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Programming
Standard Grade Computing Studies
C Wilson, 2007
[VISUAL BASIC 2005 EXPRESS EDITION]
Programming in Visual Basic Express
CONTENTS
Page
GETTING STARTED
Creating a Visual Basic Project ……………………………………………………….…. 3
Storing your Visual Basic Projects ………………………………………………………… 6
FOUNDATION
Displaying information (TextBox) …………………………………………………………. 9
Displaying Several Lines of Information (ListBox) ……………………………..………. 10
Simple Calculations ………………………………..…………………….………….…… 12
Variables & Data Types ……………….………………………………...……………….. 13
Worked Example – Area ……………………………………………………………….… 14
Installing the PrintForm Component ……………….………………….……………….. 18
Using the PrintForm Component ………………..……………………………………….. 19
SQA Task – Food Mixers ……………………….……………………………………….. 23
Loops (FOR Loop) ………………………………..……………………………………….. 25
Worked Example – Punishment Exercise! …………………………………………...... 26
SQA Task – Car Stickers ………………………………………………………………… 29
GENERAL
Modules & Sub-routines (design & code) …………………………….………………... 33
IF … THEN (Selection) ………………………….………………….….………………... 35
Worked Example – Car Sales ………………………….….…………………………….. 36
SQA Task – School Heating ………………………..….……………….……………….. 39
User Interface – MessageBox …..………………..….……………….………………… 41
User Interface – InputBox ……………………………………….……………………….. 44
Worked Example – Currency Converter …………….…………….….………………... 46
SQA Task – Car Hire …………………………………………………………..…………. 51
Running Totals & Counters ………………………..……………………………………… 53
Loops & Control Variables …………………………….…….…….……………….….….. 54
Worked Example – Rainfall Program ………………………….….…………………….. 56
SQA Task – Over Forty …………………………………..……..……….……………….. 61
CREDIT
Complex Conditions – AND / OR ………………..…………….……………….……….. 65
Loops (WHILE Loop) ……………………………………………………………………… 65
Input Validation – MessageBoxes / Pre-defined & user-defined functions ………….. 66
Program Testing ………………………………………………………………………….. 72
Worked Example – Can You Drive? ……………………………………………………. 73
SQA Task – Language Course ………………………………………….…….………... 77
Random Numbers ………………………………………………………………………….. 79
Boolean Variables ………………………………………………………………………… 80
Worked Example – Dice Game ………………………………………………………… 81
SQA Task – Guess Number ……………………………………………………………... 85
Arrays ………………………………………………………………………………………. 87
Worked Example – Golden Ticket ……………………………………………………… 91
SQA Task – Charity Lottery ……………………….……………………………………... 95
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Creating a new Visual Basic Project
When you launch Visual Basic Express your screen should look like the one below.

Click as shown to create a new programming project.
Before we can start programming, we provide Visual Basic with a name for our project.

Make sure „Windows
Application‟ is selected as
below

Enter „First Program‟ for our
project name and click „OK‟.
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You will arrive at the „form design‟ screen like the one below.
We will use this screen to create the user interface for our programs.
To create our user interface we will use the „toolbox‟ located on the left hand side of our screen.

Hover your mouse over the toolbox icon and click the little „pin‟ icon to keep the toolbox on
your screen as shown below.
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Your screen should now appear like the one below.
We will use the toolbox to create objects on our blank form by dragging them.
Users of our program use these objects to enter inputs and view outputs while our programs are
running.
The toolbox looks very complicated at first but don‟t worry! We‟re only going to use a few of the
items in it to create our programs.
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Storing your Visual Basic programming projects.
As with all your previous practical work in Computing, your programming work should be stored in
your „home directory‟ on the school‟s file server.
The Visual Basic default setting is to save your programming work on your local computer‟s hard
disk (it‟s C: drive), and we need to change this.

From the „Tools‟ menu select „Options‟ as shown.

In the Options window, select „Projects and Solutions‟ then click the button shown to select
a new location.

Navigate to your programming folder. This should be located inside the Computing folder
inside your home directory. Ask your teacher for help if necessary.

If you move to another machine in your class, you must repeat these steps again.
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Now we‟re ready to start programming…
Hooray!
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FOUNDATION LEVEL
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Displaying Information (TextBox)
In our first program we shall get Visual Basic to display a message in what is called a „textbox‟.

Create a „command button‟ and a „textbox‟ as shown below.

Double click the command button to enter program code below…
Public Class Form1
Private Sub Button1_Click(ByVal sender As System.Object, ByVal e As System.EventArgs)
Handles Button1.Click
'My First Program
'Visual Basic Express
'Your name
'Today's date
Start typing here
TextBox1.Text = "Hello World!"
Finish typing here
End Sub
End Class

Run your program and correct any mistakes if necessary. „Save All‟ when done.
Exercise:
Write a program to make the name of your favourite band / singer appear on screen
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Displaying Several Lines of Information (ListBox)
So far we have looked at getting Visual Basic to display a single line of text in a text box.
In this program we shall get Visual Basic to display a message several lines long in what is called a
„listbox‟.

Create a new project called „ListBox‟, then add a „command button‟ and a „listbox‟ as shown
below.

Double click the command button to enter program code as follows…
Public Class Form1
'Listbox Program
'Your name
'Today's date
ListBox1.Items.Add("Hello World!")
ListBox1.Items.Add("Computing is fun!")
ListBox1.Items.Add("")
ListBox1.Items.Add("And, Programming is easy!")
Start typing here
Finish typing here
End Sub
End Class

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SUMMARY
Copy the following into your jotter.
Command Button
Textbox
Allows the user to run program code when pressed.
Allows the program to display a single line of text.
E.g.
textbox1.text=”Hello”
Allows the program to display multiple lines of text.
E.g.
listbox1.items.add(“Hello”)
listbox1.items.add(“My name is Elvis”)
Listbox
To clear a listbox of text, enter
listbox1.items.clear()
To display a blank line, enter
listbox1.items.add(“”)
Any text starting with „ will be ignored by the computer.
These lines are known as comments and are used by
Comments
programmers to include short notes about the program.
Every program you write should contain some comments.
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Simple Calculations

Create a new project called „Calculate‟.

Add a „command button‟, a „listbox‟ and two „textboxes‟ as shown below.
Textbox1
Textbox2

Public Class Form1
Private Sub Button1_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles
Button1.Click
'Simple Calculations Program
'Your name
'Today's date
TextBox1.Text = ("")
TextBox2.Text = ("")
ListBox1.Items.Clear()
'clear the contents of textbox1 if any
'clear the contents of textbox2 if any
'clear the content of listbox1 if any
ListBox1.Items.Add("4 + 5")
ListBox1.Items.Add(4 + 5)
TextBox1.Text = 4 + 5
TextBox2.Text = "4+5"
End Sub
End Class

Using speech marks makes the program display the
exact text inside the speech marks.
Without speech marks the computer can display the
answer to a calculation.
Run your program to see what happens.
Do you understand it?
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Variables
Variables provide temporary storage for information that will be needed while a program is running.
A programmer can imagine a variable as being a box into which information can be placed. When
a programmer wants to store something, she or he gives a storage location a name and tells the
computer what to put there. Using that name later (the name of the variable), you can get out
(recall) the stored information at any time.
For example, a program to calculate the area of a rectangle might use the following variables.
When the program is running the data can be entered by the user and then stored, or it can be
automatically calculated by the computer and then stored. The stored data may change every time
the program is run, but the variable names remain the same.
A programmer may have as many variables in a program as she or he
needs. All that matters is that the variables have different names.
Data Types
Variables can store different types of data. The above example stores integer numbers, but there
are others. Before a variable can be used in a program it must be „declared‟.
Data Type
Examples
Visual Basic declaration
Integer
3, 7, -2, -99, 54
Dim length as integer
Decimal
1.5, 3.14, -6.758
Dim length as decimal
String
Mary, joe, dog,
Dim name as string
Sounds confusing? Don‟t worry, look at the following example…
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Worked Example - Area
We are going to write a program to allow the user to enter the length and breadth of a rectangle.
The program will then calculate and display the area.
Method:
I will take user input from two textboxes and store them in
variables called ‘length’ and ‘breadth’. I’ll then get the
computer to perform a calculation to find the area and store it
in a variable called ‘area’. Finally, I’ll display the area in a
third textbox.
To avoid confusion I’ll label all the objects on the screen.

Create a new Visual Basic project and call it „‟Area‟.

Create a „command button‟, three „labels‟ and three „textboxes‟ as shown below.
Textbox1
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Textbox2
Textbox3
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Changing „button‟ and „label‟ text
To change the text for our command button and labels do the following:

Click once on the command button to highlight it.

In the „Properties‟ window at the bottom right of the screen change the „Text‟ value from
„Button1‟ to „Calculate Area‟ as shown below.

Your command button should now look like this
(you may need to re-size it a little to see all the
text).

Repeat the above steps to change the text on the labels to „length‟, „breadth‟, and area.
Remember to highlight them first!
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Your final layout should look like the one below.

Now double click the command button to enter program code as follows…
(Notice some of the code has already been entered for you – you will get used to this)
Public Class Form1
'Area Program
'Your name
'Today‟s Date
Dim length As Decimal
Dim breadth As Decimal
Dim area As Decimal
'Create variables
length = TextBox1.Text
breadth = TextBox2.Text
'Get inputs and store them
area = length * breadth
'Calculate Area and store it
TextBox3.Text = area
'Display Area
Start typing here
Finish typing here
End Sub
End Class
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Run your program to test it works as expected.

First, enter values for length and breadth.

Now click the „Calculate Area‟ command button.

Using a calculator if needed, check that the expected result is the same as the actual result.

