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2011-01-10T19:04:00.000-08:00

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2011-01-10T18:37:00.000-08:00

LESSON 16. ARRAYS

2010-07-27T00:16:00.000-07:00

16.1 Introduction to Arrays

By definition, an array is a list of variables, all with the same data type and name. When we work with a single item, we only need to use one variable. However, if we have a list of items which are of similar type to deal with, we need to declare an array of variables instead of using a variable for each item. For example, if we need to enter one hundred names, we might have difficulty in declaring 100 different names, this is a waste of time and efforts. So, instead of declaring one hundred different variables, we need to declare only one array. We differentiate each item in the array by using subscript, the index value of each item, for example name(1), name(2),name(3) .......etc. , which will make declaring variables streamline and much systematic.

16.2 Dimension of an Array

An array can be one dimensional or multidimensional. One dimensional array is like a list of items or a table that consists of one row of items or one column of items. A twodimensional array will be a table of items that make up of rows and columns. While the format for a one dimensional array is ArrayName(x), the format for a two dimensional array is ArrayName(x,y) while a three dimensional array is ArrayName(x,y,z) . Normally it is sufficient to use one dimensional and two dimensional array ,you only need to use higher dimensional arrays if you need with engineering problems or even some accounting problems.Let me illustrates the the arrays with tables.

Table 16.1. One dimensional Array

Student Name

Name(1)

Name(2)

Name(3)

Name(4)

Name(5)

Name(6)

Table 16.2 Two Dimensional Array

Name(1,1)	Name(1,2)	Name(1,3)	Name(1,4)
Name(2,1)	Name(2,2)	Name(2,3)	Name(2,4)
Name(3,1)	Name(3,2)	Name(3,3)	Name(3,4)

16.2 Declaring Arrays

We could use Public or Dim statement to declare an array just as the way we declare a single variable. The Public statement declares an array that can be used throughout an application while the Dim statement declare an array that could be used only in a local procedure.

The general format to declare a one dimensional array is as follow:

Dim arrayName(subs) as dataType

where subs indicates the last subscript in the array.

Example 16.1

Dim CusName(10) as String

will declare an array that consists of 10 elements if the statement Option Base 1 appear in the declaration area, starting from CusName(1) to CusName(10). Otherwise, there will be 11 elements in the array starting from CusName(0) through to CusName(10)

CusName(1)

CusName(2)

CusName(3)

CusName(4)

CusName(5)

CusName(6)

CusName(7)

CusName(8)

CusName(9)

CusName(10)

Example 16.2

Dim Count(100 to 500) as Integer

declares an array that consists of the first element starting from Count(100) and ends at Count(500)

The general format to declare a two dimensional array is as follow:

Dim ArrayName(Sub1,Sub2) as dataType

Example 16.3

Dim StudentName(10,10) will declare a 10x10 table make up of 100 students' Names, starting with StudentName(1,1) and end with StudentName(10,10).

16.3 Sample Programs

(i) The code

Dim studentName(10) As String
Dim num As Integer

Private Sub addName()
For num = 1 To 10
studentName(num) = InputBox("Enter the student name", "Enter Name", "", 1500, 4500)
If studentName(num) <> "" Then
Form1.Print studentName(num)
Else
End
End If

Next
End Sub

The above program accepts data entry through an input box and displays the entries in the form itself. As you can see, this program will only allows a user to enter 10 names each time he click on the start button.

(ii)

The Code

Dim studentName(10) As String
Dim num As Integer

Private Sub addName( )
For num = 1 To 10
studentName(num) = InputBox("Enter the student name")
List1.AddItem studentName(num)
Next
End Sub
Private Sub Start_Click()
addName

End Sub

The above program accepts data entries through an InputBox and displays the items in a list box.

Lesson 15: Creating VBA Functions For MS Excel

2009-12-19T06:11:00.000-08:00

15.1 The Needs to Create VBA Functions in MS-Excel

You can create your own functions to supplement the built-in functions in Microsoft Excel spreadsheet, which are quite limited in some aspects. These user-defined functions are also called Visual Basic for Applications functions, or simply VBA functions. They are very useful and powerful if you know how to program them properly. One main reason we need to create user defined functions is to enable us to customize our spreadsheet environment for individual needs. For example, we might need a function that could calculate commissions payment based on the sales volume, which is quite difficult if not impossible by using the built-in functions alone. The code for VBA is illustrated on the right.

Table 15.1: Commissions Payment Table

Sales Volume($)	Commissons
<500	3%
<1000	6%
<2000	9%
<5000	12%
>5000	15%

In table 15.1, when a salesman attain a sale volume of $6000, he will be paid $6000x15%=$720.00. A visual basic function to calculate the commissions can be written as follows:

Function Comm(Sales_V As Variant) as Variant

If Sales_V <500 Then
Comm=Sales_V*0.03
Elseif Sales_V>=500 and Sales_V<1000 Then
Comm=Sales_V*0.06
Elseif Sales_V>=1000 and Sales_V<2000 Then
Comm=Sales_V*0.09
Elseif Sales_V>=200 and Sales_V<5000 Then
Comm=Sales_V*0.12
Elseif Sales_V>=5000 Then
Comm=Sales_V*0.15
End If

End Function

15.2 Using Microsoft Excel Visual Basic Editor

To create VBA functions in MS Excel, you can click on tools,

select macro and then click on Visual Basic Editor as shown in Figure 15.1

Figure 15.1: Inserting MS_Excel Visual Basic Editor

Upon clicking the Visual Basic Editor, the VB Editor windows will appear as shown in figure 15.2. To create a function, type in the function as illustrated in section 15.1 above After typing, save the file and then return to the Excel windows.

Figure 15.2 : The VB Editor

In the Excel window, type in the titles Sales Volume and Commissions in any two cells. By referring to figure 15.3, key-in the Comm function at cell C4 and by referencing the value in cell B4, using the format Comm(B4). Any value appear in cell B4 will pass the value to the Comm function in cell C4. For the rest of the rows, just copy the formula by dragging the bottom right corner of cell C4 to the required cells, a nice and neat table that shows the commissions will automatically appear (as shown in figure 15.3). It can also be updated anytime

Figure 15.3: MS Excel Windows- Sales Volume

Lesson 14: Creating User-Defined Functions

2009-11-27T00:11:00.000-08:00

14.1 Creating Your Own Function

The general format of a function is as follows:

Public Function functionName (Arg As dataType,..........) As dataType

Private Function functionName (Arg As dataType,..........) As dataType

* Public indicates that the function is applicable to the whole project and
Private indicates that the function is only applicable to a certain module or procedure.

Example 14.1

In this example, a user can calculate the future value of a certain amount of money he has today based on the interest rate and the number of years from now, supposing he will invest this amount of money somewhere .The calculation is based on the compound interest rate.

The code

Public Function FV(PV As Variant, i As Variant, n As Variant) As Variant

'Formula to calculate Future Value(FV)
'PV denotes Present Value
FV = PV * (1 + i / 100) ^ n

End Function

Private Sub compute_Click()

'This procedure will calculate Future Value
Dim FutureVal As Variant
Dim PresentVal As Variant
Dim interest As Variant
Dim period As Variant
PresentVal = PV.Text
interest = rate.Text
period = years.Text

'calling the funciton

FutureVal = FV(PresentVal, interest, period)
MsgBox ("The Future Value is " & FutureVal)

End Sub

Example 14.2

The following program will automatically compute examination grades based on the marks that a student obtained. The code is shown on the right.

The Code

Public Function grade(mark As Variant) As String

Select Case mark
Case Is >= 80
grade = "A"
Case Is >= 70
grade = "B"
Case Is >= 60
grade = "C"
Case Is >= 50
grade = "D"
Case Is >= 40
grade = "E"
Case Else
grade = "F"
End Select

End Function

Private Sub compute_Click()

grading.Caption = grade(mark)

End Sub

Lesson 13: String Manipulation Functions

2009-10-19T07:26:00.001-07:00

In this lesson, we will learn how to use some of the string manipulation function such as Len, Right, Left, Mid, Trim, Ltrim, Rtrim, Ucase, Lcase, Instr, Val, Str ,Chr and Asc.

(i)The Len Function

The length function returns an integer value which is the length of a phrase or a sentence, including the empty spaces. The format is

Len (“Phrase”)

For example,

Len (VisualBasic) = 11 and Len (welcome to VB tutorial) = 22

The Len function can also return the number of digits or memory locations of a number that is stored in the computer. For example,

Private sub Form_Activate ( )

X=sqr (16)

Y=1234

Z#=10#

Print Len(x), Len(y), and Len (z)

End Sub

will produce the output 1, 4 , 8. The reason why the last value is 8 is because z# is a double precision number and so it is allocated more memory spaces.

