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Chapter 1

An Overview of Computers and Programming Languages

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C++ Programming: Program Design Including Data Structures, Eighth Edition

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Objectives (1 of 2)

In this chapter, you will:

Learn about different types of computers

Explore the hardware and software components of a computer system

Learn about the language of a computer

Learn about the evolution of programming languages

Examine high-level programming languages

Discover what a compiler is and what it does

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Objectives (2 of 2)

Examine a C++ program

Explore how a C++ program is processed

Learn what an algorithm is and explore problem-solving techniques

Become aware of structured design and object-oriented design programming methodologies

Become aware of Standard C++, ANSI/ISO Standard C++, C++11, and C++14

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Introduction

Without software, a computer is useless

Software is developed with programming languages

C++ is a programming language

C++ is suited for a wide variety of programming tasks

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A Brief Overview of the History of Computers (1 of 3)

Early calculation devices

Abacus

Pascaline

Leibniz device

Jacquard’s weaving looms

Babbage machines: difference and analytic engines

Hollerith machine

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A Brief Overview of the History of Computers (2 of 3)

Early computer-like machines

Mark I

Electronic Numerical Integrator and Calculator (ENIAC)

Von Neumann architecture

Universal Automatic Computer (UNIVAC)

Transistors and microprocessors

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A Brief Overview of the History of Computers (3 of 3)

Categories of computers

Mainframe computers

Midsize computers

Micro computers (personal computers)

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Elements of a Computer System

Two main components

Hardware

Software

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Hardware

Central processing unit (CPU)

Main memory (MM) or random access memory (RAM)

Secondary storage

Input/output devices

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Central Processing Unit and Main Memory (1 of 4)

Central processing unit

Brain of the computer

Most expensive piece of hardware

Operations

Carries out arithmetic and logical operations

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Central Processing Unit and Main Memory (2 of 4)

FIGURE 1-1 Hardware components of a computer and main memory

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Central Processing Unit and Main Memory (3 of 4)

Random access memory (or main memory) is directly connected to the CPU

All programs must be loaded into main memory before they can be executed

All data must be brought into main memory before it can be manipulated

When computer power is turned off, everything in main memory is lost

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Central Processing Unit and Main Memory (4 of 4)

Main memory is an ordered sequence of memory cells

Each cell has a unique location in main memory, called the address of the cell

Each cell can contain either a programming instruction or data

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Secondary Storage

Secondary storage: device that stores information permanently

Examples of secondary storage

Hard disks

Flash drives

CD-ROMs

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Input/Output Devices

Input devices feed data and programs into computers

Keyboard

Mouse

Scanner

Camera

Secondary storage

Output devices display results

Monitor

Printer

Secondary storage

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Software

Software are programs written to perform specific tasks

System programs control the computer

Operating system monitors the overall activity of the computer and provides services such as:

Memory management

Input/output activities

Storage management

Application programs perform a specific task

Word processors

Spreadsheets

Games

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The Language of a Computer (1 of 4)

Analog signals: continuously varying continuous wave forms

Digital signals: sequences of 0s and 1s

Machine language: language of a computer

A sequence of 0s and 1s

Binary digit (bit): the digit 0 or 1

Binary code (binary number): a sequence of 0s and 1s

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The Language of a Computer (2 of 4)

Byte: a sequence of eight bits

Kilobyte (KB): 210 bytes = 1024 bytes

ASCII (American Standard Code for Information Interchange)

128 characters

A is encoded as 1000001 (66th character)

The character 3 is encoded as 0110011 (51st character)

Number systems

The decimal system (base 10) is used in our daily life

The computer uses the binary (or base 2) number system

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The Language of a Computer (3 of 4)

TABLE 1-1 Binary Units

Unit	Symbol	Bits/Bytes
Byte		8 bits
Kilobyte	KB	210 bytes = 1024 bytes
Megabyte	MB	1024 KB = 210 KB = 220 bytes = 1,048,576 bytes
Gigabyte	GB	1024MB = 210 MB = 230 bytes = 1,073,741,824 bytes
Terabyte	TB	1024 GB = 210 GB = 240 bytes = 1,099,511,627,776 bytes
Petabyte	PB	1024 TB = 210 TB = 250 bytes = 1,125,899,906,842,624 bytes
Exabyte	EB	1024 PB = 210 PB = 260 bytes = 1,152,921,504,606,846,976 bytes
Zettabyte	ZB	1024 EB5 210 EB = 270 bytes = 1,180,591,620,717,411,303,424 bytes

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The Language of a Computer (4 of 4)

Unicode is another coding scheme

65,536 characters

Two bytes (16 bits) to store a character

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The Evolution of Programming Languages (1 of 3)

Early computers were programmed in machine language

To calculate wages = rate * hours in machine language:

100100 010001 //Load

100110 010010 //Multiply

100010 010011 //Store

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The Evolution of Programming Languages (2 of 3)

Assembly language instructions are mnemonic

Instructions are written in an easy-to-remember form

An assembler translates a program written in assembly language into machine language

Using assembly language instructions, wages = rate * hours can be written as:

LOAD rate

MULT hours

STOR wages

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The Evolution of Programming Languages (3 of 3)

High-level languages include Basic, FORTRAN, COBOL, C, C++, C#, Java, and Python

Compiler: translates a program written in a high-level language into machine language

In C++, the weekly wages equation can be written as:

wages = rate * hours;

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Processing a C++ Program (1 of 4)

#include <iostream>

using namespace std;

int main()

{

cout << "My first C++ program." << endl;

return 0;

}

Sample Run:

My first C++ program.

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Processing a C++ Program (2 of 4)

Steps needed to process a C++ program

Use a text editor to create the source code (source program) in C++

Include preprocessor directives

Begin with the symbol # and are processed by the preprocessor

Use the compiler to:

Check that the program obeys the language rules

Translate the program into machine language (object program)

Use an integrated development environment (IDE) to develop programs in a high-level language

Programs such as mathematical functions are available

The library contains prewritten code you can use

A linker combines object program with other programs in the library to create executable code

The loader loads executable program into main memory

The last step is to execute the program

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Processing a C++ Program (3 of 4)

IDEs are quite user friendly

Compiler identifies the syntax errors and also suggests how to correct them

Build or Rebuild is a simple command that links the object code with the resources used from the IDE

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Processing a C++ Program (4 of 4)

FIGURE 1-2 Processing a C++ program

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Programming with the Problem Analysis–Coding–Execution Cycle

Programming is a process of problem solving

An algorithm is a step-by-step problem-solving process

A solution is achieved in a finite amount of time

FIGURE 1-3 Problem analysis–coding–execution cycle

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The Problem Analysis–Coding–Execution Cycle (1 of 5)

Step 1: Analyze the problem

Outline the problem and its requirements

Design steps (algorithm) to solve the problem

Step 2: Implement the algorithm

Implement the algorithm in code

Verify that the algorithm works

Step 3: Maintain the program

Use and modify the program if the problem domain changes

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The Problem Analysis–Coding–Execution Cycle (2 of 5)

Analyze the problem using these steps:

Step 1: Thoroughly understand the problem and all requirements

Step 2: Understand the problem requirements

Does program require user interaction?

Does program manipulate data?

What is the output?

