Computer Organization

Basics

Machine, software, and program

design

JPC and JWD © 2002 McGraw-Hill, Inc.

Computer Organization

CPU - central processing unit

Memory

Input devices

Output devices

CPU - central processing unit

„ Where decisions are made, computations are performed, and input/output requests are delegated

Memory

„ Stores information being processed by the CPU Input devices

„ Allows people to supply information to computers Output devices

Computer Organization

Memory CPU Input Devices Output Devices

CPU

Brainsof the computer

„ Arithmetic calculations are performed using the Arithmetic/Logical Unit or ALU

„ Control unit decodes and executes instructions

Arithmetic operations are performed using binary number system

Control Unit

The fetch/execute cycle is the steps the CPU takes to execute an instruction Performing the action specified by an instruction is known as executing the instruction

The program counter (PC) holds the memory address of the next instruction

Fetch the instruction to which the PC points

Increment the PC

Execute the fetched instruction

Input and Output Devices

Accessories that allow computer to perform specific tasks „ Receive information for processing

„ Return the results of processing „ Store information

Accessories that allow computer to perform specific tasks „ Receive information for processing

„ Return the results of processing „ Store information

Common input and output devices

„ Speakers Mouse Scanner

„ Printer Joystick CD-ROM

„ Keyboard Microphone DVD

Accessories that allow computer to perform specific tasks „ Receive information for processing

„ Return the results of processing „ Store information

Common input and output devices

„ Speakers Mouse Scanner

„ Printer Joystick CD-ROM

„ Keyboard Microphone DVD

Some devices are capable of both input and output

Monitor

Display device that operates like a television „ Also known as CRT (cathode ray tube)

Controlled by an output device called a graphics card Displayable area

„ Measured in dots per inch, dots are often referred to as

pixels (short for picture element)

„ Standard resolution is 640 by 480 „ Many cards support

resolution of 1280 by 1024 or better

„ Number of colors supported varies from 16 to billions 1280 pixels across screen 1024 pixels down screen Application software

„ Programs designed to perform specific tasks that are transparent to the user

System software

„ Programs that support the execution and development of other programs

„ Two major types

ŠOperating systems

ŠTranslation systems

Software

Application Software

Application software is the software that has made using computers indispensable and popular

Common application software „ Word processors

„ Desktop publishing programs „ Spreadsheets

„ Presentation managers „ Drawing programs

Application software is the software that has made using computers indispensable and popular

Common application software „ Word processors

„ Desktop publishing programs „ Spreadsheets

„ Presentation managers „ Drawing programs

Learning how to develop application software is our focus

Examples

„ Windows®, UNIX®, Mac OS X®

Controls and manages the computing resources Important services that an operating system provides

„ File system

ŠDirectories, folders, files

„ Commands that allow for manipulation of the file system

ŠSort, delete, copy

Ability to perform input and output on a variety of devices

Operating System

Translation System

Set of programs used to develop software

A key component of a translation system is a translator Some types of translators

„ Compiler

ŠConverts from one language to another „ Linker

ŠCombines resources Examples

„ Microsoft Visual C++®, CBuilder®, g++, Code Warrior®

ŠPerforms compilation, linking, and other activities.

Software Development Activities

Editing

Compiling

Linking with precompiled files „ Object files

„ Library modules Loading and executing

Software Development Cycle

Compile Link

Library routines Other object files Think Edit Load Execute Source Program

IDEs

Integrated Development Environments or IDEs „ Supports the entire software development cycle

ŠE.g., MS Visual C++, Borland, Code Warrior

Provides all the capabilities for developing software „ Editor „ Compiler „ Linker „ Loader „ Debugger „ Viewer

Engineering Software

Software engineering

„ Area of computer science concerned with building large software systems

Challenge

„ Tremendous advances in hardware have not been accompanied by comparable advances in software

Complexity Trade-off

System complexity tends to grow as the system becomes more user friendly High Low Complexity Total Software Complexity User Simplicity

Software Engineering Goals

Reliability Understandability Cost Effectiveness Adaptability Reusability Reliability

„ An unreliable life-critical system can be fatal Understandability

„ Future development is difficult if software is hard to understand Cost Effectiveness

„ Cost to develop and maintain should not exceed profit Adaptability

„ System that is adaptive is easier to alter and expand Reusability

„ Improves reliability, maintainability, and profitability

Abstraction

„ Extract the relevant properties while ignoring inessentials Encapsulation

„ Hide and protect essential information through a controlled interface

Modularity

Hierarchy Abstraction

„ Extract the relevant properties while ignoring inessentials Encapsulation

„ Hide and protect essential information through a controlled interface

Modularity

„ Dividing an object into smaller modules so that it is easier to understand and manipulate

Hierarchy Abstraction

„ Extract the relevant properties while ignoring inessentials Encapsulation

„ Hide and protect essential information through a controlled interface

Modularity

„ Dividing an object into smaller modules so that it is easier to understand and manipulate

Hierarchy

„ Ranking or ordering of objects based on some relationship between them

Software Engineering Principles

Abstraction

Encapsulation

Modularity

Hierarchy Abstraction

„ Extract the relevant properties while ignoring inessentials Encapsulation

Modularity

Extract the relevant object properties while ignoring inessentials „ Defines a view of the object

Example - car

„ Car dealer views a car from selling features standpoint

ŠPrice, length of warranty, color, …

„ Mechanic views a car from systems maintenance standpoint

ŠSize of the oil filter, type of spark plugs, …

Abstraction

Price? Oil change?

