Cit 120 Chapter 4 Notes

Front 1

What do relational operators allow you to do?

Back 1

compare numeric and char values and determine whether one is greater than, less than, or equal to the other

Front 2

What does each of these relational operators mean? Are they unary, binary, or ternary? What is their associativity?

> < >= <= == !=

Back 2

binary

exactly what I think they mean

Left-to-right associativity

== means equal to

!= means not equal to

Front 3

What does this expression mean?

x>y

Back 3

Is x greater than y?

Relational operators ask a question

Front 4

Relational expressions are ___________ expression

Back 4

Boolean

value of the expression is true or false

Front 5

What is the difference between the equality operator and the assignment operator?

Back 5

assignment: =

equality: ==

Front 6

How many relationships does >= test for? >?

Back 6

>= tests for two relationships (> and ==)

> tests for one

Front 7

What number represents true? What number represents false?

Back 7

True: 1 (but one is not the only number regarded as true)

False: 0

Front 8

What does the if statement do?

What is its general format?

Back 8

causes other statements to execute only under certain conditions. If the value in the parentheses is true, it executes the statement. If it is false, it skips the statement

if (expression)

statement;

Front 9

Compare sequence structure to decision structure

Back 9

Sequence structure: statements are executed in sequence without branching off in another direction

Decision structure: programs only execute certain algorithms under certain conditions. Actions are conditionally executed

Front 10

What is a null statement?

Back 10

An empty statement that does nothing

if (expression);

Front 11

For stylistic purposes, how is the if statement formatted?

Back 11

Even though it is really one single statement, it should be:

if (expression)

statement;

Front 12

Why should you avoid using the equality operator to compare floating-point numbers? What should you do instead?

Back 12

some fractional numbers cannot be exactly represented using binary and lead to round-off errors

use < and > to compare floating-point numbers

Front 13

For if statements, what is considered true and what is considered false?

For relational expressions, what is true and what is false?

What is the bool value false equivalent to?

Back 13

if -- true: anything other than 0

if -- false: 0 (or bool false)

relational -- true: 1

relational -- false: 0

bool false = 0

Front 14

Relational expressions are not the only thing that can be tested by if statements. Give an example of something else that the if statement can test

Back 14

if (value)

cout << "It is true!";

if the value is anything other than 0, the statement will execute

Front 15

How can you conditionally execute a block of code using an if statement?

Back 15

Enclose all of the conditionally executed statements in brackets. All statements inside the brackets should be indented

if (expression)

{

statement;

statement;

statement;

}

Front 16

Without braces, what does does if conditionally execute?

Back 16

the very next statement

Front 17

What does an if/else statement do? What is the format?

Back 17

executes one group of statements if the expression is true, and another group of statements if the expression is false

if (expression)

statement or block;

else

statement or block;

else is at the same indentation level as if

Front 18

How can if/else be used to prevent division by zero?

Back 18

If (division by zero)

statement;

else

statement; <--division by zero does not occur

Front 19

What is the purpose of nesting if statements? What is the format?

Back 19

Test more than one condition

Each if statement is indented

Front 20

What is a simpler alternative to nested if/else statements? What is the format?

Back 20

if/ else if statement --> tests a series of conditions

if (expression_1)

{

statement;

}

else if (expression_2) <-- evaluated if above are false

{

statement;

}

else if (expression_3) <-- evaluated if above are false

{

statement;

}

else

{

statement; <--- executed if none of the conditions above are true

}

Front 21

When are braces required for if, if/else, if/else if statements?

Back 21

Only when two or more statements are conditionally executed

Front 22

Is the trailing else mandatory? What are the benefits?

Back 22

No, it is optional

Useful for catching errors when none of the other conditions are true and displaying an error message

Front 23

What are two disadvantages of if/else statements compared to if/else if?

Back 23

- code can become complex, difficult to understand

- if/else statements will eventually wrap around after a certain number of indentations

Front 24

What is a flag?

Back 24

a Boolean or integer variable that signals when a condition exists

false: condition does not exist

true: condition does exist <-- flag

Front 25

How do you create/use integer flags?

Back 25

test for 1

1 = true --> flag. condition exists

0 = false

Front 26

What do logical operators do?

Back 26

connect two or more relational expressions into one, or they reverse the logic of the expression

Front 27

What are the three logical operators? What do they do? What is the format?

Back 27

&& AND connects two expressions into one. Both expressions must be true for overall condition to be true. x<2 && y > 3 <-- complete expressions

|| OR connects two expressions into one. One or both must be true for overall condition to be true. Does not matter which.

! NOT reverses the "truth" of an expression

(!(x<100)) <-- inside evaluated, then truth is reversed

Front 28

What is short circuit evaluation? When and why does it occur?

Back 28

When an entire expression is not checked

&&: first one is false, second won't be checked

||: first one is true, second won't be checked

Saves processing power/time

Front 29

What is the order of precedence of the logical operators? What is their associativity?