Step 3: If complex, divide the problem into subproblems

Analyze and design algorithms for each subproblem

Check the correctness of algorithm

Test the algorithm using sample data

Some mathematical analysis might be required

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The Problem Analysis–Coding–Execution Cycle (3 of 5)

Once the algorithm is designed and correctness is verified

Write the equivalent code in high-level language

Enter the program using a text editor

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The Problem Analysis–Coding–Execution Cycle (4 of 5)

Run code through the compiler

If compiler generates errors

Look at code and remove errors

Run code again through compiler

If there are no syntax errors

Compiler generates equivalent machine code

Link machine code with the system’s resources

Performed by the linker

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The Problem Analysis–Coding–Execution Cycle (5 of 5)

Once compiled and linked, the loader can place program into main memory for execution

The final step is to execute the program

Compiler guarantees that the program follows the rules of the language

Does not guarantee that the program will run correctly

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Example 1-1 (1 of 2)

Design an algorithm to find the perimeter and area of a rectangle

The perimeter and area of the rectangle are given by the following formulas:

perimeter = 2 * (length + width)

area = length * width

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Example 1-1 (2 of 2)

Algorithm

Get the length of the rectangle

Get the width of the rectangle

Find the perimeter with this equation:

perimeter = 2 * (length + width)

Find the area with this equation:

area = length * width

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Example 1-5 (1 of 4)

Calculate each student’s grade

There are 10 students in a class

Each student has taken five tests

Each test is worth 100 points

Design algorithms to:

Calculate the grade for each student and class average

Find the average test score

Determine the grade

Use the provided data: students’ names and test scores

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Example 1-5 (2 of 4)

Algorithm to determine the average test score

Get the five test scores

Add the five test scores

The sum of the test scores is represented by sum

Suppose average stands for the average test score:

average = sum / 5;

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Example 1-5 (3 of 4)

Algorithm to determine the grade:

if average is greater than or equal to 90

grade = A

otherwise

if average is greater than or equal to 80 and less than 90

grade = B

otherwise

if average is greater than or equal to 70 and less than 80

grade = C

otherwise

if average is greater than or equal to 60 and less than 70

grade = D

otherwise

grade = F

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Example 1-5 (4 of 4)

Main algorithm is presented below:

totalAverage = 0;

Repeat the following for each student:

Get student’s name

Use the algorithm to find the average test score

Use the algorithm to find the grade

Update totalAverage by adding current student’s average test score

Determine the class average as follows: classAverage = totalAverage / 10

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Programming Methodologies

Two popular approaches to programming design

Structured

Object-oriented

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Structured Programming

Structured design

Involves dividing a problem into smaller subproblems

Structured programming

Involves implementing a structured design

The structured design approach is also called:

Top-down (or bottom-up) design

Stepwise refinement

Modular programming

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Object-Oriented Programming (1 of 3)

Object-oriented design (OOD)

Identify components called objects

Determine how objects interact with each other

Specify relevant data and possible operations to be performed on that data

Each object consists of data and operations on that data

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Object-Oriented Programming (2 of 3)

An object combines data and operations on the data into a single unit

A programming language that implements OOD is called an object-oriented programming (OOP) language

To design and use objects, you must learn how to:

Represent data in computer memory

Manipulate data

Implement operations

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Object-Oriented Programming (3 of 3)

To create operations:

Write algorithms and implement them in a programming language

Use functions to implement algorithms

Learn how to combine data and operations on the data into a single unit called a class

C++ was designed to implement OOD

OOD is used with structured design

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ANSI/ISO Standard C++

C++ evolved from C

C++ designed by Bjarne Stroustrup at Bell Laboratories in early 1980s

Many different C++ compilers were available

C++ programs were not always portable from one compiler to another

In mid-1998, ANSI/ISO C++ language standards were approved

Second standard, called C++11, was approved in 2011

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Quick Review (1 of 3)

A computer is an electronic device that can perform arithmetic and logical operations

A computer system has hardware and software components

The central processing unit (CPU) is the brain

Primary storage (MM) is volatile; secondary storage (e.g., disk) is permanent

The operating system monitors overall activity of the computer and provides services

There are various kinds of languages

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Quick Review (2 of 3)

Compiler: translates high-level language into machine code

Algorithm:

Step-by-step problem-solving process

Arrives at a solution in a finite amount of time

Problem-solving process

Analyze the problem and design an algorithm

Implement the algorithm in code

Maintain the program

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Quick Review (3 of 3)

Structured design

Problem is divided into smaller subproblems

Each subproblem is solved

Combine solutions to all subproblems

Object-oriented design (OOD) program: a collection of interacting objects

Object: data and operations on those data

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9781337117562_ppt_ch02.pptx

Chapter 2

Basic Elements of C++

C++ Programming: Program Design Including Data Structures, Eighth Edition

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Objectives (1 of 3)

In this chapter, you will:

Become familiar with the basic components of a C++ program, including functions, special symbols, and identifiers

Explore simple data types

Discover how to use arithmetic operators

Examine how a program evaluates arithmetic expressions

Become familiar with the string data type

Learn what an assignment statement is and what it does

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Objectives (2 of 3)

Learn about variable declaration

Discover how to input data into memory using input statements

Become familiar with the use of increment and decrement operators

Examine ways to output results using output statements

Learn how to use preprocessor directives and why they are necessary

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Objectives (3 of 3)

Learn how to debug syntax errors

Explore how to properly structure a program, including using comments to document a program

Become familiar with compound statements

Learn how to write a C++ program

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Introduction

Computer program

A sequence of statements whose objective is to accomplish a task

Programming

The process of planning and creating a program

Real-world analogy: a recipe for cooking

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A Quick Look at a C++ Program (1 of 5)

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A Quick Look at a C++ Program (2 of 5)

Sample Run:

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A Quick Look at a C++ Program (3 of 5)

FIGURE 2-1 Various parts of a C++ program

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A Quick Look at a C++ Program (4 of 5)

FIGURE 2-1 Various parts of a C++ program (cont’d.)

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A Quick Look at a C++ Program (5 of 5)

Variable: a memory location whose contents can be changed

FIGURE 2-3 Memory allocation

FIGURE 2-4 Memory spaces after the statement length = 6.0; executes

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The Basics of a C++ Program

Subprogram (or function): collection of statements

When executed, accomplishes something

May be predefined or standard

Syntax rules: rules that specify which statements (instructions) are legal or valid

Semantic rules: determine the meaning of the instructions

Programming language: a set of rules, symbols, and special words

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Comments

Comments are for the reader, not the compiler

Two types

Single line: begins with //

//**************************************************************

// Given the length and width of a rectangle, this C++ program

// computes and outputs the perimeter and area of the rectangle.

//**************************************************************

Multiple line: enclosed between /* and */

You can include comments that can

occupy several lines.