Encapsulation

Steps

„ Decompose an object into parts „ Hide and protect essential information

„ Supply interface that allows information to be modified in a controlled and useful manner

Internal representation can be changed without affecting other system parts

Example - car radio

„ Interface consists of controls and power and antenna connectors

Š The details of how it works is hidden „ To install and use a radio

Modularity

Dividing an object into smaller pieces or modules so that the object is easier to understand and manipulate

Most complex systems are modular

Example - Automobile can be decomposed into subsystems „ Cooling system

ŠRadiator Thermostat Water pump

„ Ignition system

ŠBattery Starter Spark plugs

Hierarchy

Hierarchy

„ Ranking or ordering of objects based on some relationship between them

Help us understand complex systems

„ Example - a company hierarchy helps employees understand the company and their positions within it

For complex systems, a useful way of ordering similar abstractions is a taxonomy from least general to most general

Northern Timber Wolf Taxonomy

Kingdom Animalia Phylum Chordata Class Mammalia Order Carnivora Family Caninae Genus Canis

Species Canis lupus

Subspecies Canis lupus occidentalis Northern Timber Wolf

OO Design and Programming

Object-oriented design and programming methodology supports good software engineering

„ Promotes thinking in a way that models the way we think and interact with the real world

Example - watching television

„ The remote is a physical object with properties

ŠWeight, size, can send message to the television

„ The television is also a physical object with various properties

Objects

An object is almost anything with the following characteristics „ Name

„ Properties

„ The ability to act upon receiving a message

ŠBasic message types

„ Directive to perform an action

„ Request to change one of its properties

The individual digits of a binary number are referred to as bits „ Each bit represents a power of two

01011 = 0 • 24 _{+ 1 • 2}3 _{+ 0 • 2}2 _{+ 1 • 2}1 _{+ 1 • 2}0 _{= 11} 00010 = 0 • 24 _{+ 0 • 2}3 _{+ 0 • 2}2 _{+ 1 • 2}1 _{+ 0 • 2}0 _{= 2}

Binary Arithmetic

00010 + 01011 Binary addition 2 + 11 Equivalentdecimal

Binary Arithmetic

5 × 3 15 Equivalent decimal multiplication 0101 × 0011 0101 0101 0000 0000 0001111 Binary multiplication

Two’s Complement

Representation for signed binary numbers Leading bit is a sign bit

„ Binary number with leading 0 is positive „ Binary number with leading 1 is negative

Magnitude of positive numbers is just the binary representation Magnitude of negative numbers is found by

„ Complement the bits

„ Replace all the 1's with 0's, and all the 0's with 1's „ Add one to the complemented number

Two’s Complement

Performing two's complement on the decimal 7 to get -7 „ Using a five-bit representation

7 = 00111 Convert to binary 11000 Complement the bits 11000 Add 1 to the complement + 00001

11001 Result is -7 in two's complement

Two's Complement Arithmetic

Computing 8 - 7 using a two's complement representation with five-bit numbers 8 - 7 = 8 + (-7) = 1 01000 Two's complement of 8 11001 Two's complement of -7 01000 Add 8 and -7 + 11001 100001 Throw away the

high-order carry as we are

Fundamentals of C++

Basic programming elements and

concepts

JPC and JWD © 2002 McGraw-Hill, Inc.

Program statement „ Definition „ Declaration „ Action Executable unit

„ Named set of program statements

„ Different languages refer to executable units by different names

ŠSubroutine: Fortran and Basic

ŠProcedure: Pascal

ŠFunction : C++

Program Organization

C++ program

„ Collection of definitions, declarations and functions „ Collection can span multiple files

Advantages

„ Structured into small understandable units „ Complexity is reduced

„ Overall program size decreases

Object

Object is a representation of some information „ Name

„ Values or properties

ŠData members

„ Ability to react to requests (messages)!!

ŠMember functions

When an object receives a message, one of two actions are performed

„ Object is directed to perform an action „ Object changes one of its properties

// Program: Display greetings // Author(s): Ima Programmer // Date: 1/24/2001

#include <iostream> #include <string> using namespace std; int main() {

cout << "Hello world!" << endl; return 0;

}

A First Program - Greeting.cpp

Preprocessor directives

Insertion statement Ends executions

of main() which ends program Comments Function Function named main() indicates start of program

Provides simple access

Definitions Extraction Definition with initialization

Area.cpp

#include <iostream> using namespace std; int main() {

// Extract length and width

cout << "Rectangle dimensions: "; float Length;

float Width;

cin >> Length >> Width;

// Compute and insert the area

float Area = Length * Width;

cout << "Area = " << Area << " = Length " << Length << " * Width " << Width << endl; return 0;

}

Area.cpp Output

Comments

Allow prose or commentary to be included in program Importance

„ Programs are read far more often than they are written „ Programs need to be understood so that they can be

maintained

C++ has two conventions for comments „ // single line comment (preferred) „ /* long comment */(save for debugging) Typical uses

„ Identify program and who wrote it „ Record when program was written „ Add descriptions of modifications

Fundamental C++ Objects

C++ has a large number of fundamental or built-in object types The fundamental object types fall into one of three categories

„ Integer objects „ Floating-point objects „ Character objects

1

1.28345

Z

5

P

3.14

Integer Object Types

The basic integer object type is int

„ The size of an intdepends on the machine and the

compiler

ŠOn PCs it is normally 16 or 32 bits

Other integers object types „ short: typically uses less bits

„ long: typically uses more bits

Different types allow programmers to use resources more efficiently

Standard arithmetic and relational operations are available for these types

Integer Constants

Integer constants are positive or negative whole numbers Integer constant forms

„ Decimal „ Octal (base 8) ŠDigits 0, 1, 2, 3, 4, 5, 6, 7 „ Hexadecimal (base 16) ŠDigits 0, 1, 2, 3, 4, 5, 6, 7, 8, 9, a , b, c, d, e, f, A, B, C, D, E, F Consider

„ 31 oct and 25 dec

Decimal Constants

Examples „ 97 „ 40000L „ 50000 „ 23a (illegal)

The type of the constant depends on its size, unless the type specifier is used

Character Object Types

Character type charis related to the integer types

Characters are encoded using a scheme where an integer represents a particular character

ASCII is the dominant encoding scheme „ Examples

Š ' 'encoded as 32 '+'encoded as 43 Š 'A'encoded as 65 'Z'encoded as 90 Š 'a'encoded as 97 'z'encoded as 122

„ Appendix A gives the complete ASCII character set

Character Operations

Arithmetic and relational operations are defined for characters types

„ 'a' < 'b'is true

„ '4' > '3' is true

Character Constants

Explicit (literal) characters within single quotes

„ 'a','D','*'

Special characters - delineated by a backslash \ „ Two character sequences (escape codes) „ Some important special escape codes

Š \tdenotes a tab Š \ndenotes a new line Š \\denotes a backslash Š \'denotes a single

quote

Š \"denotes a double quote

„ '\t'is the explicit tab character, '\n'is the explicit new line

character, and so on

Literal String Constants

A literal string constant is a sequence of zero or more characters enclosed in double quotes