„Save All‟ when done.
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Finishing Touches – Printing Output
The PrintForm component for Visual Basic 2005 must be added to the Toolbox before you can
use it for the first time1.
Ask your teacher if you should carry out the steps below to add the
PrintForm component to your Visual Basic toolbox. This should be a
„one-off‟ task for you to complete at the machine you use for your
programming.
Installing the PrintForm Component
The following procedure describes how to add the component to the Toolbox.
To add the PrintForm component to the Toolbox
1.
Click the „Common Controls‟ heading in the toolbox to highlight it.
2.
From the Tools menu, select Choose Toolbox Items.
3.
In the Choose Toolbox Items dialog box, select PrintForm from the .NET
Framework Components list and click the checkbox next to it.
4.
Click OK to add it to the Toolbox.
1
The PrintForm Component is available as an additional download from Microsoft.com. If necessary, search for
‘PrintForm Component’. Once installed on a computer, each individual user wishing to use it must add it to their own
Visual Basic toolbox.
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Using the PrintForm Component
Once the PrintForm Component is installed, you can create an extra command button on your
program forms to allow the user to print at any time when the program is running.

Drag the PrintForm tool onto your form.

Notice that it does not actually appear on the form itself. It is displayed at the bottom of the
window as shown.

Click once on the PrintForm icon and change the „PrintAction‟ from „PrintToPrinter‟, to
„PrintToPreview as shown. This will allow you to check your printout on screen before
sending it to the printer.
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Now we need a command button to press in order to print our program while it is running…

Drag another command button onto your layout and label it „Print‟.

Double-click on this new button and add the following one line of code.
PrintForm1.Print() 'allows the user to print form
End Sub

Finish off by adding a label and entering your name on the form and by changing the text
title of the form to Area problem.
Your final screen should look like the one below.

Run your program and make sure it all works. „Save All‟ when you are happy with it.
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SUMMARY
Your finished code should look like the code below. Note that it actually contains two „subroutines‟,
one for each command button.
Public Class Form1
'Area Program
'Your name
'Today‟s Date
Dim area As Decimal
'Create variables
'Get inputs
'Calculate Area
'Display Area
End Sub
PrintForm1.Print() 'allows the user to print form
End Sub
End Class
Exercise
For each of the following tasks, make sure that all objects are labelled and that the final
output can be printed by the user.
Let your teacher see each program running when finished.
1. Write a program to enter three numbers and calculate the total.
2. Modify your program above to calculate the average of the numbers.
3. Write a program to calculate the area of a circle.
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SQA Assessment Task
Practical Abilities
Foundation Level
Your mark for this task will be used by the Scottish Qualifications Authority in deciding your overall award.
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COMPUTING
PRACTICAL ABILITIES TASK
STANDARD GRADE
FOOD MIXERS
a programming task assessing grades 5, 6 and 7
Name ________________________________________ Class _______________
Centre ________________________________________
Date _______________
Your teacher will outline how you should do this task and give you opportunities for discussion. Read and
follow all instructions carefully, use hardware and software properly and write your report neatly.
Instead of being paid an hourly rate, some workers are paid for the number of items they make each
week. Ann Hay assembles 86 food mixers and is paid £3.50 for each one. You are required to write a
program to calculate and display her earnings. The user should be asked to enter the number of
mixers and payment for each mixer. You should use meaningful variable names such as mixers.
1 DESCRIBE METHOD - Analysis
3 marks
Show that you understand what is required by describing how you will do this task.
____________________________________________________________________________
____________________________________________________________________________
____________________________________________________________________________
____________________________________________________________________________
____________________________________________________________________________
____________________________________________________________________________
____________________________________________________________________________
2 LIST STEPS - Design
2 marks
The main steps are Calculate Wage, Get Inputs, and Show Wage.
Write the steps in the correct order below.
1 __________________________________________________________________________
2 __________________________________________________________________________
3 __________________________________________________________________________
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3 ENTER PROGRAM - Implementation
5 marks
Create the program. Include internal commentary. Correct any mistakes that you make. Save your
program.
4
TEST PROGRAM - Testing
4 marks
Work out Ann’s wage for assembling 86 mixers at £3.50 each. You may use a calculator.
What was your answer? £___________
Run the program to find its answer for 86 mixers at £3.50 each.
What was the program’s answer? £___________
Work out Ann’s wage for assembling 90 mixers at £4.10 each. You may use a calculator.
What was your answer? £___________
Run the program to find its answer for 90 mixers at £4.10 each.
What was the program’s answer? £___________
Compare your answers with the program’s answer and write a comment.
____________________________________________________________________________
____________________________________________________________________________
____________________________________________________________________________
5 GET PRINTOUTS - Implementation
2 marks
Get two printouts with your name on them. One should show your code and the other a run using one set
of test data given above.
6 SUGGEST IMPROVEMENT - Evaluation
2 marks
Write down one way in which your program could be better.
____________________________________________________________________________
____________________________________________________________________________
7 JUDGE PERFORMANCE - Evaluation
2 marks
Read this task sheet again. Describe how well you think you have done the task.
____________________________________________________________________________
____________________________________________________________________________
____________________________________________________________________________
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Loops (FOR loop)
In computer programming, a loop is an instruction or sequence of instructions that is continually
repeated over and over. Instead of typing out the code 10 times we can tell the computer to repeat
a single line of code until it has done it 10 times.
Example

In a new Visual Basic project, create a „command button‟ and a listbox as shown below.

Public Class Form1
Button1.Click
Dim NumberOfTimes As Integer 'create a variable for our loop
For NumberOfTimes = 1 To 10
ListBox1.Items.Add("Hello")
Next
'loop ten times
End Sub
End Class

Start typing here
Finish typing here
Run your program. The message „Hello‟ should be displayed ten times.
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Worked Example: Punishment Exercise Program
Task
Design and write a program to write 100 punishment exercise „lines‟ for a naughty pupil. The line
to be repeated will be entered by the pupil using the keyboard (screen design on next page).
Method:
I have to write a program to write punishment exercises
lines. The program will take user input in a textbox and
then repeat it 100 times in a listbox when a command
button is pressed. I will use a FOR loop to repeat the lines.
To avoid confusion I’ll label all the objects on the screen.
Design
1. Get user to input „line‟ in textbox
2. Do 100 times
3.
Display „line‟ in listbox
4.
Display a blank line in listbox
5. Next
Code
Public Class Form1
Private Sub Button1_Click(ByVal sender As System.Object, ByVal e As
System.EventArgs)Handles Button1.Click
'Punishment Exercise Program
'by Me
'June 07
'declare variables
Dim line As String
Dim no_of_lines As Integer
line = TextBox1.Text ' get user input
'loop 100 times to complete lines
For no_of_lines = 1 To 100
ListBox1.Items.Add(line)
'display punishment exercise line
'display a blank line
Next
End Sub
End Class
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Sample Runs
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SQA Assessment Task
Practical Abilities
Foundation Level
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COMPUTING
STANDARD GRADE
CAR STICKERS
a programming task assessing grades 5, 6 and 7
Name ________________________________________ Class _______________
Centre ________________________________________
Date _______________
You are required to write a program for a firm that
makes stickers for car windows. The user should input the
sticker text at the keyboard. The program will display
that text four times as shown right. There should be a
blank line after each line of text. A FOR … NEXT loop
should be used.
YOU ARE DRIVING TOO CLOSE!
3 marks
2 marks
Write down the main steps in the program.
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5 marks
Create the program. Include internal commentary. Correct any mistakes that you make. Save it.
4 TEST PROGRAM - Testing
3 marks
Describe how you tested that your program worked.
____________________________________________________________________________
____________________________________________________________________________
____________________________________________________________________________
____________________________________________________________________________
____________________________________________________________________________
____________________________________________________________________________
2 marks
Get two printouts with your name on them. One should show your code and the other a run.
6 WRITE INSTRUCTIONS - Documentation
3 marks
Write a short explanation on how to run and use your program after it has been loaded.
____________________________________________________________________________
____________________________________________________________________________
____________________________________________________________________________
____________________________________________________________________________
2 marks
____________________________________________________________________________
____________________________________________________________________________
2 marks
____________________________________________________________________________
____________________________________________________________________________
____________________________________________________________________________
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Checklist
Before moving on to the next section, make sure you are fully happy
with the following essential skills…
User Interface
 Creating a TextBox
 Creating a ListBox
 Creating Command Buttons
 Creating Labels
Program Code
 Using a TextBox to obtain input
 Using a TextBox to display output
 Using a ListBox to display output
 Creating variables (and data types)
 Performing calculations
 FOR loop
 Program comments
You MUST let your teacher know if you are unsure about anything before continuing.
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GENERAL LEVEL
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MODULES AND SUBROUTINES
When programmers have to write big long
Area Problem
programs, they divide the program into
sections and just write a small section
Get inputs
(module) at a time.
Calculate Area
Display Area
You are not going to write a big long program, but you are going to learn how to divide a program
into sections (modules).
In Visual Basic these sections are called subroutines. Each subroutine starts with Sub and ends
with End Sub.
Here is a program you have done before. However, this time we shall use subroutines to write it.
Tip: One of the best ways to break a problem up into smaller ones is to split it into three main
sections to start with – input, process and output.
Example
Design and write a program to calculate the area of a rectangle. The
length and breadth are to be entered from the keyboard.
DESIGN
Top Level
1. Get inputs
The „top level‟ of our
2. Calculate area
design is a list of what our
3. Display area
Refinements
1.1 Prompt for and input length
1.2 Prompt for and input breadth
program will need to do.
The „refinements‟ allow
us to specify exactly how
these main steps will be
carried out.
2.1 Set area to length * breadth
Note the numbering
3.1 Display message and area
system used for each of
the refinements.
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Program Code
Public Class Form1
'Area Program with Subroutines
'C Wilson
'June 2007
'All variables must be declared before use
Dim area As Decimal
Using subroutines, shared
variables (variables used by
more than one subroutine),
are declared at the very start
of the program code. THIS IS
IMPORTANT!!!
'Main Program / Top Level
DESIGN
'Steps here are used to call subroutines
get_inputs()
calculate_area()
display_area()
End Sub
Top Level
1. Get inputs
2. Calculate area
3. Display area
Sub get_inputs()
'Prompt for, and store length and breadth
End Sub
Refinements
1.1 Prompt for and input length
Sub calculate_area()
'store the value for area in a variable
End Sub
1.2 Prompt for and input breadth
2.1 Set area to length * breadth
Sub display_area()
'display the stored value for area
End Sub
3.1 Display message and area
End Class
Note that this program also makes good use of internal comments throughout. You should do the
same in all of your own programs.