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Special Symbols

A token is the smallest individual unit of a program written in any language

C++ tokens include special symbols, word symbols, and identifiers

Special symbols in C++ include:

+ - * /

. ; ? ,

<= != == >=

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Reserved Words (Keywords)

Reserved word symbols (or keywords):

Cannot be redefined within a program

Cannot be used for anything other than their intended use

Examples include:

int

float

double

char

const

void

return

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Identifiers (1 of 2)

An identifier is the name of something that appears in a program

Consists of letters, digits, and the underscore character (_)

Must begin with a letter or underscore

C++ is case sensitive

NUMBER is not the same as number

Two predefined identifiers are cout and cin

Unlike reserved words, predefined identifiers may be redefined, but it is not a good idea

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Identifiers (2 of 2)

Legal identifiers in C++

first

conversion

payRate

TABLE 2-1 Examples of Illegal Identifiers

Illegal Identifier	Reason	A Correct Identifier
employee Salary	There can be no space between employee and Salary.	employeeSalary
Hello!	The exclamation mark cannot be used in an identifier.	Hello
one+two	The symbol + cannot be used in an identifier.	onePlusTwo
2nd	An identifier cannot begin with a digit.	second

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Whitespaces

Every C++ program contains whitespaces

Include blanks, tabs, and newline characters

Whitespaces separate special symbols, reserved words, and identifiers

Proper utilization of whitespaces is important

Can be used to make the program more readable

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Data Types

A data type is set of values together with a set of allowed operations

C++ data types fall into three categories:

Simple data type

Structured data type

Pointers

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Simple Data Types (1 of 2)

Three categories of simple data

Integral: integers (numbers without a decimal)

Can be further categorized: char, short, int, long, bool, unsigned char, unsigned short, unsigned int, unsigned long

Floating-point: decimal numbers

Enumeration: a user-defined data type

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Simple Data Types (2 of 2)

Different compilers may allow different ranges of values

TABLE 2-2 Values and Memory Allocation for Simple Data Types

Data Type	Values	Storage (in bytes)
int	–147483648 (= –231 ) to 2147483647 (= 231 – 1)	4
bool	true and false	1
char	–128 (= –27 ) to 127 (= 27 – 1)	1
long long	–9223372036854775808 (–263 ) to 9223372036854775807(263 – 1)	64

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int Data Type

Examples

-6728

+763

Positive integers do not require a + sign

A comma cannot be used within an integer

Commas are only used for separating items in a list

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bool Data Type

bool type

Two values: true and false

Purpose: to manipulate logical (Boolean) expressions

true and false

Logical values

bool, true, and false

Reserved words

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char Data Type (1 of 2)

Data type char is the smallest integral data type

It is used for single characters: letters, digits, and special symbols

Each character is enclosed in single quotes

'A', 'a', '0', '*', '+', '$', '&'

A blank space is a character

Written ' ', with a space left between the single quotes

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char Data Type (2 of 2)

Different character data sets exist

ASCII: American Standard Code for Information Interchange

Each of 128 values in ASCII code set represents a different character

Characters have a predefined ordering based on the ASCII numeric value

Collating sequence: ordering of characters based on the character set code

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Floating-Point Data Types (1 of 3)

C++ uses scientific notation to represent real numbers (floating-point notation)

TABLE 2-3 Examples of Decimal Numbers in Scientific and C11 Floating-Point Notations

Decimal Number	Scientific Notation	C++ Floating-Point Notation
75.924	7.5924 * 101	7.592400E1
0.18	1.8 * 10-1	1.800000E-1
0.0000453	4.53 * 10-5	4.530000E-5
–1.482	-1.482 * 100	-1.482000E0
7800.0	7.8 * 103	7.800000E3

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Floating-Point Data Types (2 of 3)

float: represents any real number

Range: -3.4 * 1038 to 3.4 * 1038 (four bytes)

double: represents any real number

Range: –1.7 * 10308 to 1.7 * 10308 (eight bytes)

Minimum and maximum values of data types are system dependent

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Floating-Point Data Types (3 of 3)

Maximum number of significant digits (decimal places) for float values: 6 or 7

Maximum number of significant digits for double: 15

Precision: maximum number of significant digits

float values are called single precision

double values are called double precision

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Data Types, Variables, and Assignment Statements

To declare a variable, must specify its data type

Syntax rule to declare a variable is:

dataType identifier;

Examples include:

int counter;

double interestRate;

char grade;

Assignment statement has the form: variable = expression

Example: interestRate = 0.05;

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Arithmetic Operators, Operator Precedence, and Expressions (1 of 2)

C++ arithmetic operators include:

+ addition

- subtraction (or negation)

* multiplication

/ division

% mod (modulus or remainder)

+, -, *, and / can be used with integral and floating-point data types

Modulus (%) can only be used with integral data types

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Arithmetic Operators, Operator Precedence, and Expressions (2 of 2)

When you use / with integral data types, the integral result is truncated (no rounding)

Arithmetic expressions contain values and arithmetic operators

Operands are the numbers appearing in the expressions

Operators can be unary (one operand) or binary (two operands)

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Order of Precedence

All operations inside () are evaluated first

*, /, and % are at the same level of precedence and are evaluated next

+ and - have the same level of precedence and are evaluated last

When operators are on the same level

Operations are performed from left to right (associativity)

3 * 7 - 6 + 2 * 5 / 4 + 6 means (((3 * 7) – 6) + ((2 * 5) / 4 )) + 6

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Expressions

Integral expression: all operands are integers

Yields an integral result

Example: 2 + 3 * 5

Floating-point (decimal) expression: all operands are floating-point

Yields a floating-point result

Example: 12.8 * 17.5 - 34.50

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Mixed Expressions (1 of 2)

Mixed expression

Has operands of different data types

Contains integers and floating-point

Examples of mixed expressions

2 + 3.5

6 / 4 + 3.9

5.4 * 2 – 13.6 + 18 / 2

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Mixed Expressions (2 of 2)

Evaluation rules

If operator has same types of operands

The operator is evaluated according to the type of the operands

If operator has both types of operands

Integer is changed to floating-point

Operator is evaluated

Result is floating-point

Entire expression is evaluated according to precedence rules

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Type Conversion (Casting) (1 of 2)

Implicit type coercion: when the value of one type is automatically changed to another type

Cast operator (also called type conversion or type casting): provides explicit type conversion

static_cast<dataTypeName>(expression)

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Type Conversion (Casting) (2 of 2)

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string Type

Data type string is a programmer-defined type supplied in ANSI/ISO Standard C++ library

A string is a sequence of zero or more characters enclosed in double quotation marks

A null (or empty) string is a string with no characters

Each character has a relative position in the string

Position of first character is 0

The length of a string is the number of characters in it

Example: length of "William Jacob" is 13

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Variables, Assignment Statements, and Input Statements

Data must be loaded into main memory before it can be manipulated

Storing data in memory is a two-step process:

Instruct the computer to allocate memory

Include statements in the program to put data into the allocated memory

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Allocating Memory with Constants and Variables (1 of2)

Named constant: memory location whose content cannot change during execution

Syntax to declare a named constant

In C++, const is a reserved word

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Allocating Memory with Constants and Variables (2 of 2)

Variable: memory location whose content may change during execution

Syntax to declare one or multiple variables

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Putting Data into Variables

Ways to place data into a variable

Use C++’s assignment statement

Use input (read) statements

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Assignment Statement (1 of 4)

The assignment statement takes the form:

Expression is evaluated and its value is assigned to the variable on the left side

A variable is said to be initialized the first time a value is placed into it

In C++, = is called the assignment operator

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Assignment Statement (2 of 4)

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Assignment Statement (3 of 4)

Example 2-14 illustrates a walk-through (tracing values through a sequence)

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Assignment Statement (4 of 4)

Given int variables x, y, and z. How is this legal C++ statement evaluated?

x = y = z

The assignment operator is evaluated from right to left

The associativity of the assignment operator is from right to left

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Saving and Using the Value of an Expression

Declare a variable of the appropriate data type

Assign the value of the expression to the variable that was declared

Use the assignment statement

Wherever the value of the expression is needed, use the variable holding the value

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Declaring and Initializing Variables

Not all types of variables are initialized automatically

Variables can be initialized when declared:

int first = 13, second = 10;

char ch = ' ';

double x = 12.6;

All variables must be initialized before they are used

But not necessarily during declaration

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Input (Read) Statement (1 of 3)

cin is used with >> to gather one or more inputs

This is called an input (read) statement

The stream extraction operator is >>

For example, if miles is a double variable: cin >> miles;