„ "We are even loonier than you think"

„ "Rust never sleeps\n"

„ "Nilla is a Labrador Retriever"

Floating-Point Object Types

Floating-point object types represent real numbers

„ Integer part „ Fractional part

The number 108.1517 breaks down into the following parts „ 108 - integer part

„ 1517 - fractional part

C++ provides three floating-point object types

„ float

„ double

„ long double

Floating-Point Constants

Standard decimal notation

134.123 0.15F

Standard scientific notation 1.45E6

0.979e-3L

When not specified, floating-point constants are of type double

F or f indicates single precision floating point value

L or l indicates long double floating point value

Names

Used to denote program values or components A valid name is a sequence of

„ Letters (upper and lowercase) „ Digits

ŠA name cannot start with a digit „ Underscores

ŠA name should not normally start with an underscore

Names are case sensitive

„ MyObject is a different name than MYOBJECT There are two kinds of names

„ Keywords „ Identifiers

Keywords

Keywords are words reserved as part of the language „ int, return, float, double

They cannot be used by the programmer to name things They consist of lowercase letters only

Identifiers

Identifiers should be

„ Short enough to be reasonable to type (single word is norm)

ŠStandard abbreviations are fine (but only standard

abbreviations)

„ Long enough to be understandable

ŠWhen using multiple word identifiers capitalize the first letter of each word

Examples „ Min „ Temperature „ CameraAngle „ CurrentNbrPoints

Definitions

All objects that are used in a program must be defined An object definition specifies

„ Type „ Name

General definition form

Type Id, Id, ..., Id;

Known type

List of one or more identifiers

Examples

char Response; int MinElement; float Score; float Temperature; int i; int n; char c; float x;

Objects are uninitialized with this definition form

(Value of a object is whatever is in its

assigned memory location)

Arithmetic Operators

Common „ Addition + „ Subtraction -„ Multiplication * „ Division / „ Mod % Note „ No exponentiation operator „ Single division operator

„ Operators are overloaded to work with more than one type of object

Write m*x + b

Integer Division

Integer division produces an integer result „ Truncates the result

Examples

„ 3 / 2evaluates to 1

„ 4 / 6evaluates to 0

„ 10 / 3evaluates to 3

Mod

Produces the remainder of the division Examples

„ 5 % 2evaluates to 1

„ 12 % 4evaluates to 0

Operators and Precedence

Consider mx + b

Consider m*x + b which of the following is it equivalent to

„ (m * x) + b

„ m * (x + b)

Operator precedence tells how to evaluate expressions Standard precedence order

„ () Evaluate first, if nested innermost done first

„ * / % Evaluate second. If there are several, then evaluate from left-to-right „ + - Evaluate third. If there are several,

then evaluate from left-to-right

Operator Precedence

Examples 20 - 4 / 5 * 2 + 3 * 5 % 4 (4 / 5) ((4 / 5) * 2) ((4 / 5) * 2) (3 * 5) ((4 / 5) * 2) ((3 * 5) % 4) (20 -((4 / 5) * 2)) ((3 * 5) % 4) (20 -((4 / 5) * 2)) + ((3 * 5) % 4)

Defining and Initializing

When an object is defined using the basic form, the memory allotted to it contains random information

Better idea to specify its desired value at the same time „ Exception is when the next statement is an extraction for

the object

Remember our convention of one definition per statement!

Examples

int FahrenheitFreezing = 32; char FinalGrade = 'A';

cout << "Slope of line: "; float m;

cin >> m;

cout << "Intercept: "; float b;

cin >> b;

cout << "X value of interest: "; float x;

cin >> x;

Modifying Objects

Operators and Expressions

JPC and JWD © 2002 McGraw-Hill, Inc.

Memory Depiction

float y = 12.5; 12.5 y 1001 1002 1003 1004

Memory Depiction

float y = 12.5; int Temperature = 32; 12.5 32 y Temperature 1001 1002 1003 1004 1005 1006

Memory Depiction

float y = 12.5; int Temperature = 32; char Letter = 'c'; 12.5 32 'c' y Temperature Letter 1001 1002 1003 1004 1005 1006 1007

Memory Depiction

float y = 12.5; int Temperature = 32; char Letter = 'c'; int Number; 12.5 32 'c' y Temperature Letter 1001 1002 1003 1004 1005 1006 1007

-Number 1008₁₀₀₉

Assignment Statement

Basic form „ object= expression; Celsius = (Fahrenheit - 32) * 5 / 9; y = m * x + b; Action „ Expression is evaluated

„ Expression value stored in object

Definition

int NewStudents = 6; NewStudents 6

Definition

int NewStudents = 6; int OldStudents = 21; 6 21 NewStudents OldStudents

Definition

int NewStudents = 6; int OldStudents = 21; int TotalStudents; 6 21 NewStudents OldStudents -TotalStudents

Assignment Statement

int NewStudents = 6; int OldStudents = 21; int TotalStudents;

TotalStudents = NewStudents + OldStudents; 6 21 NewStudents OldStudents ? TotalStudents

Assignment Statement

int NewStudents = 6; int OldStudents = 21; int TotalStudents;

TotalStudents = NewStudents + OldStudents; 6 21 NewStudents OldStudents 27 TotalStudents

Assignment Statement

int NewStudents = 6; int OldStudents = 21; int TotalStudents;

TotalStudents = NewStudents + OldStudents;

OldStudents = TotalStudents; 6 ? NewStudents OldStudents 27 TotalStudents

Assignment Statement

int NewStudents = 6; int OldStudents = 21; int TotalStudents;

TotalStudents = NewStudents + OldStudents;

OldStudents = TotalStudents; 6 27 NewStudents OldStudents 27 TotalStudents

Consider

Consider

int Value1 = 10; int Value2 = 20; 10 20 Value1 Value2

Consider

int Value1 = 10; int Value2 = 20; int Hold = Value1;

10 20 Value1 Value2 10 Hold

Consider

int Value1 = 10; int Value2 = 20; int Hold = Value1;

Value1 = Value2; ? 20 Value1 Value2 10 Hold

Consider

int Value1 = 10; int Value2 = 20; int Hold = Value1;

Value1 = Value2; 20 20 Value1 Value2 10 Hold

Consider

int Value1 = 10; int Value2 = 20; int Hold = Value1;

Value1 = Value2; Value2 = Hold; 20 ? Value1 Value2 10 Hold

Consider

int Value1 = 10; int Value2 = 20; int Hold = Value1;

Value1 = Value2;

Value2 = Hold;

We swappedthe values of objects Value1 and Value2 using Hold as temporary holder for Value1’s starting value!

