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CSI 1301
PROGRAMMING IN VISUAL BASIC
PART 1
Part 1
1. Visual Basic Programming2. Translating the Algorithm Declaration3. Translating Assignment Instructions4. Translating Get and Give Instructions5. Additional Material
1. Visual Basic Programming
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)
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
English
ALGORITHM
Visual Basic
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)
2. Translating the Algorithm Description
Translating the Algorithm DescriptionWhen a program is executing, the instructions and
data being processed are stored in RAMThe 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
Translating the Algorithm DescriptionVariable
• 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
Translating the Algorithm DescriptionWe 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
Translating the Algorithm DescriptionThe Visual Basic translator keeps track of where
each data item is stored in RAMWhen 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.
Translating the Algorithm DescriptionDeclaring 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 constantOption 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)
Translating the Algorithm DescriptionEnter OPTION EXPLICIT on the first line All programs begin with SUB and end with END
SUBComments 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
Translating the Algorithm DescriptionOPTION 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 = 3.14159 'PI
END SUB
Translating the Algorithm DescriptionWhere 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
3. Translating Assignment Instructions
Algorithmic Representation of Computer Functions Input
– Get informationStorage
– Store informationProcess
– Arithmetic operations
– Logic decisions
– Repeat instructionsOutput
– Give information
GET
Given/Results/Intermediates/Set
LET
IF
LOOP
GIVE
Assignment Instructions
An assignment statement is used to assign a value to a variableVariable = Expression
– The computed value of the Expression is assigned to (stored in) the variable on the left side of the = sign
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)
Assignment Instructions
The order of precedence of arithmetic operators in an expression is as follows:
Brackets ()Exponents ^Division / Multiplication *Addition +Subtraction -
Translating Assignment InstructionsLook 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
Translating Assignment InstructionsALGORITHM
X = 5 Y = X + 3
C = 2r A = r2
VISUAL BASIC
X = 5 Y = X + 3
C = 2 * PI * R A = PI * R^2
Translating Assignment InstructionsOption Explicit'Written by T. James
Sub Circles()Dim R as Single 'RadiusDim A as Single 'AreaDim C as Single 'Circumference
Const PI = 3.1415926
R = 1.2A = PI * R^2C = 2 * PI * R
End Sub
4.Translating Get and Give Instructions
From/To the User
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
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
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
GET from the User
Income = InputBox(“Enter your income”)– Stores what the user enters in the variable Income
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
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 &
Look at the METHODTranslate any GET or GIVE instructions that refer
to the user as follows.
– GIVE: MsgBox(“message”)
– GET: variable = InputBox(“prompt message”)
Translating to Visual Basic
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
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
Option Explicit
'Written By T. James
Sub CalcMark ()
Translate 1
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
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
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
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
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
MsgBox("Mark is " & Mark)
End Sub
Algorithm 1.5
5. Additional Material
Example of Complexity
Visual Basic Editor
Translation Set 1
Example of ComplexityStudent Marks
B C D E F G H I J 1 # a1 a2 a3 a4 a5 m f g 2 1 10 10 10 10 10 50 40 3 2 2 5 8 3 9 60 45 4 3 8 9 7 6 10 60 70 5 4 5 5 5 5 5 50 50 6 5 10 9 8 7 6 70 48 7 6 10 6 3 9 10 76 74 8
Example of Complexity
Calculate the final mark, based on 25% forassignments, 25% for midterm and 50% forfinal 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)
Example of ComplexityVariation 2
– “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)
Visual Basic Editor
The Visual Basic Editor– Consists of 4 windows
• Main, Code, Project Explorer, Properties
1 Main window– Title bar, menu bar & standard toolbar
2 Code window– Insert – Module
– To write code for procedures
Visual Basic Editor
3 Project Explorer 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
4 Properties window– To change properties for any worksheet or module– Properties control an object’s appearance & behaviour
Translation Set 1
Translate 2 Translate Algorithm 1.4
NAME:AVG3GIVENS:
Num1, Num2, Num3RESULTS:
Sum , AverageDEFINITION:
Sum & Average := AVG3(Num1, Num2, Num3)
METHOD:Get Num1Get Num2Get Num3Let Sum = Num1 + Num2 + Num3Let Average = Sum /3Give SumGive Average
Option Explicit'Written By T. JamesSub 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
Algorithm 1.4
Translate 3NB Div is Implemented as \ Translate Algorithm 1.6
NAME: SumDigGIVENS: NRESULTS: SumINTERMEDIATES: Tens, OnesDEFINITION: Sum := SumDig(N)METHOD:
Get N
Let Tens = N div 10Let Ones = N mod 10Let Sum = Tens + Ones
Give Sum
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
MsgBox("Total is " & Sum)
End Sub
Algorithm 1.6
Homework
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
1. Write an algorithm to sum 5 numbers. Translate the algorithm into Visual Basic code
2. Write an algorithm to compute the average of 5 numbers. Translate the algorithm into Visual Basic code
3. Write an algorithm to multiply 3 numbers. Translate the algorithm into Visual Basic code
4. Write an algorithm to multiply 2 numbers and divide the product by a third number. Translate the algorithm into Visual Basic code
1. 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
2. Write an algorithm to calculate the sum of the digits of a three digit number. Translate the algorithm into Visual Basic code
3. Write an algorithm to swap two numbers. Translate the algorithm into Visual Basic code
4. Write an algorithm to sum four numbers and return the sum in the variable x. Translate the algorithm into Visual Basic code