Chapter 4

Question 1

Relational Operators

Answer 1

• Used to compare numbers to determine relative order.
• Operators: >, <, >=, <=. ==. !=

Question 2

Relational Expressions

Answer 2

• can be assigned to a variable.
• assigns 0 for false, 1 for true

Question 3

if statement

Answer 3

• allows statements to be conditionally executed or skipped over
• to execute more than one statement as part of an if statement, enclose them in {} (creates a block of code)

Question 4

how an if statement works

Answer 4

• if the expression is true, then statement is executed

if the expressions if false, then statement is skipped

• place statement on a separate line after (expression)
• be careful testing floats and doubles for equality
• 0 is false, any other value is true

Question 5

block of code

Answer 5

code enclosed within { }

Question 6

if statement general format

Answer 6

if (expression)

statement;

Question 7

if/else statement

Answer 7

• provides two possible paths of execution

Question 8

how does an if/else statement work

Answer 8

• if the expression is true, then statement1 is executed and statement2 is skipped.
• if the expression if false, then statement1 is skipped and statement2 is executed

Question 9

if/else statement general format

Answer 9

if (expression)

statement1;

else

statement2;

Question 10

nested if statements

Answer 10

• an if statement that is nested inside another if statement
• nested if statements can be used to test more than one condition

Question 11

if/else if statement

Answer 11

• tests a series of conditions until one is found to be true
• often simpler than using nested if/else statements

Question 12

if/else if format

Answer 12

if (expression)

statement1;

else if (expression)

statement 2;

else

statement 3;

Question 13

Flags

Answer 13

• variable that signals a condition
• usually implemented as a bool variable
• can also be an integer (the value 0 is considered false, any nonzero value is considered true)
• must be assigned an initial value before it is used

Question 14

logical operators

Answer 14

• used to create relational expressions from other relation expressions
• && (AND): true if both expressions are true
• || (OR): true if either expression is true
• ! (NOT): true expression becomes false, false expression becomes true

Question 15

short circuit evaluation

Answer 15

if the value of an expressions can be determined by evaluating just the sub-expression on the left side of a logical operator, then the sub-expression on the right side will not be evaluated

Question 16

Menu-driven program

Answer 16

• program execution controlled by user selecting from a list of actions

Question 17

menu

Answer 17

list of choices on the screen

Question 18

how to implement menus

Answer 18

using if/else if statements

1. display list of numbered or lettered choices for actions
2. prompt user to make selection
3. test user selection in expression (if a match, then execute code for action. if not, then go on to next expression)

Question 19

input validation

Answer 19

• inspecting input data to determine whether it is acceptable

Question 20

what is bad input

Answer 20

• bad output will be produced from bad input

Question 21

how to validate input

Answer 21

• can perform various tests:
• range
• reasonableness
• valid menu choice
• divide by zero

Question 22

comparing characters and strings

Answer 22

• characters are compared using their ASCII values
• ‘A’ < ‘B’: (65) < (66)
• ‘1’ < ‘2’: (49) < (50)
• lowercase letters have higher ASCII codes than uppercase letters: ‘a’ > ‘Z’

Question 23

ASCII values from A to Z

Answer 23

65 - 90

Question 24

ASCII Values from a to z

Answer 24

97 - 122

Question 25

ASCII Values from 0 to 9

Answer 25

48 - 57

Question 26

the conditional operator

Answer 26

• can use to create short if/else statements

Question 27

the conditional operator format

Answer 27

expr ? expr : expr;

• the value of the conditional expression is: the second expression if the first expression is true OR the third expression if the first expression is false
• ( ) may be needed in an expression due to precedence of condition operator

Question 28

switch statement

Answer 28

• used to select among statements from several alternatives
• can be used instead of if/else if statements

Question 29

variable shadowing

Answer 29

• when inside a block within another block, can define variables with the same name as in the outer block (when in inner block, outer definition is not available; not a good idea)

Question 30

local/block scope

Answer 30

• variables defined inside { }

Question 31

when is the scope of a variable defined

Answer 31

• at the beginning of the function
• close to first use

Question 32

where is the scope of a variable

Answer 32

in the block in which it is defined, from the point of definition to the end of the block

Question 33

switch statement is good for -

Answer 33

• switch statement is a natural choice for menu-driven programs
• display the menu
• get user’s selection
• use user input as expression in switch statement
• use menu choices as expr in case statements

Question 34

switch statement format

Answer 34

switch (expression) {
case exp1: statement1;
break;
case exp2: statement2;
break;
default: statement3;
break;
}

Question 35

switch statement requirements

Answer 35

1. expression must be an integer variable or an expressions that evaluates to an integer value
2. exp1 through expn must be constant integer expressions or literals, and must be unique in the switch statement
3. default is optional
4. break is used to exit a switch statement, if it is left out the program “falls through” the remaining statements in the switch statement

Question 36

logical operator precedence

Answer 36

• highest precedence to lowest precedence (!, &&, ||)