Chapter 6 Repetition

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1 hapter 6 Repetition Section 6.1 o Loops 1. What is wrong with the following o loop? im index As Integer = 1 o While index <> 9 lstbox.items.add("hello") index += 1 Loop (A) he test variable should not be changed inside a o loop. (B) he test condition will never be true. () his is an infinite loop. () Nothing 2. What numbers will be displayed in the list box when the button is clicked? Private Sub btnisplay_lick(...) Handles btnisplay.lick im num as ouble = 10 o While num > 1 lstbox.items.add(num) num = num - 3 Loop (A) 10, 7, and 4 (B) 10, 7, 4, and 1 () 10, 7, 4, 1, and -2 () No output A 3. Which While statement is equivalent to Until num < 100? (A) While num <= 100 (B) While num > 100 () While num >= 100 () here is no equivalent While statement.

2 4. What is wrong with the following o loop? im index As Integer = 1 o While index <> 10 lstbox.items.add("hello") index += 2 Loop (A) It should have been written as a o Until loop. (B) It is an infinite loop. () he test variable should not be changed within the loop itself. () Nothing B 5. How many times will the word Happy appear in the list box when the following code is executed? im index As Integer o lstbox.items.add("happy") index += 1 Loop While index > 3 (A) 0. (B) 1 () 2 () 3 B 6. In analyzing the solution to a program, you conclude that you want to construct a loop so that the loop terminates either when (a < 12) or when (b = 16). Using a o loop, the test condition should be (A) o While (a > 12) Or (b <> 16) (B) o While (a >= 12) Or (b <> 16) () o While (a < 12) Or (b <> 16) () o While (a >= 12) And (b <> 16) (E) o While (a < 12) And (b = 16) 7. When Visual Basic executes a o While loop it first checks the truth value of the. (A) pass (B) loop () condition () statement

3 8. If the loop is to be executed at least once, the condition should be checked at the. (A) top of the loop (B) middle of the loop () bottom of the loop () Nothing should be checked. 9. A o While loop checks the While condition before executing the statements in the loop. (/) 10. If the While condition in a o While loop is false the first time it is encountered, the statements in the loop are still executed once. (/) 11. he following statement is valid. (/) o While x <> he following two sets of code produce the same output. (/) im num As Integer = 1 im num As Integer = 1 o While num <= 5 o lstbox.items.add("hello") lstbox.items.add("hello") num += 1 num += 1 Loop Loop Until (num > 5) 13. A loop written using the structure o While...Loop can usually be rewritten using the structure o...loop Until. (/) 14. A variable declared inside a o loop cannot be referred to outside of the loop. (/) 15. escribe precisely the output produced by the following segment for the inputs 4 and 2. im last, i As Integer last = Int(InputBox("Enter terminating value:")) i = 0 o While (i <= last) lstbox.items.add(i) i += 1 Loop (Input 4): (Input 2): No output

4 16. he following is an infinite loop. Rearrange the statements so that the loop will terminate as intended. x = 0 o lstbox.items.add(x) Loop Until x > 13 x += 2 Move the last statement one line up, before the Loop Until statement 17. What is wrong with the following simple password program where today's password is "intrepid"? Private Sub btnisplay_lick(...) Handles btnisplay.lick im password As String password = InputBox("Enter today's password:") o lstbox.items.add("incorrect") password = InputBox("Enter today's password:") Loop Until password = "intrepid" lstbox.items.add("password orrect. You may continue.") (A) here is no way to re-enter a failed password. (B) he Loop Until condition should be password <> "intrepid". () It will display "Incorrect." even if the first response is "intrepid". () Nothing 18. How many times will HI be displayed when the following lines are executed? im c As Integer = 12 o lstbox.items.add("hi") c += 3 Loop Until (c >= 30) (A) 5 (B) 9 () 6 () 4 (E) 10

