COEN244 Programming Methodology IIamer/teach/coen244/notes/topic01.pdfc A. Amer Introduction to C++ 14. C++ overview : Variable scope Multiple ﬁle programs: variables declared in

COEN244Programming Methodology II

Aishy Amer

Electrical & Computer Engineering Concordia University

Lecture Outline:Course introductionIntroduction to C++

well-designed programs, Data types, Variable scope, Functions,Pointers, Arrays, struct, class, Header files, Name-spaces, ..

Principles of OOPSoftware Development MethodBooks, FAQ, ..

c© A. Amer COEN244: Introduction 1

Welcome to COEN244

COEN-244 emphasizes Object-Oriented Programming (OOP)methodologies and concepts of well-designed C++ programs

OOP: increasingly important both in academia & industry

C++: emerging as a language of choice

Because C++ combinesefficiency of C + the disciplined approach to software design

using interacting modules

Course prerequisites:

good understanding and experience

with functions, arrays, pointers, and i/o streams

C++ : very complex language → expect to work many hours


Welcome to COEN244

To assist you:

Prof.: questions to C++ concepts

Tutors: questions to (practical) implementation and toassignments

PODs: questions to technical programming problems(view solutions to assignments)

Marker: questions to marking of assignments & quizzes

Help desk, helpdesk@encs: questions to computing facilities

COEN244 course website: announcements, course notes, etc.www.ece.concordia.ca/ amer/teach/coen244/

Email: Monitor your email for updates


Ethics and Professionalism

Ethics: “Disciplined dealing with moral duty” &“System of right behavior”

Professionalism: “The conduct, aims, or qualities thatcharacterize a professional person”

Academic honesty: Cheating in any form not tolerated

Do not hesitate to ask questions

Be on time

No talking during class time

Respect deadlines

Personal emergency? Inform your Prof. ASAPc© A. Amer COEN244: Introduction 4


Industry needs Engineers who..

Behave professionally: reliable, accept responsibility,...

Familiar with methodology of problems solving

Experienced in collaborating in a team

Complete problem solvers

Society needs Engineers who..

are both professional and socially responsible



A professional person

accepts responsibility fully & does not blame others for failure

is reliable - gets the job done on time

follows up on all the details

is respectful to others

has high standards of ethical behavior & does not lie or cheat

does not offer excuses in lieu of completed work

succeeds in spite of obstacles and road blocks

has justifiable self-confidence

...


C++: What/why a computer program

Computers/Programs: tools to solve real-world problems

Solving real-world problems via programs?→ Simulation of real-world systems

System: well-defined arrangement of interacting processes witha common task

Process: act of transformation of information

Model: simplified representation of a system

Simulation: reproduction of selected aspects of systembehavior through experimentation based on the model


C++: Well-designed programs

COEN244 focus: How to write well designed C++ programs

A well-designed program?

a combination of components (modules) that cooperate

to perform the common task but

are independent enough to be separately maintainable

A well designed program?

modular: classes and functions

general: can be applied for many applications/situations

maintainable: a code that the maintainer understand


C++ overview

General form of a program: declarations & executable statements .....#include <iostream> // compiler directive

using namespace std;

float Quadratic(float,float,float,float); // function declaration

int main() {

float *a; float *b = new float; //variable declarations

a = new float(10); *b= 20; //executable statements

cout("a = %f ; b= %f\n",a,b);

delete a; delete b; // free memory!!

cout << Quadratic(*a,*b,); // function call

return 0;

}

float Quadratic(float x,float a,float b,float c) // implementation

{

float result;

result = a * x * x + b * x + c;

return result;

}

c© A. Amer Introduction to C++ 9

C++ overview

Variable Declaration: based on data type

Variable? int, char, struct, object, ..

Executable Statements:cout << "Enter the size of the fabric in square meters";

cost = tax_rate*price + price;

Reserved Words and Identifiers: cannot be used otherwise

Operators: binary, e.g., +, %, *, and unary, e.g., ++, !

Control structures: if/else, while, for, switch, ...

A compound statement: a group of statements enclosed by {}This block of code is treated as a single statement{} define a new program scope:its variables can be declared within these


C++ overview : Data types

Predefined Data Types: bool, char, float, string, ...