20 10 Value1 Value2 10 Hold

Incrementing

int i = 1; i 1

Incrementing

int i = 1; i = i + 1;

Assign the value of expression i + 1to i

Evaluates to 2

i 1

2 i

Const Definitions

Modifier constindicates that an object cannot be changed

„ Object is read-only

Useful when defining objects representing physical and mathematical constants

const float Pi = 3.1415;

Value has a name that can be used throughout the program

const int SampleSize = 100;

Makes changing the constant easy

„ Only need to change the definition and recompile

Assignment Conversions

Floating-point expression assigned to an integer object is truncated

Integer expression assigned to a floating-point object is converted to a floating-point value

Consider float y = 2.7; int i = 15; int j = 10; i = y; // i is now 2 cout << i << endl; y = j; // y is now 10.0

Nonfundamental Types

Nonfundamental as they are additions to the language C++ permits definition of new types and classes

„ A class is a special kind of type Class objects typically have

„ Data membersthat represent attributes and values „ Member functionsfor object inspection and manipulation „ Members are accessed using the selection operator (.)

j = s.size();

„ Auxiliaryfunctions for other behaviors

Libraries often provide special-purpose types and classes Programmers can also define their own types and classes

Examples

Standard Template Library (STL) provides class string

EzWindows library provides several graphical types and classes

„ SimpleWindowis a class for creating and manipulating

window objects

„ RectangleShapeis a class for creating and manipulating

Class string

Class string

„ Used to represent a sequence of characters as a single object

Some definitions

string Name = "Joanne"; string DecimalPoint = "."; string empty = "";

string copy = name;

string Question = '?'; // illegal

Nonfundamental Types

To access a library use a preprocessor directive to add its definitions to your program file

#include <string>

The using statement makes syntax less clumsy „ Without it

std::string s = "Sharp"; std::string t = "Spiffy"; „ With it

using namespace std; // std contains string string s = "Sharp";

EzWindows Library Objects

Definitions are the same form as other objects Example

SimpleWindow W;

„ Most non-fundamental classes have been created so that an object is automatically initialized to a sensible value

SimpleWindowobjects have member functions to process

messages to manipulate the objects

„ Most important member function is Open()which causes

the object to be displayed on the screen

ŠExample

W.Open();

Initialization

Class objects may have several attributes to initialize Syntax for initializing an object with multiple attributes

Type Identifier(Exp1, Exp2, ..., Expn);

SimpleWindow object has several optional attributes

SimpleWindow W("Window Fun", 8, 4);

„ First attribute

ŠWindow banner „ Second attribute

ŠWidth of window in centimeters „ Third attribute

An EzWindows Program

#include <iostream>

using namespace std; #include "ezwin.h" int ApiMain() {

SimpleWindow W("A Window", 12, 12); W.Open();

cout << "Enter a character to exit" << endl; char a;

cin >> a;

return 0; }

An EzWindows Project File

RectangleShape Objects

EzWindows also provides RectangleShapefor manipulating

rectangles

RectangleShapeobjects can specify the following attributes

„ SimpleWindowobject that contains the rectangle (mandatory)

„ Offset from left edge of the SimpleWindow

„ Offset from top edge of the SimpleWindow

Š Offsets are measured in centimeters from rectangle center „ Width in centimeters

„ Height in centimeters „ Color

Š coloris an EzWindows type

RectangleShape Objects

Examples

SimpleWindow W1("My Window", 20, 20);

SimpleWindow W2("My Other Window", 15, 10);

RectangleShape R(W1, 4, 2, Blue, 3, 2); RectangleShape S(W2, 5, 2, Red, 1, 1); RectangleShape T(W1, 3, 1, Black, 4, 5); RectangleShape U(W1, 4, 9);

RectangleShape Objects

Some RectangleShapemember functions for processing

messages

„ Draw()

ŠCauses rectangle to be displayed in its associated window

„ GetWidth()

ŠReturns width of object in centimeters

„ GetHeight()

ŠReturns height of object in centimeters

„ SetSize()

ŠTakes two attributes -- a width and height -- that are used to reset dimensions of the rectangle

Another EzWindows Program

#include <iostream> using namespace std; #include "rect.h"

int ApiMain() {

SimpleWindow W("Rectangular Fun", 12, 12); W.Open();

RectangleShape R(W, 5.0, 2.5, Blue, 1, 2); R.Draw();

cout << "Enter a character to exit" << endl; char Response;

cin >> Response; return 0;

Sample Display Behavior

Compound Assignment

C++ has a large set of operators for applying an operation to an object and then storing the result back into the object Examples int i = 3; i += 4; // i is now 7 cout << i << endl; float a = 3.2; a *= 2.0; // a is now 6.4 cout << a << endl;

Increment and Decrement

C++ has special operators for incrementing or decrementing an object by one Examples int k = 4; ++k; // k is 5 k++; // k is 6 cout << k << endl; int i = k++; // i is 6, k is 7 cout << i << " " << k << endl; int j = ++k; // j is 8, k is 8 cout << j << " " << k << endl;

Class string

Some string member functions

„ size() determines number of characters in the string

string Saying = "Rambling with Gambling";

cout << Saying.size() << endl; // 22

„ substr() determines a substring (Note first position has index 0)

string Word = Saying.substr(9, 4); // with

„ find() computes the position of a subsequence

int j = Saying.find("it"); // 10

Class string

Auxiliary functions and operators „ getline() extracts the next input line

string Response;

cout << "Enter text: ";

getline(cin, Response, '\n');

cout << "Response is \"" << Response << "\"” << endl;

„ Example run

Enter text: Want what you do Response is "Want what you do"

Class string

Auxiliary operators

„ + string concatenation

string Part1 = "Me"; string Part2 = " and "; string Part3 = "You";

string All = Part1 + Part2 + Part3;

„ += compound concatenation assignment

string ThePlace = "Brooklyn"; ThePlace += ", NY";

#include <iostream> using namespace std; int main() {

cout << "Enter the date in American format: " << "(e.g., January 1, 2001) : ";

string Date;

getline(cin, Date, '\n'); int i = Date.find(" ");

string Month = Date.substr(0, i); int k = Date.find(",");

string Day = Date.substr(i + 1, k - i - 1);

string Year = Date.substr(k + 2, Date.size() - 1); string NewDate = Day + " " + Month + " " + Year; cout << "Original date: " << Date << endl;

cout << "Converted date: " << NewDate << endl; return 0;

If Control Construct

A mechanism for deciding whether an

action should be taken

JPC and JWD © 2002 McGraw-Hill, Inc.

