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Introduction to VB Programming. Chapter 3. Quotes for Today. When faced with a decision, I always ask, “What would be the most fun?” Peggy Walker It is a capital mistake to theorize before one has data. Arthur Conan Doyle. Creating a Project With Code. A Simple Program.

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Introduction to vb programming

Introduction to VB Programming

Chapter 3


Quotes for today
Quotes for Today

When faced with a decision, I always ask, “What would be the most fun?”

Peggy Walker

It is a capital mistake to theorize before one has data.

Arthur Conan Doyle


Creating a project with code

Creating a Project With Code

A Simple Program


Two types of applications 2 of the many
Two Types of Applications(2 of the many)

  • Windows Applications

    • Access Windows environment

  • Console Applications

    • Access DOS environment


Anatomy of a simple program

‘ Welcome1.vb

‘ Simple Visual Basic program

Module modFirstWelcome

Sub Main() ‘entry point of program

‘() indicates a procedure

Console.WriteLine(“Welcome to Visual Basic!”)

End Sub ‘Ends Main Procedure

End Module ‘Ends modFirstWelcome

Anatomy of a Simple Program





Class Method String


A module
A Module

  • Collectively called a module definition

  • Console modules consist of logical groupings of procedures

    • simplify program organization

  • Convention:

    • Begin all modules with “mod”

      • Example: modWelcome

    • Not case sensitive


An identifier
An Identifier

  • A series of characters

    • Consist of letters, digits & underscores (_)

    • Not case sensitive

  • Cannot

    • Begin with a digit

    • Contain spaces

  • Examples

    • Valid: modFirstWelcome, num1, SalesTax

    • Invalid: 123xyz, My Tax, 753 Room

Primitive Data Types:

Boolean Byte Char

Date Decimal Double

Integer Long Sbyte

Short Single String

Uinteger Ulong UShort


A keyword reserved word
A Keyword (Reserved Word)

  • A particular word that has a specific meaning within each programming language

  • Examples:

    • Module, End, Sub, If, For, Loop

    • For more examples refer to Pages 76

    • Not case sensitive, but VB will automatically convert to “proper” case


Keywords or reserved words
Keywords (or Reserved Words)

  • Do not try to use these words as variable names.

    • Misspelling a keyword may cause a syntax error

    • VB will assume you are creating a new identifier.

    • But…the program will not work correctly.


Spacing whitespace
Spacing (Whitespace)

  • VB ignores spaces and tabs between identifiers

    • Vertically and horizontally

  • Use vertical blank lines, tabs and horizontal spaces to make projects easier to read.



  • Console.WriteLine(“Hi!”)

    • (“Hi”) is the argument

      • Note the dot notation…

    • Classes organize groups of related methods

      • WriteLine is the method

      • Console is the class to which the method belongs


The simple program revised
The Simple Program Revised

  • Pg 78;

    • File>New Project>Console Application

    • Name = WelcomeConsole

    • Program Name = Welcome1.vb

    • Reserved words are blue, text is black

    • Change name of Module to ModWelcome

    • Writing code

    • Run program

  • Tools>Options personalizes environment



  • IntelliSense

    • When the dot (.) is keyed after Console, a list of available methods is displayed

    • Options

      • List Members – lists the members of an object.

      • Parameter Info – Lists the members of an object.

      • Quick Info – displays information in tool tips as the mouse rests on elements in your code.

      • Complete Word – completes typed words

      • Automatic Brace Matching – adds parentheses or braces as needed.


Documenting code

Documenting Code



Consistency consistency
Consistency, Consistency!

  • Just as important as commenting code

  • Reduces reader frustration

  • Makes comments & code

    • easier to understand

  • Makes debugging

    • easier

    • faster


Commenting code
Commenting Code

  • Used to identify the purpose of a piece of code, the author, creation date, requirements

    • Required in this class!

  • Indicator is the apostrophe.

    • Ex. ‘This is a comment.

  • The default color for VB is green.