(ii) The Right Function

The Right function extracts the right portion of a phrase. The format is

Right (“Phrase”, n)

Where n is the starting position from the right of the phase where the portion of the phrase is going to be extracted. For example,

Right(“Visual Basic”, 4) = asic

(iii)The Left Function

The Left$ function extract the left portion of a phrase. The format is

Left(“Phrase”, n)

Where n is the starting position from the left of the phase where the portion of the phrase is going to be extracted. For example,

Left (“Visual Basic”, 4) = Visu

(iv) The Ltrim Function

The Ltrim function trims the empty spaces of the left portion of the phrase. The format is

Ltrim(“Phrase”)

.For example,

Ltrim (“ Visual Basic”, 4)= Visual basic

(v) The Rtrim Function

The Rtrim function trims the empty spaces of the right portion of the phrase. The format is

Rtrim(“Phrase”)

.For example,

Rtrim (“Visual Basic ”, 4) = Visual basic

(vi) The Trim function

The Ttrim function trims the empty spaces on both side of the phrase. The format is

Trim(“Phrase”)

.For example,

Trim (“ Visual Basic ”) = Visual basic

(viii) The Mid Function

The Mid function extracts a substring from the original phrase or string. It takes the following format:

Mid(phrase, position, n)

Where position is the starting position of the phrase from which the extraction process will start and n is the number of characters to be extracted. For example,

Mid(“Visual Basic”, 3, 6) = ual Bas

(ix) The InStr function

The InStr function looks for a phrase that is embedded within the original phrase and returns the starting position of the embedded phrase. The format is

Instr (n, original phase, embedded phrase)

Where n is the position where the Instr function will begin to look for the embedded phrase. For example

Instr(1, “Visual Basic”,” Basic”)=8

(x) The Ucase and the Lcase functions

The Ucase function converts all the characters of a string to capital letters. On the other hand, the Lcase function converts all the characters of a string to small letters. For example,

Ucase(“Visual Basic”) =VISUAL BASiC

Lcase(“Visual Basic”) =visual basic

(xi) The Str and Val functions

The Str is the function that converts a number to a string while the Val function converts a string to a number. The two functions are important when we need to perform mathematical operations.

(xii) The Chr and the Asc functions

The Chr function returns the string that corresponds to an ASCII code while the Ascfunction converts an ASCII character or symbol to the corresponding ASCII code. ASCII stands for “American Standard Code for Information Interchange”. Altogether there are 255 ASCII codes and as many ASCII characters. Some of the characters may not be displayed as they may represent some actions such as the pressing of a key or produce a beep sound. The format of the Chr function is

Chr(charcode)

and the format of the Asc function is

Asc(Character)

The following are some examples:

Chr(65)=A, Chr(122)=z, Chr(37)=% , Asc(“B”)=66, Asc(“&”)=38

Lesson 12: Formatting Functions

2009-10-01T07:22:00.000-07:00

Formatting output is a very important part of programming so that the data can be presented systematically and clearly to the users. Data in the previous lesson were presented fairly systematically through the use of commas and some of the functions like Int, Fix and Round. However, to have better control of the output format, we can use a number of formatting functions in Visual basic.

The three most common formatting functions in VB are Tab, Space, and Format

(i) The Tab function

Tab (n); x

The item x will be displayed at a position that is n spaces from the left border of the output form. There must be a semicolon in between Tab and the items you intend to display (VB will actually do it for you automatically).

Example1

.Private Sub Form_Activate

Print "I"; Tab(5); "like"; Tab(10); "to"; Tab(15); "learn"; Tab(20); "VB"

Print Tab(10); "I"; Tab(15); "like"; Tab(20); "to"; Tab(25); "learn"; Tab(20); "VB"

Print Tab(15); "I"; Tab(20); ; "like"; Tab(25); "to"; Tab(30); "learn"; Tab(35); “VB"

End sub

The Output for example 1 is shown below:

(ii) The Space function

The Space function is very closely linked to the Tab function. However, there is a minor difference. While Tab (n) means the item is placed n spaces from the left border of the screen, the Space function specifies the number of spaces between two consecutive items. For example, the procedure

Example 2

Private Sub Form_Activate()

Print "Visual"; Space(10); "Basic"

End Sub

Means that the words Visual and Basic will be separated by 10 spaces

(iii) The Format function

The Format function is a very powerful formatting function which can display the numeric values in various forms. There are two types of Format function, one of them is the built-in or predefined format while another one can be defined by the users.

(i) The format of the predefined Format function is

Format (n, “style argument”)

where n is a number and the list of style arguments is given in the table

Style argument	Explanation	Example
General Number	To display the number without having separators between thousands.	Format(8972.234, “General Number”)=8972.234
Fixed	To display the number without having separators between thousands and rounds it up to two decimal places.	Format(8972.2, “Fixed”)=8972.23
Standard	To display the number with separators or separators between thousands and rounds it up to two decimal places.	Format(6648972.265, “Standard”)= 6,648,972.27
Currency	To display the number with the dollar sign in front, has separators between thousands as well as rounding it up to two decimal places.	Format(6648972.265, “Currency”)= $6,648,972.27
Percent	Converts the number to the percentage form and displays a % sign and rounds it up to two decimal places.	Format(0.56324, “Percent”)=56.32 %

Example 3

Private Sub Form_Activate()

Print Format (8972.234, "General Number")

Print Format (8972.2, "Fixed")

Print Format (6648972.265, "Standard")

Print Format (6648972.265, "Currency")

Print Format (0.56324, "Percent")

End Sub

Now, run the program and you will get an output like the figure below:

Lesson 11: Mathematical Functions

2009-09-08T06:53:00.000-07:00

The mathematical functions are very useful and important in programming because very often we need to deal with mathematical concepts in programming such as chance and probability, variables, mathematical logics, calculations, coordinates, time intervals and etc. The common mathematical functions in Visual Basic are Rnd, Sqr, Int, Abs, Exp, Log, Sin, Cos, Tan , Atn, Fix and Round.

(i) Rnd is very useful when we deal with the concept of chance and probability. The Rnd function returns a random value between 0 and 1. In Example 1. When you run the program, you will get an output of 10 random numbers between 0 and 1. Randomize Timer is a vital statement here as it will randomize the process.

Example 1:
          Private Sub Form_Activate
Randomize Timer
For x=1 to 10
Print Rnd
Next x
End Sub
The Output for example 1 is shown below:

Random numbers in its original form are not very useful in programming until we convert them to integers. For example, if we need to obtain a random output of 6 random integers ranging from 1 to 6, which make the program behave as a virtual die, we need to convert the random numbers using the format  Int(Rnd*6)+1. Let’s study the following example:
In this example, Int(Rnd*6) will generate a random integer between 0 and 5 because the function Int truncates the decimal part of the random number and returns an integer. After adding 1, you will get a random number between 1 and 6 every time you click the command button. For example, let say the random number generated is 0.98, after multiplying it by 6, it becomes 5.88, and using the integer function Int(5.88) will convert the number to 5; and after adding 1 you will get 6.
In this example, you place a command button and change its caption to ‘roll die’. You also need to insert a label into the form and clear its caption at the designing phase and make its font bigger and bold. Then set the border value to 1 so that it displays a border; and after that set the alignment to center. The statement Label1.Caption=Num means the integer generated will be displayed as the caption of the label.
Example 2:
           Dim num as integer
Private Sub Command1_Click ( )
Randomize Timer
Num=Int(Rnd*6)+1
Label1.Caption=Num
End Sub
Now, run the program and then click on the roll die button, you will get an output like the figure below:
The Numeric Functions
The numeric functions are Int, Sqr, Abs, Exp, Fix, Round and Log.
a) Int is the function that converts a number into an integer by truncating its decimal part and the resulting integer is the largest integer that is smaller than the number. For example, Int(2.4)=2, Int(4.8)=4, Int(-4.6)= -5, Int(0.032)=0 and so on.
b) Sqr is the function that computes the square root of a number. For example, Sqr(4)=2, Sqr(9)=2 and etc.
c) Abs is the function that returns the absolute value of a number. So Abs(-8) = 8 and Abs(8)= 8.
d) Exp of a number x is the value of e^x. For example, Exp(1)=e¹ = 2.7182818284590
e) Fix and Int are the same if the number is a positive number as both truncate the decimal part of the number and return an integer. However, when the number is negative, it will return the smallest integer that is larger than the number. For example, Fix(-6.34)= -6 while Int(-6.34)=-7.
f) Round is the function that rounds up a number to a certain number of decimal places. The Format is Round (n, m) which means to round a number n to m decimal places. For example, Round (7.2567, 2) =7.26
g) Log is the function that returns the natural Logarithm of a number. For example,
Log 10= 2.302585
Example 3
This example computes the values of Int(x), Fix(x) and Round(x,n) in a table form. It uses the Do Loop statement and the Rnd function to generate 10 numbers. The statement x = Round (Rnd * 7, 7) rounds a random number between 0 and 7 to 7 decimal places. Using commas in between items will create spaces between them and hence a table of values can be created. The program and output are shown below
Private Sub Form_Activate ()
n = 1
Print " n", "      x", "Int(x)", "Fix(x)", "Round(x, 4)"
Do While n < 11
Randomize Timer
x = Round (Rnd * 7, 7)
Print n, x, Int(x), Fix(x), Round(x, 4)
n = n + 1
Loop
End Sub

Lesson 10

2009-08-29T08:33:00.000-07:00

Lesson 10: Introduction to VB Built-in Functions

A function is similar to a normal procedure but the main purpose of the function is to accept a certain input from the user and return a value which is passed on to the main program to finish the execution. There are two types of functions, the built-in functions (or internal functions) and the functions created by the programmers.

the general format of a function is
FunctionName (arguments)

The arguments are values that are passed on to the function.

