Introduction to OO Programming in C++ and Java

The lecturer of this course

Dr Vasos PavlikaVasos.Pavlika@conted.ox.ac.ukvp4@soas.ac.ukvpavlika@lse.ac.uk VPavlika@sgul.ac.uk(Vas for short)

Course LecturerDr Vasos Pavlika, Subject Lecturer at SOAS, University of London.Subject Lecturer and online Tutor in Mathematical Economics at SOAS, University of London.Senior Teaching Fellow, SOAS, University of LondonLecturer for the Department for Continuing Education, University of Oxford.Associate Lecturer: New College, OxfordSaturday School Lecturer: The London School of Economics and Political Science.Associate Tutor: St George’s Medical School, University of London.Consultant Mathematician.Previously Senior Lecturer at the University of Westminster.Field Chair at the University of Gloucestershire

Course Book You should get a copy

Programming and Problem Solving with C++ by Nell Dale 4th EditionISBN 07637 0798-8

I will simply refer to this as Dale. E.g. Please do exercises 2-4 on page 101 in Dale.

There is also a version available that includes a student edition of the Visual C++ Program Development Studio.

NOTE: Additional Books

I may refer to the text: C++ from the Ground Up, 2nd Edition, by Herbert Schildt, ISBN: 0078824052

There are many good C++ books around, the net is also a good source of information.I will occasionally be handing out notes.

I can send you the notes (Powerpoint slides) provided you email me first so that I have your reply addresses.

Lecture Format

As of next week, each lecture will comprise a “Warm up Exercise” which consists of the writing of little programs in C++ using your understanding of the previous week’s material, occasionally you may have to give descriptive solutions.

I will be using Microsoft Powerpoint presentations to introduce the material.

There will be Tutorial Questions set weekly or fortnightly which can be used to obtain completion of the course and the associated CATS points.

A series of portfolio exercises and tutorial exercises will be set during the course, these exercises will constitute a log book of exercises that will count as the coursework component for this course.

These exercises will consists of programs as well as descriptions of topics covered in the lectures.

Portfolio Exercises

There will be two portfolio exercises for each 10 week course one in C++ the other in Java. These are assessed and counts towards the award of the CATs PointsYou can not be awarded the CATs points if your attendance falls below 70%.

Getting onto the system here at Oxford

Click TeachingTerminal1conted\ehcmurphyslawLocate quincyTools->option->Build goto compiler and type c:MinGWok

What is computer programming?

Getting a computer to do what would be extremely time consuming and inaccurate if a person was to do it.

OR

Processing input data to produce an output.

Why use Computers?

Computers we know are very good at doing repetitive tasks without making mistakes and without complaining. It would be difficult to get a human to sum the first 10,000 integers and of course to get it right, this would be child’s play for the computer.

The IDE

The IDE (Integrated Development Environment) used here at OUDCE is Quincy Go to programs Locate Quincy Right click on the mouse when on

Quincy to copy it onto the desktop Launch Quincy

The Problem is that computer programming

It is very different from what many of you have done before. It is the least “doable” subject from books. One can not just read about programming and

expect to become a master in it.Requires creative problem solving (thinking)Requires courage and confidenceRequires good organisationRequires practiceRequires a version of C++ at home

The good thing is

We are all natural problem solvers! In our lives we are constantly solving problems. What to have for lunch? Where to go on holiday? How much will I earn this week at

work?

The bad thing is

Many have difficulties generalising their day to day problem solving skills to the precision required for problem solving in computing.E.g. A very simple example

Bobs Bank

Bobs Bank

Problem Given the current rate of interest,

how much will all my customers have in their deposit accounts at the end of…

1,2,3,…N years?

We want to write a program to solve this problem.

Computers are a bit dim!

We have to detail precisely the instructions… There is no Mr Data from Star Trek here, no computer understands English!We must be able to figure out how to solve the problem first (on paper) before we attempt to write a computer program to tackle the task.