Open your earlier project called „Area‟ and change the code so it matches that above.
„Save All‟ when you have it working.
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IF … THEN (Selection)
So far our programs have done everything we have asked them to –
all the instructions we have entered have been carried out by the
computer.
Sometimes we might want the computer to choose whether or not to
run some of our code. This is known as „selection‟ and can be very
useful when programming.
Examples
If age > 17 Then
TextBox1.Text = "You can vote"
End If
If age is 19 then you can vote appears on the
screen.
If age is 12 then nothing happens.
Rather than do nothing in some situations, you can have have alternative code by using the
„else‟ command.
If test_score < 50 Then
TextBox1.Text = "Sorry, you failed."
Else
TextBox1.Text = "Well done, you passed!"
End If
Let‟s look at a worked example…
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Worked Example – Car Sales
Joe Quimby owns a second-hand car showroom. He is a very
tough boss and sets sales targets of £50,000 per day for each
of his staff!
At the end of each day he gathers in sales figures from his
staff for the day. No employees are allowed to sell less than
five cars per day or they‟re fired! Also, the total sales for the
day for each employee must be greater than £50,000 or they
will also be fired!
Write a program to calculate the total sales of five cars for an employee. The program should then
display an appropriate message saying whether the employee is fired or not. Call your Visual
Basic project „Car Sales‟.
Method:
The program will take 5 user inputs (car1, car2, car3, car4 and car5)
from TextBoxes when a command button is pressed.
I’ll then calculate the total sales for the employee.
Finally, I’ll display the total sales and then, using an IF condition, I’ll
display an appropriate message about the employee.
Screen Design
 Two command buttons – Calculate Total and Print
 Seven textboxes – 5 for car sales, 1 for total, 1 for message
 Labels as appropriate
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Program Code & Design
Public Class Form1
'Car Sales Program
'by Me
'June 07
'declare variables
Dim car1 As Decimal
Dim car2 As Decimal
Dim car3 As Decimal
Dim car4 As Decimal
Dim car5 As Decimal
Dim total As Decimal
Button1.Click
get_sales()
calculate_total()
display_message()
End Sub
Sub get_sales()
'input sales data
car1 = TextBox1.Text
End Sub
Sub calculate_total()
'calculate total sales
total = car1 + car2 + car3 + car4 + car5
End Sub
Sub display_message()
'display program outputs
TextBox6.Text = total
If total > 50000 Then
TextBox7.Text = "Well done!"
Else
TextBox7.Text = "You're fired!"
End If
End Sub
Top Level
1.
Get sales
2.
Calculate total sales
3.
Display outputs
Refinements
1.1 Prompt for and input car1 price
2.1 Set total = car1+car2+car3+car4+car5
3.1
3.2
3.3
3.4
3.5
3.6
Display total in textbox 6
if total >£50,000 then
Display “Well done!” in textbox 7
else
Display “You‟re fired!” in textbox 7
end if
Button2.Click
PrintForm1.Print()
End Sub
End Class
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Sample Runs
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COMPUTING STANDARD GRADE
SCHOOL HEATING
a programming task assessing grades 3, 4, 5 and 7
Name ________________________________________
Class _______________
Centre ________________________________________
Date _______________
The heating system in a school should be switched on if the average temperature is less than 17
degrees Celsius (˚C). The average temperature is found from the temperatures in the Art, English and
Music Departments. You are required to write a program that allows the user to input the three
temperatures. The program calculates and displays the average temperature then displays ‘Heating
should be on.’ or ‘Heating should be off.’ as appropriate.
3 marks
____________________________________________________________________________
____________________________________________________________________________
____________________________________________________________________________
____________________________________________________________________________
____________________________________________________________________________
____________________________________________________________________________
____________________________________________________________________________
____________________________________________________________________________
6 marks
On a separate sheet of paper, show the main steps and refinements.
5 marks
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5 marks
Complete the table below, by entering test data. You should enter sets of three temperatures then
calculate the average and indicate whether heating should be on or off. The first set should have an
average below 17˚C, the second set an average of exactly 17˚C and the third average should be above
17˚C. Complete the last two columns by recording the program’s output with your chosen test data.
Art
temperature
English
temperature
Music
temperature
calculated
average
temperature
calculated
on or off
program’s
average
temperature
program’s
on or off
Compare your calculations with the program’s output and write an appropriate comment.
____________________________________________________________________________
____________________________________________________________________________
____________________________________________________________________________
2 marks
Get two printouts with your name on them. One should show your code and the other a run using one of
your sets of test data.
2 marks
____________________________________________________________________________
____________________________________________________________________________
____________________________________________________________________________
____________________________________________________________________________
2 marks
____________________________________________________________________________
____________________________________________________________________________
____________________________________________________________________________
C Wilson, 2007
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Some new interface tools…
So far, all of our user interface objects have been created using the toolbox to drag objects onto
our forms. This is fine, but our screen might become „cluttered‟ with
textboxes and buttons etc. that we have no further use for after the user
has entered their information.
Visual Basic allows the programmer to use other techniques to show
some special objects on the screen only while the program is running
and at a time chosen by the programmer.
Two common examples are the „MessageBox‟ and the „InputBox‟.
The MessageBox
A „MessageBox‟ displays a message in a „dialogue box‟ and then waits for the user to click a button
before going on with the program.
Look at the following examples and the program code required to produce them on screen.
MsgBox("Bye bye!")
[The word „Demo‟ is taken from the project title.]
MsgBox("Bye bye!", , "Finish Program")
[Rather than use the project title, the programmer can code their own
title for each MessageBox. Notice that this code requires two commas
side-by-side.]
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MsgBox("Bye bye!", MsgBoxStyle.Critical, "Finish Program")
[See the „critical‟ graphic!]
The examples above are all very easy to add to your programs. The window displays a message
and waits for the user to click OK. The user has no choice but to click OK.
Now look at the following example,
MsgBox("Are you sure you want to exit?", MsgBoxStyle.YesNo, "Finish Program")
This a little more interesting – the user has a choice of
buttons to click!
This might seem all too easy, but the code required to make this choice actually work is a little
more complicated.
We have already learned that to write code to deal with selection or choice we use the IF
command. With this in mind here‟s what the design for the above MessageBox should look like…
Design
1. Prompt user to make choice
Notice that we don‟t actually need to use an
2. If choice = “yes” then
„else‟ in this case. If the user clicks „No‟ then
3.
the program will not finish.
Exit Program
4. End if
Now let‟s look at actually creating some MessageBoxes…
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To create an „Exit‟ command button with choice…
'Code for Exit command button with message box
Dim response As Integer
response = MsgBox("Are you sure you want to exit?", MsgBoxStyle.YesNo, "Finish Program")
If response = vbYes Then
End 'Exit program
End If
End Sub
To create a „Print‟ command button with choice…
'Code for printing button with message box
response = MsgBox("Are you sure you want to print?", MsgBoxStyle.YesNo, "Print")
If response = vbYes Then
PrintForm1.Print()
'Print
End If
End Sub
Exercise
For your earlier programs, „Total‟, „Average‟ and „Area‟, do the following…

Add „Exit‟ and „Print‟ command buttons to them that will present the user with a choice as
shown above. Be sure to „Save All‟ your work when done.
C Wilson, 2007
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The InputBox
An InputBox is a small window which only appears on the screen while the program is running and
input is needed from the user. The user‟s input can then be stored in a variable so that the rest of
the program can use it.
The InputBox can be especially useful when lots of inputs are
required from the user and creating lots of TextBoxes with labels
would be too time consuming and take up lots of screen space.
The code for an input box looks like this:
Variable_Name = InputBox(“Prompt”, “Title for box”)
The things in italics will be changed to suit your program.
E.g.
Dim Name As String
Name = InputBox("Please enter your name", "Enter Name")
The above example will produce this on the screen when the line of code runs:
i) Title
T
i
Prompt
t
l
e
Space for input
In this example the variable called „Name‟ would now be storing the data „Darth‟ when the user
clicks OK.
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Try this,

Create a new project called „Message‟.

Design a form like the one below.

Enter the code below for your command button.
Public Class Form1
Private Sub Button1_Click(ByVal sender As System.Object, ByVal e As System.EventArgs)Handles
Button1.Click
'InputBox Demo
'by Me
'June 07
Dim Name As String
Name = InputBox("Please enter your name", "Enter Name")
'Display message
TextBox1.Text = "Hello " & Name
End Sub
End Class

„Save All‟ when you have it working.
Exercise
Modify your program above so that it also asks your age. The program should then display, in
another textbox, a sentence like, „You are 14 years old‟.
C Wilson, 2007
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Worked Example – Currency Converter
Write a program to calculate and display a table showing the amount of currency available for each
pound. The program needs the name of the country, the currency and the exchange rate of the
currency. These will be entered from the keyboard by the user. If France is the destination, then a
message should be displayed informing the user of a special offer.
Method:
The program will take all user inputs (country, currency and exchange
rate) from inputboxes when a command button is pressed. As each is
entered I will display it in a textbox on the screen.
I will display table headings in a listbox and then use a FOR loop to
display the actual conversion table in the listbox.
I’ll use an IF condition to display a special message if the country is
France.
Since the program may be run more than once, I’ll make sure that the
listbox and all the textboxes are cleared at the start of the program.
Screen Design

Two command buttons – convert and print.

Three textboxes for output - country, currency and exchange rate.

One listbox – output conversion table.

Labels as appropriate.