In this lesson, we are going to learn two very basic but useful internal functions of Visual basic , i.e. theMsgBox( ) and InputBox ( )functions. You can also learn aboutmathematical functions, formatting functions and string manipulation functions by clicking the links at the end of this page.

10.1 MsgBox ( ) Function

The objective of MsgBox is to produce a pop-up message box and prompt the user to click on a command button before he /she can continues. This format is as follows:
yourMsg=MsgBox(Prompt, Style Value, Title)

The first argument, Prompt, will display the message in the message box. The Style Value will determine what type of command buttons appear on the message box, please refer Table 10.1 for types of command button displayed. The Title argument will display the title of the message board.

Table 10.1: Style Values

Style Value	Named Constant	Buttons Displayed
0	vbOkOnly	Ok button
1	vbOkCancel	Ok and Cancel buttons
2	vbAbortRetryIgnore	Abort, Retry and Ignore buttons.
3	vbYesNoCancel	Yes, No and Cancel buttons
4	vbYesNo	Yes and No buttons
5	vbRetryCancel	Retry and Cancel buttons

We can use named constant in place of integers for the second argument to make the programs more readable. In fact, VB6 will automatically shows up a list of names constant where you can select one of them.
Example: yourMsg=MsgBox( "Click OK to Proceed", 1, "Startup Menu")
and yourMsg=Msg("Click OK to Proceed". vbOkCancel,"Startup Menu")
are the same.
yourMsg is a variable that holds values that are returned by the MsgBox ( ) function. The values are determined by the type of buttons being clicked by the users. It has to be declared as Integer data type in the procedure or in the general declaration section.Table 10.2 shows the values, the corresponding named constant and buttons.

Table 10.2 : Return Values and Command Buttons

Value	Named Constant	Button Clicked
1	vbOk	Ok button
2	vbCancel	Cancel button
3	vbAbort	Abort button
4	vbRetry	Retry button
5	vbIgnore	Ignore button
6	vbYes	Yes button
7	vbNo	No button

Example 10.1

i. The Interface:

You draw three command buttons and a label as shown in Figure 10.1

Figure 10.1

ii. The procedure for the test button:

Private Sub Test_Click()
Dim testmsg As Integer
testmsg = MsgBox("Click to test", 1, "Test message")
If testmsg = 1 Then
Display.Caption = "Testing Successful"
Else
Display.Caption = "Testing fail"
End If

End Sub

When a user click on the test button, the image like the one shown in Figure 10.2 will appear. As the user click on the OK button, the message "Testing successful" will be displayed and when he/she clicks on the Cancel button, the message "Testing fail" will be displayed.

Figure 10.2

To make the message box looks more sophisticated, you can add an icon besides the message. There are four types of icons available in VB as shown in Table 10.3

Table 10.3

Value	Named Constant	Icon
16	vbCritical
32	vbQuestion
48	vbExclamation
64	vbInformation

Example 10.2

You draw the same Interface as in example 10.1 but modify the codes as follows:

Private Sub test2_Click()

Dim testMsg2 As Integer
testMsg2 = MsgBox("Click to Test", vbYesNoCancel + vbExclamation, "Test Message")
If testMsg2 = 6 Then
display2.Caption = "Testing successful"
ElseIf testMsg2 = 7 Then
display2.Caption = "Are you sure?"
Else
display2.Caption = "Testing fail"
End If

End Sub

In this example, the following message box will be displayed:

Figure 10.3

10.2 The InputBox( ) Function

An InputBox( ) function will display a message box where the user can enter a value or a message in the form of text. The format is

myMessage=InputBox(Prompt, Title, default_text, x-position, y-position)

myMessage is a variant data type but typically it is declared as string, which accept the message input by the users. The arguments are explained as follows:

Prompt - The message displayed normally as a question asked.
Title - The title of the Input Box.
default-text - The default text that appears in the input field where users can use it as his intended input or he may change to the message he wish to key in.
x-position and y-position - the position or the coordinate of the input box.

Example 10.3

i. The Interface

Figure 10.4

ii. The procedure for the OK button

Private Sub OK_Click()

Dim userMsg As String
userMsg = InputBox("What is your message?", "Message Entry Form", "Enter your messge here", 500, 700)
If userMsg <> "" Then
message.Caption = userMsg
Else
message.Caption = "No Message"
End If

End Sub

When a user click the OK button, the input box as shown in Figure 10.5 will appear. After user entering the message and click OK, the message will be displayed on the caption, if he click Cancel, "No message" will be displayed.

Lesson 9: Looping

2009-08-05T06:49:00.000-07:00

Visual Basic allows a procedure to be repeated many times as long as the processor until a condition or a set of conditions is fulfilled. This is generally called looping . Looping is a very useful feature of Visual Basic because it makes repetitive works easier. There are two kinds of loops in Visual Basic, the Do...Loop and the For.......Next loop

9.1 Do Loop

The formats are

a) Do While condition

Block of one or more VB statements

Loop

b)   Do
            Block of one or more VB statements
      Loop While condition

c)    Do Until condition
              Block of one or more VB statements
       Loop

d) Do
Block of one or more VB statements

Loop Until condition

9.2 Exiting the Loop
Sometime we need exit to exit a loop prematurely because of a certain condition is fulfilled. The syntax to use is known as Exit Do. You can examine Example 9.2 for its usage.

9.3 For....Next Loop

The format is:

For counter=startNumber to endNumber (Step increment)

One or more VB statements

Please refer to example 9.3a,9.3b and 9.3 c for its usage.

Sometimes the user might want to get out from the loop before the whole repetitive process is executed, the command to use is Exit For. To exit a For….Next Loop, you can place the Exit Forstatement within the loop; and it is normally used together with the If…..Then… statement. Let’s examine example 9.3 d.

Example 9.1

Do while counter <=1000

num.Text=counter

counter =counter+1

Loop

* The above example will keep on adding until counter >1000.

The above example can be rewritten as

num.Text=counter
counter=counter+1

Loop until counter>1000

Example 9.2

Dim sum, n As Integer

Private Sub Form_Activate()

List1.AddItem "n" & vbTab & "sum"

n = n + 1

Sum = Sum + n

List1.AddItem n & vbTab & Sum

If n = 100 Then

Exit Do

End If

Loop

End Sub

Explanation

In the above example, we compute the summation of 1+2+3+4+……+100. In the design stage, you need to insert a ListBox into the form for displaying the output, named List1. The program uses the AddItem method to populate the ListBox. The statement List1.AddItem "n" & vbTab & "sum" will display the headings in the ListBox, where it uses the vbTab function to create a space between the headings n and sum.

Example 9.3 a For counter=1 to 10 display.Text=counter Next	Example 9.3 b For counter=1 to 1000 step 10 counter=counter+1 Next
Example 9.3 c For counter=1000 to 5 step -5 counter=counter-10 Next *Notice that increment can be negative	Example 9.3 d Private Sub Form_Activate( ) For n=1 to 10 If n>6 then Exit For End If Else Print n End If End Sub

Lesson 8 : Select Case....End select Control Structure

2009-07-10T02:15:00.000-07:00

In the previous lesson, we have learned how to control the program flow using the If...ElseIf control structure. In this chapter, you will learn another way to control the program flow, that is, the Select Case control structure. However, the Select Case control structure is slightly different from the If....ElseIf control structure . The difference is that the Select Case control structure basically only make decision on one expression or dimension (for example the examination grade) while the If ...ElseIf statement control structure may evaluate only one expression, each If....ElseIf statement may also compute entirely different dimensions. Select Case is preferred when there exist many different conditions because using If...Then..ElseIf statements might become too messy.