Design

InstallationOperation and Maintenance

Analysis and Specification

Implementation

Testing

Developing software: the traditional approach

The Water Fall Method

The Waterfall model

Many people use “code and fix”, which means you sit at your computer, code and correct bugs when or if they are encountered.This is fine if your program is small.For programs with thousands of lines of code, you will have to do things away from the computer

Waterfall Model continued

The standard Waterfall Model for systems development is an approach that goes through the following steps:Document System Concept (what am I going to do)Identify System Requirements and Analyze them

Analysis: what is it that I am going to build?

Break the System into Pieces (Architectural Design) Design Each Piece (Detailed Design)

How am I going to achieve this?

Code the System Components and Test them Individually (Coding, Debugging, and Unit Testing)

Sometimes this is called the implementation phase

Waterfall Method continued

Integrate the Pieces and Test the System (System Testing) Deploy the System and Operate It Maintain the system updating the system when the need arises Bring out later/better editions

This model is widely used on large governmental systems, particularly by the Department of Defense (DOD).

The Waterfall Model

One of the draw backs of the Waterfall Model is that each stage in the cycle (or process) must be completed before moving on to the next stage.This can cause timing problems i.e. one simply does not have enough time to complete each task.Are there other (and hopefully better) ways of doing things?

InitialPlanning

FinalProduct

Analysis

Testing and Quality

Assurance

ReviewingPrototypes

BuildingPrototypes

Developing software: the modern approach (RAD)

RAPID APPLICATION DEVELOPMENT (RAD)

Rapid Application Development (RAD)

DEFINITION a software development process that allows usable systems to be built in as little as 60-90 days, often with some compromises.Drawback: the final product often does not meet the exact requirements originally requested, there is a trade off in requirements.

RAD continued

PRINCIPLES BEHIND THE DEFINITION

In certain situations, a usable 80% solution can be produced in 20% of the time that would have been required to produce a total solution.

In certain situations, the business requirements for a system can be fully satisfied even if some of its operational requirements are not satisfied.

In certain situations, the acceptability of a system can be assessed against the agreed minimum useful set of requirements rather than all requirements.

With conventional methods, there is a long delay before the customer gets to see any results.

With conventional methods, development can take so long that the customer's business has fundamentally changed by the time the system is ready for use.

With conventional methods, there is nothing until 100% of the process is finished, then 100% of the software is delivered.

Hopefully this is still what is required by the user

PROBLEMS ADDRESSED BY RAD

Why Use RAD?Problems with USING RAD

to prevent cost overruns(RAD needs a team already disciplined in cost management)

to prevent runaway schedules (RAD needs a team already disciplined in time management)

Good points for USING RAD

to converge early toward a design acceptable to the customer and feasible for the developers

to limit a project's exposure to the forces of change

to save development time, possibly at the expense of economy or product quality

Bobs Bank (tidy version)

Get the current interest rate (say 6%)Get the number of years ahead we want the results for (1,2,3,N)Get their current deposit valueWork out the calculation

If years equals 1 then use equation 1 and Display the results

If years equals 2 then use equation 2 and Display the results

If years equals 3 then use equation 3 and Display the results

If years equals anything else display an error message

//Bobs Bank#include <iostream>using namespace std;

int main() {double interest;double deposit;double value;int years;

cout << "hello, please enter the current interest rate : ";cin >> interest;

cout << "now, please enter the initial deposit : ";cin >> deposit;

cout << "now enter the number of years 1,2 or 3 ahead to calculate : ";cin >> years;

if (years == 1) {value = deposit*(1 + interest);cout << "Value after " << years << " year is " << value << endl;

}elseif (years == 2) {

value = deposit*(1 + interest)*(1 + interest);cout << "Value after " << years << " years is " << value << endl;

}elseif (years == 3) {

value = deposit*(1 + interest)*(1 + interest)*(1 + interest);cout << "Value after " << years << " years is " << value << endl;

}else{

cout << "Invalid number of years entered" << endl;}

//this is Bank1.cpp

return 0;}

Demo

Please see hello1.cppBank1.cppand explainShow Payroll.cpp (which is a bit advanced for week 1, look at others in folder first)

Practice, Practice, Practice

Computer programming is more like Learning a musical instrument Learning to play a new sport Driving a car

It is an active processIt is an incremental process It constantly builds from previous

knowledge

TRY NOT to get left behind as it is VERY hard to catch up!

