Introduction to Programming Using Visual Basic 2005, An (6th Edition)

The following program finds the larger of two numbers input by the user. The condition is

num1 > num2

and each action consists of a single assignment statement. With the inputs 3 and 7, the condition is false, and so the second action is taken.

Private Sub btnFindLarger_Click(...) Handles btnFindLarger.Click Dim num1, num2, largerNum As Double num1 = CDbl (txtFirstNum.Text) num2 = CDbl (txtSecondNum.Text) If num1 > num2 Then largerNum = num1 Else largerNum = num2 EndIf txtResult.Text = "The larger number is " & largerNum End Sub

[Run, type 3 and 7 into the text boxes, and press the button.]

The following program requests the costs and revenue for a company and displays the message "Break even" if the costs and revenue are equal; otherwise, it displays the profit or loss. The action following Else is another If block.

Private Sub btnShow_Click(...) Handles btnShow.Click Dim costs, revenue, profit, loss As Double costs = CDbl (txtCosts.Text) revenue = CDbl (txtRev.Text) If costs = revenue Then txtResult.Text = "Break even" Else If costs < revenue Then profit = revenue - costs txtResult.Text = "Profit is " & FormatCurrency(profit) Else loss = costs - revenue txtResult.Text = "Loss is " & FormatCurrency(loss) End If End If End Sub

[Run, type 9500 and 8000 into the text boxes, and press the button.]

The If block in the following program has a logical operator in its condition.

Private Sub btnEvaluate_Click(...) Handles btnEvaluate.Click 'Evaluate answer Dim answer As Double answer = CDbl (txtAnswer.Text) If (answer >= 0.5) And (answer <= 1) Then txtSolution.Text = "Good, " Else

[Run, type 10 into the text box, and press the button.]

The following program offers assistance to the user before presenting a quotation.

Private Sub btnDisplay_Click(...) Handles btnDisplay.Click Dim message As String message = "Skittles is an old form of bowling in which a wooden " & _ "disk is used to knock down nine pins arranged in a square." If mtxtAnswer.Text.ToUpper = "N" Then MsgBox(message, 0, "") End If txtQuote.Text = "Life ain't all beer and skittles." & _ " - Du Maurier (1894)" End Sub

[Run, type "N" into the masked text box, and press the button.]

[Press OK.]

The following program redoes Example 1 so that if the two numbers are equal, the program so reports:

Private Sub btnFindLarger_Click(...) Handles btnFindLarger.Click Dim num1, num2 As Double num1 = CDbl (txtFirstNum.Text) num2 = CDbl (txtSecondNum.Text) If (num1 > num2) Then txtResult.Text = "The larger number is " & num1 ElseIf (num2 > num1) Then txtResult.Text = "The larger number is " & num2 Else txtResult.Text = "The two numbers are equal." End If End Sub

[Run, type 7 into both text boxes, and press the button.]

The Social Security or FICA tax has two componentsthe Social Security benefits tax, which in 2005 is 6.2 percent on the first $90,000 of earnings for the year, and the Medicare tax, which is 1.45 percent of earnings. The following program calculates an employee's FICA tax for the current pay period.

Private Sub btnCalculate_Click(...) Handles btnCalculate.Click Dim ficaTaxes As Double ficaTaxes = CalcFICA(CDbl (txtToDate.Text), CDbl (txtCurrent.Text)) txtTax.Text = FormatCurrency(ficaTaxes) End Sub Function CalcFICA(ByVal ytdEarnings As Double, _ ByVal curEarnings As Double) As Double 'Calculate Social Security benefits tax and Medicare tax 'for a single pay period in 2005 Dim socialSecurityBenTax, medicareTax As Double If (ytdEarnings + curEarnings) <= 90000 Then socialSecurityBenTax = 0.062 * curEarnings ElseIf ytdEarnings < 90000 Then socialSecurityBenTax = 0.062 * (90000 - ytdEarnings) End If medicareTax = 0.0145 * curEarnings Return socialSecurityBenTax + medicareTax End Function

[Run, type 12345.67 and 543.21 into the top two text boxes, and press the button. The following is displayed in txtTax.]