The format of the Select Case control structure is show below:

Select Case expression

Case value1
Block of one or more VB statements
Case value2
Block of one or more VB Statements
Case value3
.
.
Case Else
Block of one or more VB Statements

End Select

Example 8.1

Dim grade As String

Private Sub Compute_Click( )

grade=txtgrade.Text

Select Case grade

Case "A"
result.Caption="High Distinction"

Case "A-"
result.Caption="Distinction"

Case "B"
result.Caption="Credit"

Case "C"
result.Caption="Pass"

Case Else
result.Caption="Fail"

End Select

End Sub

Example 8.2

Dim mark As Single

Private Sub Compute_Click()
'Examination Marks

mark = mrk.Text

Select Case mark

Case Is >= 85

comment.Caption = "Excellence"

Case Is >= 70

comment.Caption = "Good"

Case Is >= 60

comment.Caption = "Above Average"

Case Is >= 50

comment.Caption = "Average"

Case Else

comment.Caption = "Need to work harder"

End Select

End Sub

Example 8.3

Example 8.2 could be rewritten as follows:

Dim mark As Single

Private Sub Compute_Click()

'Examination Marks

mark = mrk.Text

Select Case mark

Case 0 to 49

comment.Caption = "Need to work harder"

Case 50 to 59

comment.Caption = "Average"

Case 60 to 69

comment.Caption = "Above Average"

Case 70 to 84

comment.Caption = "Good"

Case Else

comment.Caption = "Excellence"

End Select

End Sub

Lesson 7. Controling Program Flow

2009-05-31T06:09:00.001-07:00

In previous lessons, we have learned how to create Visual Basic code that can accept input from the user and display the output without controlling the program flow. In this chapter, you will learn how to crreate VB code that can make decision when it process input from the user, and control the program flow in the process. Decision making process is an important part of programming because it can help to solve practical problems intelligently so that it can provide useful output or feedback to the user. For example, we can write a program that can ask the computer to perform certain task until a certain condition is met.

7.1 Conditional Operators

To control the VB program flow, we can use various conditional operators. Basically, they resemble mathematical operators. Conditional operators are very powerful tools, they let the VB program compare data values and then decide what action to take, whether to execute a program or terminate the program and more. These operators are shown in Table 7.1.

Table 7.1: Conditional Operators

7.2 Logical Operators

In addition to conditional operators, there are a few logical operators which offer added power to the VB programs. There are shown in Table 7.2.

Table 7.2

* You can also compare strings with the above operators. However, there are certain rules to follows: Upper case letters are less than lowercase letters, "A"<"B"<"C"<"D".......<"Z" and number are less than letters.

7.3 Using If.....Then.....Else Statements with Operators

To effectively control the VB program flow, we shall use If...Then...Else statement together with the conditional operators and logical operators.
The general format for the if...then...else statement is

If conditions Then
VB expressions
Else
VB expressions
End If
* any If..Then..Else statement must end with End If. Sometime it is not necessary to use Else.

Example:

Private Sub OK_Click()

firstnum = Val(usernum1.Text)
secondnum = Val(usernum2.Text)
total = Val(sum.Text)
If total = firstnum + secondnum And Val(sum.Text) <> 0 Then
correct.Visible = True
wrong.Visible = False
Else
correct.Visible = False
wrong.Visible = True
End If

End Sub

Lesson 6. Working With Variables

2009-05-31T05:28:00.000-07:00

6.1 Assigning Values to Variables

After declaring various variables using the Dim statements, we can assign values to those variables. The general format of an assignment is Variable=Expression The variable can be a declared variable or a control property value. The expression could be a mathematical expression, a number, a string, a Boolean value (true or false) and more. The following are some examples:

firstNumber    =100
secondNumber =firstNumber-99
userName    ="John Lyan"
userpass.Text    = password
Label1.Visible    = True
Command1.Visible = false
Label4.Caption = textbox1.Text
ThirdNumber = Val(usernum1.Text)
total = firstNumber + secondNumber+ThirdNumber

Example 6.1

Dim firstName As String
Dim secondName As String
Dim yourName As String

Private Sub Command1_Click()
firstName = Text1.Text
secondName = Text2.Text
yourName = secondName + " " + firstName
Label1.Caption = yourName
End Sub

In this example, three variables are declared as string. For variables firstName and secondName will receive their data from the user’s input into textbox1 and textbox2, and the variable yourName will be assigned the data by combining the first two variables. Finally, yourName is displayed on Label1.

6.2 Operators in Visual Basic

To compute inputs from users and to generate results, we need to use various mathematical operators. In Visual Basic, except for + and -, the symbols for the operators are different from normal mathematical operators, as shown in Table 6.1.

Table 6.1: Arithmetic Operators

Example 6.2

Dim number1, number2, number3 as Integer
Dim total, average as variant

Private sub Form_Click()
number1=val(Text1.Text)
number2=val(Text2.Text)
number3= val(Text3.Text)
Total=number1+number2+number3
Average=Total/5
Label1.Caption=Total
Label2.Caption=Average
End Sub

In the example above, three variables are declared as integer and two variables are declared as variant. Variant means the variable can hold any data type. The program computes the total and average of the three numbers that are entered into three text boxes.

Lesson 5. Managing Visual Basic Data

2009-05-17T20:15:00.000-07:00

There are many types of data that we come across in our daily life. For example, we need to handle data such as names, addresses, money, date, stock quotes, statistics and more everyday. Similarly in Visual Basic, we have to deal with all sorts of of data, some can be mathematically calculated while some are in the form of text or other forms. VB divides data into different types so that it is easier to manage when we need to write the code involving those data.

5.1 Visual Basic Data Types

Visual Basic classifies the information mentioned above into two major data types, they are the numeric data types and the non-numeric data types.

5.1.1 Numeric Data Types

Numeric data types are types of data that consist of numbers, which can be computed mathematically with various standard operators such as add, minus, multiply, divide and more. Examples of numeric data types are examination marks, height, weight, the number of students in a class, share values, price of goods, monthly bills, fees and others. In Visual Basic, numeric data are divided into 7 types, depending on the range of values they can store. Calculations that only involve round figures or data that does not need precision can use Integer or Long integer in the computation. Programs that require high precision calculation need to use Single and Double decision data types, they are also called floating point numbers. For currency calculation , you can use the currency data types. Lastly, if even more precision is required to perform calculations that involve a many decimal points, we can use the decimal data types. These data types summarized in Table 5.1

Table 5.1: Numeric Data Types

Type	Storage	Range of Values
Byte	1 byte	0 to 255
Integer	2 bytes	-32,768 to 32,767
Long	4 bytes	-2,147,483,648 to 2,147,483,648
Single	4 bytes	-3.402823E+38 to -1.401298E-45 for negative values 1.401298E-45 to 3.402823E+38 for positive values.
Double	8 bytes	-1.79769313486232e+308 to -4.94065645841247E-324 for negative values 4.94065645841247E-324 to 1.79769313486232e+308 for positive values.
Currency	8 bytes	-922,337,203,685,477.5808 to 922,337,203,685,477.5807
Decimal	12 bytes	+/- 79,228,162,514,264,337,593,543,950,335 if no decimal is use +/- 7.9228162514264337593543950335 (28 decimal places).

5.1.2 Non-numeric Data Types

Nonnumeric data types are data that cannot be manipulated mathematically using standard arithmetic operators. The non-numeric data comprises text or string data types, the Date data types, the Boolean data types that store only two values (true or false), Object data type and Variant data type .They are summarized in Table 5.2

Table 5.2: Nonnumeric Data Types

Data Type	Storage	Range
String(fixed length)	Length of string	1 to 65,400 characters
String(variable length)	Length + 10 bytes	0 to 2 billion characters
Date	8 bytes	January 1, 100 to December 31, 9999
Boolean	2 bytes	True or False
Object	4 bytes	Any embedded object
Variant(numeric)	16 bytes	Any value as large as Double
Variant(text)	Length+22 bytes	Same as variable-length string

5.1.3 Suffixes for Literals

Literals are values that you assign to data. In some cases, we need to add a suffix behind a literal so that VB can handle the calculation more accurately. For example, we can use num=1.3089# for a Double type data. Some of the suffixes are displayed in Table 5.3.

Table 5.3

Suffix	Data Type
&	Long
!	Single
#	Double
@	Currency

In addition, we need to enclose string literals within two quotations and date and time literals within two # sign. Strings can contain any characters, including numbers. The following are few examples:

memberName="Turban, John."
TelNumber="1800-900-888-777"
LastDay=#31-Dec-00#
ExpTime=#12:00 am#

5.2 Managing Variables

Variables are like mail boxes in the post office. The contents of the variables changes every now and then, just like the mail boxes. In term of VB, variables are areas allocated by the computer memory to hold data. Like the mail boxes, each variable must be given a name. To name a variable in Visual Basic, you have to follow a set of rules.

