Programming Right From the Start with Visual Basic.NET
CHAPTER 8
Controlling Execution
True-False Questions
1.
The statement clause follows ‘If’ and the condition clause follows ‘Then’.
Answer: False
Level: Easy
Section: 8-1
Page: 176
2.
Every ‘Else’ statement has a condition clause after it.
Answer: False
Section: 8-1
Level: Easy
Page: 176
3.
A single line ‘If’ statement does not require the End If keywords.
Answer: True
Level: Easy
Section: 8-1
Page: 177
4.
An If…Then statement can be used to determine which button a user pressed in a message box.
Answer: True
Level: Easy
Section: 8-1
Page: 178
5.
There is a limit of two ElseIf statements in a multi-line If…Then construct.
Answer: False
Level: Moderate
Section: 8-1
Page: 177
6.
The Case Else is required in the Select Case statement.
Answer: False
Level: Easy
Section: 8-2
Page: 180
7.
Both the Case and Case Else are optional in the Select Case statement.
Answer: True
Level: Moderate
Section: 8-2
Page: 179
8.
After a block of statements is executed, the Select Case statement ends.
Answer: True
Level: Easy
Section: 8-2
Page: 180
9.
A range of values can be placed in the test value clause.
Answer: True
Level: Easy
Section: 8-2
Page: 180
10.
A semi-colon (;) is used to place multiple statements on a single line.
Answer: False
Level: Moderate
Section: 8-2
Page: 180
8-1
Chapter 8 – Controlling Execution
11.
In a Do…Loop a block of statements will be repeated an indeterminate number of times.
Answer: True
Level: Easy
Section: 8-3
Page: 181
12.
Every Do…Loop must have a condition expression.
Answer: True
Section: 8-3
Level: Easy
Page: 181
13.
If a While condition evaluates to true the loop will continue.
Answer: True
Level: Easy
Section: 8-3
Page: 182
14.
If an Until condition evaluates to true the loop will continue.
Answer: False
Level: Easy
Section: 8-3
Page: 182
15.
There are some situations where a While condition will work and the Until condition can’t be
used.
Answer: False
Level: Moderate
Section: 8-3
Page: 182
16.
If you want the block of statements to run at least once, use either Do While or Loop While.
Answer: False
Level: Moderate
Section: 8-3
Page: 182
17.
The For…Next statement is used to select from two or more blocks of statements.
Answer: False
Level: Easy
Section: 8-4
Page: 184
18.
Any For…Next statement can be re-written as a Do…Loop.
Answer: True
Level: Moderate
Section: 8-4
Page: 185
19.
The ‘To end’ part of a For…Next statement is optional.
Answer: False
Level: Easy
Section: 8-4
Page: 184
20.
Negative values are not allowed for the stepvalue.
Answer: False
Section: 8-4
Level: Moderate
Page: 184
21.
The For…Next loop exits when the loop variable exceeds the end value.
Answer: True
Level: Moderate
Section: 8-4
Page: 184
22.
A For…Next loop can never result in an infinite loop.
Answer: False
Section: 8-4
8-2
Level: Hard
Page: 185
Chapter 8 – Controlling Execution
23.
The Exit Sub can be used to stop processing when invalid data is entered.
Answer: True
Level: Easy
Section: 8-5
Page: 188
24.
Do Exit is used to end processing inside a loop.
Answer: False
Section: 8-5
Level: Easy
Page: 187
25.
An Exit statement inside a nested control statement will cause execution to continue immediately
after the nested control statement.
Answer: False
Level: Moderate
Section: 8-5
Page: 187
26.
Sentinel values are used to validate numeric input.
Answer: False
Section: 8-5
Level: Moderate
Page: 187
Exit If will stop execution in an If…Then block.
Answer: False
Section: 8-5
Level: Hard
Page: 187
Visual Studio will automatically fix syntax errors.
Answer: False
Section: 8-6
Level: Easy
Page: 192
27.
28.
29.
If an exception is not handled the program will end immediately.
Answer: True
Level: Easy
Section: 8-6
Page: 190
30.
There are two types of errors: syntax and logic.
Answer: False
Section: 8-6
Level: Easy
Page: 190
31.
The type of exception being caught must be defined for every Catch statement.
Answer: False
Level: Hard
Section: 8-6
Page: 191
32.
The Try…Catch statement is good for catching logic errors.
Answer: False
Level: Moderate
Section: 8-6
Page: 191
33.
Logic errors are the hardest types to find.
Answer: True
Section: 8-6
34.
Level: Easy
Page: 192
A CheckBox CheckedState property has two possible states: True and False.
Answer: False
Level: Moderate
Section: 8-7
Page: 193
8-3
Chapter 8 – Controlling Execution
35.
The CheckBox can be changed to look like a button.
Answer: True
Section: 8-7
Level: Easy
Page: 193
36.