$41.56

Suppose the user is asked to input a number into txtNumber for which the square root is to be taken. Fill in the If block so that the lines of code that follow will display either the message "Number can't be negative." or the square root of the number.

Private Sub btnSqrt_Click(...) Handles btnSqrt.Click 'Check reasonableness of data Dim num As Double num = CDbl(txtNumber.Text) If End If End Sub

Improve the block

If a < b Then If c < 5 Then txtBox.Text = "hello" End If End If

Private Sub btnDisplay_Click(...) Handles btnDisplay.Click Dim num As Double = 4 If num <= 9 Then txtOutput.Text = "Less than ten." Else If num = 4 Then txtOutput.Text = "Equal to four." End If End If End Sub

Private Sub btnDisplay_Click(...) Handles btnDisplay.Click Dim gpa As Double = 3.49 txtOutput.Clear() If gpa >= 3.5 Then txtOutput.Text = "Honors " End If txtOutput.Text &= "Student" End Sub

Private Sub btnDisplay_Click(...) Handles btnDisplay.Click Dim a As Double = 5 txtOutput.Clear() If (3 * a - 4) < 9 Then txtOutput.Text = "Remember, " End If txtOutput.Text &= "tomorrow is another day." End Sub

Private Sub btnDisplay_Click(...) Handles btnDisplay.Click Dim change As Double = 356 'Amount of change in cents If change >= 100 Then txtOutput.Text = "Your change contains " & _ Int(change / 100) & " dollars." Else txtOutput.Text = "Your change contains no dollars." End If End Sub

Private Sub btnDisplay_Click(...) Handles btnDisplay.Click Dim a as Double = 2 Dim b As Double = 3 Dim c As Double = 5 If a * b < c Then b = 7 Else b = c * a End If txtOutput.Text = CStr(b) End Sub

Private Sub btnDisplay_Click(...) Handles btnDisplay.Click Dim a, b As Double a = CDbl(InputBox("Enter a number.")) b = CDbl(InputBox("Enter another number.")) If a > b Then a += 1 Else b += 1 End If txtOutput.Text = a & " "& b End Sub

(Assume the responses are 7 and 11.)

Private Sub btnDisplay_Click(...) Handles btnDisplay.Click 'Cost of phone call from New York to London Dim length As Double InputLength(length) DisplayCost(length) End Sub

(Assume the response is 31.)

Private Sub btnDisplay_Click(...) Handles btnDisplay.Click Dim letter As String letter = InputBox("Enter A, B, or C.") If letter = "A" Then DisplayAmessage() ElseIf letter = "B" Then DisplayBmessage() ElseIf letter = "C" Then DisplayCmessage() Else txtOutput.Text = "Not a valid letter." End If End Sub Sub DisplayAmessage() txtOutput.Text = "A, my name is Alice." End Sub Sub DisplayBmessage() txtOutput.Text = "To be, or not to be." End Sub Sub DisplayCmessage() txtOutput.Text = "Oh, say, can you see." End Sub

(Assume the response is B.)

Private Sub btnDisplay_Click(...) Handles btnDisplay.Click Dim vowels As Integer 'Number of vowels ExamineLetter(vowels)

(Assume the three responses are U, b, and a.)

Private Sub btnDisplay_Click(...) Handles btnDisplay.Click Dim a As Double = 5 If (a > 2) And ((a = 3) Or (a < 7)) Then txtOutput.Text = "Hi" End If End Sub

Private Sub btnDisplay_Click(...) Handles btnDisplay.Click Dim num As Double = 5 If num < 0 Then txtOutput.Text = "neg" Else If num = 0 Then txtOutput.Text = "zero" Else txtOutput.Text = "positive" End If End If End Sub

Private Sub btnDisplay_Click(...) Handles btnDisplay.Click Dim msg As String, age As Integer msg = "You are eligible to vote" age = CInt(InputBox("Enter your age.")) If age >= 18 Then txtOutput.Text = msg Else txtOutput.Text = msg & " in "& (18 - age) & " years." End If End Sub

(Assume the response is 16.)

In Exercises 13 through 20, identify the errors.