Why, What, How, Where and When

Why are you learning to program? What will you learn? How will you learn? How will you be assessed? Where will you learn? When will you learn?

Why are you learning to Program? Or what’s in it for me?

For purely academic interest (I wish!)

To get a job and pay off your loans!

Because you want to move onto more courses here at Oxford or elsewhere.

Why are you learning to Program? Or What is in it for me?

Because it impacts on every subject you take, the programming principles you learn are applicable to other programming languages.

Learning C++ and Java here at OUDCE will enable you to pick up other languages very easily.

Why C++

Supports procedural programming and object oriented programming. What is OO programming? An object is a variable of type class What is procedural programming?

Functions/procedures C/C++ de-facto industry standard

programming language. It works on the network here (I hope! We had

problems last year!)

Why C++

Friendly development environment and good debugging tools.

Cheap for student edition C++ rather than C because I/O

friendlier, easier introduction of functions and strings.

Supports Object Oriented Programming, C does not.

Java is even nicer, does away with pointers (hides their usage somewhat)

Procedural paradigm

Sequential Program runs from top down, one command

performed, then move onto the next

Selection Can make choices in a program

Iteration Can repeat certain parts of your program

which are only terminated when certain criteria are satisfied

OO paradigm

EncapsulationPolymorphismInheritance

Both C++ and Java have these OO capabilities

We will be introducing these concepts in due course

What will you learn?

You will learn how to begin the process of problem solving and designing a solution.  You will learn how to write the

solution to a problem in an unambiguous way. 

You will learn how to verify the solution i.e. Whether it is correct. 

What will you learn?You will learn how to use the C++ development environment to build and debug your programs. You will learn how to translate

the solution into C++ code in a systematic way. 

You will learn how to verify whether the C++ code for the solution is correct. 

You will learn the basic syntax and structure of simple C++ programs.

What you will learn?

You will learn how to apply the basic control structures in C++; sequences, selection, repetition, and subprogram (function) invocation.  You will learn how to construct and use the built in data structures; integer (int), double, char, strings (strictly speaking this is not built in!), arrays, files, structs and classes You will learn the fundamentals of object oriented programming by creating classes and using objects

Overall Syllabus Goal (Term1)

To be able to: investigate and analyse a “real world

problem” Produce and verify a solution formally

Using sequences, selection, repetition and subprogram invocation.

Using C++ implement and test your solution - like we did with Bobs Bank

Introduce OO concepts

How will you learn? Lectures with demonstrations,

tutorials and portfolio exercises. You have a course book with

exercises and tutorials. (Sorry about the American bias!)

Check the internet there is a huge amount of material available

Check the library for resources Try to find your own books to

complement the course book

How will you learn?

YOU will have to take responsibility for learning to program by doing it. IT CAN NOT BE CRAMMED!

You cannot learn to program by reading a book – it is more like learning to play a musical instrument or driving a car!

This is a 10 week course worth 10 CATs points.

We estimate that you should try to put in at least 2 hours at home per week during the week away from the lab here

How will you learn? Tutors (just me this year), are here to get

you out of holes, and give one to one advice on techniques. Suggest approaches to problems NOT to solve problems for you.

I am here to answer any questions on written pre-lab and lab-exercises.

If you do not complete the set work in the tutorial it is hoped that you will complete the work in your own time as I follow on from the previous weeks lecture each week!

How will you be assessed?

Working at home/in other times. You should do this if you want any success.