5.2.1 Variable Names

The following are the rules when naming the variables in Visual Basic

It must be less than 255 characters
No spacing is allowed
It must not begin with a number
Period is not permitted

Examples of valid and invalid variable names are displayed in Table 5.4

Table 5.4

Valid Name	Invalid Name
My_Car	My.Car
ThisYear	1NewBoy
Long_Name_Can_beUSE	He&HisFather *& is not acceptable

5.2.2 Declaring Variables

In Visual Basic, one needs to declare the variables before using them by assigning names and data types. They are normally declared in the general section of the codes' windows using the Dim statement.
The format is as follows:

Dim Variable Name As Data Type

Example 5.1

Dim password As String
Dim yourName As String
Dim firstnum As Integer
Dim secondnum As Integer
Dim total As Integer
Dim doDate As Date

You may also combine them in one line , separating each variable with a comma, as follows:

Dim password As String, yourName As String, firstnum As Integer,.............

If data type is not specified, VB will automatically declare the variable as a Variant.
For string declaration, there are two possible formats, one for the variable-length string and another for the fixed-length string. For the variable-length string, just use the same format as example 5.1 above. However, for the fixed-length string, you have to use the format as shown below:

Dim VariableName as String * n, where n defines the number of characters the string can hold.

Example 5.2:

Dim yourName as String * 10

yourName can holds no more than 10 Characters.

5.3 Constants

Constants are different from variables in the sense that their values do not change during the running of the program.

5.3.1 Declaring a Constant

The format to declare a constant is

Const Constant Name As Data Type = Value

Example 5.3

Const Pi As Single=3.142

Const Temp As Single=37

Const Score As Single=100

Lesson 4. Writing the Code

2009-05-17T08:17:00.000-07:00

In lesson 2, you have learned how to enter the program code and run the sample VB programs but without much understanding about the logics of VB programming. Now, let’s get down to learning some basic rules about writing the VB program code.

Each control or object in VB can usually run many kinds of events or procedures; these events are listed in the dropdown list in the code window that is displayed when you double-click on an object and click on the procedures’ box(refer to Figure 2.3). Among the events are loading a form, clicking of a command button, pressing a key on the keyboard or dragging an object and more. For each event, you need to write an event procedure so that it can perform an action or a series of actions

To start writing an event procedure, you need to double-click an object. For example, if you want to write an event procedure when a user clicks a command button, you double-click on the command button and an event procedure will appear as shown in Figure 2.1. It takes the following format:

Private Sub Command1_Click

(Key in your program code here)

End Sub

You then need to key-in the procedure in the space between Private Sub Command1_Click............. End Sub. Sub actually stands for sub procedure that made up a part of all the procedures in a program. The program code is made up of a number of statements that set certain properties or trigger some actions. The syntax of Visual Basic’s program code is almost like the normal English language though not exactly the same, so it is very easy to learn.
The syntax to set the property of an object or to pass certain value to it is :
                            Object.Property
where Object and Property is separated by a period (or dot). For example, the statement Form1.Showmeans to show the form with the name Form1, Iabel1.Visible=true means label1 is set to be visible,Text1.text=”VB” is to assign the text VB to the text box with the name Text1, Text2.text=100 is to pass a value of 100 to the text box with the name text2, Timer1.Enabled=False is to disable the timer with the name Timer1 and so on. Let’s examine a few examples below:

Example 4.1 :
Private Sub Command1_Click
Label1.Visible = True
Label2.Visible = False
Text1.Ttext = "You're Correct!"
End Sub

Example 4.2 :
Private Sub Command1_Click
Label1.Caption="Welcome"
Picture1.Visible=True
End Sub

Example 4.3 :
Private Sub Command1_Click
Picture1.Show=True
Timer1.Enabled=True
Label1.Caption="Start Counting"
End Sub

In Example 4.1, clicking on the command button will make label1 become invisible and label2 become visible; and the text” You are correct” will appear in TextBox1. In example 4.2, clicking on the command button will make the caption label1 change to “Welcome” and Image1 will become visible.   In example 4.3 , clicking on the command button will make Picture1 show up, timer starts running and the caption of label1 change to “Start Counting”.
Syntaxes that do not involve setting of properties are also English-like, some of the commands are Print, If…Then….Else….End If, For…Next, Select Case…..End Select , End and Exit Sub. For example, Print “ Visual Basic” is to display the text Visual Basic on screen and End is to end the program. Other commands will be explained in details in the coming lessons.
Program code that involve calculations is very easy to write, you need to write them almost like you do in mathematics. However, in order to write an event procedure that involves calculations, you need to know the basic arithmetic operators in VB as they are not exactly the same as the normal operators we use, except for + and - . For multiplication, we use *, for division we use /, for raising a number x to the power of n, we use x ^n and for square root, we use Sqr(x). VB offers many more advanced mathematical functions such as Sin, Cos, Tan and Log, they will be discussed in lesson 10. There are also two important functions that are related to arithmetic operations, i.e. the functions Val and Str$ where Val is to convert text entered into a textbox to numerical value and Str$ is to display a numerical value in a textbox as a string (text). While the function Str$ is as important as VB can display a numeric values as string implicitly, failure to use Val will results in wrong calculation. Let’s examine example 4.4 and example 4.5.
Example 4.4
Private Sub Form_Activate()
Text3.text=text1.text+text2.text
End Sub

Example 4.5
Private Sub Form_Activate()
Text3.text=val(text1.text)+val(text2.text)
End Sub

When you run the program in example 4.4 and enter 12 in textbox1 and 3 in textbox2 will give you a result of 123, which is wrong. It is because VB treat the numbers as string and so it just joins up the two strings. On the other hand, running exampled 4.5 will give you the correct result, i.e., 15.

Lesson 3. Working With Controls

2009-05-17T08:11:00.000-07:00

3.1 The Control Properties

Before writing an event procedure for the control to response to a user's input, you have to set certain properties for the control to determine its appearance and how it will work with the event procedure. You can set the properties of the controls in the properties window or at runtime.

Figure 3.1 on the right is a typical properties window for a form. You can rename the form caption to any name that you like best. In the properties window, the item appears at the top part is the object currently selected (in Figure 3.1, the object selected is Form1). At the bottom part, the items listed in the left column represent the names of various properties associated with the selected object while the items listed in the right column represent the states of the properties. Properties can be set by highlighting the items in the right column then change them by typing or selecting the options available.

For example, in order to change the caption, just highlight Form1 under the name Caption and change it to other names. You may also try to alter the appearance of the form by setting it to 3D or flat. Other things you can do are to change its foreground and background color, change the font type and font size, enable or disable minimize and maximize buttons and etc.

You can also change the properties at runtime to give special effects such as change of color, shape, animation effect and so on. For example the following code will change the form color to red every time the form is loaded. VB uses hexadecimal system to represent the color. You can check the color codes in the properties windows which are showed up under ForeColor and BackColor .

Private Sub Form_Load()

Form1.Show
Form1.BackColor = &H000000FF&

End Sub

Another example is to change the control Shape to a particular shape at runtime by writing the following code. This code will change the shape to a circle at runtime. Later you will learn how to change the shapes randomly by using the RND function.

Private Sub Form_Load()

Shape1.Shape = 3

End Sub

I would like to stress that knowing how and when to set the objects' properties is very important as it can help you to write a good program or you may fail to write a good program. So, I advice you to spend a lot of time playing with the objects' properties.

I am not going into the details on how to set the properties. However, I would like to stress a few important points about setting up the properties.

You should set the Caption Property of a control clearly so that a user knows what to do with that command. For example, in the calculator program, all the captions of the command buttons such as +, - , MC, MR are commonly found in an ordinary calculator, a user should have no problem in manipulating the buttons.
A lot of programmers like to use a meaningful name for the Name Property may be because it is easier for them to write and read the event procedure and easier to debug or modify the programs later. However, it is not a must to do that as long as you label your objects clearly and use comments in the program whenever you feel necessary. T
One more important property is whether the control is enabled or not.
Finally, you must also considering making the control visible or invisible at runtime, or when should it become visible or invisible.

3.2 Handling some of the common controls

3.2.1 The Text Box

The text box is the standard control for accepting input from the user as well as to display the output. It can handle string (text) and numeric data but not images or pictures. String in a text box can be converted to a numeric data by using the function Val(text). The following example illustrates a simple program that processes the input from the user.

Example 3.1

In this program, two text boxes are inserted into the form together with a few labels. The two text boxes are used to accept inputs from the user and one of the labels will be used to display the sum of two numbers that are entered into the two text boxes. Besides, a command button is also programmed to calculate the sum of the two numbers using the plus operator. The program use creates a variable sum to accept the summation of values from text box 1 and text box 2.The procedure to calculate and to display the output on the label is shown below. The output is shown in Figure 3.2

Private Sub Command1_Click()
‘To add the values in text box 1 and text box 2
Sum = Val(Text1.Text) + Val(Text2.Text)
‘To display the answer on label 1
Label1.Caption = Sum
End Sub

Figure 3.2

3.2.2 The Label
The label is a very useful control for Visual Basic, as it is not only used to provide instructions and guides to the users, it can also be used to display outputs. One of its most important properties isCaption. Using the syntax label.Caption, it can display text and numeric data . You can change its caption in the properties window and also at runtime. Please refer to Example 3.1 and Figure 3.1 for the usage of label.
3.2.3 The Command Button
The command button is one of the most important controls as it is used to execute commands. It displays an illusion that the button is pressed when the user click on it. The most common event associated with the command button is the Click event, and the syntax for the procedure is
Private Sub Command1_Click ()
Statements
End Sub
3.2.4 The Picture Box
The Picture Box is one of the controls that is used to handle graphics. You can load a picture at design phase by clicking on the picture item in the properties window and select the picture from the selected folder. You can also load the picture at runtime using the LoadPicture method. For example, the statement will load the picture grape.gif into the picture box.
Picture1.Picture=LoadPicture ("C:\VB program\Images\grape.gif")
You will learn more about the picture box in future lessons. The image in the picture box is not resizable.

