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Programming in Visual Basic

Working with Text :

Text boxes, as the name implies, are designed to work directly with text. All text 'strings' involved within a program have to be enclosed within quotes.
For example, to assign the value "Radio" to the Item text box within the Order Entry Form, we would use the following code:

txtItem = "Radio"

Task Four :

1. Load 'QUIZ.VBP' and add 4 command buttons with captions 'Question 1', 'Question 2', 'Question 3', 'Question 4' and names cmdQ1, cmdQ2, cmdQ3, cmdQ4.

2. Set the Multiline property of the txtQuestion text box to True. This will allow long questions to word wrap.

3. Double click on the Question 1 command button and enter the following code:

Sub cmdQ1_Click ()
   txtQuestion = "What do you call a small piece of silicon which has a number of electronic circuits fabricated on it?"
   txtAnswer1 = "Byte"
   txtAnswer2 = "Chip"
   txtAnswer3 = "Port"
End Sub

Click on the Start Program button, click on the command button to see the question being displayed. Click on the End Program button when you've finished.

Exercise Four :

1. Enter code for the Question 2, Question 3, Question 4 command buttons using the following:

Question 2

A keyboard is used to

Answers

Output data
Input data
Control input devices

Question 3

Which of the following is not an output device?

Answers

Light pen
Plotter
VDU

Question 4

The programs that run on a computer are known as

Answers

Hardware
Liveware
Software

2. Check that all questions and answers are displayed correctly.

Making Decisions :

You can include decision structures in any event procedure. A decision structure will test a condition and then perform operations depending on whether or not the condition is met or not (True or Flase). A condition usually makes a comparison between two values using one of the following operators:

Operator

Meaing

Examples

Explanation

=

Equal to

txtItem ="Radio"

is the item a Radio

<>

Not Equal to

txtPrice <> 0

is the price not 0

>

Greater than

txtPrice > 12.54

is the price greater than 12.54

<

Less than

txtPrice < 10.00

is the price less than 10.00

In Visual Basic, the If...Then...Else...End if structure is used to make decisions. The If, Then and End if parts of the structure are compulsory.
The Else statement is only used when an alternative set of operationsneed to be carried out if the original condition is not met.

Examples :

To set the Price to 12.54 if the item is a radio:

If txtItem = "Radio" Then
   txtPrice = 12.54
End If

To set the address details if the name is P Brown:

If txtName = "P Brown" Then
   txtAddress1 = "East Birmingham College"
   txtAddress2 = "Garretts Green Lane"
   txtTown = "Birmingham"
   txtPostCode = "B33 0TS"
   txtPhone = "743 4471"
End If

To check if the user has chosen the correct check box for Question 1 in the quiz:

If chkAnswer2 = True Then
   Score = 1
Else
   Score = 0
End If

N.B. Notice the use of indents to line up the main parts of the stucture. This is used extensively in Visual Basic to make the program easier to follow and to make checking for the start and end of a particular structure easier.

Task Five :

1. Open the project STOCK.VBP. Add another command button with a caption of Find Item and a Name cmdFindItem.

2. Double click on this command button and add the following code:

Sub cmdFindItem_Click ()

If txtItem = "Radio" Then
   txtPrice = 12.54
End If
If txtItem = "Headphones" Then
   txtPrice = 23.5
End If
If txtItem = "Glasses" Then
   txtPrice = 13.99
End If
If txtItem = "Teddy Bear" Then
   txtPrice = 23.49
End If

End Sub

3. Click on the Start Program button, enter a valid Item e.g. Radio and click on the Find Item command button to see the price being displayed. Try the program with other valid items (Headphones, Glasses or Teddy Bear). What happens if you enter an item that is not in the list? What happens if you type radio instead of Radio? What happens when you click on the Calculate command button? (We'll come back to this shortly)

4. Stop the program and re-save the project.

Exercise Five :

1. Open the ADDRESS.VBP project and add a Find Name command button (cmdFindName)

2. Add code for this button consisting of a number of If Then ... End If statements to check for the following names and the appropriate details from the table below:

Name

Address 1

Address 2

Town

Post Code

Phone

P Brown

E. Birmingham Coll.

Garretts Green Lane

Birmingham

B33 0TS

743 4471

J. Jones

1 New Street

Solihull West

Mids

B92 6TY

706 2234

B. Jaffer

33 Green Lane

Small Heath

Birmingham

B12 3ER

356 3434

C. Henry

243 Field Road

Sheldon

Birmingham

B26 4ER

742 2323

3. Open the STOCK.VBP project and add a new label, text box and command button as shown below:

Text box name

txtStockNumber

Command button name

cmdFindNumber

4. Enter code for this new command button to check the Stock Number and update the text boxes as below:

Stock Number

Item

Price

1000

Radio

12.54

1001

Headphones

23.50

1002

Glasses

13.99

1003

Teddy Bear

23.49

1004

Rocking Horse

45.98

1005

Dinner Set

24.99

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