Boolean Algebra

Logical expressions have the one of two values - true or false „ A rectangle has three sides

„ The instructor has a pleasant smile

The branch of mathematics is called Boolean algebra

„ Developed by the British mathematician George Boole in the 19th century

Three key logical operators „ And

„ Or „ Not

Boolean Algebra

Truth tables

„ Lists all combinations of operand values and the result of the operation for each combination

Example

P Q P and Q

False False False

False True False

True False False

True True True

Boolean Algebra

Or truth table

P Q P or Q

False False False

False True True

True False True

Boolean Algebra

Not truth table

P not P

False True True False

Boolean Algebra

Can create complex logical expressions by combining simple logical expressions

Example

„ not (P and Q)

A truth table can be used to determine when a logical expression is true

P Q P and Q not (P and Q)

False False False True

False True False True

A Boolean Type

C++ contains a type named bool

Type boolhas two symbolic constants

„ true

„ false

Boolean operators

„ The andoperator is &&

„ The oroperator is ||

„ The notoperator is !

Warning

„ &and |are also operators so be careful what you type

A Boolean Type

Example logical expressions

bool P = true; bool Q = false; bool R = true; bool S = (P && Q); bool T = ((!Q) || R); bool U = !(R && (!Q));

Relational Operators

Equality operators „ == „ != Examples „ int i = 32; „ int k = 45; „ bool q = (i == k); „ bool r = (i != k);

Relational Operators

Ordering operators „ < „ > „ >= „ <= Examples „ int i = 5; „ int k = 12; „ bool p = (i < 10); „ bool q = (k > i); „ bool r = (i >= k);

Operator Precedence Revisited

Precedence of operators (from highest to lowest)

„ Parentheses „ Unary operators „ Multiplicative operators „ Additive operators „ Relational ordering „ Relational equality „ Logical and „ Logical or „ Assignment

Operator Precedence Revisited

Consider

Operator Precedence Revisited

Consider

5 * 15 + 4 == 13 && 12 < 19 || !false == 5 < 24

Yuck! Do not write expressions like this!

Operator Precedence Revisited

Consider

5 * 15 + 4 == 13 && 12 < 19 || !false == 5 < 24

However, for your information it is equivalent to ((((5 *15) + 4) == 13) && (12 < 19))

||

((!false) == (5 < 24))

Consider

5 * 15 + 4 == 13 && 12 < 19 || !false == 5 < 24

However, for your information it is equivalent to

((((5 *15) + 4) == 13) && (12 < 19)) ||

((!false) == (5 < 24))

Consider

5 * 15 + 4 == 13 && 12 < 19 || !false == 5 < 24

However, for your information it is equivalent to

((((5 *15) + 4) == 13) && (12 < 19)) ||

((!false) == (5 < 24))

Consider

5 * 15 + 4 == 13 && 12 < 19 || !false == 5 < 24

However, for your information it is equivalent to

((((5 *15) + 4) == 13) && (12 < 19)) ||

((!false) == (5 < 24))

Consider

5 * 15 + 4 == 13 && 12 < 19 || !false == 5 < 24

However, for your information it is equivalent to

((((5 *15) + 4) == 13) && (12 < 19)) ||

((!false) == (5 < 24))

Consider

5 * 15 + 4 == 13 && 12 < 19 || !false == 5 < 24

However, for your information it is equivalent to

((((5 *15) + 4) == 13) && (12 < 19)) ||

((!false) == (5 < 24))

Consider

5 * 15 + 4 == 13 && 12 < 19 || !false == 5 < 24

However, for your information it is equivalent to

((((5 *15) + 4) == 13) && (12 < 19)) ||

((!false) == (5 < 24))

Consider

5 * 15 + 4 == 13 && 12 < 19 || !false == 5 < 24

However, for your information it is equivalent to

((((5 *15) + 4) == 13) && (12 < 19)) ||

((!false) == (5 < 24))

Consider

5 * 15 + 4 == 13 && 12 < 19 || !false == 5 < 24

However, for your information it is equivalent to

((((5 *15) + 4) == 13) && (12 < 19)) ||

((!false) == (5 < 24))

Consider

5 * 15 + 4 == 13 && 12 < 19 || !false == 5 < 24

Conditional Constructs

Provide

„ Ability to control whether a statement list is executed Two constructs „ If statement Šif Šif-else Šif-else-ef „ Switch statement

ŠLeft for reading

The Basic If Statement

Syntax

if (Expression)

Action

If the Expressionis true then execute Action

Actionis either a single statement or a group of statements within braces

Expression

Action

Example

if (Value < 0) { Value = -Value; } Value < 0 Value = -Value true false

Is our number negative?

If Value is not less than zero then our number is fine as is If Value is less than

zero then we need to update its value to that of its additive

inverse

Our number is now definitely nonnegative

Sorting Two Numbers

cout << "Enter two integers: "; int Value1;

int Value2;

cin >> Value1 >> Value2; if (Value1 > Value2) {

int RememberValue1 = Value1; Value1 = Value2;

Value2 = RememberValue1; }

cout << "The input in sorted order: " << Value1 << " " << Value2 << endl;

Semantics

value2 < value1

int rememberValue1 = value1 value1 = value2

value2 = rememberValue1

true false

Are the numbers out of order

Rearrange value1 and value2 to put their values

in the proper order

The numbers were initially in order

The numbers were rearranged into the

proper order

The numbers are in order

What is the Output?

int m = 5; int n = 10; if (m < n) ++m; ++n; cout << " m = " << m << " n = " n << endl;