Private Sub btnDisplay_Click(...) Handles btnDisplay.Click Dim num As Double = 0.5 If (1 < num < 3) Then txtOutput.Text = "Number is between 1 and 3." End If End Sub

Private Sub btnDisplay_Click(...) Handles btnDisplay.Click Dim num As Double = 6 If num > 5 And < 9 Then txtOutput.Text = "Yes" Else txtOutput.Text = "No" End If End Sub

Private Sub btnDisplay_Click(...) Handles btnDisplay.Click If (2 <> 3) txtOutput.Text = "Numbers are not equal" End If End Sub

Private Sub btnDisplay_Click(...) Handles btnDisplay.Click Dim major As String major = "Computer Science" If major = "Business" Or "Computer Science" Then txtOutput.Text = "Yes" End If End Sub

Private Sub btnDisplay_Click(...) Handles btnDisplay.Click Dim numName As String, num As Double numName = "Seven" num = CDbl(InputBox("Enter a number.")) If num < numName Then txtOutput.Text = "Less than" Else txtOutput.Text = "Greater than" End If End Sub

Private Sub btnDisplay_Click(...) Handles btnDisplay.Click 'Change switch from "on" to "off", or from "off" to "on" Dim switch As String switch = InputBox("Enter On or Off.") If switch = "Off" Then switch = "On" End If

Private Sub btnDisplay_Click(...) Handles btnDisplay.Click 'Display "OK" if either j or k equals 4 Dim j As Double = 2 Dim k As Double = 3 If j Or k = 4 Then txtOutput.Text = "OK" End If End Sub

Private Sub btnDisplay_Click(...) Handles btnDisplay.Click 'Is your program correct? Dim query, answer1, answer2 As String query = "Are you sure everything in your program is correct?" answer1 = InputBox(query) answer1 = answer1.ToUpper.Substring(0, 1) If answer1 = "N" Then txtOutput.Text = "Don't patch bad code, rewrite it." Else query = "Does your program run correctly?" answer2 = InputBox(query) answer2 = answer2.ToUpper.Substring(0, 1) If answer2 = "Y" Then txtOutput.Text = "Congratulations." Else txtOutput.Text = "Something you are sure about is wrong." End If End Sub

In Exercises 21 through 26, simplify the code.

If (a = 2) Then a = 3 + a Else a = 5 End If

If Not (answer <> "y") Then txtOutput.Text = "YES" Else If (answer = "y") Or (answer = "Y") Then txtOutput.Text = "YES" End If End If

If (j = 7) Then b = 1 Else If (j <> 7) Then b = 2 End If End If

If (a < b) Then If (b < c) Then txtOutput.Text = b & " is between "& a & " and "& c End If End If

message = "Is Alaska bigger than Texas and California combined?" answer = InputBox(message) If (answer.Substring(0, 1) = "Y") Then answer = "YES" End If If (answer.Substring(0, 1) = "y") Then answer = "YES" End If If (answer = "YES") Then txtOutput.Text = "Correct" Else txtOutput.Text = "Wrong" End If

message = "How tall (in feet) is the Statue of Liberty?" feet = CDbl(InputBox(message)) If (feet <= 141) Then lstOutput.Items.Add("Nope") End If If (feet > 141) Then If (feet < 161) Then lstOutput.Items.Add("Close") Else lstOutput.Items.Add("Nope") End If End If sltOutput.Items.Add("The statue is 151 feet from base to torch.")

Write a program to determine how much to tip the server in a restaurant. The tip should be 15 percent of the check, with a minimum of $1.

A bagel shop charges 75 cents per bagel for orders of less than a half-dozen bagels and charges 60 cents per bagel for orders of a half-dozen or more bagels. Write a program that requests the number of bagels ordered and displays the total cost. (Test the program for orders of four bagels and a dozen bagels.)

A computer store sells diskettes at 25 cents each for small orders or at 20 cents each for orders of 100 diskettes or more. Write a program that requests the number of diskettes ordered and displays the total cost. (Test the program for purchases of 5 and 200 diskettes.)

A copy center charges 5 cents per copy for the first 100 copies and 3 cents per copy for each additional copy. Write a program that requests the number of copies as input and displays the total cost. (Test the program with the quantities 25 and 125.)