5 19. In the following code segment, what type of variable is counter? im temp, counter, check As Integer o temp = Int(InputBox("Enter a number.")) counter += temp If counter = 10 hen check = 0 End If Loop Until (check = 0) (A) counter (B) accumulator () sentinel () loop control variable B 20. What numbers will be displayed in the list box by the following code when the button is clicked? Private Sub btnisplay_lick(...) Handles btnisplay.lick im num As Integer = 7 o num += 1 lstbox.items.add(num) Loop Until (num > 6) lstbox.items.add(num) (A) 7 (B) 8 () 7 and 8 () 8 and calculate the number of elements in lists. (A) Sentinels (B) ounter variables () Accumulators () Nested loops B 22. calculate the sums of numerical values in lists. (A) Sentinels (B) ounter variables () Accumulator variables () Nested loops

6 23. he following are equivalent While and Until statements. (/) While (num > 2) And (num < 5) Until (num <= 2) Or (num >= 5) 24. A o Loop Until block is always executed at least once. (/) 25. A counter variable is normally incremented or decremented by 1. (/) 26. he following program uses a counter variable to force the loop to end. (/) Private Sub btnisplay_lick(...) Handles btnisplay.lick im r As ouble = 1 im t As ouble = 0 o While (t < 5000) t = 2 * t + r r += 1 lstbox.items.add(t) Loop Section 6.2 or Loops 1. When the number of repetitions needed for a set of instructions is known before they are executed in a program, the best repetition structure to use is a(n) (A) o While...Loop structure. (B) o...loop Until structure. () or... loop. () If block. 2. What is one drawback in using non-integer Step sizes of type ouble? (A) Round-off errors may cause unpredictable results. (B) Non-integer Step sizes are invalid in Visual Basic. () A non-integer Step size is never needed. () Non-integer Step sizes usually produce infinite loops. A

7 3. When the odd numbers are added successively, any finite sum will be a perfect square (e.g., = 9 and 9 = 3^2). What change must be made in the following program to correctly demonstrate this fact for the first few odd numbers? Private Sub btnisplay_lick(...) Handles btnisplay.lick im oddnumber As Integer im sum As Integer = 0 or i As Integer = 1 o 9 Step 2 'Generate first few odd numbers oddnumber = i or j As Integer = 1 o oddnumber Step 2 'Add odd numbers sum += j lstbox.items.add(sum & " is a perfect square.") (A) hange the Step size to 1 in the first or statement. (B) Move oddnumber = i inside the second or loop. () Reset sum to zero immediately before the second statement. () Reset sum to zero immediately before the first statement. 4. What does the following program do with a person's name? Private Sub btnisplay_lick(...) Handles btnisplay.lick im name, test As String im n As String = "" name = InputBox("Enter your first name:") or i As Integer = 0 o (name.length - 1) Step 2 test = name.substring(i, 1) n = test & n txtbox.ext = n It displays the name (A) in reverse order. (B) in reverse order and skips every other letter. () as it was entered. () as it was entered, but skips every other letter. B 5. Suppose the days of the year are numbered from 1 to 365 and January 1 falls on a uesday as it will in What is the correct or statement to use if you want only the numbers for the ridays in 2019? (A) or i As Integer = 3 to 365 Step 7 (B) or i As Integer = 1 to 365 Step 3 () or i As Integer = 365 o 1 Step -7 () or i As Integer = 3 o 365 Step 6 A

8 6. Given the following partial program, how many times will the statement lstbox.items.add(j + k + m) be executed? or j As Integer = 1 o 4 or k As Integer = 1 o 3 or m As Integer = 2 o 10 Step 3 lstbox.items.add(j + k + m) (A) 24 (B) 60 () 36 () 10 (E) None of the above 7. Which of the following program segments will sum the eight numbers input by the user? (A)or k As Integer = 1 o 8 s = bl(inputbox("enter a number.") s += k (B) or k As Integer = 1 o 8 a = bl(inputbox("enter a number.") s += 1 () or k As Integer = 1 o 8 a = bl(inputbox("enter a number.") a += s () or k As Integer = 1 o 8 a = bl(inputbox("enter a number.")) s += a