User-defined Data Types: class, struct, ...

int used for signed integer values (word size of the machine)also unsigned values

float used for 32 bit floating point values

double used for 64 bit double precision floating point values

char a one byte (signed) value (also unsigned char)

void can representnothing when used as the return type for a function oras a generic data type when used as the base type for apointer data type


C++ overview : Input/output

Input / output in C++I/O: a stream of consecutive bytes “from a source”/“to adestination”cin >> x; reads a (float) value from the standard input &stores it in xcout << len; writes the value of len to the standard output


C++ overview : Variable declaration

Variable declaration = a data type and a variable name

Data type can be:1. a basic type, except void2. an pointer type (including void *) or a reference type3. a struct or class

Variable name: start with letter or underscore (case sensitive)int i; <= integer

char *cPtr; <= pointer to a character

float arrayOfPoints[10]; <= array of 10 floats

unsigned char uc1, uc2, uc3; <= three separate unsigned characters.

void *genericPtr; <= indirect pointer to anything

A variable declaration can be placed anywhere in a program


C++ overview : Variable scope

Variable is known, or scoped:only within the program unit in which it was declared

Variable scope:local (function, compound statement)global: scoped within an entire programhas never been good practiceprivate (class)...

A variable declared outside of all functions in a file is accessibleby any code in that file

Data should not be directly visible to the outside worldGood practice: keep the scope of data as narrow as possible



Multiple file programs: variables declared in one file can bemade accessed by code in other files by specifying that it is anextern variable

extern declarations are often placed in an include fileIf there are multiple variables with the same name whose scopes overlap at one point in a

program, the variable with the innermost scope will be used

Any variable declared outside of all functions in a file can beaccessed by other files in the program by declaring the variableas extern in those other files

To declare variables as global within a file but they are to behidden from other program files:declare each of these variables as static



In file a.cc:

int anExternInt; // can be accessed by the file b.cc

static int aPrivateInt;

In file b.cc:

extern int anExternInt;

extern int aPrivateInt; // <= error was declared as static

A global variable is declared without the extern in only the filewith which the variable is most closely associated

It is then referenced with an extern, usually specified in aninclude file, in all other files that will use that variable


C++ overview : Constants

C++ supports the standard integer and floating point constants

Character constants can also be defined within ”: ’a’

A string constant: enclosing it between "":"COEN244 follows COEN243"

A constant string is an array of characters:its size = the number of characters in the string + 1

This extra byte at the end of the string stores a ’0’ (zero byte)considered as the terminator for the string

Most string functions assume that the zero byte terminator ispresent at the end of the string


C++ overview : Operators

Operators: binary, e.g., +, %, *, and unary, e.g., ++, !

* indirection operator: used to dereference a pointerprovide access to the data at that location

& address-of operator: used to get a pointer to a data item

() used to control the order evaluation of complex expressions

Expressions evaluation: according to the operators precedence

Every expression has a value resulting from its evaluation

C++ allows operators to be overloaded


C++ overview : Functions

C++ has only one subprogram unit called a function

Functions: function declaration and function implementation

Function definition: with formal parameters

Function call: replace formal parameters with actual parametersF. call that returns a value can be part of an expressionReturn type & formal parameter definition must be specifiedbefore the f. call

Function declaration: must define the data type for the formalparameters:used to check if usage correct

A function returns a value to the calling unit


C++ overview : Functions

The data type for the return value is specified in the functiondeclarationA void return type: does not return a valuefloat Quadratic(float,float,float,float); // declaration

float Quadratic(float x,float a,float b,float c)

{

float result;

result = a * x * x + b * x + c;

return result;

}

To maintain a variable value across function calls, declare thevariable as staticThis static is different than static to limit the scope of global variables


C++ overview : inline functions

inline Quadratic(float x,float a,float b,float c)

{

return a * x * x + b * x + c;

}

Use: the actual operation to be carried out by the function issmall (compared to the overhead of calling a function)

Speed up program execution

Parameter type checking is done but gain the faster executionas if you had written the code directly inline


C++ overview : Pointers

References: int i=5; int & r =i; //r alias to iA reference is an alternative name or alias for an objectAny operation carried out on r is then an operation on i

A reference must be initialized and cannot be changed torefer to another object

Pointers: a type of variable int* p;Value of a pointer is ?Every pointer has it own address

Linked list: a data structure where you get the practice to reallyunderstand pointers (see course website)


C++ overview : Pointers

Data types that give indirect access to an item

* is used to specify a pointer data typeis the address of an item of the specified data typeExample: int *, specifies a data type that is the address of an integer

& is used to specify a reference type& can be considered to create a new name (alias) for a dataExample: float &, an alias for a float item

& allows a variable to be accessed using the normal syntaxwhile the compiler handles the indirection for you