Write a quiz program to ask "Who was the first Ronald McDonald?" The program should display "Correct." if the answer is "Willard Scott" and "Nice try" for any other answer.

Suppose a program has a button with the caption "Quit." Suppose also that the Name property of this button is btnQuit. Write a btnQuit_Click event procedure that gives the user a second chance before ending the program. The procedure should use an input box to request that the user confirm that the program should be terminated, and then end the program only if the user responds in the affirmative.

Write a program to handle a savings-account withdrawal. The program should request the current balance and the amount of the withdrawal as input and then display the new balance. If the withdrawal is greater than the original balance, the program should display "Withdrawal denied." If the new balance is less than $150, the message "Balance below $150" should be displayed.

Write a program that requests three scores as input and displays the average of the two highest scores. The input and output should be handled by Sub procedures, and the average should be determined by a user-defined function.

A grocery store sells apples for 79 cents per pound. Write a cashier's program that requests the number of pounds and the amount of cash tendered as input and displays the change from the transaction. If the cash is not enough, the message "I need $x.xx more." should be displayed, where $x.xx is the difference between the cash and the total cost. (Test the program with six pounds and $5, and four pounds and $3.)

Federal law requires hourly employees be paid "time-and-a-half" for work in excess of 40 hours in a week. For example, if a person's hourly wage is $8 and he works 60 hours in a week, his gross pay should be

(40 x 8) + (1.5 x 8 x (60 - 40)) = $560

Write a program that requests as input the number of hours a person works in a given week and his hourly wage, and then displays his gross pay.

Write a program that requests a word (with lowercase letters) as input and translates the word into pig latin. The rules for translating a word into pig latin are as follows:

1. If the word begins with a consonant, move the first letter to the end of the word and add ay. For instance, chip becomes hipcay.

2. If the word begins with a vowel, add way to the end of the word. For instance, else becomes elseway.

The current calendar, called the Gregorian calendar, was introduced in 1582. Every year divisible by four was declared to be a leap year, with the exception of the years ending in 00 (that is, those divisible by 100) and not divisible by 400. For instance, the years 1600 and 2000 are leap years, but 1700, 1800, and 1900 are not. Write a program that requests a year as input and states whether it is a leap year. (Test the program on the years 1994, 1995, 1900, and 2000.)

Create a form with a text box and two buttons captioned Bogart and Raines. When Bogart is first pressed, the sentence "I came to Casablanca for the waters." is displayed in the text box. The next time Bogart is pressed, the sentence "I was misinformed." is displayed. When Raines is pressed, the sentence "But we're in the middle of the desert." is displayed. Run the program and then press Bogart, Raines, and Bogart to obtain a dialogue.

Write a program that allows the user to use a button to toggle the color of the text in a text box between black and red.

Write a program that allows the user ten tries to answer the question, "Which U.S. President was born on July 4?" After three incorrect guesses, the program should display the hint, "He once said, 'If you don't say anything, you won't be called upon to repeat it."' in a message box. After seven incorrect guesses, the program should give the hint, "His nickname was 'Silent Cal."' The number of guesses should be displayed in a text box. Note: Calvin Coolidge was born on July 4, 1872.

Write a program that reads a test score from a text box each time a button is clicked and then displays the two highest scores whenever a second button is clicked. Use two class-level variables to track the two highest scores.

The flowchart in Figure 5.3 (on the next page) calculates New Jersey state income tax. Write a program corresponding to the flowchart. (Test the program with taxable incomes of $15,000, $30,000, and $60,000.)

Write a program to play "Hide and Seek" with the name of our programming language. When the button is pressed, the name should disappear and the caption on the button should change to "Show Name of Language." The next time the button is pressed, the name should reappear and the caption should revert to "Hide Name of Language," and so on.

If (num < 0) Then MsgBox("Number can't be negative.", 0, "Input Error") txtNumber.Clear() txtNumber.Focus() Else txtSquareRoot.Text = CStr(Math.Sqrt(num)) End If

The word "hello" will be displayed when (a < b)is true and (c < 5)is also true. That is, it will be displayed when both of these two conditions are true. The clearest way to write the block is

If (a < b) And (c < 5) Then txtBox.Text = "hello" End If