There can be no more than three CheckBox controls on a form or in a group box.
Answer: False
Level: Moderate
Section: 8-7
Page: 193
37.
A CheckBox can have only two states.
Answer: False
Section: 8-7
Level: Easy
Page: 193
38.
The state on one CheckBox control is independent of other CheckBox controls.
Answer: True
Level: Moderate
Section: 8-7
Page: 193
39.
The state on one RadioButton control is independent of other RadioButton controls.
Answer: False
Level: Moderate
Section: 8-8
Page: 195
40.
A form, group box, or panel control can each hold a unique group of RadioButtons.
Answer: True
Level: Moderate
Section: 8-8
Page: 195
41.
Both the RadioButton and CheckBox controls have a CheckChanged event.
Answer: True
Level: Moderate
Section: 8-8
Page: 195
42.
Only the CheckChanged Event for the RadioButton being selected is called, not the
CheckChanged Event for the RadioButton automatically de-selected.
Answer: False
Level: Moderate
Section: 8-8
Page: 195
43.
Only one RadioButton in a group can be selected at a time.
Answer: True
Level: Easy
Section: 8-8
Page: 195
8-4
Chapter 8 – Controlling Execution
Multiple Choice Questions
44.
When a condition in an If…Then statements tests true:
a.) the next Else statement is activated.
b.) the next If statement is activated.
c.) the next Then statement is activated.
d.) the End If statement is activated.
e.) a condition can never test true.
Answer: c
Section: 8-1
45.
Level: Moderate
Page: 176
The End If statement is required:
a.) in all If…Then statements.
b.) in all Multi-line statements with Else.
c.) in Single Line statements.
d.) Both a and b.
e.) All of the above.
Answer: b
Section: 8-1
46.
Level: Moderate
Page: 177
Which statements are optional in an If…Then statement?
a.) If
b.) Then
c.) Else
d.) Both a and b.
e.) All of the above.
Answer: c
Section: 8-1
47.
Level: Easy
Page: 177
Which selection process is an example of multiple branches from a single expression?
a.) If…Then
b.) Select Case
c.) Do…Loop
d.) For…Next
e.) All of the above.
Answer: b
Section: 8-2
Level: Hard
Page: 179
8-5
Chapter 8 – Controlling Execution
48.
How many times is the test expression of a Select Case evaluated?
a.) 0
b.) 1
c.) 2
d.) Once for each Case.
e.) It depends on the value of the test expression.
Answer: b
Section: 8-2
49.
Level: Moderate
Page: 180
Which is not a type of Select Case test construct?
a.) simple value
b.) complex value
c.) relational value with Is
d.) range of values with To
e.) All of the above are types of test constructs.
Answer: b
Section: 8-2
50.
Level: Hard
Page: 180
What happens in a Select Case construct when a test value matches the test expression?
a.) The corresponding block of statements is run.
b.) The next Case test value is checked.
c.) The Case Else statement is run.
d.) The Select Case construct is exited.
e.) An error is generated.
Answer: a
Section: 8-2
51.
Level: Moderate
Page: 180
Do...Loop is an iterative statement because it:
a.) selects a block of statements to run.
b.) runs the same block of statements repeatedly.
c.) selects a block of statements and runs it repeatedly.
d.) selects a block of statements and runs it a specified number of times.
e.) All of the above.
Answer: b
Section: 8-3
52.
Level: Hard
Page: 181
Which is true of a Do…Loop?
a.) The While condition goes after the Do keyword.
b.) The Until condition goes after the Do keyword.
c.) The While condition goes after the Loop keyword.
d.) The Until condition goes after the Loop keyword.
e.) All of the above.
Answer: e
Section: 8-3
Level: Easy
Page: 181
8-6
Chapter 8 – Controlling Execution
53.
Which Do…Loop statement should be used to process test scores where a test score over 100 is a
signal to stop the processing?
a.) Do While Score > 100
b.) Do Until Score > 100
c.) Loop While Score > 100
d.) Loop Until Score > 100
e.) All of the above are valid for this situation.
Answer: b
Section: 8-3
54.
Level: Hard
Page: 182
In the For…Next statement the default value for the Step is:
a.) -1
b.) 0
c.) 1
d.) 2
e.) There is no default for the step value.
Answer: c
Section: 8-4
55.
Level: Easy
Page: 184
The For…Next Loop is used when:
a.) a choice is made based on a Boolean condition.
b.) a block of statements is executed an unknown number of times.
c.) a block of statements is executed a known number of times.
d.) Both a and b.
e.) All of the above.
Answer: c
Section: 8-4
56.
Level: Easy
Page: 184
The advantage of For…Next loops over Do…Loops is that they are:
a.) easier to read and maintain.
b.) less prone to being infinite loops.
c.) good for working with arrays.
d.) Both a and b.
e.) All of the above.