Causes the computer to get a value of type double and places it in the variable miles

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Input (Read) Statement (2 of 3)

Using more than one variable in cin allows more than one value to be read at a time

Example: if feet and inches are variables of type int, this statement:

cin >> feet >> inches;

Inputs two integers from the keyboard

Places them in variables feet and inches respectively

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Input (Read) Statement (3 of 3)

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Increment and Decrement Operators

Increment operator (++): increase variable by 1

Pre-increment: ++variable

Post-increment: variable++

Decrement operator: (--) decrease variable by 1

Pre-decrement: --variable

Post-decrement: variable--

What is the difference between the following?

x = 5;

y = ++x;

x = 5;

y = x++;

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Output (1 of 4)

The syntax of cout and << is:

Called an output statement

The stream insertion operator is <<

Expression evaluated and its value is printed at the current cursor position on the screen

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Output (2 of 4)

A manipulator is used to format the output

Example: endl causes the insertion point to move to beginning of next line

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Output (3 of 4)

The new line character (new line escape sequence) is '\n'

May appear anywhere in the string

Examples

cout << "Hello there.";

cout << "My name is James.";

Output:

Hello there.My name is James.

cout << "Hello there.\n";

cout << "My name is James.";

Output :

Hello there.

My name is James.

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Output (4 of 4)

TABLE 2-4 Commonly Used Escape Sequences

	Escape Sequence	Description
\n	Newline	Cursor moves to the beginning of the next line
\t	Tab	Cursor moves to the next tab stop
\b	Backspace	Cursor moves one space to the left
\r	Return	Cursor moves to the beginning of the current line (not the next line)
\\	Backslash	Backslash is printed
\'	Single quotation	Single quotation mark is printed
\"	Double quotation	Double quotation mark is printed

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Preprocessor Directives (1 of 2)

C++ has a small number of operations

Many functions and symbols needed to run a C++ program are provided as collection of libraries

Every library has a name and is referred to by a header file

Preprocessor directives are processed by the preprocessor program

All preprocessor commands begin with #

No semicolon is placed at the end of these commands

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Preprocessor Directives (2 of 2)

Syntax to include a header file

For example:

#include <iostream>

Causes the preprocessor to include the header file iostream in the program

Preprocessor commands are processed before the program goes through the compiler

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namespace and Using cin and cout in a Program

cin and cout are declared in the header file iostream, but within std namespace

To use cin and cout in a program, use the following two statements:

#include <iostream>

using namespace std;

‹#›

Using the string Data Type in a Program

To use the string type, you need to access its definition from the header file string

Include the following preprocessor directive:

#include <string>

‹#›

Creating a C++ Program (1 of 3)

A C++ program is a collection of functions, one of which is the function main

The syntax of the function main used in this book has this form:

‹#›

Creating a C++ Program (2 of 3)

Source code is comprised of preprocessor directives and program statements

The source code file (source file) contains the source code

The compiler generates the object code (file extension .obj)

Executable code (file extension .exe) results when object code is linked with the system resources

The first line of the function main is called the heading of the function:

int main()

‹#›

Creating a C++ Program (3 of 3)

The statements enclosed between the curly braces ({ and }) form the body of the function

A C++ program contains two types of statements:

Declaration statements declare things, such as variables

Executable statements perform calculations, manipulate data, create output, accept input, etc.

‹#›

Debugging: Understanding and Fixing Syntax Errors (1 of 2)

Sample program with line numbers added on the left

‹#›

Debugging: Understanding and Fixing Syntax Errors (2 of 2)

Compile the program

Compiler will identify the syntax errors

The line numbers where the errors occur are specified:

ExampleCh2_Syntax_Errors.cpp

c:\examplech2_syntax_errors.cpp(9): error C2146: syntax error:

missing ';' before identifier 'num'

c:\examplech2_syntax_errors.cpp(11): error C2065: 'tempNum':

undeclared identifier

‹#›

Program Style and Form: Syntax

Syntax rules indicate what is legal and what is not legal

Errors in syntax are found in compilation

int x; //Line 1

int y //Line 2

double z; //Line 3

y = w + x; //Line 4

Compilation errors would occur at:

Line 2 (missing semicolon)

Line 4 (identifier w used but not declared)

‹#›

Use of Blanks

In C++, you use one or more blanks to separate numbers when data is input

Blanks are also used to separate reserved words and identifiers from each other and from other symbols

Blanks must never appear within a reserved word or identifier

‹#›

Use of Semicolons, Brackets, and Commas

All C++ statements end with a semicolon

Also called a statement terminator

{ and } are not C++ statements

Can be regarded as delimiters

Commas separate items in a list

Declaring more than one variable following a data type

‹#›

Semantics

Semantics: set of rules that gives meaning to a language

Possible to remove all syntax errors in a program and still not have it run

Even if it runs, it may still not do what you meant it to do

Example: 2 + 3 * 5 and (2 + 3) * 5

Both are syntactically correct expressions but have different meanings

‹#›

Naming Identifiers

Identifiers can be self-documenting

CENTIMETERS_PER_INCH

Avoid run-together words

annualsale

Solutions may include:

Capitalizing the beginning of each new word: annualSale

Inserting an underscore just before a new word: annual_sale

‹#›

Prompt Lines

Prompt lines: executable statements that inform the user what to do

cout << "Please enter a number between 1 and 10 and "

<< "press the return key" << endl;

cin >> num;

Always include prompt lines when input is needed from users

‹#›

Documentation

A well-documented program is easier to understand and modify

You use comments to document programs

Comments should appear in a program to:

Explain the purpose of the program

Identify who wrote it

Explain the purpose of particular statements

‹#›

Form and Style

Consider two ways of declaring variables:

Method 1

int feet, inches;

double x, y;

Method 2

int feet,inches; double x,y;

Both are correct; however, the second is harder to read

‹#›

9781337117562_ppt_ch03.pptx

Chapter 3

Input/Output

C++ Programming: Program Design Including Data Structures, Eighth Edition

‹#›

Objectives (1 of 2)

In this chapter, you will:

Learn what a stream is and examine input and output streams

Explore how to read data from the standard input device

Learn how to use predefined functions in a program

Explore how to use the input stream functions get, ignore, putback, and peek

‹#›

Objectives (2 of 2)

Become familiar with input failure

Learn how to write data to the standard output device

Discover how to use manipulators in a program to format output

Learn how to perform input and output operations with the string data type

Learn how to debug logic errors

Become familiar with file input and output

‹#›

I/O Streams and Standard I/O Devices (1 of 3)

I/O: sequence of bytes (stream of bytes) from source to destination

Bytes are usually characters, unless program requires other types of information

Stream: sequence of characters from the source to the destination

Input stream: sequence of characters from an input device to the computer

Output stream: sequence of characters from the computer to an output device

‹#›

I/O Streams and Standard I/O Devices (2 of 3)

Use iostream header file to receive data from keyboard and send output to the screen

Contains definitions of two data types:

istream: input stream

ostream: output stream

Has two variables:

cin: stands for common input

cout: stands for common output

‹#›

I/O Streams and Standard I/O Devices (3 of 3)

Variable declaration is similar to:

istream cin;

ostream cout;

To use cin and cout, the preprocessor directive #include <iostream> must be used

Input stream variables: type istream

Output stream variables: type ostream

‹#›

cin and the Extraction Operator >> (1 of 7)

The syntax of an input statement using cin and the extraction operator >> is

The extraction operator >> is binary

Left-side operand is an input stream variable

Example: cin

Right-side operand is a variable

‹#›

cin and the Extraction Operator >> (2 of 7)

No difference between a single cin with multiple variables and multiple cin statements with one variable in each statement

cin >> payRate >> hoursWorked; cin >> payRate; cin >> hoursWorked;

When scanning, >> skips all whitespace

Blanks and certain nonprintable characters

>> distinguishes between character 2 and number 2 by the right-side operand of >>

If type char or int (or double), the 2 is treated as a character or as a number 2, respectively

‹#›

cin and the Extraction Operator >> (3 of 7)

TABLE 3-1 Valid Input for a Variable of the Simple Data Type

Data Type of a	Valid Input for a
char	One printable character except the blank.
int	An integer, possibly preceded by a + or - sign.
double	A decimal number, possibly preceded by a + or - sign. If the actual data input is an integer, the input is converted to a decimal number with the zero decimal part.