3.2.5 The Image Box
The Image Box is another control that handles images and pictures. It functions almost identically to the picture box. However, there is one major difference, the image in an Image Box is stretchable, which means it can be resized. This feature is not available in the Picture Box. Similar to the Picture Box, it can also use the LoadPicture method to load the picture. For example, the statement loads the picture grape.gif into the image box.
Image1.Picture=LoadPicture ("C:\VB program\Images\grape.gif")
3.2.6 The List Box
The function of the List Box is to present a list of items where the user can click and select the items from the list. In order to add items to the list, we can use the AddItem method. For example, if you wish to add a number of items to list box 1, you can key in the following statements
Example 3.2

Private Sub Form_Load ( )

List1.AddItem “Lesson1”
List1.AddItem “Lesson2”
List1.AddItem “Lesson3”
List1.AddItem “Lesson4”

End Sub
The items in the list box can be identified by the ListIndex property, the value of the ListIndex for the first item is 0, the second item has a ListIndex 1, and the second item has a ListIndex 2 and so on
3.2.7 The Combo Box
The function of the Combo Box is also to present a list of items where the user can click and select the items from the list. However, the user needs to click on the small arrowhead on the right of the combo box to see the items which are presented in a drop-down list. In order to add items to the list, you can also use the AddItem method. For example, if you wish to add a number of items to Combo box 1, you can key in the following statements
Example 3.3
Private Sub Form_Load ( )

Combo1.AddItem “Item1”
Combo1.AddItem “Item2”
Combo1.AddItem “Item3”
Combo1.AddItem “Item4”

End Sub

3.2.8 The Check Box
The Check Box control lets the user selects or unselects an option. When the Check Box is checked, its value is set to 1 and when it is unchecked, the value is set to 0. You can include the statements Check1.Value=1 to mark the Check Box and Check1.Value=0 to unmark the Check Box, as well as use them to initiate certain actions. For example, the program will change the background color of the form to red when the check box is unchecked and it will change to blue when the check box is checked. You will learn about the conditional statement If….Then….Elesif in later lesson. VbRed and vbBlue are color constants and BackColor is the background color property of the form.
3.2.9 The Option Box

The Option Box control also lets the user selects one of the choices. However, two or more Option Boxes must work together because as one of the Option Boxes is selected, the other Option Boxes will be unselected. In fact, only one Option Box can be selected at one time. When an option box is selected, its value is set to “True” and when it is unselected; its value is set to “False”. In the following example, the shape control is placed in the form together with six Option Boxes. When the user clicks on different option boxes, different shapes will appear. The values of the shape control are 0, 1, and 2,3,4,5 which will make it appear as a rectangle, a square, an oval shape, a rounded rectangle and a rounded square respectively.
Example 3.4
Private Sub Option1_Click ( )
Shape1.Shape = 0
End Sub

Private Sub Option2_Click()
Shape1.Shape = 1
End Sub

Private Sub Option3_Click()
Shape1.Shape = 2
End Sub

Private Sub Option4_Click()
Shape1.Shape = 3
End Sub

Private Sub Option5_Click()
Shape1.Shape = 4
End Sub

Private Sub Option6_Click()
Shape1.Shape = 5
End Sub

3.2.10 The Drive List Box
The Drive ListBox is for displaying a list of drives available in your computer. When you place this control into the form and run the program, you will be able to select different drives from your computer as shown in Figure 3.3

Figure 3.3 The Drive List Box
3.2.11 The Directory List Box
The Directory List Box is for displaying the list of directories or folders in a selected drive. When you place this control into the form and run the program, you will be able to select different directories from a selected drive in your computer as shown in Figure 3.4
Figure 3.4 The Directory List Box

3.2.12 The File List Box
The File List Box is for displaying the list of files in a selected directory or folder. When you place this control into the form and run the program, you will be able to shown the list of files in a selected directory as shown in Figure 3.5
You can coordinate the Drive List Box, the Directory List Box and the File List Box to search for the files you want. The procedure will be discussed in later lessons.

Lesson 2. Building Visual Basic Applications

2009-05-12T06:48:00.000-07:00

2.1 Creating Your First Application

In this section, we will not go into the technical aspects of Visual Basic programming yet, what you need to do is just try out the examples below to see how does in VB program look like:

Example 2.1.1 is a simple program. First of all, you have to launch Microsoft Visual Basic 6. Normally, a default form with the name Form1 will be available for you to start your new project. Now, double click on Form1, the source code window for Form1 as shown in figure 2.1 will appear. The top of the source code window consists of a list of objects and their associated events or procedures. In figure 2.1, the object displayed is Form and the associated procedure is Load.

Figure 2.1 Source Code Window

When you click on the object box, the drop-down list will display a list of objects you have inserted into your form as shown in figure 2.2. Here, you can see a form with the name Form1, a command button with the name Command1, a Label with the name Label1 and a Picture Box with the name Picture1. Similarly, when you click on the procedure box, a list of procedures associated with the object will be displayed as shown in figure 2.3. Some of the procedures associated with the object Form1 are Activate, Click, DblClick (which means Double-Click) , DragDrop, keyPress and more. Each object has its own set of procedures. You can always select an object and write codes for any of its procedure in order to perform certain tasks.

You do not have to worry about the beginning and the end statements (i.e. Private Sub Form_Load.......End Sub.); Just key in the lines in between the above two statements exactly as are shown here. When you press F5 to run the program, you will be surprise that nothing shown up .In order to display the output of the program, you have to add the Form1.show statement like in Example 2.1.1 or you can just use Form_Activate ( ) event procedure as shown in example 2.1.2. The command Print does not mean printing using a printer but it means displaying the output on the computer screen. Now, press F5 or click on the run button to run the program and you will get the output as shown in figure 2.4.

You can also perform arithmetic calculations as shown in example 2.1.2. VB uses * to denote the multiplication operator and/ to denote the division operator. The output is shown in figure 2.3, where the results are arranged vertically.

Figure 2.2: List of Objects

Figure 2.2: List of Procedures

Example 2.1.1

Private Sub Form_Load ( )

Form1.show

Print “Welcome to Visual Basic tutorial”

End Sub

Figure 2.4 : The output of example 2.1.1

Example 2.1.2

Private Sub Form_Activate ( )

Print 20 + 10
Print 20 - 10
Print 20 * 10
Print 20 / 10

End Sub

Figure 2.5: The output of example 2.1.2

You can also use the + or the & operator to join two or more texts (string) together like in example 2.1.4 (a) and (b)

Example 2.1.4(a)

Private Sub
A = Tom
B = “likes"
C = “to"
D = “eat"
E = “burger"
Print A + B + C + D + E
End Sub

Example 2.1.4(b)

Private Sub
A = Tom
B = “likes"
C = “to"
D = “eat"
E = “burger"
Print A & B & C & D & E
End Sub

The Output of Example 2.1.4(a) &(b) is as shown in Figure 2.7.

2.2 Steps in Building a Visual Basic Application

Step 1 : Design the interface

Step 2 : Set properties of the controls (Objects)

Step 3 : Write the event procedures

Lesson 1. Introduction to Visual Basic 6

2009-05-12T06:38:00.000-07:00

1.1 The concept of computer programming

Before we begin Visual Basic 6 programming, let us understand some basic concepts of programming. According to Webopedia, a computer program is an organized list of instructions that, when executed, causes the computer to behave in a predetermined manner. Without programs, computers are useless. Therefore, programming means designing or creating a set of instructions to ask the computer to carry out certain jobs which normally are very much faster than human beings can do.

A lot of people think that computer CPU is a very intelligent thing, which in actual fact it is a dumb and inanimate object that can do nothing without human assistant. The microchips of a CPU can only understand two distinct electrical states, namely, the on and off states, or 0 and 1 codes in the binary system. So, the CPU only understands a combinations of 0 and 1 codes, a language which we called machine language. Machine language is extremely difficult to learn and it is not for us laymen to master it easily. Fortunately , we have many smart programmers who wrote interpreters and compilers that can translate human language-like programs such as BASIC into machine language so that the computer can carry out the instructions entered by the users. Machine language is known as the primitive language while Interpreters and compilers like Visual Basic are called high-level language. Some of the high level computer languages beside Visual Basic are Fortran, Cobol, Java, C, C++, Turbo Pascal, and etc .