Answer: e
Section: 8-4
57.
Level: Moderate
Page: 185
Which is not a valid Exit statement?
a.) Exit Do
b.) Exit For
c.) Exit Form
d.) Exit Select
e.) Exit Sub
Answer: c
Section: 8-5
Level: Moderate
Page: 187
8-7
Chapter 8 – Controlling Execution
58.
A sentinel value:
a.) is used to prevent infinite loops.
b.) must be a negative value.
c.) signals the end of a list of data.
d.) Both a and b.
e.) All of the above.
Answer: c
Section: 8-5
59.
Level: Easy
Page: 187
Which function should be used to validate that input is not a string before performing arithmetic
operations?
a.) IsArithmetic
b.) IsNotString
c.) IsNumeric
d.) IsString
e.) IsValue
Answer: c
Section: 8-5
60.
Level: Moderate
Page: 189
Which is not a type of error programmers look for?
a.) Logic
b.) Runtime
c.) Superficial
d.) Syntax
e.) All are errors programmers look for.
Answer: c
Section: 8-6
61.
Level: Easy
Page: 190
Which action will raise an exception?
a.) Dividing by zero.
b.) Assigning the string “Hi” to an integer variable.
c.) Accessing an empty CD drive.
d.) Both a and b.
e.) All of the above.
Answer: e
Section: 8-6
Level: Easy
Page: 190
8-8
Chapter 8 – Controlling Execution
62.
An Exception is another name for a:
a.) compile error.
b.) logic error.
c.) runtime error.
d.) superficial error.
e.) syntax error.
Answer: c
Section: 8-6
Level: Moderate
Page: 190
63.
What is the most number of states a CheckBox can have?
a.) 0
b.) 1
c.) 2
d.) 3
e.) 4
Answer: d
Level: Moderate
Section: 8-7
Page: 193
64.
What is the standard prefix for the name of a CheckBox?
a.) chb
b.) chk
c.) ckb
d.) ckx
e.) cbx
Answer: b
Section: 8-7
65.
Level: Easy
Page: 193
A CheckBox can also appear as a(n):
a.) button.
b.) RadioButton.
c.) ScrollBar.
d.) Both a and b.
e.) All of the above.
Answer: a
Section: 8-7
66.
Level: Easy
Page: 195
What is the standard prefix for the name of a RadioButton?
a.) rad
b.) rab
c.) rdo
d.) rdb
e.) rbt
Answer: a
Section: 8-8
Level: Easy
Page: 195
8-9
Chapter 8 – Controlling Execution
67.
How many RadioButtons in a Group Box can be selected at the same time?
a.) 0
b.) 1
c.) 2
d.) 3
e.) 4
Answer: b
Section: 8-8
68.
Level: Easy
Page: 195
Which event is activated when a RadioButton is selected?
a.) Checked
b.) CheckedChanged
c.) Selected
d.) SelectedChanged
e.) SelectionChanged
Answer: b
Section: 8-8
Level: Moderate
Page: 196
Fill in the Blank Questions
69.
Else statements are run when the previous ___condition___ is false.
Level: Moderate
Section: 8-1
Page: 177
70.
A(n) ___nested if ___ statement has an If statement embedded inside another If statement.
Level: Moderate
Section: 8-1
Page: 177
71.
The ElseIf statement is followed by a condition, the ___Else___ statement is not.
Level: Moderate
Section: 8-1
Page: 177
72.
The ___Is___ keyword is used with a relational test clause of a Select Case statement.
Level: Moderate
Section: 8-2
Page: 180
73.
When no test value of a Select Case statement matches the text expression the ___Case Else___
block of statements are run.
Level: Moderate
Section: 8-2
Page: 180
74.
Every Case in the Select Case statement is followed by a ___test value clause___
Level: Hard
Section: 8-2
Page: 179
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Chapter 8 – Controlling Execution
75.
By using a(n) ___comma___ multiple test constructs can be placed after a single Case.
Level: Moderate
Section: 8-2
Page: 180
76.
For a Do…Loop the condition should follow the ___Do___ keyword if the block of statements
should not be executed in some situations.
Level: Moderate
Section: 8-3
Page: 182
77.
The ___While___ condition continues processing the loop if it evaluates true.
Level: Easy
Section: 8-3
Page: 182
78.
The ___Until___ condition continues processing the loop if it evaluates false.
Level: Easy
Section: 8-3
Page: 182
79.
In a For…Next Statement the ___loop variable___ is automatically changed each time the loop is
executed.
Level: Moderate
Section: 8-4
Page: 184
80.
The ___For…Next___ statement is used when the loop is executed a fixed number of times.
Level: Easy
Section: 8-4
Page: 184
81.
It is optional to put the loopvariable after the ___Next___ statement.
