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Design the User Interface
Prototype - a partially completed
version of an application that
demonstrates the “look and feel” of
the finished product
Usability Testing - end user or client
tests design of user interface using a
prototype
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Basic 6
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Making Decisions with the
Learning to Add Game
Hands-On Exercise 2
 Create
the Learning to Add Project
 Add Controls to Display the Problem
 Set Common Properties
 Set Individual Control Properties
 Add More Images and Set Properties
 Add Picture Box Controls for Icon
Buttons
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Basic 6
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Making Decisions with the
Learning to Add Game
Hands-On Exercise 2 (continued)
 Add
Banner Comments
 Add the Load Form Procedure
 Add the Checkmark Picture Procedure
 Add the Arrow Picture Procedure
 Run and Save your Project
 Test and Debug your Project
 Print your Project Code and Exit
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Basic 6
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For...Next Loop Structure
For counter = start To end Step increment
statements
Next counter
Where
Counter is tested to see if less than end.
If so, repeat loop again. If not, go to
statement after Next.
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Basic 6
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Do While...Loop Structure
Do While condition
statements
Loop
Where
The condition is tested, and if true the loop is
repeated. When the condition is false, the loop
statements are skipped the statement after Loop
is executed.
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Do Until...Loop Structure
Do Until condition
statements
Loop
Where
The condition is tested, and if false the loop is
repeated. When the condition is true, the loop
statements are skipped the statement after Loop
is executed.
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Basic 6
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Do Until...Loop Structure
‘Calculate the factorial of a number
given by user
Dim Factorial As Double
Dim I As Integer
User gives
number
I = 1
Factorial = 1
Do While I <= Val (txtAnswer.text)
Factorial = Factorial + 1
I = I + 1
Loop
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Loops with the Marching Band Project
Hands-On Exercise 3
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Create the Marching Band Project
Add Command Buttons and a Timer
Add Controls to Display the Band
Add Banner Comments
Add Code for Buttons and the Form
Add Code to Add Animation
Run, Save, Test and Debug Your Project
Create a Copy of the Project
Change Animation Code
Update, Run, Save, Test and Debug
Exit Visual Basic
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Basic 6
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Summary ...
 Fundamental programming demonstrated
 Variables vs. Constants
 Data types
 Local vs Global variables
 Functions and Procedures
 Control structures: sequence, selection and
repetition
Exploring MS Visual
Basic 6
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Summary
Statements
 Dim,
Static, Const
 Public, Private
 Sub, Function
 Do...Loop, Do While...Loop, Do Until...Loop
 For Each...Next, For...Next
 If...Then...Else
 Select Case
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Basic 6
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Practice with Visual Basic
1. Learning to Subtract Game
2. Wind Chill in Celsius
3. Heat Index
4. Rock, Paper, Scissors Game
5. Creating Variables
6. Event-driven Programming
7. For...Next Loop
8. Digital Clock
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Basic 6
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Case Studies
Calculate a Formula
Weather Calculations
More Fun and Games
More Web Resources for Visual Basic
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