Getting Started with VB 6.0

Visual Basic is an object-oriented programming language that uses the Microsoft Windows platform. The programs that are created using Visual Basic will look and act like standard Windows programs. Visual Basic provides one the tools to create windows with elements such as menus, text boxes, command buttons, option buttons, list boxes and scroll bars.

This tutorial does not completely cover all ‘basis' of Visual Basic. This is just basically an over view to learn a bit about VB. Databases, Crystal Reports and others are not included to keep this tutorial under 500 pages and to keep carpal tunnel from occurring.

This tutorial was written assuming that you possibly have some programming knowledge. Like what an IF / THEN / ELSE statement is. So, if you have taken Basic Or QBasic, that's ideal before reading this tutorial.

Also, it would not help much reading this tutorial if you do not have VB 6.0 on your computer. I think you can download it from Kazaa Lite (kinda big though) if you do not have it. But get it if you don't have it, open it and read this.

Procedural vs. Non-Procedural Languages

Procedural Languages - Programming languages that have a set plan that you follow to execute a program. You have a series of statements that you execute where you start with the first statement. The statements are executed in order from beginning to end. The program terminates after the last statement is executed.

• FORTRAN


• COBOL


• BASIC


• C


• PASCAL

Non-Procedural Languages - Object-Oriented programming languages that are Event-driven. Here you don't just have a series of statements that are executed, you have several choices of different things you can do in a program. You select the event that you want to occur. Only the code for that event is executed.

• Visual Basic


• C++


• DELPHI


• JAVA

Labels, Text Boxes and Command Buttons

Label - A control that is used to display text as a caption. Labels cannot be altered by the used. They are simply used to display headings and results of processing as well as other information on a form. Labels begin with a .lbl extension.

• lblName


• lblAddress


• lblCity

Text Box - Control that is used to enter information onto a form. Text boxes can have focus and are the primary means of providing input to a project in Visual Basic. Text boxes begin with the prefix of .txt

• txtSponge


• txtBob


• txtNum1

Command Buttons - Control used to activate a procedure. When a command button is clicked on or activated using an access key, and event will take place (the code behind the command button is executed.) Command buttons begin with the prefix .cmd

Types of Errors

• Syntax Errors - Compiler errors that occur when your project code is converted to machine language. These are errors that occur when you violate the syntax rules of Visual Basic. VB will highlight these errors in RED.


• Run-Time Errors - Errors that occur when programming is actually executing. These types of errors will cause the program to terminate abnormally. Examples of run-time errors are division by zero, or trying to do calculations with non-numeric data. VB will display a dialog box, pull up the affected code on screen, and highlight where the error occurred in YELLOW.


• Logical Errors - Errors which allow your project to run, but will produce incorrect results. These errors are tough to find and debug because no error message will be displayed or highlighted. You will have to dig through the code to find the error(s). Examples would be : Adding 3 instead of subtracting 3, or displaying the wrong info in a label.

Special Functions and Methods

VAL() - A function that will convert a string to a numeric value. It begins with the left-most character of the string. If that character is a numeric digit, decimal point or a sign, VAL will convert the character to a numeric and move on to the next character. Once a non-numeric character is found, the VAL function will stop.

PrintForm - A method that will print the current form on the printer. This is executed during run-time.

FORMAT - This is used to format a variable. Variables can be formatted as fixed numbers, currency and percents.

< var > = FORMAT( < var > ," < type of format > ")

lblTotal = Format(lblTotal,"Currency") 'Formats number with a $ and two decimal places. 
lblArea = Format(lblTotal,"Fixed") ' Formats number as decimal with two decimal places.
LblPctTotal = Format(lblPctTotal,"Percent") 'Formats number as percent with two decimal places and adds % to end of number.