9 8. What will be displayed by the following program when the button is clicked? Private Sub btnisplay_lick(...) Handles btnisplay.lick im a As String, n, c As Integer a = "HIGHBAK" n = Int(Int(a.Length / 2)) c = 0 or k As Integer = 0 o n 1 If a.substring(k, 1) > a.substring(7 k, 1) hen c += 1 End If txtbox.ext = Str(c) (A) 1 (B) 2 () 3 () 4 (E) 5 9. In a or statement of the form shown below, what is the default step value when the "Step c" clause is omitted? or i As Integer = a o b Step c (A) the same as a (B) the same as b () 0 () What will be displayed when the following lines are executed? txtbox.lear() or k As Integer = 1 o 3 txtbox.ext &= "AB".Substring(4 k, 1) (A) AB (B) BA () BA () BA (E) B E

10 11. Which loop computes the sum of 1/2 + 2/3 + 3/4 + 4/ /100? (A) or n As Integer = 1 o 99 s += n / (1 + n) (B) or q As Integer = 100 o 1 s += (q + 1) /q () or d As Integer = 2 o 99 s = 1 / d + d / (d + 1) () or x As Integer = 1 o 100 s += 1 / (x + 1) A 12. How many times will PEE be displayed when the following lines are executed? or c As Integer = 15 to -4 Step -6 lstbox.items.add("pee") (A) 1 (B) 2 () 3 () What will be displayed by the following program when the button is clicked? Private Sub btnisplay_lick(...) Handles btnisplay.lick im s As ouble s = 0 or k As Integer = 1 o 5 If k / 2 = Int(k / 2) hen s += k End If txtbox.ext = Str(s) (A) 12 (B) 9 () 15 () 6

11 14. How many lines of output are produced by the following program segment? or i As Integer = 1 o 3 or j As Integer = 1 o 3 or k As Integer = i to j lstbox.items.add("programming is fun.") (A) 8 (B) 9 () 10 () Assuming the following statement, what is the or... loop's counter variable? or yr As Integer = 1 o 5 (A) 1 (B) 5 () o () yr 16. What is the value of j after the end of the following code segment? or j As Integer = 1 to 23 lstbox.items.add("he counter value is " & j) (A) 22 (B) 23 () 24 () j no longer exists 17. A or... loop with a positive step value continues to execute until what condition is met? (A) he counter variable is greater than the terminating value. (B) he counter variable is equal to or greater than the terminating value. () he counter variable is less than the terminating value. () he counter variable is less than or equal to the terminating value. A

12 18. Which of the following loops will always be executed at least once when it is encountered? (A) a or... loop (B) a o loop having posttest form () a o loop having pretest form () none of the above. B 19. Which of the following are valid for an initial or terminating value of a or... loop? (A) a numeric literal (B) info.length, where info is a string variable () a numeric expression () All of the above 20. What is the data type of the variable num if Option Infer is set to On and the statement im num = 7.0 is executed? (A) Integer (B) ecimal () ouble () String (E) Boolean 21. he value of the counter variable should not be altered within the body of a or loop. (/) 22. he body of a or... loop in Visual Basic will always be executed once no matter what the initial and terminating values are. (/) 23. If the terminating value of a or... loop is less than the initial value, then the body of the loop is never executed. (/) 24. If one or... loop begins inside another or... loop, it must also end within this loop. (/) 25. he value of the counter variable in a or... loop need not be a whole number. (/) 26. One must always have a statement paired with a or statement. (/)