The If-Else Statement

Syntax if (Expression) Action₁ else Action₂

If Expressionis true then execute Action₁otherwise execute Action₂

if (v == 0) { cout << "v is 0"; } else { cout << "v is not 0"; } Expression Action₁ Action₂ true false

Finding the Max

cout << "Enter two integers: "; int Value1;

int Value2;

cin >> Value1 >> Value2; int Max; if (Value1 < Value2) { Max = Value2; } else { Max = Value1; }

Finding the Max

Value1 < Value2

Max = Value2 Max = Value1

true false

Is Value2 larger than Value1 Yes, it is . So Value2 is

larger than Value1. In this case, Max is set

to Value2

No, its not. So Value1 is at least as large as

Value2. In this case, Max is set to Value1

Either case, Max is set correctly

Selection

It is often the case that depending upon the value of an expression we want to perform a particular action Two major ways of accomplishing this choice

„ if-else-if statement

Šif-else statements “glued” together „ Switch statement

An If-Else-If Statement

if ( nbr < 0 ){

cout << nbr << " is negative" << endl; }

else if ( nbr > 0 ) {

cout << nbr << " is positive" << endl; }

else {

cout << nbr << " is zero" << endl; }

A Switch Statement

switch (ch) {

case 'a': case 'A': case 'e': case 'E': case 'i': case 'I': case 'o': case 'O': case 'u': case 'U':

cout << ch << " is a vowel" << endl; break;

default:

cout << ch << " is not a vowel" << endl; }

cout << "Enter simple expression: "; int Left;

int Right; char Operator;

cin >> Left >> Operator >> Right;

cout << Left << " " << Operator << " " << Right << " = ";

switch (Operator) {

case '+' : cout << Left + Right << endl; break; case '-' : cout << Left - Right << endl; break; case '*' : cout << Left * Right << endl; break; case '/' : cout << Left / Right << endl; break; default: cout << "Illegal operation" << endl; }

Iterative Constructs

Mechanisms for deciding under what

conditions an action should be

repeated

JPC and JWD © 2002 McGraw-Hill, Inc.

Determining Average Magnitude

Suppose we want to calculate the average apparent brightness of a list of five star magnitude values

„ Can we do it?

ŠYes, it would be easy

Suppose we want to calculate the average apparent brightness of a list of five star magnitude values

„ Can we do it

ŠYes, it would be easy

Suppose we want to calculate the average apparent brightness of a list of 8,479 stars visible from earth

„ Can we do it

ŠYes, but it would be gruesome without the use of iteration

C++ Iterative Constructs

Three constructs „ while statement „ for statement „ do-while statement

While Syntax

Logical expression that determines whether the action is to be executed

while ( Expression ) Action

Action to be iteratively performed until logical

expression is false

While Semantics

Expression Action true false Expression is evaluated at the start of each iteration of the loop If Expression is true, Action is executed _{If Expression is} false, program execution continues with next statement

Computing an Average

int listSize = 4;

int numberProcessed = 0; double sum = 0;

while (numberProcessed < listSize) { double value;

cin >> value; sum += value; ++numberProcessed; }

double average = sum / numberProcessed ; cout << "Average: " << average << endl;

Execution Trace

int listSize = 4;

int numberProcessed = 0; double sum = 0;

while (numberProcessed < listSize) { double value;

cin >> value; sum += value; ++numberProcessed; }

double average = sum / numberProcessed ; cout << "Average: " << average << endl;

Suppose input contains: 1 5 3 1 6

Execution Trace

int listSize = 4;

int numberProcessed = 0;

double sum = 0;

while (numberProcessed < listSize) { double value;

cin >> value; sum += value; ++numberProcessed; }

double average = sum / numberProcessed ; cout << "Average: " << average << endl;

numberProcessed

Suppose input contains: 1 5 3 1 6

4 listSize 0

Execution Trace

int listSize = 4; int numberProcessed = 0; double sum = 0;

while (numberProcessed < listSize) { double value;

cin >> value; sum += value; ++numberProcessed; }

double average = sum / numberProcessed ; cout << "Average: " << average << endl;

numberProcessed sum

Suppose input contains: 1 5 3 1 6

4

listSize

0 0

Execution Trace

int listSize = 4;

int numberProcessed = 0; double sum = 0;

while (numberProcessed < listSize) {

double value; cin >> value; sum += value; ++numberProcessed; }

double average = sum / numberProcessed ; cout << "Average: " << average << endl;

numberProcessed sum

Suppose input contains: 1 5 3 1 6

4 listSize 0 0

Execution Trace

int listSize = 4; int numberProcessed = 0; double sum = 0;

while (numberProcessed < listSize) {

double value;

cin >> value; sum += value; ++numberProcessed; }

double average = sum / numberProcessed ; cout << "Average: " << average << endl;

numberProcessed sum value

Suppose input contains: 1 5 3 1 6

4

listSize

0 0

--Execution Trace

int listSize = 4;

int numberProcessed = 0; double sum = 0;

while (numberProcessed < listSize) { double value;

cin >> value;

sum += value; ++numberProcessed; }

double average = sum / numberProcessed ; cout << "Average: " << average << endl;

numberProcessed sum value

Suppose input contains: 1 5 3 1 6

4 listSize 0 0 1

Execution Trace

int listSize = 4; int numberProcessed = 0; double sum = 0;

while (numberProcessed < listSize) { double value;

cin >> value;

sum += value;

++numberProcessed; }

double average = sum / numberProcessed ; cout << "Average: " << average << endl;

numberProcessed sum value

Suppose input contains: 1 5 3 1 6

4 listSize 0 0 1 1

Execution Trace

int listSize = 4;

int numberProcessed = 0; double sum = 0;

while (numberProcessed < listSize) { double value;

cin >> value; sum += value;

++numberProcessed;

