Review for Final (Part 2) School of Business Eastern Illinois University © Abdou Illia, Spring 2003...

Review for Final (Part 2)

School of BusinessEastern Illinois University

© Abdou Illia, Spring 2003

(Week 15, Friday 5/2/2003)

- IF Blocks- Evaluating conditions

3IF Statements

Allow a program to decide on a course of action– Based on whether a certain condition is true or false

If condition Then Statement(s)Else Other Statement(s)End If

Syntax

Condition is an expression that is evaluated to True or False

If condition is true, Statement(s) are executed. If condition is false, Other Statement(s) are executed.

If Credits > 10 Then Tuition = 1000Else Tuition = 100 * CreditsEnd If

Example

4Conditions

Expressions involving:– Relational operators (<, >, >=, =, ….)– Logical operators (And, Or, Not)– Arithmetic operations

If (letterGrade = “A”) Or (letterGrade = “B”) Then picOutput.Print “Good Work”Else picOutput.Print “Grade is C or D”End If

Example

5Relational operators

Can be applied to:– numbers– strings

MathematicalNotation

Visual Basic Notation Numeric Meaning

= = Equal to

# <> Unequal to

< < Less than

> > Greater than

<= <= Less than or equal to

>= >= Greater than or equalto

6Relational operators applied to strings

Computer uses a special coding system to compare character strings

String1 is said to be less than String2 if String1 precede String2 alphabetically according to ANSI table (See Appendix A).

“Chase” < “Chaz” True

“ Cat” < “Cat” True (because of the spaces)

“Pay” < “Pay “ True (because of the spaces)

“Jones” <> “James” True

“Hope” < “Hopeful” True

Examples of comparing character strings

7Logical operators

The three Logical Operators are: Not, And, Or

Not: Negates a single expression. Example: Suppose answer = “Y”

Not (answer = “y”) is true

And: Combines two expressions; each expression must be True for the entire expression to be True. Example: Suppose answer = “Y”

(answer = “Y”) And (answer = “y”) is False

Or: Combines two expressions; either expression (or both expressions) must be True for the entire expression to be True. Example: Suppose answer = “Y”

(answer = “Y”) Or (answer = “y”) is True

8VB operators hierarchy

First, Arithmetic operations (^ , *, /, +, -) are carried out– ^ executed first– * and / executed second– + and – executed third– Note: If parentheses are used, expressions in parentheses are

performed first according to those precedence rules.

Second, Expressions involving relational operators (>, <, =, >=, <=, …) are evaluated to True or False

Third, Logical operators are applied in the order Not, And, Or.

In the event of a tie, the leftmost operator is applied.

9Determine whether the following conditions are true or false?

1 <= 1

Answer: True

“car” < “cat”

Answer: True (because alphabetically “car” precedes “cat”)

“Dog” < “dog”

Answer: True (because Uppercase precedes lowercase)

(“Y” < > “X”) And (143.55 < 143.55)

Answer: False (Because 143.55 is not less than 143.55)


(0 = 14) Or (6 ^ 2 - 3 <= 4 / 2 + 8)

Answer: False

Not (6 = 7) And ( 44 > 33)

Answer: True

In the next two cases, suppose that n = 4

(2 < n) And (n < 6)

Answer: True

(2 < n) Or (n = 6)

Answer: true


In the next cases, assume a = 2 and b = 3

3 * a = 2 * b

Answer: True

(5 – a) * b < 7

Answer: False

b <= 3

Answer: True

a ^ b = b ^ a

Answer: false


In the next cases, assume a = 2 and b = 3

a ^ (5 – 2) > 7

Answer: True

(a < b) Or (b < a)

Answer: True

(a * a < b) Or Not (a * a < a)

Answer: True

Not (a < b) Or Not (a < (b + a))

Answer: False

13Determine the output displayed in the picture box when the command button is clicked.

Private Sub cmdDisplay_Click()

Dim a As Single

a = 5

If 3 * a – 4 < 9 Then

picOutput.Print “Remember, ”

End If

picOutput.Print “Tomorrow is another day.”

End Sub

Answer: Tomorrow is another day.



Dim Gpa As Single

Gpa = 3.49

If Gpa >= 3.5 Then

picOutput.Print “Honors”;

End If

picOutput.Print “Student”

End Sub

Answer: Student



Dim a As Single

a = 5

If (a > 2) And (a = 3 Or a <7) Then

picOutput.Print “Hi”

End If

End Sub

Answer: Hi

Do LoopsSelect Case Blocks

17Do Loops (using While)

Used to repeat a sequence of statements while a condition is True

Do While Condition Statement(s)Loop

Syntax 1

Private Sub cmdDisplay_Click() Dim Num As Integer

' Display the numbers from 1 to 10 Num = 1 Do While Num <= 10 picNumbers.Print Num; Num = Num + 1 LoopEnd Sub

Example

Do Statement(s)Loop While Condition

Syntax 2

Condition involve:– Relational operators (<, >, >=, ….)– Logical operators (And, Or, Not)

Same rules than Condition in IF Blocks (seen before Spring Break)

18Do Loops (using Until)

Used to repeat a sequence of statements until a condition becomes True

Do Statement(s)Loop Until condition

Syntax 4

Private Sub cmdDisplay_Click() Dim Num As Integer

' Display the numbers from 1 to 10 Num = 1 Do Until Num > 10 picNumbers.Print Num; Num = Num + 1 LoopEnd Sub

Example

Do Until conditon Statement(s)Loop

Syntax 3

Note: To get the same result using While and Until, Conditions should be opposites. For instance, While Num <= 10 is the same as Until Num > 10