Level: Moderate
Section: 8-4
Page: 184
82.
In the For…Next statement the step value default is ___1___.
Level: Easy
Section: 8-4
Page: 184
83.
The ___Exit Select__ statement is used to immediately stop execution in a Select Case statement.
Level: Easy
Section: 8-5
Page: 187
84.
The Exit Sub statement can be used to stop execution before arithmetic operations are applied to
___invalid (or string)___ data.
Level: Moderate
Section: 8-5
Page: 188
85.
The ___sentinel___ value is used to signal that there is no more data to process.
Level: Easy
Section: 8-5
Page: 187
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Chapter 8 – Controlling Execution
86.
The ___Try…Catch___ statement is used to prevent exceptional situations from crashing the
program.
Level: Moderate
Section: 8-6
Page: 191
87.
Exceptions are examples of ___Runtime___ errors.
Level: Easy
Section: 8-6
Page: 190
88.
Misspelling Dim as Din will cause a(n) ___Syntax (or compile)___ error.
Level: Easy
Section: 8-6
Page: 190
89.
The hardest type of error to find is typically a(n) ___Logic___ error.
Level: Easy
Section: 8-6
Page: 191
90.
The three letter prefix for a CheckBox control is ___chk___.
Level: Easy
Section: 8-7
Page: 193
91.
The ___ThreeState___ property of a CheckBox will make it have a third type of Checked
property.
Level: Hard
Section: 8-7
Page: 193
92.
The ___Appearance___ property of a CheckBox will make it look like a button.
Level: Easy
Section: 8-7
Page: 193
93.
The three letter prefix for a RadioButton control is ___rad___.
Level: Easy
Section: 8-8
Page: 195
94.
The RadioButton is best used when a user’s group of choices is ___mutually exclusive___.
Level: Hard
Section: 8-8
Page: 195
95.
To work together a group of RadioButtons must be in a single ___container___.
Level: Moderate
Section: 8-8
Page: 195
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Chapter 8 – Controlling Execution
Essay Questions
96.
What are the three types of errors that can occur in a computer program? Describe each.
A syntax (or compiler) error occurs when the syntax rules of the language are violated. This can
include misspelled keywords, misplaced keywords, violations data type conversions rules,
variable declaration rules, etc. The program cannot be run until all syntax errors are fixed, but
the compiler identifies all of these errors. Visual Studio puts wavy lines under each instance of a
syntax error and puts the error message in a ToolTip, making it easier to find and fix. These are
the easiest errors to find.
A runtime error occurs when the processing of data or external elements violates rules of the
programming language. Examples include dividing by zero, applying arithmetic operations to
strings, performing an operation on the wrong data type, accessing a floppy disk drive when no
disk is in the drive, or trying to access a database on another computer when the network is
down. These errors occur because of factors outside of the program (the data input, drives, and
networks) the errors can not be detected as it is being written. The developer must anticipate that
these errors will occur and use the Try…Catch statement to trap and handle these errors.
Without the Try…Catch statement these errors will cause the program to crash, and this must not
be allowed to happen.
A logic error occurs when there are no syntax or runtime errors but the program does not work
as specified because of inaccurate implementation of the code. One example of this is if the
programmer intends to add two variables together but uses a multiplication symbol (Sum = VarA
* VarB) instead of the addition symbol (Sum = VarA + VarB). Syntactically both statements are
accurate, but the multiplication version is the wrong logic needed to solve the problem.
Logic errors are only detected with accurate, thorough testing or extensive use of the software.
The tendency to trust the output of machines can lead users to accept inaccurate output. The
users must realize what the answer should be and compare this result with the actual output to
detect an error.
97.
(a) Write a For loop that will get 10 numbers and then display the average in a message box.
Make sure the input is valid and include variable declarations.
Dim Sum As Double = 0D
Dim Count, Index As Integer
Dim Input As String
For Index = 1 To 10
Input = InputBox("Enter a Number")
If IsNumeric(Input) Then
Sum = Sum + CDbl(Input)
Count = Count + 1
End If
Next
MsgBox("The Average is: " & (Sum / Count))
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Chapter 8 – Controlling Execution
(b) Write a Do loop that will get 10 numbers and then display the average in a message box.
Make sure the input is valid and include variable declarations.
Dim Sum As Double = 0D
Dim Count As Integer = 0I
Dim Input As String
Do
Input = InputBox("Enter a Number")
If IsNumeric(Input) Then
Sum = Sum + CDbl(Input)
Count = Count + 1
End If
Loop While Count < 10
MsgBox("The Average is: " & (Sum / Count))
(c) What is the advantage of the Do Loop solution?
The Do Loop is better because the For loop will not have 10 values if invalid data is
entered. The Do Loop will run until the correct data is entered, the For loop will only
run 10 times, whether the data is good or bad.
8 - 14