FormatCurrency - This function will take a number and format it as currency with two decimal places and a $ sign. There is only one argument, the number you want to format.

lblSum = FormatCurrency(NumToFormat)
lblTotalAmount = FormatCurrency(curTotal)

FormatNumber - This function will format a number as a decimal with a set number of decimal places. The first argument is the number you want to format. The second is the number of decimal places you want the number to have.

lblTotal = FormatNumber(NumToFormat,NumOfDecimalPlaces)
lblSum = FormatNumber(Sum,2)

FormatPercent - This function will take the number and format it as a percent. The function will multiply by 100 and add a percent sign to the end of the number. The number by default will be rounded to zero decimal places unless you specify a 2nd argument.

lblTotalPct = FormatPercent(NumToFormatAsPercent)
lblSumPct = FormatPercent(NumToFormatAsPercent, NumOfPlaces)
lblCurrInterest = FormatPercent(CurrentInterest)

FormatDate and Time - This function will take a string and format it as a Date, Time or both. The first argument is the date or time to be formatted. The 2nd argument is the format of date/time you wish to use.

lblCurrentDate = FormatDateTime(StartingDate, vbShortDate)
lblCurrentDate = FormatDateTime(EndingDate, vbLongDate)
lblCurrentTime = FormatDateTime(StartingTime, vbShortTime)
lblCurrentTime = FormatDateTime(StartingTime, vbLongTime)

Variables and Constants

Option Explicit - A statement that will force you to declare all variables used in your program. If you fail to declare a variable, an error will occur when you run your program.

DECLARING A VARIABLE:

When you declare a variable, VB reserves space in the computers memory and assigns it a name. When declaring variables, there are certain rules that must be followed.

• Variables must begin with a letter.


• Can consist of letters, digits and the underscore.


• Cannot contain any spaces or periods.


• Must be 1 to 255 positions in length


• Cannot use Reserved Words as variable names.

DIM inNum1 as Integer
DIM strName as String
DIM curTotalAmount as Currency

DECLARING A CONSTANT:

Constants are always declared using the keyword CONST. You give the constant a name, data type and value. Once a value is declared a constant, it can never be changed again in the program. Trying to change a constant will cause an error. The rules for variables also apply to constants.

DIM sngPI as Single = 3.14
DIM curTaxRate as Currency = .07

NAMED CONSTANTS - These are constants that you name yourself with the CONST keyword. Named constants can come in the form as numeric constants and string constants.

NUMERIC CONSTANTS - Constants that can contain only the digits 0-9, a decimal pt and sign.

STRING CONSTANTS - Constants that can contain letters, digits, and special characters such as @#$%^&*. String constants must be enclosed in double quotes.

INSTRINCT CONSTANTS - System-Defined constants that are built into VB.

• vbRed


• vbGreen


• vbBlue


• Checked


• vbYellow


• UnChecked

SCOPES OF VARIABLES:

3 LEVELS OF SCOPE:

• Global Variable - Variable accessible anywhere in VB, in all forms that are a part of the project.


• Module-Level Variable - Variable that to all procedures on the form in which it is declared.


• Local Variable - Variable accessible only in the procedure which it was declared.

PROPERTIES

Default Property - Automatically selects a cmd button when the user presses the < ENTER > key. To make a cmd button a default button, you set its DEFAULT property to TRUE. Only one command button per form can have its default property set to true. When the program is run, this cmd button will be highlighted.

Cancel Property - The button that is selected when the user presses the < ESC > key. To set a cmd button to the cancel button, you set its CANCEL property to TRUE. Only one cmd button per form can have its cancel button set to true.

TabStop Property - Represents all controls on a form that can receive focus. If the TabStop property is TRUE, a control can receive focus. If it is FALSE, then it cannot.

TabIndex Property

• 0 - Left Justify


• 1 - Right Justify


• 2 - Center

lblTotal.Visible = True 'label will be displayed on the form.
lblTotal.Visible = False 'label will not be displayed on the form.

• 0 - Solid


• 1 - Transparent


• 2 - Horizontal Line


• 3 - Vertical Line


• 4 - Upward Diagonal


• 5 - Downward Diagonal


• 6 - Cross


• 7 - Diagonal Cross

Square.FillStyle = 0 
Square.FillStyle = 8 

Option Buttons... Formats

Option Buttons - Group of controls where only one can be selected at a time.

Check Boxes - Group of controls where more than one can be selected at a time.

Frame - Control that often acts as a container for a group of option buttons or check boxes.

Image - Type of control that is used to hold a graphic.
Shape - Type of control used to place rectangles, squares, ovals and circles on a form.

OPTION BUTTONS:

The VALUE property of the option button is set TRUE if you want it to be selected, otherwise, FALSE.

Set the option buttons CAPTION property to the text you want to appear next to the option button.

