1. PROGRAMMING IN VISUAL BASIC PART 1
CSI 1301
PROGRAMMING IN VISUAL BASIC
PART 1

2. Part 1 1. Visual Basic Programming
2. Translating the Algorithm Declaration
3. Translating Assignment Instructions
4. Translating Get and Give Instructions
5. Additional Material

3. 1. Visual Basic Programming

4. Visual Basic Programming
Visual Basic is a programming language for Windows applications
We will use it to:
Run our algorithms on a computer
Use the computer as the computing agent
Assist us in making more effective use of Excel
To provide a suitable user interface in our worksheets
To express complex logic in formulas (see the slides titled Example of Complexity in the Additional Material at the end of this lecture)

5. Visual Basic Programming
Creating an algorithm can be difficult
Think through the problem and solve it without using a computer
However, with an algorithm, writing the program becomes easy
Translate the instructions in the algorithm to Visual Basic instructions
ALGORITHM
English
Visual Basic

6. Visual Basic Programming
Problems encountered in developing an algorithm
Comprehension problems (“Misinterpretation”)
Process problems (“How do I solve it?)
Problems encountered in a Visual Basic program
Syntax errors (Grammatical and spelling mistakes)
Semantic errors (Program runs but errors in logic lead to incorrect results)
Run time errors (Program fails when running ie. dividing by zero)

7. 2. Translating the Algorithm Description

8. Translating the Algorithm Description
When a program is executing, the instructions and data being processed are stored in RAM
The following parts of the Algorithm Description tell us what data is to be stored and processed by our program
Givens
Intermediates
Results
Each data item can be either a variable or a constant

9. Translating the Algorithm Description
Variable
Is an address in RAM that has a name and contains a value
The value can change as the code is executed
Can hold only one value at a time
Constant
Has a value that does not change as the code is executed
A meaningful name used in place of a value
Names
Begin with a letter
Maximum of 255 characters in length
Contain only letters, numbers and _ (underscore)
Not case sensitive
Cannot be a Visual Basic reserved word

10. Translating the Algorithm Description
We tell the Visual Basic translator what type of data is to be processed by our program by defining data types
Each data type determines
The kind of data which can be stored in RAM
The range of possible values
How many bytes of RAM will be used to store it
The type of operations that can be performed on the data
The Visual Basic translator can then
Determine how and where to store that data in RAM
Tell us if we try to do something silly in our program
15 + “joe smith” = ???
Store text in a numeric variable

11. Translating the Algorithm Description
The Visual Basic translator keeps track of where each data item is stored in RAM
When we want to reference the value of a data item, we simply use its name. The Visual Basic translator knows where to go in RAM to find the value.

12. Translating the Algorithm Description
Declaring variables and constants in a program
Done with a DIM statement for a variable
Also specify the data type with the As clause
Advantages
Code is easier to read
Speeds up execution of code
Conserves memory space
Done with a CONST statement for a constant
Option Explicit must be used in the first line
Forces all variables and constants to be declared
(also useful to detect misspelled variable and constant names)

13. Translating the Algorithm Description
Enter OPTION EXPLICIT on the first line
All programs begin with SUB and end with END SUB
Comments are lines that are ignored by the computer.
We use them to make our code easier to read
Everything to the right of a ‘ (single quote) is a comment
Look at GIVENS, INTERMEDIATES and RESULTS
Each entry must be declared
Also define the type for each variable

14. Translating the Algorithm Description
OPTION EXPLICIT
'WRITTEN BY T. JAMES
SUB myprogram ()
DIM studnum as String*7 'Student Number
DIM MT as Single 'Midterm Exam
DIM FE as Single 'Final Exam
DIM NG as Single 'Numeric Grade
CONST PI = 'PI
END SUB

15. Translating the Algorithm Description
Where do we enter this code?
In the Visual Basic Editor in Excel
To open the Editor
select Tools – Macro – Visual Basic Editor
or right click a worksheet tab and select View Code (not recommended)
or press Alt + F11
Then select Insert – Module
Then enter the code
The Visual Basic Editor is described in more detail in the Additional Material at the end of these lecture slides