Entering a char value into an int or double variable causes serious errors, called input failure

‹#›

cin and the Extraction Operator >> (4 of 7)

When reading data into a char variable

>> skips leading whitespace, finds and stores only the next character

Reading stops after a single character

To read data into an int or double variable

>> skips leading whitespace, reads + or - sign (if any), reads the digits (including decimal for floating-point variables)

Reading stops on whitespace or a non-digit character

‹#›

cin and the Extraction Operator >> (5 of 7)

‹#›

cin and the Extraction Operator >> (6 of 7)

‹#›

cin and the Extraction Operator >> (7 of 7)

‹#›

Using Predefined Functions in a Program (1 of 3)

A function (subprogram) is a set of instructions

When activated, it accomplishes a task

main executes when a program is run

Other functions execute only when called

C++ includes a wealth of functions

Predefined functions are organized as a collection of libraries called header files

‹#›

Using Predefined Functions in a Program (2 of 3)

Header file may contain several functions

To use a predefined function, you need the name of the appropriate header file

You also need to know:

Function name

Number of parameters required

Type of each parameter

What the function is going to do

‹#›

Using Predefined Functions in a Program (3 of 3)

To use pow (power), include cmath

Two numeric parameters

Syntax: pow(x,y) = xy

x and y are the arguments or parameters

In pow(2,3), the parameters are 2 and 3

‹#›

cin and the get Function

The get function

Inputs next character (including whitespace)

Stores in memory location indicated by its argument

The syntax of cin and the get function

varChar is a char variable

It is the argument (or parameter) of the function

‹#›

cin and the ignore Function (1 of 2)

ignore function

Discards a portion of the input

The syntax to use the function ignore is:

intExp is an integer expression

chExp is a char expression

If intExp is a value m, the statement says to ignore the next m characters or all characters until the character specified by chExp

‹#›

cin and the ignore Function (2 of 2)

‹#›

The putback and peek Functions (1 of 2)

putback function

Places previous character extracted by the get function from an input stream back to that stream

peek function

Returns next character from the input stream

Does not remove the character from that stream

‹#›

The putback and peek Functions (2 of 2)

Syntax for putback

istreamVar: an input stream variable (such as cin)

ch is a char variable

Syntax for peek

istreamVar: an input stream variable (such as cin)

ch is a char variable

‹#›

The Dot Notation between I/O Stream Variables and I/O Functions: A Precaution

In the statement

cin.get(ch);

cin and get are two separate identifiers separated by a dot

Called the dot notation, the dot separates the input stream variable name from the member, or function, name

In C++, the dot is the member access operator

‹#›

Input Failure

Things can go wrong during execution

If input data does not match corresponding variables, the program may run into problems

Trying to read a letter into an int or double variable will result in an input failure

If an error occurs when reading data

Input stream enters the fail state

‹#›

The clear Function

Once in a fail state, all further I/O statements using that stream are ignored

The program continues to execute with whatever values are stored in variables

This causes incorrect results

The clear function restores the input stream to a working state

The syntax of the function clear is:

‹#›

Output and Formatting Output

Syntax of cout when used with <<

expression is evaluated

value is printed

manipulator is used to format the output

Example: endl

‹#›

setprecision Manipulator

Syntax

Outputs decimal numbers with up to n decimal places

Must include the header file iomanip

#include <iomanip>

‹#›

fixed Manipulator

fixed outputs floating-point numbers in a fixed decimal format

Example: cout << fixed;

Disable by using the stream member function unsetf

Example: cout.unsetf(ios::fixed);

scientific manipulator outputs floating-point numbers in scientific format

‹#›

showpoint Manipulator

showpoint forces output to show the decimal point and trailing zeros

Examples

cout << showpoint;

cout << fixed << showpoint;

‹#›

C++14 Digit Separator

Reading and writing of long numbers can be error prone

In C++, commas cannot be used to separate the digits of a number

C++14 introduces digit separator ' (single-quote character)

Example: 87523872918 can be represented as 87'523'872'918

‹#›

setw

Outputs the value of an expression in a specified number of columns

cout << setw(5) << x << endl;

If number of columns exceeds the number of columns required by the expression

Output of the expression is right-justified

Unused columns to the left are filled with spaces

Must include the header file iomanip

‹#›

Additional Output Formatting Tools

Additional formatting tools that give you more control over your output:

setfill manipulator

left and right manipulators

unsetf manipulator

‹#›

setfill Manipulator

Output stream variables can use setfill to fill unused columns with a character

Example:

cout << setfill('#');

‹#›

left and right Manipulators

left manipulator left-justifies the output

Disable left by using unsetf

right manipulator right-justifies the output

‹#›

Types of Manipulators

Two types of manipulators

Those with parameters

Those without parameters

Parameterized stream manipulators require the iomanip header

setprecision, setw, and setfill

Manipulators without parameters require the iostream header

endl, fixed, scientific, showpoint, and left

‹#›

Input/Output and the string Type

An input stream variable (such as cin) and >> operator can read a string into a variable of the data type string

The extraction operator:

Skips any leading whitespace characters

Stops reading at a whitespace character

The function getline reads until end of the current line

‹#›

Debugging: Understanding Logic Errors and Debugging with cout statements

Syntax errors are reported by the compiler

Logic errors are typically not caught by the compiler

Spot and correct using cout statements

Temporarily insert an output statement

Correct the problem

Remove output statement

‹#›

File Input/Output

A file is an area in secondary storage to hold info

File I/O is a five-step process

Include fstream header

Declare file stream variables

Associate the file stream variables with the input/output sources – referred to as opening the files

Use the file stream variables with >>, <<, or other input/output functions

Close the files

‹#›

Quick Review (1 of 3)

Stream: infinite sequence of characters from a source to a destination

Input stream: from a source to a computer

Output stream: from a computer to a destination

cin: common input

cout: common output

To use cin and cout, include iostream header

‹#›

Quick Review (2 of 3)

get reads data character-by-character

ignore skips data in a line

putback puts last character retrieved by get back to the input stream

peek returns next character from input stream, but does not remove it

Attempting to read invalid data into a variable causes the input stream to enter the fail state

‹#›

Quick Review (3 of 3)

The manipulators setprecision, fixed, showpoint, setw, setfill, left, and right can be used for formatting output

Include iomanip for the manipulators setprecision, setw, and setfill

Header fstream contains the definitions of ifstream and ofstream

‹#›

9781337117562_ppt_ch04.pptx

Chapter 4

Control Structures I (Selection)

C++ Programming: Program Design Including Data Structures, Eighth Edition

‹#›

Objectives (1 of 2)