C++ overview: Pointers - ’NULL’ vs. ’\0’ Constant

int* pi = new int[100]; // allocate memory for 100 integers

if(pi == NULL) { // tests if allocation ok (pointer was created)

cout<< "Out of memory\n"; exit(0); // exit program

}

’NULL’ is a Named Constant for ’0’ pointer

Defined in iostream.h

In gcc/g++ compliers:it is not used as named constant for ’\0’ (null terminator)

Under Linux: use ’NULL’ as a substitute for 0 onlysee example above

null character (null terminator) ’\0’: a ASCII character with the value zero

in C++/C: it serves as a reserved character used to signify the end of a string


C++ overview : Arrays

int Asize=10;

float arrayOfPoints[Asize]; <= array of 10 floats

Array declaration: using [] with an integer size

Array of elements of any data typean array of char: char name[20];an array of struct: Student std[48];

Strings: arrays of type char, last element is ’0’

1D or 2D arrays


C++ overview : struct

struct is a way to create user-defined data types

struct has data members only (more later)

struct <struct_name> {

<struct data members> ;

};

----------------------------|-----------------------

struct Grade | struct Student

{ //Members of the struct | {

float assignments; | string name;

float quiz; | int id;

float midterm; | int GPA;

float final; | }

} |

----------------------------|--------------------------

Grade g; | Student s;

g.quiz = 9.7; | cin>> s.id;

cout << g.quiz; |


C++ overview: Classes

Object-oriented programming (OOP): software in a way thatmodels the real world

OOP: way of thinking oriented to objects

Real-world problems have objectsObjects define the problem

Class: an effective way to create user-defined data types

Class has both types of members: data and functions

A real-world problem: Automated banking system

Class BankAccount { // A Bank Account = a real object

Private Data:

int number; float balance;

Operations:

deposit(); withdraw();

};c© A. Amer Introduction to C++ 27


Differentiate: class implementation and class declaration

Class declaration: used by compiler to validate class use &are typically put in header files

Classes: bind data and operations together

class <class_name> {

public:

<member functions> ;

private:

<member data>

};

class Player {

public:

Player();

void move(); void attack(); void getBall();

private:

int health; int strength; int agility;

};

-----------------------------------------------

Player p,q; // p,q: objects of type Player;

// Player: class

p.move(); p.getBall(); //apply functions on p



class Cylinder { //class declaration in cylinder.h

private: //data

double radius, height; // data fields to access

public: //operations

void setCylinder(double r, double h); // set cylinder data

double getVolume() // compute volume

void scaleCylinder(double factor) // scale dimensions

void printCylinder() // print object state

};

// -------- Class implementation in cylinder.cpp

void Cylinder::setCylinder(double r, double h) // set cylinder data

{ radius = r; height = h; }

double Cylinder:: getVolume() // compute volume

{ return height * radius * radius * 3.141593; }

void Cylinder:: scaleCylinder(double factor) // scale dimensions

{ radius *= factor; height *= factor; }

void Cylinder:: printCylinder() // print object state

{ cout << "radius: " <<radius << " height: " <<height <<endl; }

==> Cylinder c,d; c.setCylinder(1.5,3.3);



Examples: Time, Date, Student, Vehicle, ...

describe a Vehicle?Vehicle is engine? Vehicle is red?

In practice: data members are private

Member functions which must be called from outside the class:public

Member functions which are only called from within the class:private

Each class has its own separate scope


C++ overview: Classes and objects

A class: A definition of something

A class: an entity that defines the attributes of an object

(Attributes: data and operations)

Object: an instance of a class

A bank Account is a class

A particular bank account (e.g., yours) is an object


C++ overview : Classes Hierarchy

Classes are organized in a hierarchy: base & derived classes

Define a new class similar to a predefined class:Bank-Account ⇐ Saving Account ⇐ International Account

The new class (derived class):similar to the original class (base class)but with additional attributes

Derived class inherits all attributes of a base class


C++ overview : Header files

Declarations (functions, struct, class) are placed intoa separate file, header file

It holds the external interface to the declarationsIt must be placed at start of any file that will use the declaration// in testComplex.cc

#include <stream.h> // a compiler directive

#include <stdlib.h> // a standard header file

#include "Complex.h" // a local (user-defined) header file

//as if the information in those files was directly typed here

int main() { ... }

#include<..> : compiler searches for the files in the "standard"directory

#include"..": compiler searches for the files in local directory& standard directory


C++ overview: Name-spaces

C++ supports modular programming through namespace

A namespace is a logical unit that contains related declarationsand definitions

namespace: symbol collections which are qualified by namesuch as types, variables, functions