16. 3. Translating Assignment Instructions

17. Algorithmic Representation of Computer Functions
Input
Get information
Storage
Store information
Process
Arithmetic operations
Logic decisions
Repeat instructions
Output
Give information
GET
Given/Results/Intermediates/Set
LET IF
LOOP
GIVE

18. Assignment Instructions
An assignment statement is used to assign a value to a variable
Variable = Expression
The computed value of the Expression is assigned to (stored in) the variable on the left side of the = sign

19. Assignment Instructions
X = 5
Take the value of 5 and store it in X
Y = X + 3
Take the value of X (5) and add 3 to get 8
Store 8 in Y
X = X + 1
NOT AN ALGEBRAIC EQUATION
Take the value of X (5) and add 1 to get 6
Store 6 in X (replacing the value of 5)

20. Assignment Instructions
The order of precedence of arithmetic operators in an expression is as follows:
Brackets ()
Exponents ^
Division /
Multiplication *
Addition
Subtraction

21. Translating Assignment Instructions
Look at the METHOD.
Translate any instruction with an = sign as an assignment statement
Each assignment statement is one line of code
Write each in the proper form
Variable = Expression

22. Translating Assignment Instructions
ALGORITHM
X = 5
Y = X + 3
C = 2r
A = r2
VISUAL BASIC
X = 5
Y = X + 3
C = 2 * PI * R
A = PI * R^2

23. Translating Assignment Instructions
Option Explicit
'Written by T. James
Sub Circles()
Dim R as Single 'Radius
Dim A as Single 'Area
Dim C as Single 'Circumference
Const PI =
R = 1.2
A = PI * R^2
C = 2 * PI * R
End Sub

24. 4.Translating Get and Give Instructions
From/To the User

25. GET/GIVE from/to the User
At the most basic level, our programs
get information from the user (input) via the keyboard or mouse, and
give information to the user (output) via the screen
Therefore, we need Visual Basic instructions to
read user input from the keyboard or mouse, and
write information on the screen

26. GET from the User
An InputBox is used to get information that is entered by the user at the keyboard
Variable = InputBox(“prompt message”, “title”, “default input”, Xcor, Ycor)
Variable stores the information entered by the user
Prompt message describes what we want the user to enter
Title appears in the title bar at the top of the InputBox
Default input shows a sample of the type of information to be entered
Xcor and Ycor are the X and Y axes coordinates that position the InputBox on the screen

27. GET from the User
Frequently, we do not need to specify the title, default input or positioning coordinates
Then the Visual Basic instruction to get information from the user can be simplified to
Variable = InputBox(“prompt message”)
Name = InputBox(“Enter your Name”)
When this statement is executed, an InputBox will appear on the user’s screen
The InputBox will contain the text, Enter your Name
It will also contain a rectangle
The information entered by the user will appear in this rectangle
The InputBox will also contain an OK button
When the user has entered his/her name, he/she will click the OK button and the information entered will be stored in the variable Name

28. GET from the User Income = InputBox(“Enter your income”)
Stores what the user enters in the variable Income

29. GIVE to the User
A MsgBox is used to send information to the screen for the user to view
We will explore the full capabilities of the MsgBox later
For now, we can use the following statement
MsgBox(“message”)
Message is the information that will be displayed in the MsgBox on the screen
The MsgBox will also contain an OK button
When the user has read the message, he/she will click the OK button and the MsgBox will disappear from the screen

30. GIVE to the User MsgBox(“The Tax is “ & Tax)
Takes the string “The Tax is “ and concatenates it with the value of the variable Tax
Displays the result on the screen in a MsgBox
Concatenation can also be accomplished with +
Preferable to use &

31. Translating to Visual Basic
Look at the METHOD
Translate any GET or GIVE instructions that refer to the user as follows.
GIVE: MsgBox(“message”)
GET: variable = InputBox(“prompt message”)

32. Translate 1 Translate Algorithm 1.5 Option Explicit
'Written By T. James
Translate 1
Translate Algorithm 1.5
NAME: CalcMark
GIVENS: A1, A2, A3
RESULTS: Mark
INTERMEDIATES: Total, MaxMark (Constant)
DEFINITION:
Mark := CalcMark(A1, A2, A3)
METHOD:
Set MaxMark = 140
Get A1
Get A2
Get A3
Let Total = A1 + A2 + A3
Let Mark = Total/MaxMark * 100
Give Mark