Do not simply rely on exercises that I set, please work from your book.

If you want you can email me your work each week to look at and to give you feedback.

How will you be assessed?

At the end of each term you will be awarded the 10 CATs points (if you have enrolled of course and created appropriate programs and written answers), you receive confirmation of the award from the University of Oxford

NOT FROM ME.

Resources and To Do List! You need to purchase a course book,

and attempt exercises for next week. Brush up on your basic windows skills,

learn to; rename files create folders and subfolders copy & move files to and from hard

disk and floppy disk delete files and folders

Resources and To Do List!

I will email the Powerpoint presentation to each of you after each lecture for you to have, tutorial questions will be given in the lectures. I will also send source code for demonstration programs.

You may want to download a free IDE and compiler these are available on the internet. E.g.http://www.bloodshed.net/dev/devcpp.html

There is even talk of a site for our course, I will look into this for next week.

Resources and To Do List!

Summary Get C++ on your computer at

home. Send me an email. Buy Course book and do initial pre-

tutorial work. Buy USB disks to take your work

home etc.

The infamous Hello_World program

See programs in Week 1 folder and explain

C++ Week 1.

Elements of a C++ Program.In this text one will be introduced to C++ programming. The material arose from the teaching material used to deliver an Introductory Programming module in C++ here at Oxford over the past 10 years.The first question one may wish to address is what is the shortest C++ program one can write? We will answer this question in due course.

The anatomy of a C++ program

Every C++ program has one main section (actually a function), where program execution starts and terminates. From within main we may declare variables (quantities whose value change during run time), one may make calls to small blocks of code usually called functions which may carry out certain tasks e.g. find the average of a set of numbers passed to the function (this means values that the function acts on, more to be said about this later). Returning to the question what is the smallest program one can write the solution is:

Smallest C++ program

Returning to the question what is the smallest program one can write? The solution is:

main() { }

Shortest C++ program

There is no need to use #include, (you may ask what is #include, this is a compiler directive to include some library files that comes with the systemi.e. a command to the compiler to include some pre written code such as the file iostream) as there is no input or output so we do not need the iostream library (on some earlier versions such as Turbo C++ one has to use iostream.h).

Explanation continuedThere is no need to specify a return value for main(). However, although C and C++ implicitly assume an integer return value for main() you should normally return an int (short for integer) explicitly. Usually return 0;

You do not need to declare an input parameter type for main() but it is better to use (void). int main(void)

Explanation continued

You do not need put any code inside main() but normally you should specify return 0; to indicate to the operating system that everything is working satisfactorily. Some compilers will give an error message if this is not included not all.

#includes

These are libraries. When you send the file to the compiler, the preprocessor substitutes the #include with the contents of the specified library file. In this way you can create and use modules that define functions that you only add to your code when you need them. If you included all the libraries in your programs, they would take a considerable amount of time to process.There are lots of different libraries available for many different purposes.

#include

Note that input/output is defined in a library, so if you want your program to be able to do anything useful you need to use #include <iostream>. In the Turbo C++ IDE environment we have to declare these libraries using the .h extension. So one would write #include <iostream.h>.

Namespaces

A namespace allows you to use your own names without worrying about conflicts with names that other programmers may have used for their own variables etc. However you need to make it explicit that you are using a standard namespace by using namespace std; i.e. using the .std (standard extension). This is only appropriate for ANSI C++ (American National Standards Institute).See namespace1.cpp in directory

Namespaces

If you forget to add this line to your code, the compiler will be unable to recognise any of the keywords you are using (again only appropriate in ANSI C++).

Elements of a C++ program

cout <<cout is the name of the standard output stream, normally the console. The << operator reads the argument that follows it and places it in the output stream that precedes it.>> is known as the extraction operator<< is known as the insertion operatorHere are some valid cout statements:

cout<<

cout << "Hello"; //"Hello" is a string //literal, the term after the // is a comment and ignored by the compiler during compilation. cout << 27; // 27 is an integer valuecout << 2+3; // 2+3 is an expressionCalculations can be made after the insertion operator

cout <<

cout << "result = " << 5+7; One can concatenate operators on a line. Concatenate means to join (amalgamate strings) more about this later.

