Starting out with Visual C# - Chapter 4
A(n)_________ Expression has a value of either true or false.
Boolean Expression
how can you read the selected item from a ListBox while preventing an exception from occurring if no item is selected.
By checking the SelectedIndex to see if the value is set to -1 before reading.
How do you get the item that is selected in a ListBox?
By taking its string value from the SelectedItem property.
How do you determine in code whether a RadioButton control or a checkBox Control is selected
CheckSelected property
case statement
Contains cases to test against the testExpression
bool data type
Creates variables which hold true or false values
A__________________ Structure executes a set of statements only under certain conditions
Decision Structure (Selection Structure)
TryParse
Determines whether a string contains a value that can be converted to a specific data type before its actually converted. prevents exceptions from being thrown
You need to test a condition and then execute one set of statements if the condition is true. If the condition is false, you need to execute a different set of statements. What structure will you use
Dual-alternative decision structure
A __________ is a Boolean variable that signals when some condition exists in the program
flag
Dual-alternative decision structure
has two possible paths of execution one for a true Boolean expression and one for a false Boolean expression.
You use a(n) ____________ Statement to write a single-alternative decision structure
if
The _______ operator takes a Boolean expression as its operand and it reverses its logical value.
!
When determining whether a number is inside a range, which logical operator is it best to use?
&&
a compound Boolean expression created with the _______ operator is only true if both sub-expressions are true
&&
a ListBox's index numbering starts at
0
What is meant by the term "Conditionally Executed"
A code is only executed if the right conditions are met
What is a flag and how does it work.
A flag is a Boolean value which tags a piece of code for the programmer to see.
Sequence Structure
A set of statements that execute in the order that they appear.
if-else Statement
A statement which will execute one block of statements if its Boolean expression is true, or another block if its Boolean expression is false
What is a decision structure?
A type of control structure based on If - Then statements
testExpression
A variable or an expression that gives an integer, string or bool value (Cannot be a decimal)
Flag
A variable that signals when some condition exists in the program
What is a Flag Variable
A variable which signals when a condition exists in the program.
Boolean expression
An expression that can be evaluated as either true or false
T/F: a single-alternative decision structure tests a condition and then takes one path if the condition is true and one path if the condition is false
False, A dual-decision structure does this
The text expression i a switch statement can be a double or decimal value
False, it can be anything but those two things
The tryParse method throw an exception if the string argument cannot be converted
False, it tries all conversion methods, one will always work.
if an item is not selected in a ListBox, the control's selectIndex property will be set to 0
False, it will be set to -1
to store items in a ListBox, you add them to the controls text property.
False, you add them to the Item property
T/F: you can write any program using only sequence structures
False, you need other code to make a program work
What types of relationships between numeric values can you test with relational operators?
Greater-than or equal to, Less than or equal to, equal to, or not equal to
Short-Circuit evaluation
If one side of the expression is true in a logical OR operators, the other side is not checked, if either side of a logical And Statement is false, the other side is not checked.
In an if-else statement, under which circumstances do the statements that appear after the else clause execute?
If the Boolean expression stated in the if clause is false.
How do you add items to a ListBox using the properties window?
In the Items property
Switch Statements
Let the value of a variable or an expression determine which path of execution of the program will take.
&&, ||, and ! are __________ operators
Logical
Control Structure
Logical design that controls the order in which a set of statements executes.
A ________ decision structure is written inside another decision structure
Nested
If several RadioButton controls have been crated in the same Group Box, how many of them may be selected at one time?
One
If several __________ controls exist in a GroupBox, only one of them may be selected at a time
RadioButton
the symbols >, <, and == are all _______________ Operators.
Relational
Logical NOT (!) operator
Reverses the truth of a Boolean expression
Decision Structure (Selection Structure)
Specific action is performed only if a certain condition exists. if the condition does not exist, the action is not performed.
Briefly describe how the && operator Works.
The && operator makes a Boolean's logical value true if both subexpressions are also true.
Multiple CheckBox controls in the same GroupBox can be selected at the same time
True
T/F: A decision structure can be nested inside of another decision structure.