}

double average = sum / numberProcessed ; cout << "Average: " << average << endl;

numberProcessed sum value

Suppose input contains: 1 5 3 1 6

4 listSize 0 1 1 1

Execution Trace

int listSize = 4; int numberProcessed = 0; double sum = 0;

while (numberProcessed < listSize) {

double value; cin >> value; sum += value; ++numberProcessed; }

double average = sum / numberProcessed ; cout << "Average: " << average << endl;

numberProcessed sum value

Suppose input contains: 1 5 3 1 6

4

listSize

1 1 1

Execution Trace

int listSize = 4;

int numberProcessed = 0; double sum = 0;

while (numberProcessed < listSize) {

double value;

cin >> value; sum += value; ++numberProcessed; }

double average = sum / numberProcessed ; cout << "Average: " << average << endl;

numberProcessed sum value

Suppose input contains: 1 5 3 1 6

4 listSize 1 1

--Execution Trace

int listSize = 4; int numberProcessed = 0; double sum = 0;

while (numberProcessed < listSize) { double value;

cin >> value;

sum += value; ++numberProcessed; }

double average = sum / numberProcessed ; cout << "Average: " << average << endl;

numberProcessed sum value

Suppose input contains: 1 5 3 1 6

4

listSize

1 1 5

Execution Trace

int listSize = 4;

int numberProcessed = 0; double sum = 0;

while (numberProcessed < listSize) { double value;

cin >> value;

sum += value;

++numberProcessed; }

double average = sum / numberProcessed ; cout << "Average: " << average << endl;

numberProcessed sum value

Suppose input contains: 1 5 3 1 6

4 listSize 1 1 5 6

Execution Trace

int listSize = 4; int numberProcessed = 0; double sum = 0;

while (numberProcessed < listSize) { double value;

cin >> value; sum += value;

++numberProcessed;

}

double average = sum / numberProcessed ; cout << "Average: " << average << endl;

numberProcessed sum value

Suppose input contains: 1 5 3 1 6

4 listSize 1 6 5 2

Execution Trace

int listSize = 4;

int numberProcessed = 0; double sum = 0;

while (numberProcessed < listSize) {

double value; cin >> value; sum += value; ++numberProcessed; }

double average = sum / numberProcessed ; cout << "Average: " << average << endl;

numberProcessed sum value

Suppose input contains: 1 5 3 1 6

4 listSize 2 6 5 6

Execution Trace

int listSize = 4; int numberProcessed = 0; double sum = 0;

while (numberProcessed < listSize) {

double value;

cin >> value; sum += value; ++numberProcessed; }

double average = sum / numberProcessed ; cout << "Average: " << average << endl;

numberProcessed sum value

Suppose input contains: 1 5 3 1 6

4 listSize 2 6 --2

Execution Trace

int listSize = 4;

int numberProcessed = 0; double sum = 0;

while (numberProcessed < listSize) { double value;

cin >> value;

sum += value; ++numberProcessed; }

double average = sum / numberProcessed ; cout << "Average: " << average << endl;

numberProcessed sum value

Suppose input contains: 1 5 3 1 6

4 listSize 2 6 3 2

Execution Trace

int listSize = 4; int numberProcessed = 0; double sum = 0;

while (numberProcessed < listSize) { double value;

cin >> value;

sum += value;

++numberProcessed; }

double average = sum / numberProcessed ; cout << "Average: " << average << endl;

numberProcessed sum value

Suppose input contains: 1 5 3 1 6

4 listSize 2 6 3 9

Execution Trace

int listSize = 4;

int numberProcessed = 0; double sum = 0;

while (numberProcessed < listSize) { double value;

cin >> value; sum += value;

++numberProcessed;

}

double average = sum / numberProcessed ; cout << "Average: " << average << endl;

numberProcessed sum value

Suppose input contains: 1 5 3 1 6

4 listSize 2 9 3 3

Execution Trace

int listSize = 4; int numberProcessed = 0; double sum = 0;

while (numberProcessed < listSize) {

double value; cin >> value; sum += value; ++numberProcessed; }

double average = sum / numberProcessed ; cout << "Average: " << average << endl;

numberProcessed sum value

Suppose input contains: 1 5 3 1 6

4 listSize 3 9 3 3

Execution Trace

int listSize = 4;

int numberProcessed = 0; double sum = 0;

while (numberProcessed < listSize) {

double value;

cin >> value; sum += value; ++numberProcessed; }

double average = sum / numberProcessed ; cout << "Average: " << average << endl;

numberProcessed sum value

Suppose input contains: 1 5 3 1 6

4 listSize 3 9 --3

Execution Trace

int listSize = 4; int numberProcessed = 0; double sum = 0;

while (numberProcessed < listSize) { double value;

cin >> value;

sum += value; ++numberProcessed; }

double average = sum / numberProcessed ; cout << "Average: " << average << endl;

numberProcessed sum value

Suppose input contains: 1 5 3 1 6

4 listSize 3 9 1 3

Execution Trace

int listSize = 4;

int numberProcessed = 0; double sum = 0;

while (numberProcessed < listSize) { double value;

cin >> value;

sum += value;

++numberProcessed; }

double average = sum / numberProcessed ; cout << "Average: " << average << endl;

numberProcessed sum value

Suppose input contains: 1 5 3 1 6

4 listSize 3 9 1 10

Execution Trace

int listSize = 4; int numberProcessed = 0; double sum = 0;

while (numberProcessed < listSize) { double value;

cin >> value; sum += value;

++numberProcessed;

}

double average = sum / numberProcessed ; cout << "Average: " << average << endl;

numberProcessed sum value

Suppose input contains: 1 5 3 1 6

4 listSize 3 10 1 4

Execution Trace

int listSize = 4;

int numberProcessed = 0; double sum = 0;

while (numberProcessed < listSize) {

double value; cin >> value; sum += value; ++numberProcessed; }

double average = sum / numberProcessed ; cout << "Average: " << average << endl;

numberProcessed sum value

Suppose input contains: 1 5 3 1 6

4 listSize 3 10 1 4

Execution Trace

int listSize = 4; int numberProcessed = 0; double sum = 0;

while (numberProcessed < listSize) { double value;

cin >> value; sum += value; ++numberProcessed; }

double average = sum / numberProcessed ;

cout << "Average: " << average << endl; numberProcessed

sum

Suppose input contains: 1 5 3 1 6

4 listSize 3 10 average _2.5 4

Execution Trace

int listSize = 4;

int numberProcessed = 0; double sum = 0;

while (numberProcessed < listSize) { double value;

cin >> value; sum += value; ++numberProcessed; }

double average = sum / numberProcessed ;

cout << "Average: " << average << endl;

numberProcessed sum average

Suppose input contains: 1 5 3 1 6

4 listSize 3 10 2.5 4

Execution Trace

int listSize = 4; int numberProcessed = 0; double sum = 0;

while (numberProcessed < listSize) { double value;

cin >> value; sum += value; ++numberProcessed; }

double average = sum / numberProcessed ; cout << "Average: " << average << endl;