13 27. If the initial value is greater than the terminating value in a or... loop, the statements within are still executed one time. (/) 28. When one or... loop is contained within another, the name of the counter variable for each or... loop may be the same. (/) 29. A or... loop cannot be nested inside a o loop. (/) 30. he following code segment is valid. (/) If (firstletter > "A") hen or x As Integer = 1 to 100 lstbox.items.add(x) End If 31. In a or... loop, the initial value should be greater than or equal to the terminating value if a negative step is used and the body of the loop is to be executed at least once. (/) 32. If the counter variable of a or... loop will assume values that are not whole numbers, then the variable must not be of type Integer. (/) 33. he step value of a or... loop can be given by a numeric literal, variable, or expression. (/) 34. he variable index declared with the statement or index As Integer = 0 o 5 cannot be referred to outside of the or loop. (/) 35. When Option Infer is set to On, a statement of the form im num = 7 is valid. (/)

14 36. What is displayed in the text box when the button is clicked? Private Sub btnisplay_lick(...) Handles btnisplay.lick im word As String = "Alphabet" im abbreviation As String = "" or i As Integer = 0 o word.length - 1 If word.substring(i, 1).oUpper <> "A" hen abbreviation &= word.substring(i, 1) End If txtbox.ext = abbreviation lphbet Section 6.3 List Boxes and Loops 1. Which of the following expressions refers to the contents of the last row of the list box? (A) lstbox.items(lstbox.items.ount) (B) lstbox.items(lstbox.items.ount - 1) () lstbox.items(ount) () lstbox.items.ount B 2. Which of the following expressions refers to the contents of the first row of the list box? (A) lstbox.items(0) (B) lstbox.items(1) () lstbox.items.irst () lstbox.items(irst) A 3. Each item in a list box is identified by an index number. he first item in the list is assigned which of the following values as an index? (A) a randomly assigned value (B) 1. () a value initially designated by the programmer () 0 4. he following lines of code display all the items of lstbox. (/) or n As Integer = 1 to lstbox.items.ount lstbox2.items.add(lstbox.items(n)) 5. he number of items in ListBox1 is ListBox1.Items.ount. (/)

15 6. If no item in a list box is selected, the value of lstbox.selectedindex is 0. (/) 7. Which of the statements will unhighlight any highlighted item in lstbox? (A) lstbox.selecteditem = Nothing (B) lstbox.selecteditem = "" () lstbox.selectedindex = 0 () lstbox.selectedindex = A list box named lstbox has its Sorted property set to rue and contains the three items at, og, and Gnu in its Items collection. If the word Elephant is added to the Items collection at run time, what will be its index value? (A) 2 (B) 1 () 3 () 0 A 9. A list box named lstbox has its Sorted property set to alse and contains the three items at, og, and Gnu in its list. If the word Elephant is added to the list at run time, what will be its index value? (A) 2 (B) 1 () 3 () If a program contains procedures for both the lick and oublelick events on a list box and the user double-clicks on the list box, only the lick event will be raised. (/) 11. If a list box has its sorted property set to rue and the list box contains all numbers, then the values in the list box will always be in increasing numerical order. (/) 12. If a list box contains all numbers, then which of the following values can be calculated without using a loop? (A) average value of the numbers (B) largest number () smallest number () number of numbers

16 13. Which of the following is not a type of event that can be raised by user selections of items in a list box? (A) lick event (B) SelectedIndexhanged event () illown event () oublelick event 14. he value of lstbox.items(n) is the nth item in the list box. (/) 15. he sorted property can only be set to rue at design time. (/) 16. he data type is most suited to a flag. (A) Boolean (B) Integer () ecimal () ouble (E) String A 17. A variable that keeps track of whether a certain situation has occurred is called (A) a counter. (B) an accumulator. () a switch. () a flag.

Chapter 6 Repetition. 6.1 Do Loops 6.2 For...Next Loops 6.3 List Boxes and Loops

Chapter 6 Repetition. 6.1 Do Loops 6.2 For...Next Loops 6.3 List Boxes and Loops Chapter 6 Repetition 6.1 Do Loops 6.2 For...Next Loops 6.3 List Boxes and Loops 1 6.1 Do Loops Pretest Form of a Do Loop Posttest Form of a Do Loop 2 Do Loops A loop is one of the most important structures