Inputboxes for user input.
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Program Design
Top Level
1.
2.
3.
4.
Clear previous data
Get data
Display table
Special Offer
Refinements
1.1
1.2
1.3
1.4
Clear Textbox1
Clear Textbox2
ClearTextbox3
Clear Listbox1
2.1
2.2
2.3
2.4
2.5
2.6
Prompt for and input country
Display country in textbox1
Prompt for and input currency
Display currency in textbox2
Prompt for and input exchange rate
Display exchange rate in textbox 3
3.1
3.2
3.3
3.4
3.5
Display table headings in listbox columns – pounds and currency
Display blank line
Do 20 times
Display pounds in column 1, pounds*exchange rate in column 2
Next
4.1
4.2
4.3
4.4
If country is France then
Display message in listbox – We‟ll convert your currency back for free
Display message in listbox – We like France!
End if
Note that only the steps for solving the problem need to be shown in your designs. If you
wish to include other buttons such as „Exit‟ and „Print‟, you do not need to add them to your
design.
C Wilson, 2007
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Program Code
Public Class Form1
'Currency Converter Program
'Joe Bloggs
'June 07
Dim country As String
Dim currency As String
Dim exchange_rate As Decimal
Private Sub Button1_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles Button1.Click
'Main Program
Top Level
clear_data()
get_data()
display_table()
special_offer()
1.
2.
3.
4.
Clear previous data
Get data
Display table
Special Offer
End Sub
Refinements
Sub clear_data()
'clear textboxes and listboxes if program has already been run
TextBox1.Text = ""
TextBox2.Text = ""
TextBox3.Text = ""
End Sub
Sub get_data()
'Allow user to supply input via inputboxes and display in textboxes
country = InputBox("Please enter country...")
TextBox1.Text = country
currency = InputBox("Please enter currency...")
TextBox2.Text = currency
exchange_rate = InputBox("Please enter exchange rate...")
TextBox3.Text = exchange_rate
End Sub
Sub display_table()
'Output Table headings
ListBox1.Items.Add("Pounds" & VbTab & currency)
ListBox1.Items.Add("") 'prints a blank line
1.1
1.2
1.3
1.4
Clear Textbox1
Clear Textbox2
ClearTextbox3
Clear Listbox1
2.1
2.2
2.3
2.4
2.5
2.6
Prompt for and input country
Display country in textbox1
Prompt for and input currency
Display currency in textbox2
Prompt for and input exchange rate
Display exchange rate in textbox 3
3.1 Display table headings
3.2 Display blank line
'loop to output conversion from 1 to 20 pounds
Dim pounds As Integer
For pounds = 1 To 20
ListBox1.Items.Add(pounds & VbTab & pounds * exchange_rate)
Next
End Sub
3.3 Do 20 times
3.4
Display table row
3.5 Next
Sub special_offer()
'Display special offer if appropriate
If country = "france" Then
ListBox1.Items.Add("We'll convert your currency back for free!")
ListBox1.Items.Add("We like France!")
End If
End Sub
4.1 If country is France then
4.2
Display message in listbox …
4.3
Display message in listbox …
4.4 End if
PrintForm1.Print()
End Sub
End Class
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Sample Runs
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SQA Assessment Task
Practical Abilities
General Level
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COMPUTING
STANDARD GRADE
CAR HIRE
Your teacher will outline how you should do this task and give you opportunities for discussion. Read and follow all
instructions carefully, use hardware and software properly and write your report neatly.
Cherair Car Hire Company has a range of cars for rent. Charges start at £20 a day for the cheapest
to £70 a day for the most expensive. Cherair requires a program that gives customers printed details
of charges. The program asks the user for a car make, model and daily rate then displays a table of
daily charges for between one and fourteen days. If the make is Ford, a message indicating a gift of
a free road atlas is displayed.
An example of output is shown below. The output from your program may look different but must
meet the specification.
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3 marks
____________________________________________________________________________
____________________________________________________________________________
____________________________________________________________________________
____________________________________________________________________________
____________________________________________________________________________
____________________________________________________________________________
6 marks
5 marks
Enter the program listing. Include internal commentary. Correct any mistakes that you make. Save the
listing.
5 marks
On a separate sheet of paper, show how you tested that your program worked properly. Use two sets of
test data, one involving a Ford car and one not. Compare your expected output with the program’s output
and write an appropriate comment.
2 marks
Get two printouts with your name in the footer. One should show your listing and the other a run using
one of your sets of test data.
2 marks
____________________________________________________________________________
____________________________________________________________________________
2 marks
____________________________________________________________________________
____________________________________________________________________________
C Wilson, 2007
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RUNNING TOTALS & COUNTERS
Often a program will require the user to enter a list of data that includes numbers. The program
may be required to output the total of this numeric data or output a count of the number of times a
specific item of data was entered.

Keeping a „running total‟ is easy – simply add each number
entered onto the value of a variable that might be called „total‟.

Keeping a „count „ might require a little more care – if a certain condition is
met, then add one to the value of our counter.

In either case, it is very important to set the value of the running total and counter to zero
before the user starts to enter their data.
Examples
count = 0
…
If answer = correct Then
count = count + 1
End If
In a program adding a sequence of
numbers, each numbered entered is
added to a running total.
In a quiz program, if the user‟s answer is correct, one is
added to the count, if not, nothing happens, so „count‟ stays
the same.
running_total = 0
…
For loop_counter = 1 To 3
number = InputBox("Enter a number...")
running_total = running_total + number
Next
TextBox1.Text = running_total
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LOOPS & CONTROL VARIABLES
Examples of loops used so far have always been „fixed loops‟ – they have always been carried out
a number of times decided by the programmer.
Sometimes, the number of loops should be decided by the user‟s actions when the program is
actually running. This requires an additional input by the user to specify the number of times some
code should be looped.
Example
The following design and code could be for a program to help a teacher enter class lists.
The program would start by asking how many pupils are in the class and then use a loop to allow
the teacher to enter the names of the required number of pupils.
Design
1.
prompt for and input class size
2.
loop for 1 to class size times
3.
enter name
4.
add name to list
5.
end loop
Code
Dim class_size As Integer
Dim name As String
class_size = InputBox("Enter class size", "Class Lists")
Dim loops As Integer
For loops = 1 To class_size
name = InputBox("Enter name", "Class Lists")
ListBox1.Items.Add(name)
Next
C Wilson, 2007
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Totals & Counters – an everyday example…
You empty out your pockets and find the following coins…
You want to know two things:
1. How much money you have found in total,
2. Being a little greedy, how many of them were pound coins?
Sounds easy? Of course it is. Your years of experience just allow you to work it out. But what if
you had to tell a computer how to do it? It actually takes quite a bit of thought to work out just how
you managed to do this simple thing, but here goes…
Study the following table and design very carefully before moving on.
Coin
Total
Count of £1 coins
£1
£1
1
50p
£1.50
10p
£1.60
£1
£2.60
50p
£3.10
5p
£3.15
2p
£3.17
2p
£3.19
5p
£3.24
1p
£3.25
20p
£3.45
£1
£4.45
5p
£4.50
Design
set total to 0
set pound_counter to 0
2
prompt for and enter no_of_coins
For each coin
Examine coin
Set total = total + coin_value
If coin_value is £1 Then
Set pound_counter = pound_counter + 1
End If
Next coin
3
display total
display pound_counter
It‟s not until you actually look at the design that you realise how well programmed your own brain
already is!
C Wilson, 2007
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Worked Example – Rainfall Program
Meteorologists are involved in the study of weather from information
obtained from the land, sea and air. One area of study is rainfall
patterns.
In order to speed things up, a meteorologist would like to
computerise the recording and analysis of this work and has asked
you to write a computer program to deal with this.
Design and write a program to allow the user to input daily rainfall figures for an entire month. The
program should then display the total rainfall amount for the month and the number of days on
which there was no rain at all.
Method:
The program will take all user inputs (month, number of
days and daily rainfall in mm) from InputBoxes when a
command button is pressed. As each is entered I will
display it on the screen.
Since the number of days in a month can vary I will use a
FOR loop to allow the user to enter daily rainfall figures
until the number of days in the month has been reached.
Screen Design
TextBox1
As the data is entered by the user, I’ll keep a
running total for the rainfall and a counter to
keep a track of the number of ‘dry days’
entered. I’ll use an IF condition to update the
dry days counter.
When all the rainfall figures for the month have
been entered, I’ll display the final values for the
total rainfall and the dry days counter.
Since the program may be run more than once,
I’ll make sure that the listbox and all the
textboxes are cleared at the start of the program.
ListBox1
TextBox2
TextBox3
[Notice that this screen design also uses the „GroupBox‟ tool to group
together some of the objects on the screen. Try it!]
C Wilson, 2007
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Program Design
Top Level
1.
setup
2.
enter rainfall data
3.
display summary
Refinments
1.1
Clear TextBox1
1.2
Clear TextBox2
1.3
Clear TextBox3
1.4
Clear ListBox1
1.5
set total to zero
1.6
set dry days counter to zero
2.1
Prompt for and enter month
2.2
Display month in TextBox
2.3
Prompt for and input no. of days
2.4
Loop for no. of days
2.5
prompt for and input rainfall for day
2.6
Display rainfall in listbox
2.7
set total = total + rainfall
2.8
If rainfall = 0 Then
2.9
set dry_days = dry_days + 1
2.10
End If
2.11
End loop
2.12
Display message “Thank you”
3.1
Display total
3.2
Display no. of dry days
C Wilson, 2007
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Program Code
Public Class Form1
'Rainfall Survey Program
'by Me
'June 07
Dim month As String
Dim no_of_days As Integer
Dim rainfall As Decimal
Dim total As Decimal
Dim dry_days As Integer
Button1.Click
Top Level
clear_screen()
enter_data()
display_summary()
1.
2.
3.
setup
enter rainfall data
display summary
End Sub
Sub clear_screen()
„clear previously entered data and zero counters
TextBox1.Text = ""
TextBox2.Text = ""
TextBox3.Text = ""
total = 0
dry_days = 0
End Sub
Refinments
1.1
Clear Textbox1
1.2
Clear Textbox2
1.3
Clear Textbox3
1.4
Clear Listbox1
1.5
Set total to zero
1.6
Set dry days counter to zero
Sub enter_data()
'Allow user to enter all data and update running totals and counts
2.1
Prompt for and enter month
2.2
Display month in TextBox
month = InputBox("Enter month...", "Month")
2.3
Prompt for and input no. of days
TextBox1.Text = month
no_of_days = InputBox("Enter no. of days in month...", "Days")
2.4
Loop for no. of days
3.1
3.2
Display Total
Display no. of dray days
Dim day As Integer
2.5
prompt for and input rainfall for day
For day = 1 To no_of_days
rainfall = InputBox("Enter rainfall in (mm) for day " & day, "Rainfall Data")
ListBox1.Items.Add("Day " & day & VbTab & rainfall)
2.6
Display rainfall in listbox
total = total + rainfall
2.7
set total = total + rainfall
2.8
dry_days = dry_days + 1
2.9
set dry_days = dry_days + 1
End If
2.10
End If
Next
2.11
End loop
MsgBox("Thank you")
2.12
Display message “Thank you”
End Sub
Sub display_summary()
'display summary of entered data
TextBox2.Text = total
TextBox3.Text = dry_days
End Sub
C Wilson, 2007
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Sample Run(1)
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Sample Run(2)
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COMPUTING
STANDARD GRADE
OVER FORTY
Name ________________________________________
Class _______________
Centre ________________________________________
Date _______________
You are required to write a program to count the number of pupils in a class of twelve who score over
40 in a test out of 60. The pupils’ marks are to be entered at the keyboard. The output is a message
that indicates the number of pupils who score more than 40.
3 marks
____________________________________________________________________________
____________________________________________________________________________
____________________________________________________________________________
____________________________________________________________________________
____________________________________________________________________________
____________________________________________________________________________
____________________________________________________________________________
____________________________________________________________________________
6 marks
5 marks
C Wilson, 2007
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5 marks
Complete the table below, firstly by writing three more sets of test data under the twelve marks listed.
The given marks are all above 40. The next set should all be below 40. The next set should have marks
above, below and including 40. The last set should only have marks 39, 40 and 41. Complete the second
column by counting and writing down how many marks in each set are over 40. Complete the last column
by recording the program’s output with your test data.
pupils’ marks
my count
over 40
program’s count
over 40
46, 54, 51, 41, 49, 58, 45, 44, 53, 50, 57, 43
Compare your count of marks over 40 with the program’s output and write an appropriate comment.
____________________________________________________________________________
____________________________________________________________________________
____________________________________________________________________________
2 marks
Get two printouts with your name on them. One should show your code and the other a run using one of
the sets of test data above.
2 marks
____________________________________________________________________________
____________________________________________________________________________
____________________________________________________________________________
____________________________________________________________________________
2 marks
____________________________________________________________________________
____________________________________________________________________________
____________________________________________________________________________
C Wilson, 2007
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Checklist
Before moving on to the next section, make sure you are fully happy
with the following essential skills…
User Interface
 Displaying a MessageBox
 Using an InputBox for user input
Program Design
 Top Level & Refinements
Program Code
 Running Totals & Counters
 FOR loops with control variables
You MUST let your teacher know if you are unsure about anything before continuing.
C Wilson, 2007
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CREDIT LEVEL
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Complex conditions – AND, OR
A "complex condition" contains two or more simple conditions linked by „logic operators‟ (AND and
OR). They are frequently used in IF statements and some types of programming loops.
Examples
When might I wear shorts and a T-shirt?
IF it is summer AND it is hot THEN
I‟ll wear shorts and a T-shirt
END IF
Any other times?
IF (it is summer AND it is hot) OR (it is winter AND I‟ve gone completely mad!) THEN
I‟ll wear shorts and a T-shirt
END IF
Some example code dealing with test marks might require a complex condition like this…
If score1 > 50 And score2 > 50 Then
TextBox1.Text = "You passed both the tests."
End If
Loops (WHILE loop)
A complex condition can also be used to test whether or not a section of program code should run.
This can be done using a special type of loop known as a WHILE loop.
In a WHILE loop, the condition is first evaluated. If the condition is true, the code within the loop is
then executed.
Example Design
1.
Prompt for and get user to enter age
2.
WHILE age < 0 OR age > 120 DO
3.
4.
Prompt for and get user to enter age
ENDWHILE
A WHILE loop differs to a FOR loop because:



A FOR loop will always run code within the loop a pre-determined number of times.
A WHILE loop will run code within the loop an unknown number of times – it often depends
on the user.
A WHILE loop may not run the code in the loop at all in some cases!
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Input Validation
Users are constantly inputting data to running programs. They also make mistakes – particularly
when called upon to enter data via the keyboard.
„Input validation‟ means to check that data entered by the user while the
program is running is „valid‟ or „allowable‟. Any attempt by the user to
enter „illegal data‟ will be rejected by the program.
It is perfectly possible that invalid data entered by a user might cause a
program to crash and data to be lost.
A good programmer will take every step possible to prevent their
programming crashing or producing inaccurate results due to invalid
data being entered by the user.
Whilst it is impossible to predict every possible mistake a user might make in using a program
there are some basic methods of validating input and preventing problems from occurring.
Some basic approaches to validation we will look at are:
1. MessageBoxes
2. Pre-defined functions
3. User defined functions
1.
MessageBoxes
We have already met messageboxes. Message boxes are useful methods of input validation
because they restrict input by the user. A typical example of such restriction would be a
messagebox presenting the user with a „Yes‟ or „No‟ button choice as below.
The only input possible here by the user is to click on „Yes‟ or „No‟.
There are no other inputs possible and the user cannot type any
input at this point.
By programming code to deal with this messagebox, the
programmer can be sure that user input will always be valid.
Simple!
C Wilson, 2007
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2.
Pre-defined functions.
Earlier testing of your programs may have thrown up some small problems when run that the use
of some pre-defined functions might be able to prevent.
A pre-defined function is a piece of pre-written code that is actually part of the programming
language. Many programming languages will actually have a library of these pre-defined functions,
each of which is designed to perform a frequently needed task for the programmer.
Here are a few useful Visual Basic pre-defined functions:
Function Example Code
Val
Int
Description
number = Val("2457")
'sets number to 2457.
number = Val(" 2 45 7")
'sets number to 2457
number = Val("24 and 57") 'sets number to 24.
number = Val(TextBox1.Text)
„converts an empty toxtebox value to 0.
It is particularly useful for
converting empty textboxes to the
value 0 in order to avoid program
crashes.
MyNumber = Int(99.8) ' Returns 99.
The Int function returns integer
portions of numbers. In the case of
a negative number, the Int function
returns the first negative integer
less than or equal to the number
MyNumber = Int(-99.8) ' Returns -100.
MyNumber = Int(-99.2) ' Returns -100.
mynumber = CInt(99.8)
CInt
' Returns 100.
mynumber = CInt(-99.8) ' Returns -100.
mynumber = CInt(-99.2) ' Returns -99.
UCase
The Val function actually returns
the numbers contained in the data.
Val stops converting at the first
character that cannot be
interpreted as a numeric digit or
white space.
City = InputBox("Enter capital city of France...")
If UCase(City) = "PARIS" Then
Correct = Correct + 1
Else
MsgBox("Wrong!")
End If
CInt rounds to the nearest integer
instead of „truncating‟ the fractional
part of numbers as the Int function
does.
UCase converts lowercase letters
to uppercase.
Very useful for text comparisons
(e.g. quiz programs) where a
match is required but, the
programmer cannot anticipate the
exact use of capital letters made
by the user.
These may seem a little confusing at the moment but these pre-defined functions may be useful to
refer back to in later problems.
C Wilson, 2007
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3.
User-defined functions – Input Validation
Programming languages like Visual Basic can have a pre-defined function library containing
hundreds of useful operations like the ones described earlier. Even so, during the course of
developing a programming project the need for a specific function may arise that is not part of the
built-in function library. That‟s why many languages, such as Visual Basic, give programmers the
ability to create their own functions.
One typical example of the need for this is the ability to validate numeric input by the user.
E.g. When entering a value for age it would be silly (invalid) to enter an age like -16 or 200.
Using what‟s called a „range check‟ it is possible for a programmer to write a very flexible function
that can validate numeric input made by the user in a variety of different situations.
Example:
A program might ask the user to enter the following information about pupil test scores:
 Name
 English (out of 20)
 Maths (out of 25)
 French (out of 30)
 Computing (out of 30)
 Geography (out of 40)
 Physics (out of 25)
 Art (out of 30)
It is impossible to validate a name (there‟s just too many possibilities), but the program can validate
the scores entered as between a minimum and maximum score.
Design – Validate number
1. Prompt user to enter a number
2. WHILE number is <= min OR number >= max
3.
Prompt user to re-enter number
4. ENDWHILE
The above design could be applied to the entry of each of the subject test scores. There are two
ways of doing this:
1. Just repeatedly enter the similar code over and over for each score – lots of code!
2. Use a function – write a function that tells the computer how to apply this idea to each
score entered and then call it appropriately each time required – less lines of code.
Compare the following example solutions…
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Repeatedly entering the similar code…
pupil_name = InputBox("Enter name...")
english = InputBox("Enter English test score...")
While english < 0 Or english > 20
MsgBox("Please enter a whole number between 0 and 20", , "Error!")
english = InputBox("Enter English test score...")
End While
maths = InputBox("Enter Maths test score...")
While maths < 0 Or maths > 25
maths = InputBox("Enter Maths test score...")
End While
french = InputBox("Enter French test score...")
While french < 0 Or french > 30
french = InputBox("Enter french test score...")
End While
Extension:
Reduce program
crashes by using
Val (inputbox…
computing = InputBox("Enter computing test score...")
While computing < 0 Or computing > 30
computing = InputBox("Enter computing test score...")
End While
geography = InputBox("Enter geography test score...")
While geography < 0 Or geography > 40
geography = InputBox("Enter geography test score...")
End While
physics = InputBox("Enter physics test score...")
While physics < 0 Or physics > 25
physics = InputBox("Enter physics test score...")
End While
art = InputBox("Enter art test score...")
While art < 0 Or art > 30
art = InputBox("Enter art test score...")
End While
Using a function…
pupil_name = InputBox("Enter name...")
english = validate_number(0, 20, "Enter English test score...")
maths = validate_number(0, 25, "Enter Maths test score...")
french = validate_number(0, 30, "Enter French test score...")
computing = validate_number(0, 30, "Enter Computing test score...")
geography = validate_number(0, 40, "Enter Geography test score...")
physics = validate_number(0, 25, "Enter Physics test score...")
art = validate_number(0, 30, "Enter Art test score...")
Extension:
Reduce program
crashes by using
Val (inputbox…
Function validate_number(ByVal min, ByVal max, ByVal message)
Dim number As Decimal
number = InputBox("Please enter a whole number between " & min & " and " & max, message)
While number < min Or number > max
MsgBox("Please enter a number between " & min & " and " & max, , "Error!")
number = InputBox("Please enter a number between " & min & " and " & max, message)
End While
Return number
End Function
Obviously, using a function requires less lines of code. In fact if more test scores were included,
the function method would only add one more line of code per test score. Without the function,
each additional test score would require an additional five lines of code per test. Each of these
lines would require some customisation to suit the particular test.
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SUMMARY
Using functions to validate the input of numeric variables is very efficient in terms of time to
develop code and also the number of lines of code required to program.
Functions actually work by coding a procedure or set of rules, and then supplying data to that
particular set of rules.
The following example of validation supplies three items of data (or „parameters‟) to validate input:
 min
 max
 message
…
grade = validate_number(1, 7, "Enter your computing grade...")
„function call
…
Extension:
Reduce program
crashes by using
Val (inputbox…
End While
Return number
End Function
The parameters within the function are substituted with data supplied by the code which „calls‟ the function.
In the example above the parameter values are entered as follows:



All occurrences of the parameter min become the value „1‟
All occurrences of the parameter max become the value „7‟
All occurrences of the parameter „message‟ become „Enter your computing grade…”
The function above named „validate_number‟ can be used to validate whole numbers in your own
programs without a single line being changed. Only the „function call‟ line of code should be
tailored to suit the problem you are solving.
.
Exercise
You should now enter and save this function code (and only the function code) using a text
editor such as „WordPad‟. This will allow you to easily „copy & paste‟ this code into your future
Visual Basic programs when required. Save the code with the filename „validate‟.
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Extension – Functions for validating integers & validating decimals
So now we know how to use a function to validate numeric input within a minimum and maximum.
This is very useful, but one problem still remains.
Consider a program to accept football scores. In this case data entered should lie within an
acceptable range, but should also only be accepted if it is a whole number or integer such as 0, 1,
2, 3, 4 etc. but nothing in between. It is impossible to score 2.5 goals!
Validating decimals (e.g. 3.14)
This is the same code as earlier – only the name has been changed in order to clarify its purpose.
Function validate_decimal(ByVal min, ByVal max, ByVal message)
number = Val(InputBox("Please enter a whole number between " & min & " and " & max, message))
number = Val(InputBox("Please enter a number between " & min & " and " & max, message))
End While
Return number
End Function
Validating integers (e.g. 3)
It only takes a couple of changes to our earlier function, but now we can ensure that the program
will only accept integers within our range.
Function validate_integer(ByVal min, ByVal max, ByVal message)
number = Val(InputBox("Please enter a whole number between " & min & " and " & max, message))
While number < min Or number > max Or (Int(number) <> number)
number = Val(InputBox("Please enter a WHOLE number between " & min & " and " & max, message))
End While
Return number
End Function
Keeping both of these functions in a „code
library‟ helps programmers to quickly write
programs with correctly validated input when
possible.
C Wilson, 2007
Note that both these user-defined functions also make use
of the pre-defined function ‘Val’ as discussed earlier.
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Program Testing
Once a program has been written, there then follows the testing stage. The most crucial aspect is
to test that the program does what it is supposed to do and does not crash.
Test Data
A programmer should create sets of test data to feed the software to find out how it behaves. Here
are some of the important points about making up such sets:
 The expected results from a test data set must be known in advance, so that they can be
checked against the actual results.
 One set should test “normal” operation of the software, to
make sure that there are no unexpected results in ordinary
use.
 One set should test the operation “limits” of the software,
to make sure that the boundary conditions are handled
properly.
 One set should test “exceptions” to the normal operating
conditions. This set will show whether or not the software
can react to unexpected inputs in an effective way, without
crashing.
Testing must be systematic and comprehensive.
It is systematic when you plan a table of test data with expected outcomes and then test the
program with that data. It is comprehensive when you test as many eventualities as possible.
For example if you were testing a program that took in marks out of 100 in a test you must test:
Normal Data
Test Data
45
78
26
Expected Result
Data accepted
Data accepted
Data accepted
Actual Result
As expected.
As expected.
As expected.
Comment
Program appears OK
Program appears OK
Program appears OK
Limits
Test Data
0
100
Expected Result
Data accepted
Data accepted
Actual Result
As expected
As expected
Comment
Program appears OK
Program appears OK
Exceptions
Test Data
-5
109
34.75
Five
x
Expected Result
Not Accepted
Not Accepted
Not Accepted
Not accepted
Not accepted
Actual Result
Not Accepted
Accepted
Not Accepted
Not Accepted
Not accepted
Comment
Prompt to re-enter
Prompt to re-enter
Program continues!!!
Program crash!!!
Program crash!!!
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Worked Example – Can you drive?
A program is required to ask the user to enter their age and then
what type of driving license (if any) that person holds.
You may drive a car if you are in possession of a full driving
license or if you are at least 17 years old in possession of a
provisional driving license (you must have an experienced full
license holder with you though).
Design and write a program to allow the user to enter their age and license type. The program
should then display a summary of the user inputs together with a statement indicating their
entitlement to drive a car..
Method:
The program will take all user inputs (age and license type) from
InputBoxes when a command button is pressed. All inputs will later be
summarised in a ListBox.
The license type will be a number entered by the user as follows:
1. no license of any type
2. provisional license
3. full license
Since all input is numeric, it will be validated.
I will use an ‘IF’ statement with a ‘complex condition’ to work out if a
person is allowed to drive.
Finally, I will display a summary on the screen.
ListBox1
TextBox1
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Program Design
Top Level
1.
2.
3.
4.
Clear the screen and initialise variables
Get inputs
Calculate entitlement to drive
Display entitlement to drive
Refinements
2.1
2.2
Prompt for, and validate, age
Prompt for, and validate, current license type from menu
2.1.1
2.1.2
2.1.3
2.1.4
2.1.5
Obtain user input
WHILE number is < min allowed OR number > max allowed DO
Display error message
Obtain user input
ENDWHILE
Refine step 2.2
As 2.1 above (but without a function in this case)
3.1
3.2
3.3
3.3
Set „can drive‟ entitlement to "no"
IF license type = 3 OR (age >= 17 AND license type = 2) THEN
set „can drive‟ to "yes"
END IF
4.1
4.2
4.3
4.4
4.5
4.6
Display 2 blank lines
IF „can drive‟ = "yes" THEN
Display "You can drive a car."
ELSE
Display "You are not allowed to drive a car."
ENDIF
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Program Code
Public Class Form1
'Can you drive?
'by Me
'June 07
Dim age As Integer
Dim license_type As Integer
Dim can_drive As String
'Top Level / Main Program
setup()
Top Level
get_inputs()
calculate_output()
display_output()
1.
Clear the screen and initialise variables
End Sub
Sub setup()
can_drive = "no"
TextBox1.Clear()
End Sub
Sub get_inputs()
'validate age using a function
age = validate_number(0, 100, "Enter your age")
ListBox1.Items.Add("Age:" & vbTab & vbTab & age)
2.
3.
4.
Get inputs
Calculate entitlement to drive
Display entitlement to drive
Refinements
2.1
2.2
Prompt for, and validate, age
Prompt for, and validate, current license type from menu
'validate license type (a number) using hand-typed code
'note: vbCR stands for 'carriage return' and means 'take a new line'
license_type = InputBox("Enter a license type (1-3)" & vbCr & "1. None" & vbCr & "2. Provisional" & vbCr & "3. Full")
While license_type < 1 Or license_type > 3
license_type = InputBox("Error! Enter a license type (1-3)" & vbCr & "1. None" & vbCr & "2. Provisional" & vbCr & "3. Full")
End While
ListBox1.Items.Add("License type:" & vbTab & license_type)
End Sub
2.1.1
Obtain user input
'from code library
2.1.2
WHILE number is not in range DO
End While
Return number
2.1.3
Display error message
End Function
Sub calculate_output()
'if you have a full license you can drive...
'OR, if you are at least 17 AND have a provisional license you can drive
If license_type = 3 Or (age >= 17 And license_type = 2) Then
can_drive = "yes"
End If
End Sub
Sub display_output()
'display program output in textbox
If can_drive = "yes" Then
TextBox1.Text = "You can drive a car."
Else
TextBox1.Text = "You are not allowed to drive a car."
End If
End Sub
End Class
C Wilson, 2007
4.1
4.2
4.3
4.4
4.5
2.1.4
2.1.5
3.1
3.2
3.3
Obtain user input
ENDWHILE
IF license type …
set „can drive‟ to "yes"
END IF
IF „can drive‟ = "yes" THEN
Display "You can drive a car."
ELSE
Display "You are not allowed to drive a car."
ENDIF
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Sample Runs
Program Testing
Normal Data
Test Data
Age = 17, license type =1
Age = 17, license type = 2
Age = 40, license type = 3
Expected Result
Can‟t drive.
Can drive.
Can drive
Actual Result
As expected.
As expected.
As expected.
Comment
Program appears OK
Program appears OK
Program appears OK
Limits
Test Data
Exceptions
Test Data
Age = -99
Age = 17.5
Age = Five
License type = to kill
License type = -99
C Wilson, 2007
Expected Result
Can‟t drive.
Can drive
Actual Result
As expected
As expected
Comment
Program appears OK
Program appears OK
Expected Result
Not Accepted
Not Accepted
Not Accepted
Not accepted
Not accepted
Actual Result
Not Accepted
Accepted
Not Accepted
Not Accepted
Not accepted
Comment
Program appears OK
Program continues OK.
Program crash
Program crash
Program continues OK.
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COMPUTING
STANDARD GRADE
LANGUAGE COURSE
Your teacher will outline how you should do this task and give you opportunities for
discussion. Read and follow all instructions carefully, use hardware and software
properly and write your report neatly using the headings given below.
Students taking a language course must pass examinations in French and German or French and
Spanish to pass. A pass is half marks or more. A program is required to take in the three marks
which are validated as being whole numbers between 0 and 30. The output indicates if the student has
passed or failed and gives the percentage mark to the nearest whole number.
Examples of output are shown. The outputs from your program may look different but must meet the
specification.
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3 marks
6 marks
Show the main steps and refinements.
5 marks
listing.
6 marks
Describe in detail how you tested fully that your program – including input validation - worked as
specified.
2 marks
Get two printouts with your name in the footer. One should show your listing. The other printout should
show a run using one of your sets of test data. It should demonstrate input validation and show accurate
output.
6 CHANGE PROGRAM - Maintenance
2 marks
Describe how you would change the program to make a pass in Italian an additional requirement to pass
the course.
2 marks
Suggest one way in which your program could be better apart from the maintenance given above.
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Random numbers
Many programs require the use of random data. For example, a game should be different every
time you play it, otherwise it would become very boring.
Generating random events or data is performed by programming the computer to calculate random
numbers and then using these numbers to decide what happens next.
In order to generate random numbers the programmer uses a pre-defined function to initialize a
random number generator and then writes a line of code to produce a random number within an
appropriate range.
Example – throwing a dice
In the real world, when we throw a dice we do not know what the outcome will be. All we do know
is that the result will be a number between 1 and 6.
Randomize()
dice = Int(6 * Rnd() + 1)
The code on the left could be used to simulate throwing a
dice and will generate a random number between 1 and 6.
The number generated will then be assigned to the variable
named „dice‟.
All that‟s missing is the code to display the number (variable
name is dice
How does it work?
It is important to understand the above code in order to generate our own random numbers.
Visual Basic programmers use the formula below:
randomnum = int(highestno - lowestno+1) *rnd() + lowestno)
Examples
Range required
1 to 6
0 to 6
4 to 18
50 to 100
Code
Number = Int(6 * Rnd() + 1)
[Don‟t forget to use the Randomize() function before entering your code!]
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Boolean variables
So far we have covered the data types: Integer, Decimal and String. Another
important data type is Boolean.
Boolean variables hold only two possible values, True or False. They should
have names that make it obvious what is meant when they are True or False.
For example, ValidMark should be true if the mark is valid otherwise false, if
the mark is invalid.
Boolean variables are sometimes called Flags or Switches as they are either On (True) or Off
(False).
Example – “Are we there yet?” (The Simpsons)
During a long car journey,…You know the one.
This rather silly example illustrates the idea of testing for a condition
and, when the condition is met, the boolean variable is allowed to
change its value.
In this case, a loop is allowed to terminate as a result of the change to
the value of the Boolean variable.
Design
Set destination to false
While destination is false do
Ask “Are we there yet?”
If answer is “yes”
Set destination to true
End if
End while
Display “Coooool!”
Program Code
Dim destination As Boolean = False
Dim answer As Integer
While destination = False
'loop while boolean variable has value 'false'
answer = MsgBox("Are we there yet?", MsgBoxStyle.YesNo, "Message from Bart...")
If answer = vbYes Then
destination = True
'set boolean variable to 'true' - can now exit loop
End If
End While
MsgBox("Coooool!", , "Message from Bart")
Code it and see – you only require a single command button on your form!
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Worked Example – Dice Game
You have been asked to write a computer program to simulate a
game of dice. To spice things up a little, the game will involve
simulated money at stake.
Players will start off with £100 to gamble. Once they have lost all
their money they can no longer play.
Players will throw two dice. Each time a player throws a double, they win £20, and this should be
added to their „bank balance‟.
If a player throws a double-six, they win £50!
Method:
The program will simulate throwing dice by repeatedly generating two random
numbers between 1 and 6 inclusive.
The two random numbers will be compared using an IF condition. If they are the
same the player wins, and £20 pounds is added to their balance.
Using a complex IF condition, the program will also test for a double six and add
£50 pounds to the players balance if appropriate.
The program will display meaningful messages at all times and update the players
balance after every throw.
The program must stop when the player’s balance reaches zero.
Screen Design
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Program Design
Top Level
1.
2.
3.
4.
5.
6.
7.
8.
9.
Display balance
If player has money left (balance >0) , let them roll dice
Set win to false
Roll dice
Note: only steps 4,5 and 6
Check result
need to be refined.
Display result
Else
Display “You‟re out of money!”
End if
Refinements
4.1
4.2
4.3
Generate random number for dice 1
Generate random number for dice 2
Display dice 1 and dice 2
5.1
5.2
5.3
5.4
5.5
5.6
5.7
5.8
5.9
5.10
If a double is rolled (dice 1 = dice 2)
Set win to true
If double is „double 6‟
Set balance = balance + £50
Else
Set balance = balance + £20
End if
Else
Not a double, set balance = balance -10
End if
6.1
6.2
6.3
6.4
6.5
6.6
If win is true
Display message “You win!”
Else
Display message “You lose.”
End if
Display updated balance in textbox1
C Wilson, 2007
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Program Code
Public Class Form1
'Dice Game
'by Me
'June 07
Dim dice1 As Integer
Dim dice2 As Integer
Dim win As Boolean = False
Dim balance As Decimal = 100
Private Sub Form1_Load(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles
MyBase.Load
'subroutine attached to loading form - will display balance when program starts
TextBox1.Text = balance
End Sub
Button1.Click
If balance > 0 Then
'if player still has money, let them play
win = False
'set winning throw to false
roll_dice()
check_result()
display_result()
Else
'no money left to gamble
MsgBox("You're out of money!", MsgBoxStyle.Critical, “Dice Game”)
End If
End Sub
Sub roll_dice()
' code for generating random num is...
' ...randomnum = int(highestno - lowestno+1) *rnd() + lowestno)
Randomize()
dice1 = Int(6 * Rnd() + 1)
'random number for dice 1
dice2 = Int(6 * Rnd() + 1)
'random number for dice 2
ListBox1.Items.Add(dice1 & " , " & dice2)
'display dice throw
End Sub
Sub check_result()
If dice1 = dice2 Then
win = True
If dice1 And dice2 = 6 Then
balance = balance + 50
Else
balance = balance + 20
End If
Else
win = False
balance = balance – 10
End If
End Sub
'a winning throw
'set winning throw to true
'with a double six!
'wins £50
'just any other double, wins £20
'a losing throw
'lose £10
Sub display_result()
If win = True Then
ListBox1.Items.Add("You win!")
Else
ListBox1.Items.Add("You lose.")
End If
TextBox1.Text = balance
End Sub
End Class
C Wilson, 2007
'update balance on screen
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Sample Runs
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COMPUTING
STANDARD GRADE
GUESS NUMBER
A program is required to prompt the user to guess a randomly-chosen whole number between 1 and
20. The input should be validated. If the guess is incorrect, the user should be told if the target
number is bigger or smaller. This process should continue until the target number is guessed correctly.
The user should then be told how many valid guesses were made.
An example of output is shown below. The output from your program may look different but must
meet the specification.
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1
DESCRIBE METHOD - Analysis
3 marks
6 marks
5 marks
listing.
6 marks
specified.
2 marks
output.
6 WRITE TECHNICAL GUIDE - Documentation
3 marks
Write a short technical guide that describes how to install the programming language that you used and
the system requirements.
3 marks
Describe how you would change the program to make it count the total number of guesses and not just
the valid ones.
2 marks
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Arrays
Imagine you have been asked to write a
program that will allow the user to enter a list of
the names of five people and then display these
names on the screen. Here is the sort of
program you might write.
DO NOT TYPE THIS IN!!!
Public Class Form1
'5 Names without an array
'by Me
'June 07
Dim name1 As String
Dim name2 As String
Dim name3 As String
Dim name4 As String
Dim name5 As String
Button1.Click
get_names()
display_names()
End Sub
Sub get_names()
name1 = InputBox("Type in name 1 ")
End Sub
Sub display_names()
ListBox1.Items.Add(name1)
End Sub
End Class
Imagine changing this program to deal with 250 names, or even over a million names!
There is an easier way to write this kind of program involving the use of „arrays‟ rather than simple
„variables‟.
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Remember we said earlier, that variables were just boxes in the computers memory. Inside these
boxes we can store a single item of data or information.
Image if we could store more than one item of data inside a variable…
To make things a little clearer…