Suppose input contains: 1 5 3 1 6

Stays in stream until

extracted

Power of Two Table

const int TableSize = 20;

int i = 0; long Entry = 1;

cout << "i" << "\t\t" << "2 ** i" << endl;

while (i < TableSize) {

cout << i << "\t\t" << Entry << endl; Entry = 2 * Entry;

++i; }

Better Way of Averaging

int numberProcessed = 0; double sum = 0;

double value;

while ( cin >> value ) {

sum += value; ++numberProcessed; }

double average = sum / numberProcessed ; cout << "Average: " << average << endl;

What if list is empty? The value of the input operation corresponds to

true only if a successful extraction was made

Even Better Way of Averaging

int numberProcessed = 0; double sum = 0;

double value;

while ( cin >> value ) {

sum += value; ++numberProcessed; }

if ( numberProcessed > 0 ) {

double average = sum / numberProcessed ; cout << "Average: " << average << endl; }

else {

cout << "No list to average" << endl; }

The For Statement

Syntax

for (ForInit; ForExpression; PostExpression)

Action Example

for (int i = 0; i < 3; ++i) { cout << "i is " << i << endl; }

ForExpr Action true false ForInit PostExpr Evaluated once at the beginning of the for statements's

execution _{evaluated at the}The ForExpr is start of each iteration of the loop If ForExpr is true, Action is executed After the Action

has completed, the PostExpression is evaluated If ForExpr is false, program execution continues with next statement

After evaluating the PostExpression, the next iteration of the loop starts

Execution Trace

for (int i = 0; i < 3; ++i) {

cout << "i is " << i << endl; }

cout << "all done" << endl;

Execution Trace

for (int i = 0; i < 3; ++i) {

cout << "i is " << i << endl; }

cout << "all done" << endl;

i ₀

Execution Trace

for (int i = 0; i < 3; ++i) {

cout << "i is " << i << endl;

}

cout << "all done" << endl;

i is 0

Execution Trace

for (int i = 0; i < 3; ++i) { cout << "i is " << i << endl;

}

cout << "all done" << endl;

i is 0

i ₀

Execution Trace

for (int i = 0; i < 3; ++i) {

cout << "i is " << i << endl; }

cout << "all done" << endl;

i is 0

Execution Trace

for (int i = 0; i < 3; ++i) {

cout << "i is " << i << endl; }

cout << "all done" << endl;

i ₁

Execution Trace

for (int i = 0; i < 3; ++i) {

cout << "i is " << i << endl;

}

cout << "all done" << endl;

i is 0 i is 1

Execution Trace

for (int i = 0; i < 3; ++i) { cout << "i is " << i << endl;

}

cout << "all done" << endl;

i is 0 i is 1

i ₁

Execution Trace

for (int i = 0; i < 3; ++i) {

cout << "i is " << i << endl; }

cout << "all done" << endl;

i is 0 i is 1

Execution Trace

for (int i = 0; i < 3; ++i) {

cout << "i is " << i << endl; }

cout << "all done" << endl;

i is 0 i is 1

i ₂

Execution Trace

for (int i = 0; i < 3; ++i) {

cout << "i is " << i << endl;

}

cout << "all done" << endl;

i is 0 i is 1 i is 2

Execution Trace

for (int i = 0; i < 3; ++i) { cout << "i is " << i << endl;

}

cout << "all done" << endl;

i is 0 i is 1 i is 2

i ₂

Execution Trace

for (int i = 0; i < 3; ++i) {

cout << "i is " << i << endl; }

cout << "all done" << endl;

i is 0 i is 1 i is 2

Execution Trace

for (int i = 0; i < 3; ++i) {

cout << "i is " << i << endl; }

cout << "all done" << endl;

i is 0 i is 1 i is 2

i ₃

Execution Trace

for (int i = 0; i < 3; ++i) { cout << "i is " << i << endl; }

cout << "all done" << endl;

i is 0 i is 1 i is 2 all done

Table Revisiting

const int TableSize = 20;

long Entry = 1;

cout << "i" << "\t\t" << "2**i" << endl;

for (int i = 0; i <= TableSize; ++i) { cout << i << "\t\t" << Entry << endl; Entry *= 2;

}

Table Revisiting

const int TableSize = 20;

long Entry = 1;

cout << "i" << "\t\t" << "2**i" << endl;

for (int i = 0; i < TableSize; ++i) { cout << i << "\t\t" << Entry << endl; Entry = 2 * Entry;

}

cout << "i is" << i << endl; // illegal

Displaying a Diagonal

SimpleWindow W("One diagonal", 5.5, 2.25); W.Open();

for (int j = 1; j <= 3; ++j) {

float x = j * 0.75 + 0.25; float y = j * 0.75 - 0.25; float Side = 0.4;

RectangleShape S(W, x, y, Blue, Side, Side); S.Draw();

}

Displaying Three Diagonals

SimpleWindow W("Three diagonals", 6.5, 2.25); W.Open();

for (int i = 1; i <= 3; ++i) {

for (int j = 1; j <= 3; ++j) {

float x = i - 1 + j * 0.75 + 0.25; float y = j * 0.75 - 0.25;

float Side = 0.4;

RectangleShape S(W, x, y, Blue, Side, Side); S.Draw();

}

} _{The scope of i includes the inner loop.}

The scope of j is just the inner loop.

int Counter1 = 0; int Counter2 = 0; int Counter3 = 0; int Counter4 = 0; int Counter5 = 0; ++Counter1;

for (int i = 1; i <= 10; ++i) {

++Counter2; for (int j = 1; j <= 20; ++j) { ++Counter3; } ++Counter4; } ++Counter5;

cout << Counter1 << " " << Counter2 << " "

<< Counter3 << " " << Counter4 << " "

<< Counter5 << endl;

For Into While

Observation

„ The for statement is equivalent to

{ ForInit; while (ForExpression) { Action; PostExpression; } }

Counting Characters

int NumberOfNonBlanks = 0; int NumberOfUpperCase = 0; char c; while (cin >> c) { ++NumberOfNonBlanks; if ((c >= 'A') && (c <= 'Z')) { ++N