Back 29

!

&&

||

left-to-right

Front 30

The ! operator has a higher precedence than many C++ operators. What should you do to avoid an error?

Back 30

Enclose in parenthesis

(!(expression))

Front 31

What is the best way to determine if a number is in range?

Out of range?

Back 31

In range: && x >= #1 && x<=#2

Out of range: || x < #1 || x > #2

Front 32

Is 5 < x < 20 valid in C++?

Back 32

NO

connect the two separate expressions with &&

Front 33

What is a menu driven program do? How do you create one?

Back 33

Allows a user to choose from a list of options

nested if/else if statements

Front 34

What is input validation?

Back 34

process of inspecting data given to the program by the user and determining if it is valid

Don't assume the user followed the input instructions. Check the data.

else statements are great for this when none of the other conditions are met

Front 35

Can relational operators be used to compare characters and string objects?

Back 35

Yes. They all have ASCII values

Front 36

Which has higher-value ASCII codes, uppercase or lowercase?

Back 36

lowercase

Front 37

How can you determine whether one string object is alphabetically before another string object?

Back 37

<

relational operators

compares the first character of each. If they match, it moves on to the second. If they match, it moves on to the third. Stops comparing once there is a mismatch and determines which is first alphabetically.

The one that is first alphabetically will have a lower ASCII score

Front 38

True or false:

'1' == 1

Back 38

false

the character 1 has an ASCII value different than the integer 1

Front 39

What does the conditional operator do? How many operands does it require? What is the format?

Back 39

? --> conditional operator. ternary operator (3 operands)

create short conditional expressions that work life if/else statements

expression1? expression2 : expression3;

expression 1 is tested

expression 2 executes if true

expression 3 executes if false

parentheses are helpful but not required

(x<20)? (a=2) : (a=3)

If x<20, a=2, else a=c

Front 40

In C++, all expressions have a ____________, and this includes conditional expressions

Explain in the context of

j = k < 90? 25 : 32;

Back 40

value

sets j equal to the value of the conditional statement (25 if less than 90, 32 if greater than or equal to 90)

Front 41

cout << "Your grade is: " << (score < 60? "Fail." : "Pass.");

What are the () around the conditional operator necessary?

What is the if/else equivalent of this statement?

Back 41

<< has a higher precedence than the conditional operator. () ensure that the correct string value of the grade is outputted after the condition is evaluated

if (score < 60)

cout << "Your grade is: Fail.";

else

cout << "Your grade is: Pass.";

Front 42

When does a branch occur? What does a switch statement do?

Back 42

A branch occurs when one part of the program causes another part to execute

The switch statement lets the value of a variable or expression determine where the program will branch

Front 43

What is the general format of a switch statement?

Back 43

switch (IntegerExpression)

{

case ConstantExpression:

statement;

statement;

break;

case Constant Expression:

statement;

statement;

break;

default:

statement;

}

Front 44

Explain the parts of a switch expression:

- switch (integerexpression)

- case constantexpression

- break

- default

Back 44

- integer expression can be a variable of an integer data including char, or an expression whose value is an integer data type

- constant expression of the case statement: constant expression must be an integer literal or an integer named constant. Program branches to a group of statements after the case expression matches

- break: case statements show the program where to start executing, and break statements show it where to stop

- default: break isn't necessary after it but it's nice for consistency

Front 45

What is one of the best features of switch statements? How do you take advantage of it?

Back 45

Fall through

If break statements are carefully, consciously omitted, then all statements after the first matching case statement until the first break statement will be executed

e.g., three levels of a model. level 3 has all 3 feature --> fall through all 3. Level 2 has 2 features --> fall through 2. Level 1 has 1 --> last feature only

also useful if you want a bunch of cases to have the same expression

case 'a':

case 'A':

statement;

break;

Front 46

Is the default section of a switch statement required?

Back 46

no

Front 47

Can the expression following the word case be a variable, relational expression, or logical expression?

Back 47

No

must be an integer literal or an integer named constant

Front 48

What is the scope of a variable limited to?

Back 48

the block in which it is defined

Front 49

When is it a good idea not to define variables at the top of a program? Where should they be defined instead?

Back 49

Useful in longer programs

Define near the part of the program where they're used so the purpose of the variable is more evident

Front 50

Variables defined inside a set of braces have ____ _____ or _____ ______

Back 50

local scope or block scope

Front 51

T or F: When a block is nested inside another block, a variable defined in the inner block may have the same name as a variable defined in the outer block. As long as the variable in the inner block is visible, the variable in the outer block will be hidden

Back 51

true, but it's still bad practice to reuse variable names

Front 52

How do you arrange for console insertions and keyboard extractions of Boolean values to print/read as true/false rather than 1/0?

Back 52

cout << boolalpha;

cin >> boolalpha;

persists throughout program