In the previous example we know we are storing names.

We know we are storing five names.

These five items of data are very similar in nature, so it‟s like storing a list of data.

Why on earth then, should we waste time creating 5 very similar variables (or 250, or over a
million similar items of data)?
The idea of storing a „list‟ of data, rather than using several individual variables, is what is known
as an „array‟.

Using an array, we can still access each individual item of data on the list if we need to.

Each individual item in the array has its own position, or location on the list.
Comparison of separate variables with an array…
Using individual variables…
Using an array…
Dim name1 As String
Name1 Homer
Dim name2 As String
Name2 Marge
Dim name3 As String
Name3 Bart
Dim firstname(5) As String
1
2
3
4
5
Homer
Marge
Bart
Lisa
Maggie
This is the name of the
array in memory.
This is the data stored in
location firstname(4)
Dim name4 As String
Name4 Lisa
Dim name5 As String
Name5 Maggie
This is the element number
or location for each item of
data in the name array.
In order to use special array variables like this we have to learn some new commands…
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Arrays – Typical examples of code used

Create an array. The code
required to create the array could
be something like this2.
Note: we specify the name of the
array, its size, and its data type.

1
Homer
2
Marge
3
Bart
4
Lisa
5
Maggie
Store a single item of data. The code required to store „Bart‟ in element number 3 is
firstname(3) = "bart"

Display a single item of data. The code required to
display the contents of element number 4 could be
ListBox1.Items.Add(Firstname(4))
Get the idea? Now look at this…

Display the entire array. The code required
to display the entire list of all names can be
easily written using a FOR loop as follows.
Dim row As Integer
For row = 1 To 5
ListBox1.Items.Add(firstname(row))
Next
This code would be just as simple
with a list of a million names!