1.2 What programs can you create with Visual Basic 6?

With VB 6, you can create any program depending on your objective. For example, you can create educational programs to teach science , mathematics, language, history , geography and so on. You can also create financial and accounting programs to make you a more efficient accountant or financial controller. For those of you who like games, you can create those programs as well. Indeed, there is no limit to what program you can create ! There are many such programs in this tutorial, so you must spend more time on the tutorial in order to learn how to create those programs. If you wish to see some of the sample programs, you can take a look at the link below:

VB Sample Programs

1.3 The Visual Basic 6 Integrated Development Environment

Before you can program in VB 6, you need to install Visual Basic 6 in your computer. If you do not own a copy of Visual Basic 6 software yet , you can purchase it from Amazon.com by clicking the link below:

Microsoft Visual Basic 6.0 Professional

Basically any present computer system should be able to run the program, be it a Intel Pentium II, Intel Pentium III, Intel Pentium IV or even AMD machines, Visual Basic 6 can run without any problem. It might not be true for VB2008, older machines might not be able to run VB2008 as it takes up much more resources, therefore I still prefer VB 6 as it is light and easy to program. It is still very useful and powerful, and I am happy to know that Microsoft Windows Vista can support VB 6. However, if you prefer to learn VB 2008, you can refer VB 2008 Tutorial.
On start up, Visual Basic 6.0 will display the following dialog box as shown in figure 1.1. You can choose to either start a new project, open an existing project or select a list of recently opened programs. A project is a collection of files that make up your application. There are various types of applications that we could create, however, we shall concentrate on creating Standard EXE programs (EXE means executable program). Now, click on the Standard EXE icon to go into the actual Visual Basic 6 programming environment.

Timeline of Visual Basic (VB1 to VB6)

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* Project 'Thunder' was initiated
* Visual Basic 1.0 (May [[1991]]) was released for Windows at the Comdex/Windows World trade show in Atlanta, Georgia.
[[Image:VBDOS-icon.PNG|right|VB DOS Logo]]
[[Image:Microsoft Visual Basic for MS-DOS (Professional Edition Version1.00).png|thumb|right|300px|Visual Basic for MS-DOS]]
* Visual Basic 1.0 for [[DOS]] was released in September [[1992]]. The language itself was not quite compatible with Visual Basic for Windows, as it was actually the next version of Microsoft's DOS-based BASIC compilers, [[QuickBASIC]] and BASIC Professional Development System. The interface used the [[Character Oriented Windows|"COW" (Character Oriented Windows)]] interface, using [[extended ASCII]] characters to simulate the appearance of a [[Graphical user interface|GUI]].
* Visual Basic 2.0 was released in November [[1992]]. The programming environment was easier to use, and its speed was improved. Notably, forms became instantiable objects, thus laying the foundational concepts of class modules as were later offered in VB4.
* Visual Basic 3.0 was released in the summer of [[1993]] and came in Standard and Professional versions. VB3 included version 1.1 of the [[Microsoft Jet Database Engine]] that could read and write Jet (or Access) 1.x databases.
* Visual Basic 4.0 (August [[1995]]) was the first version that could create [[32-bit]] as well as [[16-bit]] Windows programs. It also introduced the ability to write non-GUI classes in Visual Basic. Incompatibilities between different releases of VB4 caused installation and operation problems. While previous versions of Visual Basic had used VBX controls, Visual Basic now used OLE controls (with files names ending in .OCX) instead. These were later to be named ActiveX controls.
* With version 5.0 (February [[1997]]), Microsoft released Visual Basic exclusively for [[32-bit]] versions of Windows. Programmers who preferred to write 16-bit programs were able to import programs written in Visual Basic 4.0 to Visual Basic 5.0, and Visual Basic 5.0 programs can easily be converted with Visual Basic 4.0. Visual Basic 5.0 also introduced the ability to create custom user controls, as well as the ability to compile to native Windows executable code, speeding up calculation-intensive code execution. A free, downloadable Control Creation Edition was also released for creation of [[ActiveX|ActiveX control]]s. It was also used as an introductory form of Visual Basic: a regular .exe project could be created and run in the IDE, but not compiled.
* Visual Basic 6.0 (Mid [[1998]]) improved in a number of areas {{cite web| url=http://www.insteptech.com/techLibrary/vbClassic/vb6_news.htm| title = What's new in VB6? | www.insteptech.com | publisher = www.insteptech.com | author = www.insteptech.com | year = [[2005-07-22]]}} including the ability to create web-based applications. VB6 has entered Microsoft's "non-supported phase" as of March [[2008]]. Although the Visual Basic 6.0 development environment is no longer supported, the runtime is supported on Windows Vista, Windows Server 2008 and Windows 7 [http://msdn.microsoft.com/en-us/vbrun/ms788708.aspx Support Statement for Visual Basic 6.0 on Windows Vista, Windows Server 2008 and Windows 7.
* Mainstream Support for Microsoft Visual Basic 6.0 ended on [[March 31]], [[2005]]. Extended support ended in March 2008.[http://msdn2.microsoft.com/en-us/vbrun/ms788707.aspx Product Family Life Cycle Guidelines for Visual Basic 6.0] In response, the Visual Basic user community expressed its grave concern and lobbied users to sign a petition to keep the product alive.[http://www.classicvb.org/petition/ Petition to Microsoft] Microsoft has so far refused to change their position on the matter. (but see {{cite web| url= http://www.infoq.com/news/2009/03/vb6_on_win7 |title = Visual Basic 6.0 to be Supported on Windows 7| InfoQ | accessdate = 2009-03-05| publisher = The Register| author = Al Tenhundfeld | year = [[2009-03-04]]}}) Ironically, around this time (2005), it was exposed that Microsoft's new anti-spyware offering, [[Windows Defender|Microsoft AntiSpyware]] (part of the [[GIANT Company Software]] purchase), was coded in Visual Basic 6.0.{{cite web| url=http://www.theregister.co.uk/2005/07/22/microsoft_spyware_vb6/| title = MS Anti-Spyware built on MS Abandonware | The Register| accessdate = 2006-10-04| publisher = The Register| author = Andrew Orlowski and Carey Bishop | year = [[2005-07-22]]}}Its replacement, Windows Defender, was rewritten as C++ code.[http://www.winsupersite.com/reviews/windefender_beta2.asp Paul Thurrott's SuperSite for Windows: Windows Defender Beta 2 Review]

==Evolution of Visual Basic==

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VB 1.0 was introduced in [[1991]]. The drag and drop design for creating the user interface is derived from a prototype form generator developed by [[Alan Cooper]] and his company called ''Tripod''. Microsoft contracted with Cooper and his associates to develop Tripod into a programmable form system for Windows 3.0, under the code name ''Ruby'' (no relation to the [[Ruby (programming language)|Ruby programming language]]).

Tripod did not include a programming language at all. Microsoft decided to combine Ruby with the Basic language to create Visual Basic.

The Ruby interface generator provided the "visual" part of Visual Basic and this was combined with the "EB" Embedded BASIC engine designed for Microsoft's abandoned "Omega" database system. Ruby also provided the ability to load [[dynamic-link library|dynamic link libraries]] containing additional controls (then called "gizmos"), which later became the [[Visual Basic Extension|VBX]] interface{{cite web| url=http://www.forestmoon.com/BIRTHofVB/BIRTHofVB.html| title = The Birth of Visual Basic}}.