When assigning an option button, a variable name always starts out with the prefix, opt

If you want an event to occur when you click on an opt button, you can double-click on the opt button to place code behind the opt button.

CHECK BOXES:

The VALUE property of the option button is set to CHECKED if you want it to be selected, otherwise, set it to UNCHECKED.

• 0 - UnChecked


• 1 - Checked


• 2 - Grayed

If you want an event to occur when you click on a chk box, double-click the button to place code behind.

IMAGES:

Click on the images PICTURE property and locate the folder or drive where the picture is located.

Set images STRECH property to TRUE. This will size the pic to the size of the control you have defined on the form.

SHAPES:

• 0 - Rectangle


• 1 - Square


• 2 - Oval


• 3 - Circle


• 4 - Rounded Rectangle


• 5 - Rounded Square

LINES

Use the crosshair pointer to drag a line across the screen. You may rotate the line in any direction and stretch it until releasing the move button.

Focus - Refers to the currently selected control on the form. This can be indicated by an | - Beam, selected text, highlighted caption or dotted border. The control with focus is ready to receive input.

SetFocus - A built-in function that when executed will move the cursor to the control and give that control focus. SetFocus can be used with txt boxes, cmd buttons, opt buttons and chk boxes.

txtNum1.setFocus 'will place cursor in the text box.
cmdCalc.setFocus 'will hilight this command button.
optBlue.setFocus 'will put dotted lines around this opt button. 

Working With Strings

Concatenation - Refers to combining two or more smaller strings into a larger string. In VB, you can either use the & or + symbols to do concatenation.

StrFirstName + " " + strMiddleInitial + ". " + StrLastName
StrFirstName & " " + strMiddleInitial & ". " + StrLastName

Formats

(This code would go in the FORM LOAD [ by double clicking empty space on the form.])

< Name of Form > - This is the actual name of the form as you have saved it in your program.

If you named your form SQUARE, you would code the statement in the following way:

SQUARE.Top = (Screen.Height - SQUARE.Height)/2
SQUARE.Left = (Screen.Height - SQUARE.Width)/2

Input Boxes, Message and List Boxes

Input Box - A function that will display a message and allow the user to enter information in a text box. In the Input box you can display a message called a prompt, which will help the user decide what information he needs to enter in the text box.

The input box will have a txt box with the prompt above it and two command buttons, OK and CANCEL. The OK will accept whatever input the user enters and place it in the variable on the left hand side of the equals sign. The CANCLEL button will ignore any input entered by the user and return the user back to the form that is currently open.

StrName = InputBox("Enter your name", "Sponge Bob")
StrCareer = InputBox("Enter your workplace", "Nickelodeon")

The prompt must be enclosed in quotes. The title must also be in quotes and will appear in the Title Bar of the Input Box. If no title is entered, the title of the project will appear in the Title Bar.

• Form_Load


• Command Buttons


• Option Buttons


• Check Boxes

Form Load

Form_Load - Code executed as the project is loading. The first time a form is displayed in a project, VB generates an event knows as FORM_LOAD. Any code in Form Load is then executed.

• Code to center the form in the middle of the screen


• Code to initialize variables


• Code for input boxes so the user can enter info.


• Display info in labels on the form.

To get the FORM_LOAD event to enter code, again; double click on an empty area on the form. The FORM_LOAD event begins and ends with the following procedure headings:

Private Sub Form_Load()
InputBoxes.Top = Screen.Height - InputBoxes.Height)/2
InputBoxes.Left = Screen.Width - InputBoxes.Width)/2
StrName = InputBox("Enter your name", " Nickelodeon Inc.")
LblName = StrName
End Sub

Message Boxes and List Boxes

Message Box - A special type of VB statement/function that displays a window in which you can display a message to a user. The message box can be a statement or function and has the name, MsgBox.

• Message


• Optional Icon


• Title Bar Caption


• Command Buttons

MESSAGE BOX STATEMENT

The message box statement is designed to be on a line by itself. The syntax of the MsgBox is show here:

MsgBox "Sponge Bob is -Jester's brother!",vbInformation, "Nickelodeon Inc."

Prompt - The message you want to appear in the message box.
Buttons/Icons - This determines what command buttons and/or icons that will appear on the message box. (This portion is optional.)