Store a list of user data. Rather than have all the names entered by the programmer
when writing the code, we can also use a FOR loop to allow the user to enter their own
names into the array.
Dim person As Integer
For person = 1 To 5
firstname(person) = InputBox("Enter a name", "Address Book")
Next

Prompt for, and display a single item of data. We can even retrieve individual items of
information.
Dim element As Integer
element = InputBox("Enter a number between 1 and 5", "Address Book")
MsgBox("You picked " & firstname(element))
2
VB Express uses ‘zero-indexing’ and so will actually create 6 elements – the extra being firstname(0). We will ignore this element
at this level.
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Task
Design the form shown and then enter the
program code below.
NOTE: Be careful when entering your
code. Each command button calls only
one subroutine.
i.e. There are four command buttons –
each one calls its own subroutine code
below.
Experiment by running the program several
times and make sure you fully understand
its workings before moving on.
Public Class Form1
'Address Book using arrays
'by Me
'June 07
'Code to automatically enter 5 items of data defined by the programmer into the firstname array
firstname(1) = "homer"
firstname(2) = "marge"
firstname(3) = "bart"
firstname(4) = "lisa"
firstname(5) = "maggie"
End Sub
'Code to allow the program user to enter ANY 5 items of data for storage in the firstname array
Dim person As Integer
For person = 1 To 5
firstname(person) = InputBox("Enter a firstname", "Address Book")
Next
End Sub
'It doesn't matter how the data was stored in the array.
'This code will display whatever data has been most recently stored in the five elements.
Dim row As Integer
For row = 1 To 5
ListBox1.Items.Add(firstname(row))
Next
End Sub
'Allow the user to query the array
Dim element As Integer
element = InputBox("Enter a number between 1 and 5", "Address Book")
MsgBox("You picked " & firstname(element))
End Sub
End Class
C Wilson, 2007
- 90 -
Worked Example - Golden Ticket
Willy Wonka and his chocolate factory have fallen on hard times.
His chocolate is just not as popular as it used to be.
Remembering the success of his earlier promotional event
involving an international hunt for five „golden tickets‟, he is now
hoping to repeat this success. This time he is desperate enough to
offer many more golden tickets than before. In fact, he is
considering hiding one in every fifty Wonka Bars produced, each at
a reduced sale price of 49 pence.
Out of curiosity, he has asked you to write a program that will
simulate the purchase of Wonka Bars where one in every fifty bars
could be a winner with a golden ticket inside.
Method:
The program will prompt the user to continue to buy as many Wonka Bars as
he/she wishes, so a while loop will be required.
We will keep a running total/count of three things:

The amount of money spent on Wonka Bars (at 49p each)

The number of bars bought in our search for a golden ticket

The number of golden tickets found
Since, on average, one in every fifty bars will be a winner, we will use an array
(with fifty elements) to simulate each batch of fifty Wonka Bars produced. We
will set each element of this array to be ‘no win’. Following this, we will select
one element of this array at random, and change its element from ‘no win’ to
‘golden ticket’.
Next, we allow the user to buy a Wonka Bar. Every time the user buys a Wonka
Bar another random number will be generated (between one and fifty). If this
number is the same as the Wonka Bar golden ticket number, the user is a winner.
Each time the user purchases a Wonka Bar the running totals/counts must be
updated. The user should also be informed whether or not they are a winner each
time they buy a Wonka Bar.
C Wilson, 2007
- 91 -
Program Design
1.
2.
3.
4.
5.
6.
7.
Initialise counters and total variables
While user wishes to buy more chocolate
Hide Golden Ticket
Buy Chocolate
Update Summary
As if user would like to buy more chocolate
End While
Hide Golden Ticket
3.1
3.2
3.3
3.4
3.5
For chocolate_bar = 1 To 50
Set all elements of ticket array to “no win”
Next
Select random number between 1 and 50 inclusive as winner
Set ticket array (winner) as "Golden Ticket!"
Buy Chocolate
4.1
4.2
4.3
Select random number between 1 and 50 inclusive as purchased bar of chocolate
Set amount_spent to amount_spent + price
Set bars_bought to bars_bought + 1
Update Summary
5.1
5.2
5.3
If random bar purchased equals random winner
Set golden_tickets to golden_tickets + 1
Display „congratulations‟ message and summary of bars bought and amount spent.
5.4
5.5
Else
5.6
End If
5.7
5.8
5.9
Display amount spent in textbox
Display no. of bars bought in textbox
Display no. of golden tickets in textbox
Display „sorry‟ message and summary of bars bought and amount spent.
C Wilson, 2007
- 92 -
Program Code
Public Class Form1
Dim ticket(50) As String
Dim winner As Integer
Dim bar_purchased As Integer
Dim amount_spent As Decimal
Dim bars_bought As Integer
Dim golden_tickets As Integer
Public Const price As Decimal = 0.49
Private Sub Button1_Click_1(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles Button1.Click
setup()
1.
Set up counters and total variables
2.
While user wishes to buy more chocolate
While response <> vbNo
3.
Hide Golden Ticket
hide_golden_ticket()
4.
Buy Chocolate
buy_chocolate()
update_summary()
5.
Update Summary
response = MsgBox("Would you like to buy more?", MsgBoxStyle.YesNo, "Buy Chocloate?")
End While
6.
As if user would like to buy more chocolate
End Sub
7.
End While
Sub setup()
amount_spent = 0
bars_bought = 0
golden_tickets = 0
End Sub
Sub hide_golden_ticket()
'there should be no guarantee that buying 50 bars will get a golden ticket
'so every time a bar is purchased, the winning ticket moves position in array
'Nasty!
'Set all bars to no win...
Dim chocolate_bar As Integer
ticket(chocolate_bar) = "No win."
Next
Hide Golden Ticket
3.1
3.2
3.3
3.4
3.5
Set all elements of ticket array to “no win”
Next
Select random number between 1 and 50 inclusive as
winner
Set ticket array (winner) as "Golden Ticket!"
'then set a random ticket element to golden ticket!
Randomize()
winner = Int(50 * Rnd()) + 1
ticket(winner) = "Golden Ticket!"
End Sub
Buy Chocolate
Sub buy_chocolate()
'pick a bar of chocolate at random (from the sweety shop counter)
Randomize()
bar_purchased = Int(50 * Rnd()) + 1
amount_spent = amount_spent + price
bars_bought = bars_bought + 1
End Sub
4.1
4.2
4.3
Select random number between 1 and 50 inclusive as
purchased bar of chocolate
Set amount_spent to amount_spent + price
Set bars_bought to bars_bought + 1
Sub update_summary()
Update Summary
'open the bar of chocolate...Is there a golden ticket?
'if the random number for the golden ticket = random number for the chocolate bar purchased...
5.1
If random bar purchased equals random winner
If bar_purchased = winner Then
5.2
Set golden_tickets to golden_tickets + 1
golden_tickets = golden_tickets + 1
RichTextBox1.Text = "Congratulations. You have won a golden ticket!!! Willie Wonka looks forward to seeing you (and one family member), at
the Chocolate Factory soon. You have purchased " & bars_bought & " bars of chocolate, spending £ " & amount_spent & ". We hope you enjoy your
visit!"
5.3
Display „congratulations‟ message and
summary of bars bought and amount spent.
Else
'if the random number for the golden ticket is different to the current random number for golden ticket...
RichTextBox1.Text = "Sorry. No golden ticket this time!!! Willie Wonka looks forward to seeing you, if only you would buy more chocolate and
find a golden ticket. You have purchased " & bars_bought & " bars of chocolate, spending £ " & amount_spent & ". We hope you're enjoying your
chocolate!"
End If
'update summary details
TextBox1.Text = "£ " & amount_spent
TextBox2.Text = bars_bought
TextBox3.Text = golden_tickets
End Sub
End Class
C Wilson, 2007
5.4
5.5
Else
5.6
End If
5.7
5.8
5.9
Display amount spent in textbox
Display no. of bars bought in textbox
Display no. of golden tickets in textbox
Display „sorry‟ message and summary of bars
bought and amount spent.
- 93 -
Sample Runs
C Wilson, 2007
- 94 -
COMPUTING
STANDARD GRADE
CHARITY LOTTERY
A group of twelve office workers decides to have a weekly charity lottery. Each worker is asked to
contribute £1 and a draw is made. The winner gets half of the contributions with the other half going
to charity. If the person selected has not paid that week, all contributions go to charity. You are
required to write a program that selects a winner from a set of workers’ names read from data
statements and held in an array. The user is asked if the selected person has paid that week. The
input should be validated. An appropriate message is given.
Examples of output are shown. The outputs from your program may look different but must meet the
specification.
C Wilson, 2007
- 95 -
1
DESCRIBE METHOD - Analysis
3 marks
6 marks
3
ENTER PROGRAM - Implementation
5 marks
listing.
6 marks
specified.
2 marks
output.
3 marks
Describe how you would change the program to make it ask if each worker had contributed before the
draw was made.
2 marks
C Wilson, 2007
- 96 -
Checklist
Well, we‟re just about done. Here‟s your final checklist…
User Interface
 No new skills
Program Code
 Complex conditions – AND/OR
 WHILE loop
 Input validation
 Pre-defined functions
 User defined functions
 Generating random numbers
 Boolean variables
 Arrays – create, store single item, display single item, display entire array, store list in array
Evaluation
 Program testing – normal data, limits, exceptions
Now, just for fun… some maths!
Design and write a program which will be useful for a Primary
school to assist young children in learning arithmetic. The
program should allow pupils to enter answers to 10 different
addition sums. Only two numbers will require to be added in
each sum, the two numbers being chosen at random and not
being greater than 10.
The program should indicate whether the pupil‟s answers are correct or not and on completion a
summary of the number of correct answers should be given.
C Wilson, 2007
- 97 -

basic feed line vbcr visual

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