In this chapter, you will:

Learn about control structures

Examine relational operators

Discover how to use the selection control structures if, if…else

Examine int and bool data types and logical (Boolean) expressions

Examine logical operators

Explore how to form and evaluate logical (Boolean) expressions

‹#›

Objectives (2 of 2)

Learn how relational operators work with the string type

Become aware of short-circuit evaluation

Learn how the conditional operator, ?:, works

Learn how to use pseudocode to develop, test, and debug a program

Discover how to use a switch statement in a program

Learn how to avoid bugs by avoiding partially understood concepts

Learn how to use the assert function to terminate a program

‹#›

Control Structures (1 of 2)

A computer can proceed:

In sequence

Selectively (branch): making a choice

Repetitively: looping

By calling a function

The two most common control structures are:

Selection

Repetition

‹#›

Control Structures (2 of 2)

FIGURE 4-1 Flow of execution

‹#›

Selection: if and if...else

An expression that evaluates to true or false is called a logical expression

“8 is greater than 3” is true

‹#›

Relational Operators

TABLE 4-1 Relational Operators in C++

Operator	Description
==	equal to
!=	not equal to
<	less than
<=	less than or equal to
>	greater than
>=	greater than or equal to

Each relational operator is a binary operator (requires two operands)

Expressions using these operators always evaluate to true or false

‹#›

Relational Operators and Simple Data Types

You can use the relational operators with all three simple data types

‹#›

Comparing Characters

In an expression of char values using relational operators:

The result depends on the machine’s collating sequence

ASCII character set

Logical (Boolean) expressions:

Include expressions such as 4 < 6 and 'R' > 'T’

Return an integer value of 1 if the logical expression evaluates to true

Return an integer value of 0 otherwise

‹#›

One-Way Selection (1 of 2)

One-way selection syntax

The statement is:

Executed if the value of the expression is true

Bypassed if the value is false; program goes to the next statement

The expression is also called a decision maker

The statement following the expression is also called the action statement

‹#›

One-Way Selection (2 of 2)

FIGURE 4-2 One-way selection

‹#›

Two-Way Selection (1 of 2)

Two-way selection syntax

If expression is true, statement1 is executed; otherwise, statement2 is executed

statement1 and statement2 are any C++ statements

‹#›

Two-Way Selection (2 of 2)

FIGURE 4-3 Two-way selection

‹#›

int Data Type and Logical (Boolean) Expressions

Earlier versions of C++ did not provide built-in data types that had Boolean values

Logical expressions evaluate to either 1 or 0

Logical expression value was stored in a variable of the data type int

You can use the int data type to manipulate logical (Boolean) expressions

‹#›

bool Data Type and Logical (Boolean) Expressions

The data type bool has logical (Boolean) values true and false

bool, true, and false are reserved words

The identifier true has the value 1

The identifier false has the value 0

‹#›

Logical (Boolean) Operators and Logical Expressions (1 of 5)

Logical (Boolean) operators enable you to combine logical expressions

TABLE 4-2 Logical (Boolean) Operators in C++

Operator	Description
!	not
&&	and
\|\|	or

‹#›

Logical (Boolean) Operators and Logical Expressions (2 of 5)

TABLE 4-3 The ! (Not) Operator

Expression	!(Expression)
true (nonzero)	false (0)
false (0)	true (1)

‹#›

Logical (Boolean) Operators and Logical Expressions (3 of 5)

TABLE 4-4 The && (And) Operator

Expression1	Expression2	Expression1 && Expression2
true (nonzero)	true (nonzero)	true (1)
true (nonzero)	false (0)	false (0)
false (0)	true (nonzero)	false (0)
false (0)	false (0)	false (0)

‹#›

Logical (Boolean) Operators and Logical Expressions (4 of 5)

TABLE 4-5 The || (Or) Operator

Expression1	Expression2	Expression1 \|\| Expression2
true (nonzero)	true (nonzero)	true (1)
true (nonzero)	false (0)	true (1)
false (0)	true (nonzero)	true (1)
false (0)	false (0)	false (0)

‹#›

Logical (Boolean) Operators and Logical Expressions (5 of 5)

‹#›

Order of Precedence (1 of 5)

Relational and logical operators are evaluated from left to right

The associativity is left to right

Parentheses can override precedence

‹#›

Order of Precedence (2 of 5)

TABLE 4-6 Precedence of Operators

Operators	Precedence
!, +, - (unary operators)	first
*, /, %	second
+, -	third
<, <=, >=, >	fourth
==, !=	fifth
&&	sixth
\|\|	seventh
= (assignment operator)	last

‹#›

Order of Precedence (3 of 5)

‹#›

Order of Precedence (4 of 5)

‹#›

Order of Precedence (5 of 5)

‹#›

Relational Operators and the string Type (1 of 5)

Relational operators can be applied to variables of type string

Strings are compared character by character, starting with the first character

Comparison continues until either a mismatch is found or all characters are found equal

If two strings of different lengths are compared and the comparison is equal to the last character of the shorter string

The shorter string is less than the larger string

‹#›

Relational Operators and the string Type (2 of 5)

‹#›

Relational Operators and the string Type (3 of 5)

Expression	Value/Explanation
str1 < str2	true str1 = "Hello" and str2 = "Hi". The first character of str1 and str2 are the same, but the second character 'e' of str1 is less than the second character 'i' of str2. Therefore, str1 < str2 is true.
str1 > "Hen"	false str1 = "Hello". The first two characters of str1 and "Hen" are the same, but the third character 'l' of str1 is less than the third character 'n' of "Hen". Therefore, str1 > "Hen" is false.
str3 < "An"	true str3 = "Air". The first characters of str3 and "An" are the same, but the second character 'i' of "Air" is less than the second character 'n' of "An". Therefore, str3 < "An" is true.

‹#›

Relational Operators and the string Type (4 of 5)

Expression	Value/Explanation
str1 == "hello"	false str1 = "Hello". The first character 'H' of str1 is less than the first character 'h' of "hello" because the ASCII value of 'H' is 72, and the ASCII value of 'h' is 104. Therefore, str1 == "hello" is false.
str3 <= str4	true str3 = "Air" and str4 = "Bill". The first character 'A' of str3 is less than the first character 'B' of str4. Therefore, str3 <= str4 is true.
str2 > str4	true str2 = "Hi" and str4 = "Bill". The first character 'H' of str2 is greater than the first character 'B' of str4. Therefore, str2 > str4 is true.

‹#›

Relational Operators and the string Type (5 of 5)

Expression	Value/Explanation
str4 >= "Billy"	false str4 = "Bill". It has four characters and "Billy" has five characters. Therefore, str4 is the shorter string. All four characters of str4 are the same as the corresponding first four characters of "Billy", and "Billy" is the larger string. Therefore, str4 >= "Billy" is false.
str5 <= "Bigger"	true str5 = "Big". It has three characters and "Bigger" has six characters. Therefore, str5 is the shorter string. All three characters of str5 are the same as the corresponding first three characters of "Bigger", and "Bigger" is the larger string. Therefore, str5 <= "Bigger" is true.