33. Translate 1 Translate Algorithm 1.5 NAME: CalcMark Option Explicit
'Written By T. James
Translate 1
Sub CalcMark ()
Translate Algorithm 1.5
NAME: CalcMark
GIVENS: A1, A2, A3
RESULTS: Mark
INTERMEDIATES: Total
MaxMark(Constant)
DEFINITION:
Mark := CalcMark(A1, A2, A3)
METHOD:
Set MaxMark = 140
Get A1
Get A2
Get A3
Let Total = A1 + A2 + A3
Let Mark = Total/MaxMark * 100
Give Mark

34. Translate 1 Translate Algorithm 1.5 GIVENS: A1, A2, A3 RESULTS: Mark
Option Explicit
'Written By T. James
Sub CalcMark ()
Translate 1
Dim A1 as Integer
Dim A2 as Integer
Dim A3 as Integer
Dim Mark as Single
Dim Total as Integer
Const MaxMark =140
Translate Algorithm 1.5
NAME: CalcMark
GIVENS: A1, A2, A3
RESULTS: Mark
INTERMEDIATES: Total MaxMark (Constnat)
DEFINITION:
Mark := CalcMark(A1, A2, A3)
METHOD:
Set MaxMark = 140
Get A1
Get A2
Get A3
Let Total = A1 + A2 + A3
Let Mark = Total/MaxMark * 100
Give Mark

35. Translate 1 Translate Algorithm 1.5 Option Explicit
‘Written By T. James
Sub CalcMark ()
Dim A1 as Integer
Dim A2 as Integer
Dim A3 as Integer
Dim Mark as Single
Dim Total as Integer
Const MaxMark = 140
Translate 1
Translate Algorithm 1.5
NAME: CalcMark
GIVENS: A1, A2, A3
RESULTS: Mark
INTERMEDIATES: Total
MaxMark (Constant)
DEFINITION:
Mark := CalcMark(A1, A2, A3)
METHOD:
Set MaxMark = 140
Get A1
Get A2
Get A3
Let Total = A1 + A2 + A3
Let Mark = Total/150 * 100
Give Mark
A1 = InputBox("A1?")
A2 = InputBox("A2?")
A3 = InputBox("A3?")

36. Translate 1 Translate Algorithm 1.5 Option Explicit
'Written By T. James
Sub CalcMark ()
Dim A1 as Integer
Dim A2 as Integer
Dim A3 as Integer
Dim Mark as Single
Dim Total as Integer
Const MaxMark = 140
A1 = InputBox("A1?")
A2 = InputBox("A2?")
A3 = InputBox("A3?")
Translate 1
Translate Algorithm 1.5
NAME: CalcMark
GIVENS: A1, A2, A3
RESULTS: Mark
INTERMEDIATES: Total,
MaxMark (Constant)
DEFINITION:
Mark := CalcMark(A1, A2, A3)
METHOD:
Set MaxMark = 140
Get A1
Get A2
Get A3
Let Total = A1 + A2 + A3
Let Mark = Total/MaxMark * 100
Give Mark
Total = A1 + A2 + A3
Mark = Total/150 * 100

37. Translate 1 Translate Algorithm 1.5 Give Mark Option Explicit
'Written By T. James
Sub CalcMark ()
Dim A1 as Integer
Dim A2 as Integer
Dim A3 as Integer
Dim Mark as Single
Dim Total as Integer
Const MaxMark = 140
A1 = InputBox("A1?")
A2 = InputBox("A2?")
A3 = InputBox("A3?")
Total = A1 + A2 + A3
Mark = Total/150 * 100
Translate 1
Translate Algorithm 1.5
NAME: CalcMark
GIVENS: A1, A2, A3
RESULTS: Mark
INTERMEDIATES: Total,
MaxMark (Constant)
DEFINITION:
Mark := CalcMark(A1, A2, A3)
METHOD:
Set MaxMark = 140
Get A1
Get A2
Get A3
Let Total = A1 + A2 + A3
Let Mark = Total/150 * 100
Give Mark
MsgBox("Mark is " & Mark)
End Sub