It aims at avoiding name conflicts

using namespace X;

introduces all symbols in namespace X into the currentcontext without qualificationExample using namespace std;cin and cout are introduced


C++ overview: Namespaces

using X::y;

symbol y is introduced as being an abbreviation for X::ye.g. using std::iostream; −− > iostream introduced

You can create your own namespace

Example:namespace foo { void bar(); }

Call with:foo::bar() orusing namespace foo;bar();

Do not put using statements in header files


C++ overview: Namespaces

The namespace feature solve the problem of name conflicts:

When a team tries to link libraries provided by differentprogrammers the use of identical global identifiers will cause aname collision

The namespace feature surrounds the external declarationsof a library with a unique namespace that eliminates thepotentialfor such name conflicts

(The namespace solution assumes that two programmers do not usethe same namespace identifier!)


C++: some recommendation

Constant variable and functions: never modify

Type Casting:int(SomeNumber) (char*)i char*(i) //syntax error

nearly all safe conversions are implicit in C++

Explicit cast: something potentially dangerous

Logical errors

Example: An array index exceeds the array size

C++ environments: rich libraries → Do not re-invent the wheel

Use manual pages under Unix: man <command>

Example: man nint (rounding), man pow (power), man g++,


Principles of OOP: Client/Server model

A server:a class that provides services to objects or programsExample: the class Complex is a provider of services forComplex number processing functionalitiesaddComplex(...); printComplex(..); compareCircle(..)

A client:a class or program that uses the services (functionalities)of a server classa client requests services from a server (class) by invokingone of its functionsExample: c.setCylinder(..); x.addComplex(y);

c© A. Amer Principles of OOP 38

Principles of OOP: Client/Server model

Example: main() is the client of the server “Complex class”int main() {

Complex x,y,z;

z= x+y;

z.print(); z.isEqual(y);

...

}

A good server provides services with a minimum effortfrom the client

Implementation details are hidden from the client:it should not be required to know how the server provides theservices


Principles of OOP

Pushing responsibility from client classes to server classes

Minimize coordination and communication among classes

Minimizing visibility of program elements to other programelements

Making program code self-explanatory

Functions versus classes:

Functions access the same data? Do they belong together?

C++ solution: binding together functions and data

Classes protect private data

C++ solution: private and public members


Principles of OOP Software Development Method

ChallengeTremendous advances in hardware; slower comparableadvances in software

Software Engineering (SE): concerned with building largesoftware systems

Objectives of SE:Reliability: An unreliable life-critical system can be fatalUnderstandability: Future development very difficult ifsoftware is hard to understandCost Effectiveness: Cost to develop and maintain codeAdaptability: adaptive systems easier to alter and expandRe-usability: Improves reliability and maintainability, andreduces development costs



Problem Analysis - (Correct Problem)

Identify data objectsGoal to model propertiesDetermine Input / Output dataConstraints on the problem

Design

Decompose into smaller problemsTop-down design (divide and conquer)Develop Algorithm (Desk check)



Implementation : Writing the algorithm

Testing :

Verify the program meets requirementsSystem and Unit test

Documentation : Key part in the development process


C++ Books, FAQ, ..

Richard Johnsonbaugh and Martin Kalin, Object-Oriented Programming in C++, 2nd Edition,Prentice Hall, 2000, 615 pages, ISBN: 0130158852.Effective C++ by Scott Meyers, 2005, ISBN 0321334876.Victor Shtern, Core C++: A Software Engineering Approach, Prentice Hall PTR, 2000, ISBN0-13-085729-7, 1237 pagesFrank Friedman and Elliot Koffman, Problem Solving, Abstraction, and Design Using C++, 3dedition, Addison-Wesley, 2000, ISBN 0-201-61277-1Paul Wang, Standard C++ with OOP, Brooks/Cole, ISBN 0-534-3731-0, 2000, 2d edition, 570pagesBjarne Stroustrup, The C++ Programming Language, AT&T, 1997Bjarne Stroustrup’s C++ web page and Glossary: http://www.research.att.com/ bs/C++.htmlErich Gamma, Richard Helm, Ralph Johnson, and John Vlissides,Design Patterns Elements of Reusable Object-Oriented Software,Addison Wesley Professional Computing Series, 1994, 416 pages, ISBN 0-201-63361-2C++ FAQ LiteReview of C++: http://ftp.cs.rochester.edu/ nelson/courses/csc_173/review


Documents

COEN244 Programming Methodology IIamer/teach/coen244/notes/topic01.pdfc A. Amer Introduction to C++ 14. C++ overview : Variable scope Multiple ﬁle programs: variables declared in