‹#›

Compound (Block of) Statements (1 of 2)

A compound statement (block of statements) has this form:

A compound statement functions like a single statement

‹#›

Compound (Block of) Statements (2 of 2)

if (age > 18)

{

cout << "Eligible to vote." << endl;

cout << "No longer a minor." << endl;

}

else

{

cout << "Not eligible to vote." << endl;

cout << "Still a minor." << endl;

}

‹#›

Multiple Selections: Nested if (1 of 2)

When one control statement is located within another, it is said to be nested

An else is associated with the most recent if that has not been paired with an else

‹#›

Multiple Selections: Nested if (2 of 2)

‹#›

Comparing if…else Statements with a Series of if Statements (1 of 2)

‹#›

Comparing if…else Statements with a Series of if Statements (2 of 2)

‹#›

Short-Circuit Evaluation

Short-circuit evaluation: evaluation of a logical expression stops as soon as the value of the expression is known

‹#›

Comparing Floating-Point Numbers for Equality: A Precaution

Comparison of floating-point numbers for equality may not behave as you would expect

Example:

1.0 == 3.0/7.0 + 2.0/7.0 + 2.0/7.0 evaluates to false

Why? 3.0/7.0 + 2.0/7.0 + 2.0/7.0 = 0.99999999999999989

A solution is checking for a tolerance value

Example: if fabs(x – y) < 0.000001

‹#›

Associativity of Relational Operators: A Precaution (1 of 2)

#include <iostream>

using namespace std;

int main()

{

int num;

cout << "Enter an integer: ";

cin >> num;

cout << endl;

if (0 <= num <= 10)

cout << num << " is within 0 and 10." << endl;

else

cout << num << " is not within 0 and 10." <<

endl;

return 0;

}

‹#›

Associativity of Relational Operators: A Precaution (2 of 2)

num = 5

0 <= num <= 10	= 0 <= 5 <= 10
	= (0 <= 5) <= 10	(Because relational operators are evaluated from left to right)
	= 1 <= 10	(Because 0 <= 5 is true, 0 <= 5 evaluates to 1)
	= 1 (true)

num = 20

0 <= num <= 10	= 0 <= 20 <= 10
	= (0 <= 20) <= 10	(Because relational operators are evaluated from left to right)
	= 1 <= 10	(Because 0 <= 20 is true, 0 <= 20 evaluates to 1)
	= 1 (true)

‹#›

Avoiding Bugs by Avoiding Partially Understood Concepts and Techniques

Must use concepts and techniques correctly

Otherwise solution will be either incorrect or deficient

If you do not understand a concept or technique completely

Do not use it

Save yourself an enormous amount of debugging time

‹#›

Input Failure and the if Statement

If an input stream enters a fail state:

All subsequent input statements associated with that stream are ignored

Program continues to execute

The code may produce erroneous results

Use if statements to check status of input stream

If the input stream enters the fail state, include instructions that stop program execution

‹#›

Confusion Between the Equality (==) and Assignment (=) Operators

C++ allows you to use any expression that can be evaluated to either true or false as an expression in the if statement

if (x = 5)

cout << "The value is five." << endl;

The appearance of = in place of == resembles a silent killer

It is not a syntax error

It is a logical error

‹#›

Conditional Operator (?:)

Conditional operator (?:)

Ternary operator: takes three arguments

Syntax for the conditional operator

If expression1 is true, the result of the conditional expression is expression2

Otherwise, the result is expression3

Example: max = (a >= b) ? a : b;

‹#›

Program Style and Form (Revisited): Indentation

A properly indented program:

Helps you spot and fix errors quickly

Shows the natural grouping of statements

Insert a blank line between statements that are naturally separate

Two commonly used styles for placing braces

On a line by themselves

Or left brace is placed after the expression, and the right brace is on a line by itself

‹#›

Using Pseudocode to Develop, Test, and Debug a Program

Pseudocode (or just pseudo) is an informal mixture of C++ and ordinary language

Helps you quickly develop the correct structure of the program and avoid making common errors

Use a wide range of values in a walk-through to evaluate the program

‹#›

switch Structures (1 of 4)

switch structure is an alternate to if-else

switch (integral) expression is evaluated first

Value of the expression determines which corresponding action is taken

Expression is sometimes called the selector

‹#›

switch Structures (2 of 4)

FIGURE 4-4 switch statement

‹#›

switch Structures (3 of 4)

One or more statements may follow a case label

Braces are not needed to turn multiple statements into a single compound statement

When a case value is matched, all statements after it execute until a break is encountered

The break statement may or may not appear after each statement

switch, case, break, and default are reserved words

‹#›

switch Structures (4 of 4)

‹#›

Avoiding Bugs: Revisited

To output results correctly

Consider whether the switch structure must include a break statement after each cout statement

‹#›

Terminating a Program with the assert Function

Certain types of errors are very difficult to catch

Example: division by zero

The assert function is useful in stopping program execution when certain elusive errors occur

‹#›

The assert Function (1 of 2)

Syntax

expression is any logical expression

If expression evaluates to true, the next statement executes

If expression evaluates to false, the program terminates and indicates where in the program the error occurred

To use assert, include cassert header file

‹#›

The assert Function (2 of 2)

assert is useful for enforcing programming constraints during program development

After developing and testing a program, remove or disable assert statements

The preprocessor directive #define NDEBUG must be placed before the directive #include <cassert> to disable the assert statement

‹#›

Quick Review (1 of 3)

Control structures alter normal control flow

Most common control structures are selection and repetition

Relational operators: ==, <, <=, >, >=, !=

Logical expressions evaluate to 1 (true) or 0 (false)

Logical operators: ! (not), && (and), || (or)

‹#›

Quick Review (2 of 3)

Two selection structures are one-way selection and two-way selection

The expression in an if or if...else structure is usually a logical expression

No stand-alone else statement exists in C++

Every else has a related if

A sequence of statements enclosed between braces, { and }, is called a compound statement or a block of statements

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Quick Review (3 of 3)

Using assignment in place of the equality operator creates a semantic error

The execution of a switch structure handles multiway selection

The execution of a break statement ends a switch statement

Use assert to terminate a program if certain conditions are not met

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9781337117562_ppt_ch05.pptx

Chapter 5

Control Structures II (Repetition)

C++ Programming: Program Design Including Data Structures, Eighth Edition

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Objectives (1 of 2)

In this chapter, you will:

Learn about repetition (looping) control structures

Learn how to use a while loop in a program

Explore how to construct and use counter-controlled, sentinel-controlled, flag-controlled, and EOF-controlled repetition structures

Learn how to use a for loop in a program

Learn how to use a do…while loop in a program

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Objectives (2 of 2)

Examine break and continue statements

Discover how to form and use nested control structures

Learn how to avoid bugs by avoiding patches

Learn how to debug loops

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Why Is Repetition Needed?

Repetition allows efficient use of variables

It is possible to input, add, and average multiple numbers using a limited number of variables

Consider the code to determine the average number of calories burned each day doing regular exercise

Method 1: Declare a variable for each day and enter the number of calories burned, add the values and store in a variable for the week’s total, and divide the total by 7 to find the average

Method 2: Create a loop that reads a number into a variable and adds it to a variable that contains the sum of the numbers (only two variables needed)

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while Looping (Repetition) Structure (1 of 3)

A while loop is one of three repetition, or looping structures in C++

Syntax of the while statement

The statement can be simple or compound

The expression acts as a decision maker and is usually a logical expression

The statement is called the body of the loop

The parentheses are part of the syntax

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while Looping (Repetition) Structure (2 of 3)

FIGURE 5-1 while loop

The expression provides an entry condition to the loop

The statement (body of the loop) continues to execute until the expression is no longer true

An infinite loop continues to execute endlessly

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while Looping (Repetition) Structure (3 of 3)

The preceding while loop produces the following output:

0 5 10 15 20

The variable i in Example 5-1 is called the loop control variable (LCV)

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while Looping (Repetition) Structure (cont’d.)