MESSAGE BOX FUNCTION:

The message box function will appear on the right hand side of the equals sign. Also, if your msg box is a function, you must enclose arguments in ( ).

IntRes = MsgBox("Are my fingers tired?", vbYesNo + vbQuestion,"My Question")

Private Sub cmdCheck_Click()
If val(txtNum1) > val(txtNum2) Then
MsgBox "First Number is greater than second", vbInformation, "Comparing Numbers"
ElseIf val(txtNum2) > val(txtNum1) Then
MsgBox "Second Number is greater than the first", vbInformation, "Comparing Numbers"
Else
MsgBox "The two numbers are equal", vbInformation, "Comparing Numbers"
End If
End Sub

LIST BOXES:

List Box - A type of control used to hold a list of items from which the user can select one item from the list. You should use the lst prefix when naming list boxes.

If your values are strings, they must be enclosed in double quotes. When items are added to the list, they are given an index. The first item added to the list will have an index of zero the 2nd of one, and so forth.

lstSchools.AddItem "Harvard"
lstSchools.Additem "Yale"
lstSchools.Additem "Princeton"
lstSchools.Additem "Brown"
lstSchools.Additem "Cornell"
lstSchools.ListIndex = 3

ListIndex PROPERTY :

The listIndex property will highlight an item in the list when the program is run. Only one item can be set with the listIndex property. The format of List Index property is shown here:

lstSchools.ListIndex = 3 'This will highlight the 4th school in lstSchools.

Sorted PROPERTY:

This will sort the items in your list alphabetically if the SORTED property is set to TRUE. This will also re-index the items in your list. If the ListIndex property is used, the highlighted item will change.

Clear METHOD:

lstSchools.Clear

RemoveItem METHOD:

This will remove one item from the list. When using RemoveItem, youmust include the index of the item to remove.

LstSchools.RemoveItem 3

This will remove the item in the lstSchools list box with the index of 3, which is the 4th item in the list.

LstCount - The listCount property is used to hold the number of items in the list. ListCount will always be one more than the highest element in the list.

Sub Procedures, Random Numbers

Procedure - A unit of code that performs a specific task and can be called from other locations of the program.

PURPOSES OF PROCEDURES:

• Breaks large sections of code into smaller units of code that perform a specific task.


• Makes it easier to debug and maintain program.


• Cuts down on the amount of code that has to be written and eliminates duplication of code.

TYPES OF PROCEDURES:

Sub Procedure - A procedure that performs a task but DOES NOT return values back to the calling module.

Function Procedure - A procedure that performs a task and RETURNS a value back to the calling module. With function procedures, the value is returned back to the calling module using the function name.

CREATING A NEW SUB PROCEDURE:

1. Display the code window for the form


2. Select ADD PROCEDURE from the TOOLS menu


3. Enter the name of the procedure in the text box next to where it says NAME


4. Select PRIVATE for SCOPE


5. Click OK


6. You will be given the procedure shell. Type in the contents of your procedure


7. Click on the code button to exit the procedure

Private Sub AddNumbers()
Sum = val(txtNum1) + val(txtNum2)
LblSum = Sum
End Sub

Private Sub cmdCalculate_Click()
AddNumbers
End Sub

Private Function AddNumbers()
AddNumbers = val(txtNum1) + val(txtNum2)
End Function

Private Sub cmdCalculate_Click()
LblSum = AddNumbers()
End Sub

WITH STATEMENT

The WITH keyword allows you to cut down on coding when dealing with properties of controls.

lblEmployee.Font.Name = dlgCommon.FontName
lblEmployee.Font.Bold = dlgCommon.FontBold
lblEmployee.Font.Italic = dlgCommon.FontItalic

With lblEmployee.Font
.Name = dlgCommon.FontName
.Bold = dlgCommon.FontBold
.Italic = dlgCommon.FontItalic
End With

COMMON DIALOG CONTROL

Allows your project to use the dialog boxes that are provided as part of the Windows environment to set properties for a control such as font, font size and color.

FEATURES OF THE DIALOG CONTROL:

• You only need common dialog control on your form


• You cannot change the controls size


• The location of the control does NOT matter


• The control will be invisible when the program runs


• Dialog controls are stored with an extension of .ocx


• When naming Dialog controls, begin with a prefix of dlg


• The common dialog box may not appear in your toolbox. It is a custom * control and will need to be added to your project before you can use it.