19Do Loops

Used to display all or selected items from a file– Using EOF function

Private Sub cmdDisplay_Click() Dim Name As String, Phone As String picPhones.Cls

Open "A:\Phone.txt" For Input As #1 Do While Not EOF(1) Input #1, Name, Phone picPhones.Print Name, Phone Loop Close #1End Sub

Example

"Bert", "123-4567""Ernie", "987-6543""Grover", "246-8321""Oscar", "135-7900"

Phone.txt

20Replace each statement containing Until with an equivalent statement containing a While, and vice versa. Loop Until AccountBalance >= 1200

Answer: Loop While AccountBalance < 1200

Do While Amount = 100

Answer: Do Until Amount < > 100

Do Until Name = "Bob"

Answer: Do While Name < > "Bob"

Do While (a > 1) And (a < 3)

Answer: Do Until (a <= 1) Or (a >= 3)

21Simple program using a Do loop

The world population reached 6 billion people in 1999 and was growing at the rate of 1.4 percent each year. Assuming that the population will continue to grow at the same rate, write a program to determine when the population will exceed 10 billion.

Private Sub cmdCalculate_Click( ) Dim Year As Integer, Population As Single Year = 1999 Population = 6000000000 Do Until Population > 10000000000 Population = Population + (0.014 * Population) Year = Year + 1 Loop

picOutput.Print "The answer is: "; YearEnd Sub

22For …Next

Repeats a group of statements a specified number of times

For…Next are used when we know exactly how many times a loop should be executed.

Private Sub cmdDisplay_Click() Dim i As integer picTable.Cls For i = 1 To 5 picTable.Print i; i^2 Next iEnd Sub

Example

For counter = start To end

Statement(s)

Next [counter]

Where:

counter is a numeric variable used as a loop counter

start is the initial value of counter

end is the final value of counter

Private Sub cmdDisplay_Click() Dim i As integer picTable.Cls i = 1 Do While i <= 5 picTable.Print i; i^2 i = i + 1 LoopEnd Sub

Same example using Do loop

23Select Case Blocks

Very efficient decision-making structures:– Simplifies choosing among several actions

Avoid using Nested IF and ElseIf statements

Actions based on the value of an expression called selector

Select Case Selector Case ValueList1 Action1 Case ValueList2 Action2 : Case Else

Action of last resortEnd Select

SyntaxAge = Val(txtAge.Text)Select Case Age Case 5 Category = "5-year old" Case 13 To 19 Category = "Teenager" Case Is > 65 Category = "Senior" Case Else Category = "Everyone else"End Select

Example

24Select Case Statements

Selectors can be:– Numeric or string variables. Example: Select Case FirstName– Expressions. Example: Select Case Left(EmployeeName, 1)

Select Case Selector Case ValueList1 Action1 Case ValueList2 Action2 : Case Else

Action of last resortEnd Select

Syntax

ValueList items must be separated by commas

ValueList can be:– A constant– An expression– An inequality sign preceded by Is and

followed by a constant, a variable, or an expression

– A range expressed in the form a To b.

x = 2 : y = 3Num = Val(txtNumber.Text)Select Case Num Case y – x, x picOutput.Print "Buckle my shoes"End Select

Grade = Val(txtBox.Text)Select Case Grade Case Is >= 90 picOutput.Print "A"End Select

Grade = Val(txtBox.Text)Select Case Grade Case 60 To 89 picOutput.Print "Pass"End Select

25Problem 1: Assigning letter grades(To be done in class)

Write a Click event procedure associated to the command button cmdShow that asks the user to type in an exam score and:

– Assigns a letter grade based on the scale in the table below. The variable to be assigned the letter grade as value should be named Grade

– Displays the score typed by the user and the letter grade in picBox.

Score Letter grade

90-100 A

80-89 B

70-79 C

60-69 D

0-59 F

txtScore

cmdShow picBox

26

Problem 1: Assigning letter grades

Private Sub cmdShow_Click() Dim Score As Single Score = Val(txtScore.Text) Select Case Score Case 90 To 100 Grade = "A" Case 80 To 89 Grade = "B" Case 70 To 79 Grade = "C" Case 60 To 69 Grade = "D" Case 0 To 59 Grade = "F" End Select picBox.Print Score; GradeEnd Sub

Score Letter grade

90-100 A

80-89 B

70-79 C

60-69 D

0-59 F

txtScore

cmdShow picBox

27Problem 2: IRS

IRS informants are paid cash rewards based on the value of the money recovered.

Write a Click event procedure associated to the command button cmdReward that asks the user to type in the Amount recovered and:

– Determine the Reward based on the following rule: 10% for up to $75000 recovered, 15% for a recovered amount greater than 75000 but less than $100000; and 18% for more than $100000.

– Displays the calculated reward in picReward. txtAmount

cmdShow

picReward

28Problem 2: IRS

Private Sub cmdShowReward_Click() Dim Amount As Single Amount = Val(txtAmount.Text) Select Case Amount Case Is <= 75000 Reward = 0.1 * Amount Case Is <= 100000 Reward = 0.15 * Amount Case Is > 100000 Reward = 0.18 * Amount End Select picReward.Print "The reward is "; RewardEnd Sub

txtAmount

cmdShow

picReward

- One-dimensional arrays- Two-dimensional arrays- Sequential Files

30One-dimensional arrays

See hard copy received to prepare for exam 3

Copy available at: http://www.eiu.edu/~a_illia/cis2000/notes/AllReview.htm

31Two-dimensional arrays



32Sequential Files



List boxCombo box

34List box and Combo box

See Answer to Exercises received in class.

See Quiz 3 (available at http://www.eiu.edu/~a_illia/cis2000/notes/AllReview.htm)

Review for Final (Part 2) School of Business Eastern Illinois University © Abdou Illia, Spring 2003...

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Transcript of Review for Final (Part 2) School of Business Eastern Illinois University © Abdou Illia, Spring 2003...