===Timeline of Visual Basic (VB1 to VB6)===
* Project 'Thunder' was initiated
* Visual Basic 1.0 (May [[1991]]) was released for Windows at the Comdex/Windows World trade show in Atlanta, Georgia.
[[Image:VBDOS-icon.PNG|right|VB DOS Logo]]
[[Image:Microsoft Visual Basic for MS-DOS (Professional Edition Version1.00).png|thumb|right|300px|Visual Basic for MS-DOS]]
* Visual Basic 1.0 for [[DOS]] was released in September [[1992]]. The language itself was not quite compatible with Visual Basic for Windows, as it was actually the next version of Microsoft's DOS-based BASIC compilers, [[QuickBASIC]] and BASIC Professional Development System. The interface used the [[Character Oriented Windows|"COW" (Character Oriented Windows)]] interface, using [[extended ASCII]] characters to simulate the appearance of a [[Graphical user interface|GUI]].
* Visual Basic 2.0 was released in November [[1992]]. The programming environment was easier to use, and its speed was improved. Notably, forms became instantiable objects, thus laying the foundational concepts of class modules as were later offered in VB4.
* Visual Basic 3.0 was released in the summer of [[1993]] and came in Standard and Professional versions. VB3 included version 1.1 of the [[Microsoft Jet Database Engine]] that could read and write Jet (or Access) 1.x databases.
* Visual Basic 4.0 (August [[1995]]) was the first version that could create [[32-bit]] as well as [[16-bit]] Windows programs. It also introduced the ability to write non-GUI classes in Visual Basic. Incompatibilities between different releases of VB4 caused installation and operation problems. While previous versions of Visual Basic had used VBX controls, Visual Basic now used OLE controls (with files names ending in .OCX) instead. These were later to be named ActiveX controls.
* With version 5.0 (February [[1997]]), Microsoft released Visual Basic exclusively for [[32-bit]] versions of Windows. Programmers who preferred to write 16-bit programs were able to import programs written in Visual Basic 4.0 to Visual Basic 5.0, and Visual Basic 5.0 programs can easily be converted with Visual Basic 4.0. Visual Basic 5.0 also introduced the ability to create custom user controls, as well as the ability to compile to native Windows executable code, speeding up calculation-intensive code execution. A free, downloadable Control Creation Edition was also released for creation of [[ActiveX|ActiveX control]]s. It was also used as an introductory form of Visual Basic: a regular .exe project could be created and run in the IDE, but not compiled.
* Visual Basic 6.0 (Mid [[1998]]) improved in a number of areas {{cite web| url=http://www.insteptech.com/techLibrary/vbClassic/vb6_news.htm| title = What's new in VB6? | www.insteptech.com | publisher = www.insteptech.com | author = www.insteptech.com | year = [[2005-07-22]]}} including the ability to create web-based applications. VB6 has entered Microsoft's "non-supported phase" as of March [[2008]]. Although the Visual Basic 6.0 development environment is no longer supported, the runtime is supported on Windows Vista, Windows Server 2008 and Windows 7 [http://msdn.microsoft.com/en-us/vbrun/ms788708.aspx Support Statement for Visual Basic 6.0 on Windows Vista, Windows Server 2008 and Windows 7.
* Mainstream Support for Microsoft Visual Basic 6.0 ended on [[March 31]], [[2005]]. Extended support ended in March 2008.[http://msdn2.microsoft.com/en-us/vbrun/ms788707.aspx Product Family Life Cycle Guidelines for Visual Basic 6.0] In response, the Visual Basic user community expressed its grave concern and lobbied users to sign a petition to keep the product alive.[http://www.classicvb.org/petition/ Petition to Microsoft] Microsoft has so far refused to change their position on the matter. (but see {{cite web| url= http://www.infoq.com/news/2009/03/vb6_on_win7 |title = Visual Basic 6.0 to be Supported on Windows 7| InfoQ | accessdate = 2009-03-05| publisher = The Register| author = Al Tenhundfeld | year = [[2009-03-04]]}}) Ironically, around this time (2005), it was exposed that Microsoft's new anti-spyware offering, [[Windows Defender|Microsoft AntiSpyware]] (part of the [[GIANT Company Software]] purchase), was coded in Visual Basic 6.0.{{cite web| url=http://www.theregister.co.uk/2005/07/22/microsoft_spyware_vb6/| title = MS Anti-Spyware built on MS Abandonware | The Register| accessdate = 2006-10-04| publisher = The Register| author = Andrew Orlowski and Carey Bishop | year = [[2005-07-22]]}}Its replacement, Windows Defender, was rewritten as C++ code.[http://www.winsupersite.com/reviews/windefender_beta2.asp Paul Thurrott's SuperSite for Windows: Windows Defender Beta 2 Review]

==Characteristics present in Visual Basic==

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Visual Basic has the following traits which differ from C-derived languages:
* Multiple assignment available in C language is not possible. A = B = C does not imply that the values of A, B and C are equalled. The boolean result of "Is B = C?" is stored in A. The result stored in A could therefore be false(0) or true(-1)
* [[Boolean datatype|Boolean]] constant True has numeric value −1.In most languages, True is mapped to a non zero numeric value, often 1 or -1. This is because the Boolean data type is stored as a 16-bit signed integer. In this construct −1 evaluates to 16 binary 1s (the Boolean value True), and 0 as 16 0s (the Boolean value False). This is apparent when performing a Not operation on a 16 bit signed integer value 0 which will return the integer value −1, in other words True = Not False. This inherent functionality becomes especially useful when performing logical operations on the individual bits of an integer such as And, Or, Xor and Not.[http://vb.mvps.org/tips/Truth.asp Microsoft Basic Logical Expression Evaluation] This definition of True is also consistent with BASIC since the early 1970s Microsoft BASIC implementation and is also related to the characteristics of CPU instructions at the time.
* Logical and bitwise operators are unified. This is unlike some C-derived languages (such as [[Perl]]), which have separate logical and bitwise operators. This again is a traditional feature of BASIC.
* Variable [[array]] base. Arrays are declared by specifying the upper and lower bounds in a way similar to Pascal and [[Fortran]]. It is also possible to use the Option Base statement to set the default lower bound. Use of the Option Base statement can lead to confusion when reading Visual Basic code and is best avoided by always explicitly specifying the lower bound of the array. This lower bound is not limited to 0 or 1, because it can also be set by declaration. In this way, both the lower and upper bounds are programmable. In more subscript-limited languages, the lower bound of the array is not variable. This uncommon trait does exist in [[Visual Basic .NET]] but not in [[VBScript]].
: OPTION BASE was introduced by ANSI, with the standard for ANSI Minimal BASIC in the late 1970s.
* Relatively strong integration with the [[Microsoft Windows|Windows operating system]] and the [[Component Object Model]].
* [[Rounding#Round-to-even method|Banker's rounding]] as the default behavior when converting real numbers to integers with the Round function.
* Integers are automatically promoted to reals in expressions involving the normal division operator (/) so that division of an odd integer by an even integer produces the intuitively correct result. There is a specific integer divide operator (\) which does truncate.
* By default, if a variable has not been declared or if no type declaration character is specified, the variable is of type [[Variant type|Variant]]. However this can be changed with Deftype statements such as DefInt, DefBool, DefVar, DefObj, DefStr. There are 12 Deftype statements in total offered by Visual Basic 6.0. The default type may be overridden for a specific declaration by using a special suffix character on the variable name (# for Double, ! for Single, & for Long, % for Integer, $ for String, and @ for Currency) or using the key phrase As (type). VB can also be set in a mode that only explicitly declared variables can be used with the command Option Explicit.

Language features

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Like the BASIC programming language, Visual Basic was designed to be easy to learn and use. The language not only allows programmers to create simple GUI applications, but can also develop complex applications. Programming in VB is a combination of visually arranging components or controls on a form, specifying attributes and actions of those components, and writing additional lines of code for more functionality. Since default attributes and actions are defined for the components, a simple program can be created without the programmer having to write many lines of code. Performance problems were experienced by earlier versions, but with faster computers and native code compilation this has become less of an issue.

Although programs can be compiled into native code executables from version 5 onwards, they still require the presence of runtime libraries of approximately 1 MB in size. This runtime is included by default in Windows 2000 and later, but for earlier versions of Windows like 95/98/NT it must be distributed together with the executable.

Forms are created using drag-and-drop techniques. A tool is used to place controls (e.g., text boxes, buttons, etc.) on the form (window). Controls have attributes and event handlers associated with them. Default values are provided when the control is created, but may be changed by the programmer. Many attribute values can be modified during run time based on user actions or changes in the environment, providing a dynamic application. For example, code can be inserted into the form resize event handler to reposition a control so that it remains centered on the form, expands to fill up the form, etc. By inserting code into the event handler for a keypress in a text box, the program can automatically translate the case of the text being entered, or even prevent certain characters from being inserted.

Visual Basic can create executables (EXE files), ActiveX controls, or DLL files, but is primarily used to develop Windows applications and to interface database systems. Dialog boxes with less functionality can be used to provide pop-up capabilities. Controls provide the basic functionality of the application, while programmers can insert additional logic within the appropriate event handlers. For example, a drop-down combination box will automatically display its list and allow the user to select any element. An event handler is called when an item is selected, which can then execute additional code created by the programmer to perform some action based on which element was selected, such as populating a related list.

Alternatively, a Visual Basic component can have no user interface, and instead provide ActiveX objects to other programs via Component Object Model (COM). This allows for server-side processing or an add-in module.

The language is garbage collected using reference counting, has a large library of utility objects, and has basic object oriented support. Since the more common components are included in the default project template, the programmer seldom needs to specify additional libraries. Unlike many other programming languages, Visual Basic is generally not case sensitive, although it will transform keywords into a standard case configuration and force the case of variable names to conform to the case of the entry within the symbol table entry. String comparisons are case sensitive by default, but can be made case insensitive if so desired.

The Visual Basic compiler is shared with other Visual Studio languages (C, C++), but restrictions in the IDE do not allow the creation of some targets (Windows model DLL's) and threading models.