RETRIEVING THE COMMON DIALOG CONTROL:

1. click on Project


2. click on Components


3. Scroll down and find Microsoft Common Dialog Control 6.0


4. Click the check box next to it to select it.


5. Click OK and it will be placed in your tool box.


6. Click on Dialog Control and place it on your form.

CHANGING FONTS:

With txtName.Font
.Bold = dlgCommon.FontBold
.Italic = dlgCommon.FontItalic
.Name = dlgCommon.FontName
.Size = dlgCommon.FontSize
End With

CHANGING COLOR:

dlgCommon.ShowColor 'Brings up the color box
txtName.ForeColor = dlgCommon.Color 'Applies it to the font

RANDOM NUMBERS

Randomize - Tells VB to randomly generate numbers for the rnd statement. Using randomize will allow the rnd statement to generate an entirely random set of numbers that do not follow any recognizable pattern.

Num = Int((10 - 1 + 1)* rnd + 1)

Num = Int((100 - 10 + 1)* rnd + 1)

INT() FUNCTION:

Converts a floating point value to an integer by truncating off any remainder that the number has. ( INT(4.656) will return a value of 4. )

Menus, Combo Boxes and QB Color

Menu - A drop-down list of items displayed below a menu name on the screen from which you selected one item.

In Windows and VB a menu consists of a menu bar with menu names, each of which drops down to display a list of menu commands. You can use menu commands in place of or in addition to the command buttons to activate a procedure.

Menu commands are actually controls and have events and properties. Each menu command has a Name property and a Click event, similar to a command button. To create a menu for your form, you will use the Visual Basic Menu Editor, which accessible by pressing < CTRL > + E or Click on Menu Editor Icon.

PARTS OF THE MENU:

Name - Indicates the name of the menu control and what the control is referred to by the program. When naming, start out with the prefix, "mnu" . For example, if you had a menu control for FILE, you would name it, mnuFile

SUBMENU - A list of commands that appear underneath a menu command, a menu within a menu. To create a submenu, press the right arrow key to move to the next level.

Menu List Box - Shows the list of all menu items that have been created and the indication levels. You can move up, down, left and right by clicking on the name of the menu item and then clicking on one of the four arrow buttons.

Separator Bars - A horizontal line that separates one menu from another. To define a separator bar, type a single hyphen ( - ) for the caption and give it a name. Even though you can never reference the separator bar in the code, you still have to give it a name. If you have more than one separator bar, each one has to have a unique name. ( mnuSep1,mnuSep2,...ect. )

Short Cut Keys - You can create a keyboard short cut key for a menu item when its created. Select a short cut key for your menu item by selecting it from the list provided. The purpose of the short cut is to give you an alternative to going through a menu to perform a task.

Checked - If you want a check mark to appear next to an item in your menu, you would put a check here. Check marks are normally for options that you want to be toggled on and off.

Enabled - If you want the user to be able to select a menu item, this will be checked. By default, all are enabled. If unchecked, this menu item will be dimmed out. You can also change this property in the actual code. ( mnuStar.Enabled = False )

Visible - Determines whether a menu item is displayed on the screen or not. If there is a check in this check box, the menu item will be displayed on the screen. If the box is not checked, the menu item will not be displayed. This property can also be changed in the actual code. ( mnuStar.Visible = True )

Insert - Click on this if you want to insert an item into the middle of a menu. The item will be inserted at the location of the current item. All items below that point will be moved down.

Delete - Will delete the highlighted menu, Cancel will close the menu editor without saving changes and OK will save changes to the menu and close the menu editor.

COMBO BOXES

Combo Box - A type of control used to hold a list of items from which the user selects one from a pull down menu.

DIFFERENCES BETWEEN A LIST BOX AND A COMBO BOX:

• With a list box, there is no pull down menu, user scrolls through the list using scroll bars and selects the item of his/her/OtHeR choice. With a combo box, the user click on a down arror, a pull down menu is displayed and the user chooses by clicking one on the list.


• You can type your own entry into the list with a combo box. With a list box, you cannot type in your own entries.

• Using the List property


• Using the AddItem method

ADDING ITEMS TO THE LIST USING THE LIST PROPERTY: