Lecture 10: Control Flow. Selection (Decision) structures.

Lecture 10: Control Flow. Selection (Decision) structures

2

Lecture Contents:

Quiz on C++ Functions The if statement (“then” version) The if statement (“then – else” version) Nested if...else statements versus

sequence of if statements Demo programs Exercises

3

Quiz #2on

C++ Functions

44.

Control Structures

Three methods of processing a program– In sequence– Branching– Looping

Branch: altering the flow of program execution by making a selection or choice

Loop: altering the flow of program execution by repetition of statement(s)

55.

Flow of Execution

6

The if statement (“then” version)

Syntax and flowchart fragment:

if (<expression>) <statement>;

7

The if statement (“then” – else version)

Syntax and flowchart fragment:

if (<expression>) <statement_1>;

else <statement_2>;

8

Nested if…else statements vs. sequence of if statements

Nested if … else … statements. Example: ambiguity with two ifs and one else clause// increment n_pos, n_zero, n_neg// depending on the value of x if (x > 0) n_pos = n_pos + 1; if (x < 0) n_neg = n_neg + 1; else n_zero = n_zero + 1; The rule: An else is matched with the last if that

doesn’t have its own else.

9


Nested if … else … statements. The rule: An else is matched with the last if that doesn’t have its own else.

Example:// increment n_pos, n_zero, n_neg// depending on the value of xif (x > 0)n_pos = n_pos + 1;else if (x < 0) n_neg = n_neg + 1;

else n_zero = n_zero + 1;

10


Sequence of if statements Example:// increment n_pos, n_zero, n_neg// depending on the value of xif ( x > 0 ) n_pos = n_pos + 1;if ( x < 0 ) n_neg = n_neg + 1;if ( x == 0 ) n_zero = n_zero + 1;// less efficient version because all// three conditions are always tested

11

Else If clauseA variation of the IF…”THEN”…ELSE statement uses several conditions with ELSE and IF keywords:

if (condition1) action1 else if (condition2) action2 else if (condition3) action3 else action4

Any number of ELSE IF clauses is permitted.• The conditions are evaluated from the top, and if one of them is True, the

corresponding block of statements (action I ) is executed.• The ELSE clause will be executed if none of the previous expressions is True.• Example comes on next slide.

12

Else If clause

cout << “\nEnter score:”; cin >> score;

if (score < 60) Result = “Fail”; else if (score < 75) Result = “Pass”; else if (score < 90) Result = “Very good”; else

Result = “Excellent”;

13

Else If clause

The order of comparisons is vital in an IF…THEN…ELSE IF… statements. Try to switch the first two conditions of the last page code and you may get quite unexpected results

if (score < 75) Result = “Pass”; else if (score < 60) Result = “Fail”; else if (score < 90) Result = “Very good”; else Result = “Excellent”; Let’s assume score is 48. The first condition checked (48<75) will return True and

it will assign “Pass” to Result, and then it will skip the other remaining clauses.ERROR in the algorithm implemented! A student can’t pass a test with grade < 60.MORAL: Be careful and test your code if it uses ELSE IF clauses.

14

Muiltiple IF…THEN… structures versus Else If clause

After True condition is found, C++ executes the associated stmts and skips the remaining clauses. It continues program execution with stmt immediately after last ELSE clause. All following ELSE IF clauses are skipped, and the code runs a bit faster. That’s why the complicated ELSE IF structure should be preferred to the equivalent series of simple IF… statements shown below:

if (score < 60) Result = “Fail”; if (score < 75) Result = “Pass”; if (score < 90) Result = “Very good”; if (score >=90) Result = “Excellent”;

C++ will evaluate the conditions of all the IF stmts, even if the score is less than 50.

15

More on if statement(s)

Extract from Friedman/Koffman, chapter 4

Selection Structures: if and switch Statements

Chapter 4

17

Selection Statements

– In this chapter we study statements that allow alternatives to straight sequential processing. In particular:• if statements (do this only if a condition is true)• if-else statements (do either this or that)• Logical expressions (evaluate to true or false)• Boolean operators (not: ! and: && or: ||)

18

4.1 Control Structures

– Programs must often anticipate a variety of situations.

– Consider an Automated Teller Machine:• ATMs must serve valid bank customers. They must

also reject invalid PINs.

• The code that controls an ATM must permit these different requests.

• Software developers must implement code that anticipates all possible transactions.

19

4.2 Logical Expressions

Declarationint month = 9;Expression is(month > 9) False

(month < 9) False

(month >= 9) True

(month <= 9) True

20

Boolean Variables

bool variable Included with C++ compiler

bool leapYear;

leapYear = true; // Non zero return value

leapYear = false; // Zero return value

21

Boolean Expressions

Examples (Write T for True, or F for False): int n1 = 55;

int n2 = 75;

n1 < n2 // _____

n1 > n2 // _____

(n1 + 35) > n2 // _____

(n1-n2) < 0.1 // _____

n1 == n2 // _____

22

Logical Expressions

– Logical expressions often use these relational operators:

> Greater than< Less than>= Greater than or equal<= Less than or equal== Equal!= Not equal

23

Logical Operators

Logical operator (&& means AND) used in an if...else statement:

( (tryIt >= 50) && (tryIt <= 1500) )

Logical operator (| | means OR) used in an if...else statement:

( (tryIt < 50) | | (tryIt > 1500) )

24

Using &&

Assume tryIt = 90, Is tryIt within the range of 50 and 1500 ?

( (tryIt >= 50) && (tryIt <= 1500) )

( ( 90 >= 50) && ( 90 <= 1500) )

( 1 && 1 )

1

25

Using ||

Assume tryIt = 99 Is tryIt outside the range of 50 and 1500 ?

( (tryIt < 50) || (tryIt > 1500) )

( ( 99 < 50) || ( 99 > 1500) )

( 0 || 0 )

0

26

Truth Tables for Boolean Operators

Truth tables for Logical operators !, ¦¦, &&– ! means unary NOT /negation/ operator– && means binary AND /conjunction/ operator– ¦¦ means binary OR /disjunction/operator– 1 is a symbol for true, 0 is a symbol for false

Operation Result Operation Result Operation Result! 0! 1

10

1 ¦¦ 11 ¦¦ 00 ¦¦ 10 ¦¦ 0

1110

1 && 11 && 00 && 10 && 0

1000

27

Truth Tables for Boolean Operators or Logical Functions

Boolean operators = Logical functions Arguments are logical/boolean values –

false/true or 0/1 Unary logical NOT function, denoted !

Arg Function0 1 !0 = 11 0 !1 = 0

28


Boolean operators = Logical functions Arguments are logical/boolean values –false/true or 0/1 Binary logical AND function, denoted &&, a && b

Arg1 Arg2 Function 0 0 0 0 && 0 = 0 0 1 0 0 && 1 = 0 1 0 0 1 && 0 = 0 1 1 1 1 && 1 = 1

29


Boolean operators = Logical functions Arguments are logical/boolean values –false/true or 0/1 Binary logical OR function, denoted ||, a || b

Arg1 Arg2 Function 0 0 0 0 || 0 = 0 0 1 1 0 || 1 = 1 1 0 1 1 || 0 = 1 1 1 1 1 || 1 = 1

30


Boolean operators = Logical functions Arguments are logical/boolean values –false/true or 0/1

Binary logical EOR function, denoted , a bArg1 Arg2 Function 0 0 0 0 0 = 0 0 1 1 0 1 = 1 1 0 1 1 0 = 1 1 1 0 1 1 = 0

31

Bit-wise logical operators

& - bit wise AND operator | - bit wise OR operator

32

De Morgan laws

In logic, De Morgan's laws (or De Morgan's theorem) are rules in formal logic relating pairs of dual logical operators in a systematic manner expressed in terms of negation. The relationship so induced is called De Morgan duality.

Augustus De Morgan originally observed that in classical propositional logic the following relationships hold:

not (P and Q) = (not P) or (not Q) not (P or Q) = (not P) and (not Q)

http://en.wikipedia.org/wiki/Logic

http://en.wikipedia.org/wiki/Formal_logic

http://en.wikipedia.org/wiki/Logical_operator

http://en.wikipedia.org/wiki/Logical_negation

http://en.wikipedia.org/wiki/Propositional_logic

33

Boolean Algebra

Full set of boolean binary functionsArgs Functions a ea b n o o d r r0 0 0 0 0 0 0 0 0 0 1 1 1 1 1 1 1 10 1 0 0 0 0 1 1 1 1 0 0 0 0 1 1 1 11 0 0 0 1 1 0 0 1 1 0 0 1 1 0 0 1 11 1 0 1 0 1 0 1 0 1 0 1 0 1 0 1 0 1

34

Boolean Algebra

Minimal /basic/ set of boolean functions

– Negation or logical not

not a !a

– Conjunction or logical multiplication

a and b a && b

– Disjunction or logical addition

a or b a || b

35

Boolean Algebra

Exclusive OR formulated through basic functions

a b = (not a and b) or (a and not b)

a b = (!a && b) || (a && !b)

36

Precedence of Operators

Precedence: most operators are evaluated (grouped) in a left-to-right order:– a / b / c / d is equivalent to

(((a/b)/c)/d) Assignment operators group in a right-to-

left order so the expression – x = y = z = 0.0 is equivalent to

(x=(y=(z=0.0)))

37

Operator Description Grouping Highest ::

() Scope resolution Function call

Left to right

Unary !, +, - Not, unary plus/minus Right to left

Multiplicative * / % Multipy/divide/remainder Left to right

Additive + - Binary plus, minus Left to right

Input/Output >> << Extraction / insertion Left to right

Relational < > <= >=

Less/Greater than Less/Greater or equal

Left to right

Equality == != Equal, Not equal Left to right

and && Logical and Left to right

or ¦¦ Logical or Left to right

Assignment = Assign expression Right to left

Precedence of Operators

38

Boolean Assignment

bool same;

same = true;

Form: variable = expression;

Example: same = (x = = y);

39

4.3 Introduction to the if Dependent Control Statement

– The if is the first statement that alters strict sequential control.

– General form

if ( logical-expression ) true-part ;

• logical-expression: any expression that evaluates to nonzero (true) or zero (false).

• In C++, almost everything is true or false.

40

if Control Statementswith Two Alternatives

– The logical expression is evaluated. When true, the true-part is executed and the false-part is disregarded. When the logical expression is false, the false-part executes.

– General Form

if ( logical-expression ) true-part ;else false-part ;

41

What happens when an if statement executes?

• After the logical expression of the if statement evaluates, the true-part executes only if the logical expression was true.

gross >100.0

False

net=gross-tax net=gross True

42

Programming Tip

Using = for == is a common mistake. For example the following statements are legal:

int x = 25;

Because assignment statements evaluate to the

expression on the right of =, x = 1 is always

1, which is nonzero, which is true:

if (x = 1) // should be (x == 1)

43

4.4 if Statements with Compound Alternatives

– General form (also known as a block): {

statement-1 ; statement-2 ;

...statement-N ;

} – The compound statement groups together many

statements that are treated as one.

44

Writing Compound Statements

if (transactionType == 'c'){ // process check cout << "Check for $" << transactionAmount << endl; balance = balance - transactionAmount;}else{ // process deposit cout << "Deposit of $" << transactionAmount << endl; balance = balance + transactionAmount;}

45

4.6 Checking the Correctness of an Algorithm

Verifying the correctness of an algorithm is a critical step in algorithm design and often saves hours of coding and testing time.

We will now trace the execution of the refined algorithm for the payroll problem solved in the last section.

46

4.7 Nested if Statements and Multiple Alternative Decisions

– Nested logic is one control structure containing another similar control structure.

– An if...else inside another if...else. e.g. (the 2nd if is placed on the same line as the 1st):

47

Example of nested logic

if(x > 0)

numPos = numPos + 1;

else

if(x < 0)

numNeg = NumNeg + 1;

else

numZero = numZero + 1;

48

Example of nested logic

X numPos numNeg numZero

3.0 _______ _______ _______

-3.6 _______ _______ _______

4.0 _______ _______ _______

Assume all variables initialized to 0

49

Writing a Nested if as a Multiple-Alternative Decision

Nested if statements can become quite complex. If there are more than three alternatives and indentation is not consistent, it may be difficult to determine the logical structure of the if statement.

50

Function displayGrade

void displayGrade ( int score)

{

if (score >= 90) cout << "Grade is A " << endl;

else if (score >= 80) cout << "Grade is B " << endl;

else if (score >= 70) cout << "Grade is C " << endl;

else if (score >= 60) cout << "Grade is D " << endl;

else cout << "Grade is F " << endl;

}

51

Order of Conditions

if (score >= 60)

cout << "Grade is D " << endl;

else if (score >= 70)

cout << "Grade is C " << endl;


cout << "Grade is B " << endl;


cout << "Grade is A " << endl;

else

cout << "Grade is F " << endl;

52

Short Circuit Evaluation

(single == ‘y’ && gender == ‘m’ && age >= 18) – If single is false, gender and age aren’t evaluated

(single == ‘y’ || gender == ‘m’ || age >= 18)– If single is true, gender and age are not evaluated

53

4.9 Common Programming Errors

Failing to use { and } if(Grade >= 3.5)

// The true-part is the first cout only

cout <<"You receive an A !!!";

cout <<"You made it by " << (Grade-3.5) << " points";

else <<<< Error >>>>

54

Common Programming Errors

There are no compile time errors next, but there is an intent error.

else cout << "Sorry, you missed an A. "; cout << "You missed it by " << 3.5-Grade << " points"; With the above false part, you could get this

confusing output (when Grade = 3.9): You received an A !!!. You made it by 0.4 points.You missed it by -0.4 points

55

Corrected Version:

if(Grade >= 3.5){ cout << "You received an A !!! " << endl; cout << "You made it by " << (Grade-3.5) << " points"; // Do other things if desired}else { cout << " You did NOT receive an A !!! "; cout << "You missed it by " << (3.5-Grade) <<" points";}

56

Exercise 10.1

Build programs based on branch algorithms:

To add, subtract, multiply, and divide two

integer values checking the valid divisor (!=0) condition

57

Exercise 10.2

Build programs based on branch algorithms: To associate noise loudness with the effect of noise

using a table data:

Loudness in decibels(db) Perception

50 or lower quiet

51-90 annoying

91-110 very annoying

Above 110 uncomfortable

58

Exercise 10.3


To implement nested if statements using sample flow chart algorithms

59

Exercise 10.4


To compute area of a triangle by Heron’s formulae

60

Exercise 10.5


To test an integer value as a valid leap year (divisible by 4 but not by 100, except that years divisible by 400)

61

Exercise 10.6


To find roots (solutions) of a linear equation bx + c = 0

62

Exercise 10.7


To find roots (solutions) of a quadratic equation ax2 + bx + c = 0

63

Before lecture end

Lecture:

Control Flow. Selection (decision) structures

More to read:

Friedman/Koffman, Chapter 04

Copyright © 2007 Pearson Education, Inc. Publishing as Pearson Addison-Wesley

Chapter 4: Selection Structures: if and switch Statements

Problem Solving,

Abstraction, and Design using C++ 5e

by Frank L. Friedman and Elliot B. Koffman

65Copyright © 2007 Pearson Education, Inc. Publishing as Pearson Addison-Wesley

Objectives

• Become familiar with selection statements

• Compare numbers, characters, and strings

• Use relational, equality, and logical operators

• Write selection statements with one or two alternatives

• Select among multiple choices


4.1 Control Structures

• Regulate the flow of execution

• Combine individual instructions into a single logical unit with one entry point and one exit point.

• Three types: sequential, selection, repetition


Sequential Execution

• Each statement is executed in sequence.

• A compound statement is used to specify sequential control:{

statement1;statement2;

.

.

.

statementn;}


4.2 Logical Expressions

• C++ control structure for selection is the if statement.

• E.g.:if (weight > 100.00)

shipCost = 10.00;

else

shipCost = 5.00;


Relational and Equality Operators

• Logical expressions (conditions) are used to perform tests for selecting among alternative statements to execute.

• Typical forms:variable relational-operator variable

variable relational-operator constant

variable equality-operator variable

variable equality-operator constant

• Evaluate to Boolean (bool) value of true or false


Table 4.1 Rational and Equality Operators


Example

x

x <= 0

-5

-5

true


Example

x y

x >= y

-5

-5

false

7

7


Logical Operators

• && (and)

• || (or)

• ! (not)

• Used to form more complex conditions, e.g.(salary < minSalary) || (dependents > 5)

(temperature > 90.0) && (humidity > 0.90)

winningRecord && (!probation)


Table 4.3 && Operator


Table 4.4 || Operator


Table 4.5 ! Operator


Table 4.6 Operator Precedence


Example

flagx y z

3.0 4.0 2.0 false

x + y / z <= 3.5

2.0

5.0

false


Example

flagx y z

3.0 4.0 2.0 false

! flag || (y + z >= x - z)

6.0 1.0

true

true

true


Table 4.7 English Conditions as C++ Expressions


Comparing Characters and Strings

• Letters are in typical alphabetical order

• Upper and lower case significant

• Digit characters are also ordered as expected

• String objects require string library– Compares corresponding pairs of characters


Table 4.8 Examples of Comparisons


Boolean Assignment

• Assignment statements have general form

variable = expression;

• E.g.: (for variable called same of type bool)

same = true;

same = (x == y);


Additional Examples

• inRange = (n > -10) && (n < 10);

• isLetter = ((‘A’ <= ch) && (ch <= ‘Z’)) ||

((‘a’ <= ch) && (ch <= ‘z’));

• even = (n % 2 == 0);


Writing bool Values

• Boolean values are represented by integer values in C++– 0 for false– non-zero (typically 1) for true

• Outputting (or inputting) bool type values is done with integers


4.3 The if Control Structure

• Allows a question to be asked, e.g. “is x an even number.”

• Two basic forms– a choice between two alternatives– a dependent (conditional) statement


if Statement with Two Alternatives

• Form: if (condition)

statementT

else

statementF

• E.g.: if (gross > 100.00) net = gross - tax;else net = gross;


Figure 4.4 Flowchart of if statement with two alternatives


if Statement with Dependent Statement

• When condition evaluates to true, the statement is executed; when false, it is skipped

• Form: if (condition)

statementT

• E.g.: if (x != 0) product = product * x;


Figure 4.5 Flowchart of if statement with a dependent


4.4 if Statements with Compound Alternatives

• Uses { } to group multiple statements

• Any statement type (e.g. assignment, function call, if) can be placed within { }

• Entire group of statements within { } are either all executed or all skipped when part of an if statement


Example 4.11

if (popToday > popYesterday)

{

growth = popToday - popYesterday;

growthPct = 100.0 * growth / popYesterday;

cout << “The growth percentage is “ << growthPct;

}


Example 4.11 (continued)

if (transactionType == ‘c’)

{ // process check

cout << “Check for $” << transactionAmount << endl;

balance = balance - transactionAmount;

}

else

{ // process deposit

cout << “Deposit of $” << transactionAmount << endl;

balance = balance + transactionAmount;

}


Program Style

• Placement of { } is a stylistic preference

• Note placement of braces in previous examples, and the use of spaces to indent the statements grouped by each pair of braces.


Tracing an if Statement

• Hand tracing (desk checking) is a careful step-by-step simulation on paper of how the computer would execute a program’s code.

• Critical step in program design process

• Attempts to verify that the algorithm is correct

• Effect shows results of executing code using data that are relatively easy to process by hand


Table 4.9 Step-by-Step Hand Trace of if statement


Decision Steps in Algorithms

• Algorithm steps that select from a choice of actions are called decision steps

• Typically coded as if statements


Case Study: Statement

Your company pays its hourly workers once a week. An employee’s pay is based upon the number of hours worked (to the nearest half hour) and the employee’s hourly pay rate. Weekly hours exceeding 40 are paid at a rate of time and a half. Employees who earn over $100 a week must pay union dues of $15 per week. Write a payroll program that will determine the gross pay and net pay for an employee.


Case Study: Analysis

The problem data include the input data for hours worked and hourly pay and two required outputs, gross pay and net pay. There are also several constants: the union dues ($15), the minimum weekly earnings before dues must be paid ($100), the maximum hours before overtime must be paid (40), and the overtime rate (1.5 times the usual hourly rate). With this information, we can begin to write the data requirements for this problem. We can model all data using the money (see Section 3.7) and float data types.


Case Study: Data Requirements

• Problem ConstantsMAX_NO_DUES = 100.00

DUES = 15.00

MAX_NO_OVERTIME = 40.0

OVERTIME_RATE = 1.5


Case Study: Data Requirements

• Problem Inputfloat hours

float rate

• Problem Outputfloat gross

float net


Case Study: Program Design

The problem solution requires that the program read the hours worked and the hourly rate before performing any computations. After reading these data, we need to compute and then display the gross pay and net pay. The structure chart for this problem (Figure 4.6) shows the decomposition of the original problem into five subproblems. We will write three of the subproblems as functions. For these three subproblems, the corresponding function name appears under its box in the structure chart.


Figure 4.6 Structure chart for payroll problem


Case Study: Initial Algorithm

1.Display user instructions (function instructUser).

2.Enter hours worked and hourly rate.3.Compute gross pay (function computeGross).4.Compute net pay (function computeNet).5.Display gross pay and net pay.


Case Study: instructUser Function

• Global constants - declared before function main

MAX_NO_DUES

DUES

MAX_NO_OVERTIME

OVERTIME_RATE


Case Study: instructUser Function

• Interface– Input Arguments

• none

– Function Return Value• none

– Description• Displays a short list of instructions and information

about the program for the user.


Case Study: computeGross Function


• float hours

• float rate

– Function Return Value• float gross


Case Study: computeGross Function

• FormulaGross pay = Hours worked Hourly pay

• Local Datafloat gross

float regularPay

float overtimePay


Case Study: computeGross Function - Algorithm

3.1 If the hours worked exceeds 40.0 (max

hours before overtime)

3.1.1 Compute regularPay

3.1.2 Compute overtimePay

3.1.3 Add regularPay to overtimePay

to get gross

Else

3.1.4 Compute gross as house * rate


Case Study: computeNet Function


• float gross

– Function Return Value• float net

• Formulanet pay = gross pay - deductions

• Local Datafloat net


Case Study: computeNet Function - Algorithm

4.1 If the gross pay is larger than $100.00

4.1.1 Deduct the dues of $15 from gross

pay

Else

4.1.2 Deduct no dues


Listing 4.1 Payroll problem with functions


Listing 4.1 Payroll problem with functions (continued)


Listing 4.2 Sample run of payroll program with functions


Global Constants

• Enhance readability and maintenance– code is easier to read– constant values are easier to change

• Global scope means that all functions can reference


Identifier Scope

• Variable gross in main function

• Local variable gross in function computeGross.

• No direct connection between these variables.


Data Flow Information and Structure Charts

• Shows which identifiers (variables or constants) are used by each step

• If a step gives a new value to a variable, it is consider an output of the step.

• If a step uses the value of an variable without changing it, the variable is an input of the step.

• Constants are always inputs to a step.


Software Development Method

1. Analyze the problem statement

2. Identify relevant problem data

3. Use top-down design to develop the solution

4. Refine subproblems starting with an analysis similar to step 1


4.6 Checking Algorithm Correctness

• Verifying the correctness of an algorithm is a critical step in algorithm design and often saves hours of coding and testing time


Example - Trace of Payroll Problem

1. Display user instructions.

2. Enter hours worked and hourly rate.

3. Compute gross pay.

3.1. If the hours worked exceed 40.0 (max hours before overtime)

3.1.1. Compute regularPay.

3.1.2. Compute overtimePay.

3.1.3. Add regularPay to overtimePay to get gross.

else

3.1.4. Compute gross as hours * rate.


Example - Trace of Payroll Problem

4. Compute net pay.

4.1. If gross is larger than $100.00

4.1.1. Deduct the dues of $15.00 from gross pay.

else

4.1.2. Deduct no dues.

5. Display gross and net pay.


4.7 Nested if Statements and Multiple-Alternative Decisions

• Nested logic is one control structure containing another similar control structure

• E.g. one if statement inside another

• Makes it possible to code decisions with several alternatives


Example of Nested Logic

if (x > 0)


else

if (x < 0)

numNeg = numNeg + 1;

else // x must equal 0



Example of Nested Logic

X numPos numNegnumZero

3.0 _______ _______ _______

-3.6 _______ _______ _______

0 _______ _______ _______

Assume all variables initialized to 0


Comparison of Nested if to Sequence of if Statements

if (x > 0)


if (x < 0)


if (x == 0)



Writing a Nested if as a Multiple-Alternative Decision

• Nested if statements can become quite complex. If there are more than three alternatives and indentation is not consistent, it may be difficult to determine the logical structure of the if statement.


Multiple-Alternative Decision Form

if (condition1)

statement1;

else if (condition2)

statement2;.

.

.

else if (conditionn)

statementn;

else

statemente;


Multiple-Alternative Example

if (x > 0)


else if (x < 0)


else



Function displayGrade

void displayGrade (int score)

{

if (score >= 90)








else


}


Order of Conditions Matters

if (score >= 60)








else



Table 4.12 Decision Table for Example 4.16


Listing 4.4 Function computeTax


Short Circuit Evaluation

(single == ‘y’ && gender == ‘m’ && age >= 18) – If single is false, gender and age are not

evaluated

(single == ‘y’ || gender == ‘m’ || age >= 18)– If single is true, gender and age are not

evaluated

137

Thank You

For

Your Attention!

Lecture 10: Control Flow. Selection (Decision) structures.

Documents

Transcript of Lecture 10: Control Flow. Selection (Decision) structures.