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Case 1: Counter-Controlled while Loops

When you know exactly how many times the statements need to be executed

Use a counter-controlled while loop

counter = 0; //initialize the loop control variable

while (counter < N) //test the loop control variable

{

counter++; //update the loop control variable

}

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Case 2: Sentinel-Controlled while Loops

A sentinel variable is tested in the condition

The loop ends when the sentinel is encountered

The following is an example of a sentinel-controlled while loop:

cin >> variable; //initialize the loop control variable

while (variable != sentinel) //test the loop control variable

{

cin >> variable; //update the loop control variable

}

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Example 5-5: Telephone Digits

Example 5-5 provides an example of a sentinel-controlled loop

The program converts uppercase letters to their corresponding telephone digit

The sentinel value is #

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Case 3: Flag-Controlled while Loops

Flag-controlled while loop: uses a bool variable to control the loop

isFound = false; //initialize the loop control variable

while (!isFound) //test the loop control variable

{

if (expression)

isFound = true; //update the loop control variable

}

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Number Guessing Game

Example 5-6 implements a number guessing game using a flag-controlled while loop

Uses the function rand of the header file cstdlib to generate a random number

rand() returns an int value between 0 and 32767

To convert to an integer >= 0 and < 100:

rand() % 100

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Case 4: EOF-Controlled while Loops (1 of 2)

An end-of-file (EOF)-controlled while loop is a good choice when it is difficult to select a sentinel value

The logical value returned by cin can determine if there is no more input

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Case 4: EOF-Controlled while Loops (2 of 2)

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eof Function

The function eof can determine the end of file status

eof is a member of data type istream

Syntax for the function eof

istreamVar is an input stream variable, such as cin

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9781337117562_ppt_ch06.pptx

Chapter 6

User-Defined Functions

C++ Programming: Program Design Including Data Structures, Eighth Edition

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Objectives (1 of 2)

In this chapter, you will:

Learn about standard (predefined) functions and discover how to use them in a program

Learn about user-defined functions

Examine value-returning functions , including actual and formal parameters

Explore how to construct and use a value-returning, user-defined function in a program

Learn about function prototypes

Learn how to construct and use void functions

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Objectives (2 of 2)

Discover the difference between value and reference parameters

Explore reference parameters and value-returning functions

Learn about the scope of an identifier

Examine the difference between local and global identifiers

Discover static variables

Learn how to debug programs using drivers and stubs

Learn function overloading

Explore functions with default parameters

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Introduction

Functions allow complicated programs to be divided into manageable pieces

Functions are often called modules

They are like miniature programs that can be combined to form larger programs

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Predefined Functions (1 of 2)

In C++, a function is similar to that of a function in algebra

It has a name

It does some computation

Some of the predefined mathematical functions are:

pow(x, y)

sqrt(x)

floor(x)

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Predefined Functions (2 of 2)

Predefined functions are organized into separate libraries

I/O functions are in iostream header

Math functions are in cmath header

To use predefined functions, you must include the header file using an include statement

See Table 6-1 in the text for some common predefined functions

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User-Defined Functions

Value-returning functions have a return type

Return a value of a specific data type using the return statement

Void functions do not have a return type

Do not use a return statement to return a value

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Value-Returning Functions (1 of 3)

To use these functions, you must:

Include the appropriate header file in your program using the include statement

Know the following items:

Name of the function

Number of parameters, if any

Data type of each parameter

Data type of the value returned, called the type of the function

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Value-Returning Functions (2 of 3)

Can use the value returned by a value-returning function by:

Saving it for further calculation

Using it in some calculation

Printing it

A value-returning function is used:

In an assignment

As a parameter in a function call

In an output statement

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Value-Returning Functions (3 of 3)

Heading (or function header): the first line of the function

Example: int abs(int number)

The body is the function’s code that accomplishes the task

Formal parameter: a variable declared in the heading

Example: number

Actual parameter: a variable or expression listed in a call to a function

Example: x = pow(u, v)

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Syntax: Value-Returning Function

Syntax

functionType is also called the data type or return type

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Syntax: Formal Parameter List

FIGURE 6-1 Various parts of the function abs

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Function Call

Syntax to call a value-returning function

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Syntax: Actual Parameter List

The syntax of the actual parameter list is:

The formal parameter list can be empty

A call to a value-returning function with an empty formal parameter list is:

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return Statement

A function returns its value via the return statement

It passes this value outside the function

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Syntax: return Statement (1 of 2)

The return statement has this syntax:

In C++, return is a reserved word

When a return statement executes

The function immediately terminates

Control goes back to the caller

When a return statement executes in the function main, the program terminates

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Syntax: return Statement (2 of 2)

FIGURE 6-2 Various parts of the function larger

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Function Prototype

A function prototype is the function heading without the body of the function

The general syntax of the function prototype of a value-returning function is:

It is not necessary to specify the variable name in the parameter list

The data type of each parameter must be specified

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Value-Returning Functions: Some Peculiarities (1 of 2)

int secret(int x)

{

if (x > 5) //Line 1

return 2 * x; //Line 2

}

A correct definition of the function secret is:

int secret(int x)

{

if (x > 5) //Line 1

return 2 * x; //Line 2

return x; //Line 3

}

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Value-Returning Functions: Some Peculiarities (2 of 2)

Examples pointing out that the return statement only returns one value

return x, y; //only the value of y will be returned

int funcRet1()

{

int x = 45;

return 23, x; //only the value of x is returned

}

int funcRet2(int z)

{

int a = 2;

int b = 3;

return 2 * a + b, z + b;

//only the value of z + b is returned

}

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More Examples of Value-Returning Functions (1 of 2)

char courseGrade(int score)

{

switch (score / 10)

{

case 0:

case 1:

case 2:

case 3:

case 4:

case 5:

return 'F';

case 6:

return 'D';

case 7:

return 'C';

case 8:

return 'B';

case 9:

case 10:

return 'A';

}

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More Examples of Value-Returning Functions (2 of 2)

In addition to Example 6-3 courseGrade, other examples are given in the text

Example 6-4 (rolling a pair of dice)

Example 6-5 (Fibonacci number)

Example 6-6 (palindrome)

Example 6-7 (cable company)

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Flow of Compilation and Execution (1 of 2)

Execution always begins at the first statement in the function main

Other functions are executed only when called

Function prototypes appear before any function definition

The compiler translates these first

The compiler can then correctly translate a function call

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Flow of Compilation and Execution (2 of 2)

A function call transfers control to the first statement in the body of the called function

When the end of a called function is executed, control is passed back to the point immediately following the function call

A function’s returned value replaces the function call statement

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Void Functions (1 of 4)

User-defined void functions can be placed either before or after the function main

If user-defined void functions are placed after the function main

The function prototype must be placed before the function main

A void function does not have a return type

A return statement without any value is typically used to exit the function early

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Void Functions (2 of 4)

Formal parameters are optional

A call to a void function is a stand-alone statement

The function definition of void functions with parameters has the following syntax:

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Void Functions (3 of 4)

Formal parameter list syntax

Function call syntax

Actual parameter list syntax

string::size_type	An unsigned integer (data) type
string::npos	The maximum value of the (data) type string::size_type, a number such as 4294967295 on many machines

computer programme

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Data Type	Array	struct
Arithmetic	No	No
Assignment	No	Yes
Input/output	No (except strings)	No
Comparison	No	No
Parameter passing	By reference only	By value or by reference
Function returning a value	No	Yes