True
T/F: The if-else statement is a dual-alternative decision structure
True
What special values can you store in a bool variable?
True & False values
Items Property
Where you add selectable items to a listBox control
What is a single-alternative decision structure?
a control structure which provides only one alternative decision.
What is a control structure?
a logical system of controlling the order in which statements execute
Listbox Index
a number that identifies the item's position in the list box, which is stored in the Items property
Output Variable
a variable that is passed as an argument to a method, and when the method is finished, a value is stored in the variable
Conditionally executed
action performed only when a certain condition is true
Logical AND (&&) OR (||) operators
allow you to connect multiple Boolean expressions to create a compound expression.
SelectedIndex property
allows you to see the index of selected items and if index is set to -1 prevent a no item selected error.
Multiple-alternative decision structure
allows you to test the value of a variable or an expression and then use that value to determine which statement or set of statements to execute.
What is a Boolean Expression?
an expression evaluated as either true or false
What is a compound Boolean expression?
an expression which uses more than one Boolean expressions at one time
If several CheckBox controls have been created in the same GroupBox, how many of them may be selected at one time?
as many as you want
Describe how dual-alternative decision structures work.
by providing two pathways for execution. one for a true Boolean expression, and one for a false Boolean expression
In code, how do you determine whether a RadioButton or a checkbox control has been selected
by seeing the checked property and whether it is set to true of
how do you add items to a listBox control using the properties window?
by adding them to the items property
Checked-Changed event
causes an action to immediately take place when you check a check box
ListBox Control
creates a list box on an applications form that allows users to select one or more items from the list.
Nested decision structures
decision structures which appear inside other decision structures. commonly done when a program needs to test more than one condition.
The _______________ section of a switch statement is branched to if none of the case values match the test expression
default
relational operator
determines whether a specific relationship exists between two values, comparative operator
Checked property
determines whether the control is selected or deselected
A ______________ Structure tests a condition and then takes one path if the condition is true and another path if the condition is false
dual-alternative decision
Write an if statement that determines whether the variable sales is greater than or equal to 10,000. if it is, assign 0.2 to the variable commisionRate.
if (sales >= 10000) { commissionRate = 0.2; }
Write an if-else statement that works like this: If the sales variable is greater than or equal to 50,000, the commissionRate Variable should be assigned the value 0.2. otherwise, the commissionRate variable should be assigned the value 0.1.
if (sales >= 50,000) { commissionRate = 0.2; } else { commissionRate = 0.1; }
Write an if statement that determines whether the variable y is equal to 20. If it is assign 0 to the variable X.
if (y == 20) { x = 0; }
How can you determine whether an item has been selected in a ListBox
if the selectedIndex is not equal to -1
you use a(n) ______________ statement to write a dual alternative decision structure.
if-else
Input Validation
input is inspected by the program before it is processed and if it is invalid it is discarded and the user is prompted to enter correct data.
selectItem property
property where selected items in a listBox are stored
single-alternative decision structure
provides only one alternative path of execution
you can use the __________________ property to determine whether an item is selected in a listBox
selectedIndex
The ________ property holds the item that is selected in a listBox control.
selectedItem
A __________________ Structure provides one alternative path of execution.
single-alternative decision
Check box
small box which works similar to radio buttons but they are not mutually exclusive
Out keyword
specifies that the target variable is an output variable
What are the two arguments that you pass to a TryParse Method
string and data type
You use the ___________ statement to create a multiple alternative decision structure.
switch
Briefly describe how the || operator works.
the || operator makes a boolean's logical value true if atleast one of the subexpressions are also true.
A compound Boolean expression can be created with the && operator is true only when both sub-expressions are true
true
The ________________ family of methods can be used to convert a string to a specific data type without throwing an exception
tryParse
Radio Buttons
used if you want the user to select one choice from several possible choices
Logical operators
used to create complex Boolean statements
Mutually exclusive selection
when selecting something automatically deselects any other similar objects in the same group
Default statement
where the testExpression doesn't match any of the cases
a compound Boolean expression created with the ______ operator is true if either of its sub-expressions are true
||