CS 111 CH 4

precedence of logical operators

!, &&, ||. NOT operator has highest precedence. use parentheses to avoid errors.

&&

(AND) connects two expressions into one. both expressions must be true for the overall expression to be true.

!

(NOT) reverses the "truth" of an expression. it makes a true expression false and vice versa

||

(OR) connects two expression into one. one or both expressions must be true for the overall expression to be true. it is only necessary for one to be true.

local scope

(block scope) variables defined inside a set of braces have ______ _______. they may only be used in the part of the program between their definition and the block's closing brace.

0

= false. any expression that haves a value of _____ is considered false by the if statement. this includes the bool value false, which is equivalent to _____.

1

= true. the bool value true = _____.

almost anywhere

C++ allows you to create variables _______ _____ in a program

avoid

_____ giving inner variables the same name as outer variables

numeric data

______ _____ is compared in C++ by using *rational operators*

flag

a bool variable that signals when some condition exists in the program. when ____ = false, it indicates that the condition does not exist. when ____ = true, it means the condition does exist. integers can also be _____s.

decision structure

a program to execute some statements only under certain circumstances. in a _____ _____'s simplest form, a specific action is taken only when a specific condition exists. if the condition does not match, the action is not performed.

menu

a screen displaying a set of choices the user selects from

binary

all of the relational operators are _____, which means they *use two operands*

null statement

an empty statement that does nothing. will prematurely terminate the if statement, which disconnects it from the following statements.

relational expression

an example of a _____ _____ is x > y. ____ ____s have a higher precedence than the assignment operator.

if/else statement

an expansion of the if statement. if the expression is true, a statement or block of statements is executed. else, if the statement is false, a separate group of statements is executed.

default

an optional _______ section comes after all the case statements. does not need a break statement.

non 0 value

any _____ _____ ____ is considered true by the if statement.

trailing else clause

appears at end of the if/else if statements, is optional, but in many citations, it is used to catch errors.

indenting and spacing

are for human readers, not the compiler.

logical operators

can combine two or more relational expressions into one

break

case statements show the program where o start executing in the block and the _____ statements show the program where to stop.

OR operator

complete expressions must be provided for the ____ ____. temperature > 100 || temperature < 0

conditional operator

consists of the question mark (?) and the colon (:) is a ternary operator

conditional expression

consists of three sub-expressions separated by the ? and : symbols. format expression ? expression : expression. the first expression is tested. if it is true, the second expression executes. if the first one is false, the third expression is executed.

==, =

do not confuse the equality operator (____ ____) with the assignment operator (______). e.g. the expression x = 2 is always true.

semicolons

do not mark the end of a line. but the end of a complete C++ statement

indented

do not write code that is not properly ______

relational operator

each _____ ____ determines whether a specific relationship exists between 2 values. all ____ _____s are *left-to-right associative*

one level

each time you press the tab key, you are indenting ____ _____

block of code

enclosing a group of statements inside a set of braces. all statements inside the braces should be indented

==

equal to. determines if the operand on its left is equal to the one on its rigtht.

>

greater than

>=

greater than or equal to. determines whether the operand on its left is greater than or equal to the operand on the right.

short circuit evaluation

if the sub-expression on the left side of an && operator is false, the right side will not be checked. if the sub-expression of the left side of an || operator is true, the right side will not be checked

top

it is a common practice to define all of a function's variables at the _____ of a function

logical operators have

left-to-right associativity

<

less than

<=

less than or equal to. determines whether the operand on its left is less than or equal to the operand on its right.

higher

lowercase letters have _____ ASCII codes than uppercase letters.

if/else if statement

makes certain types of nested decision logic simpler to write. braces needed if more than one statement is conditionally executed.

division by zero

mathematically impossible to perform, and causes a program to crash.

!=

not equal to. determines if the operand on its left is not equal to the one on its right.

imput validations

numbers are checked to ensure they are within a range of possible values. values are checked for their "reasonableness". items selected from a menu or others sets of choices are checked to ensure they are available options. variables are checked for values that might cause problems (such as division by 0)

case

on the next line s the beginning of a block containing several ______ statements. after the word _____ is a constant expression (must be int), followed by a colon. the constant expression may be an integer literal ir an integer named constant

if statement

one way to code a decision. if the value of the expression inside the parentheses is true, the statement is executed. otherwise, it is skipped. usu. span more than one line, but are technically one long statement.

continuously executed

performed only when a certain condition exists. it only executes under the condition that the expression in the parentheses is true.

boolean expressions

relational expressions are also known as ______ _____. their value can only be *true or false*

Not Operator

reverses truths or falsehoods. !true = false. !false = true.

nested

sometimes a if statement must be _____ inside another if statement

sequence structure

statements are executed in sequence without branching off in another direction

switch

tests the value of an integer expression and then uses that value to determine which set of statements to branch to. the first line of the statements starts with the word ____, followed by an integer expression inside parentheses

<< operator

the << operator has a higher precedence than the ?: operator

nested if/else statements disadvantages

the code can grow complex and become difficult to understand. can become too long to display on the computer screen without horizontal scrolling

if statement style rules

the conditionally executed statement should appear on the line after the if statement. the conditionally executed statement should be indented one "level" from the if statement.

conditionaly

the if statement can _____ execute a block of statements enclosed in braces

invalid validation

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

menu system

the switch statement is a natural mechanism for building ______ _______

name

when a block is nested inside another block, a variable defined in the inner block may have the same ______ as a variable defined in the outer block

comes into scope

when a program is running and it enters the section of code that constitutes a variable's scope, it is said that the variable _____ _____ _____

&& operator

when determining whether a number is inside a numeric range, it's best to use the ____ ____. e.g. x >= 20 && x <= 40

|| operator

when determining whether a number is outside a range use the ____ _____ e.g x < 20 || x > 40

string objects

when two ____ ____ are compared, it is actually the *ASCII* value of the characters making up the strings that are being compared. one by one, each character in the first operand is compared with the character in the corresponding position in the second operand.

ASCII

when two characters are compared, their _____ values are actually being compared. '0' - '9' = 48 - 54. 'A' - 'Z' = 65 - 90. 'a' - 'z' = 97 - 122. blank = 32. period = 46.

parentheses

when writing more complex comparisons, it helps to enclose the relational expression in ______

"fall through"

without break statements, the program "_____ _____"all of the statements below the one with the matching case expression. if you want the same set of statements for multiple case expressions.

complete expressions

you must provide _____ _____ on both sides of the && operator. e.g. temperature > 1 && temperature < 0

C++ does not allow

you to check numeric ranges with expressions such as 5< x <20