    • Note: for those of you who might be colorblind to green, the comment color property can be changed within the environment controls. But…Don’t do it in here or in the Lab…



  • Explains

    • what is going on or

    • what is being described

  • Denoted by a single quotation mark (‘)

  • Example

    ‘Input variable

    Dim Principal As Single‘The original loan amount

    Dim Address As String‘Shipping address for client


Comment levels
Comment Levels

  • Application Level

    • Name - name of application

    • Author/Company - who created it

    • Add-ins - are there any other modules or code objects necessary to run this program

    • Purpose of Program - what is the program supposed to do?

    • System Requirements - what is the system upon which this program will operate


Comment levels1
Comment Levels

  • Module Level

    • Necessary when multiple programmers are working on a project.

    • Useful when planning to reuse the code.

    • Same parameters as before, but with addition of

      • Dependencies –

        • declares what is required as input for the module to work (Passing parameters)


Comment levels2
Comment Levels

  • Procedure Level

    • Used to describe to programmers what the procedure does and how it does it.

    • Used for user-defined and non-obvious procedures and functions.

      • Ex. A new form of the Square Root function

    • Helps during a multi-programmer project

      • Lets other programmers know who to contact when there are questions or problems with the code.


Comment levels3
Comment Levels

  • Code Level

    • To specify what a piece code is doing

    • To specify that a piece of code needs further attention

    • Use these as suggestions for consistency

      • ‘ Generic comment - explanation

      • ‘??? Questionable code - useful for debugging

      • ‘!!! Code requires attention - useful for reminders or where to provide additional work.

      • ‘-MLM- Include your initials for comment referencing


Comment comment comment
Comment, Comment, Comment!

  • Provides

    • meaning to code

    • additional information to other programmers

    • reasons why one method was used over another for future maintenance

  • Makes Maintenance EASIER!


Console writeline revisited
Console.WriteLine Revisited

  • Dim number1 as Integer

  • Number1 = Console.ReadLine()

    • ReadLine() is a method that causes the program to pause and wait for user input.

    • After the value is entered by keyboard, the user presses the Enter key to send the value to the program.

  • Example:

    Console.WriteLine(“The sum is ” & sumofNumbers)


Basic components of vb

Basic Components of VB

Variables &Assignment Statements



  • A Variable

    • Is a temporary storage location for information

    • Clears upon exit of either the program or the procedure

    • Examples:

      • Sum SalesTax SquareRoot

      • Count Sales_Tax Principal


Variable declarations
Variable Declarations

  • Name of a variable is any valid identifier

    • Cannot be keywords

    • Maximum length is 255 characters

    • Must begin with a letter

    • Must contain only letters, numbers and underscores.

    • VB is not case sensitive so

      • uppercase and lowercase letters are treated in the same way.

  • Variable’s Type - what type of information each variable may contain.


Variable declarations1
Variable Declarations

  • Declaration of Variables

    • Provides the Variable Name and its data type

    • Ex. DimsumAsInteger

    • VB always initializes variables to Zero for numbers and the Null set for characters and strings

Variable Identifier

Variable’s Data Type


Variable declarations changes from vb6 to vb net
Variable Declarations Changes from VB6 to VB.Net

  • New data types

    • Char

    • Unsigned Integers

      • Ulong - 8 bytes

      • Uinteger - 4 bytes

      • Ushort - 2 bytes

      • Sbyte - 1 byte

  • Lost data types

    • Currency

    • Variant – A great thing!

    • Image (use PictureBox instead)

  • Note about Unsigned Integers - They are non-CLS compliant and not supported by all .Net languages

    • --Avoid using--


More changes from vb6 to vb net
More Changes from VB6 to VB.Net

  • Replacements

    • RadioButtons replaces OptionButton

    • GroupBox replaces Frame

    • SelectedIndex in ListBox replaces ListIndex

    • Images are added to PictureBox’s by using the System.Drawing.Image.FromFile method


Variable declarations2
Variable Declarations

  • Declarations made

    • in the General DeclarationSection are available throughout the entire program.

      • This is Global Scope.

    • inside a procedure are available only within the procedure

      • This is Local Scope.

  • Both will be discussed in more detail later.