38. Example of Complexity Visual Basic Editor Translation Set 1
5. Additional Material
Example of Complexity
Visual Basic Editor
Translation Set 1

39. Example of Complexity
Student Marks

40. Example of Complexity
Calculate the final mark, based on 25% for assignments, 25% for midterm and 50% for final examination
insert the following formula in cell j2 & copy it to the other cells in column j
=0.5*(SUM(c2:g2))+0.25*h2+0.5*i2
Variation 1
“If the student failed the final exam, then he/she fails the course.”
=IF(i2>=50,formula as above,i2)

41. Example of Complexity Variation 2 Variation 3
“If the student failed the final exam, then the weighted sum of 1/3 midterm mark and 2/3 final exam mark must be 50 or more for the student to pass the course.”
=IF(i2<50,IF((h2/3)+(2*i2/3)>=50,as above,i2),as above)
Variation 3
Assign letter grades to the final marks
a more complex case
(more nesting required)
the need to write code
(a user defined function)

42. Visual Basic Editor The Visual Basic Editor Main window Code window
Consists of 4 windows
Main, Code, Project Explorer, Properties
Main window
Title bar, menu bar & standard toolbar
Code window
Insert – Module
To write code for procedures

43. Visual Basic Editor Project Explorer window Properties window
Shows the open project (name of file containing the project)
Shows the worksheets & modules in the project (in a format similar to Windows Explorer)
Has 3 buttons
View Code: view the code in the module selected
View Object: view the worksheet selected
Toggle Folders: control the display of the folder
Properties window
To change properties for any worksheet or module
Properties control an object’s appearance & behaviour

44. Translation Set 1

45. Translate 2 Translate Algorithm 1.4 Option Explicit
'Written By T. James
Sub AVG3 ()
Dim Num1 as Integer
Dim Num2 as Integer
Dim Num3 as Integer
Dim Sum as Integer
Dim Average as Single
Num1 = InputBox("Num1?")
Num2 = InputBox("Num2?")
Num3 = InputBox("Num3?")
Sum = Num1 + Num2 + Num3
Average = Sum/3
MsgBox("SUM = " & Sum)
MsgBox("Average = " & Average)
End Sub
Translate Algorithm 1.4
NAME:AVG3
GIVENS:
Num1, Num2, Num3
RESULTS:
Sum , Average
DEFINITION:
Sum & Average
:= AVG3(Num1, Num2, Num3)
METHOD:
Get Num1
Get Num2
Get Num3
Let Sum = Num1 + Num2 + Num3
Let Average = Sum /3
Give Sum
Give Average

46. Translate 3 NB Div is Implemented as \
Option Explicit
'Written By T. James
Sub SumDig ()
Dim N as Integer
Dim Sum as Integer
Dim Tens as Integer
Dim Ones as Integer
N = InputBox("2 Dig Num?")
Tens = N \ 10
Ones = N mod 10
Sum = Tens + Ones
Translate Algorithm 1.6
NAME: SumDig
GIVENS: N
RESULTS: Sum
INTERMEDIATES: Tens, Ones
DEFINITION: Sum := SumDig(N)
METHOD:
Get N
Let Tens = N div 10
Let Ones = N mod 10
Let Sum = Tens + Ones
Give Sum
MsgBox("Total is " & Sum)
End Sub

47. Homework

48. What value is assigned to z by the statement below, assuming z, a, b, w and y have respectively the values 8, 3, 9, 2 et –5.
z = z - (a + b / 2) + w * -y

49. Write an algorithm to sum 5 numbers.
Translate the algorithm into Visual Basic code
Write an algorithm to compute the average of 5 numbers.
Write an algorithm to multiply 3 numbers.
Write an algorithm to multiply 2 numbers and divide the product by a third number.

50. Write an algorithm to swap two numbers.
Write an algorithm to calculate the average mark out of 100, given three assignment marks, each of which is marked out of 20.
Translate the algorithm into Visual Basic code
Write an algorithm to calculate the sum of the digits of a three digit number.
Write an algorithm to swap two numbers.
Write an algorithm to sum four numbers and return the sum in the variable x.