Assignment statements
Assignment Statements

  • Assigns a value, variable or expression to a variable

    • Syntax: VariableName = value or variable or expression

    • A variable is placed on the left of the equal sign (=)

      • Think of the “=” as “takes on the value of”

    • The value to be stored in the variable appears on the right.

      • The value is made up of the following:

        • A value

        • An expression

        • A variable (Identifier)

    • Ex. sum = count + 3


Assignment statements1
Assignment Statements

  • When a value is stored in a variable (on the left side of the assignment operator), it replaces the existing data.

    • This is known as destructive read-in.

      • Ex. sum= 3 + 5

  • When a variable is used (on the right side of the assignment operator), the value stored in the variable is preserved.

    • This is known as nondestructive read-in.

      • Ex. sum = count + 1


Arithmetic in vb

Arithmetic in VB

And Operator Precedence


Arithmetic in vb1
Arithmetic in VB

  • The arithmetic operators used in VB use several special characters:

    • ^ indicates exponentiation

    • * indicates multiplication

    • \ indicates Integer division

  • Arithmetic expressions are written in straight-line form.

    • Ex. a ^ b


Arithmetic in vb2
Arithmetic in VB

  • Most operators are binary, requiring 2 operands.

    • Ex. sum + value

  • However, the unary operator (+, -) requires only one operand.

    • Ex. -3, +3


Special arithmetic operators
Special Arithmetic Operators

  • Integer Division (\)

    • Supports Byte, Short, Integer, or Long Data Types

    • results in an Integer result

      • Ex. 8 \ 2 = 4 and 9 \5 = 1

    • Note: Floating point numbers are coerced to Long (a narrowing conversion) quietly (behind the scene) before Integer Division takes place.

      • Ex. 7.7\4 = 2 because 8 \ 4 = 2.

      • the whole part of the floating point result and the rest is truncated.



Special arithmetic operators1
Special Arithmetic Operators

  • Modulus (Mod) results in an Integer remainder after Integer Division.

    • Ex. X Mod Y = the remainder after X is divided by Y. If the result is 0, then X is evenly divisible by Y.

    • Ex. 10 Mod 4 = 2; 10.8 Mod 4 = 3

  • Note:

    • if the Result is defined as a floating point, the result will be the floating point remainder

    • Use of the Mod with floating point will introduce a hidden conversion from Single or Double to Integer – possible loss of data



Modulus examples


4 ) 10




4.8) 10.0



4.8 rounds to 5

Modulus Examples


Modulus examples1


5 ) 12.6



Modulus Examples


9.35) 47.90




Operator precedence
Operator Precedence

  • Reflects a hierarchical order

  • Aids evaluation of expressions

    • Boolean Relational Operators have the lowest precedence. (to be discussed later)

  • Using parentheses ( )is recommended to:

    • Avoid syntax errors

    • Clarify the meaning of the comparison

  • Evaluation Trees are used to check logic


Order of operator precedence
Order of Operator Precedence

See Appendix A


Line continuation
Line Continuation

  • Permits a long line of code to be divided into two lines.

    • Must be surrounded by at least one space

    • Must not have anything after the “_”

  • Improves readability

  • Example:

    MessageBox.Show(“The Square Root of 2 is “ & root, _ “The Square Root of 2”)


String concatenation
String Concatenation

  • Concatenation Operator is the ampersand “&”

  • Is a binary operator

  • Combines two strings

  • Example:

    MessageBox.Show(“The square root of 2 is ” & root)

    • Note: If the variable (in this case root) is not a String, VB will automatically create a String representation of the argument.


Common programming errors

Common Programming Errors

Syntax Errors


Syntax errors
Syntax Errors

  • A syntax error, also called a compile error, is a violation of a language’s syntax.

  • Occurs when:

    • statements are missing information

    • statements have extra information

    • names are misspelled

    • punctuation is missing (missing parentheses)


Syntax errors help
Syntax Errors - Help

  • VB

    • indicates syntax errors by underlining the suspect code with a red line

    • provides an explanation in the Task List window

    • Provides a tool tip explaining what VB.Net thinks is wrong, if you rest the mouse on the error.



Classes &