The new line character

To end a line of output you can use << "\n" or << endl;The “\n” is inherited from the C language (inherit here is not in the sense of the OO term, to be met much later on the course). They are followed by the semicolon. These statements are a LINE FEED directing the cursor to the next line also known as the new line character.

Variables

A variable is a segment of memory that has been reserved for a data item that may change value at run-time i.e. when we run the program. Integer variables are numbers that do not have a fractional part (non-decimal numbers).They can be declared using the code below: int x; so x is now an integer variable which can change during program execution but can only store integers.

More on variables

double variables are real variables (as in real numbers). They can store “larger” numbers than can an int (integers). These are declared using the double keyword (reserved word). Float variables are like doubles but “smaller” declared using the keyword float. Since memory is no longer in such short supply they are falling into disuse

More on variables If you do not initialise a numeric variable when you declare it (i.e. give it a starting value), be sure you initialise it before you read it! You can declare and initialise several variables at conception

For example: int x = 1, y = 3;

Here two integer variables have been declared and set equal to 1 and 3 respectively

= is the assignment operator not to be confused with the equality operator of mathematics or the == in comparisons

More on variables

in these last two statements two variables x and y have been declared. They have also been initialised with the values 1 and 3 respectively

Strings

If you want to use strings remember to use #include<string>Strings are arrays of char (character) data. (or #include<string.h>)Note: When you declare strings, enclose them in " ". char data is enclosed in ‘’ , (single quotes). Non initialised strings are empty, "".

Reserved Words

The C++ compiler uses words like int, double, float etc, and they are therefore reserved, this means that they have special meaning in C++. They are not to be used to declare variables in a program. This means that one can not declare a variable with the name double. In short: Do not use them as variable names.C++ like Java is case sensitive

Identifiers

Identifiers are used to name variables. They must always begin with a letter; subsequent characters may be a letter, number or underscore _ but not a space or other character. An illegal identifier would be 1Time because the variable starts with a numeral and not a letter. Note that C++ is case sensitive so that you can use num1 and NUM1 in your code without confusion. One could also use Int as an identifier but this would not be desirable.

cin

cin is the name of the standard input stream, normally the keyboard. The >> operator reads data from the input stream that precedes it and places it in the argument that follows it. Take note of the following characteristics. the >> operator ignores leading white spaces (<space>, <newline> and <tab> characters) and takes as its input the first characters or numbers in the input stream (from the keyboard or a file). The behaviour depends on whether it is expecting numeric or character data.

cin example

For example we could use: int x; cin >> x;One would probably assist the user by giving them a prompt informing them that a value for x is required.

cin example

When reading integer data, >> may take a + or - as a leading character and continues to read in numeric data until it encounters a non-integer character (white space, non-numeric or decimal point). In the above example, typing +492A will place 492 into the input stream.

cin example

double b; cin >> b;

cin example

When reading floating point data, >> may take a + or - as a leading character and stops at non-numeric, but decimal points are accepted. In the above example, typing .67a will place 0.67 in the input stream.string s; cin >> s;

cin example

When reading string data, >> skips leading white space and reads everything into the input stream up to but not including the next white space.Here is an example of how >> deals with different data types in the input stream.

cin again

int i; double d; string s; cin >> i >> d >> s;

input

Input i d s12 5.9 London 12 5.9

London-3 6.6 Paris -3 6.6 Paris33.54 Hong Kong 33 0.54 Hong

Assignment statements.

Assignments take the form Variable = Expression

// Note it is not read as equals in this context// but as BECOMES as it is

in Turbo Pascal and other languages.Note: Do not confuse the assignment operator = with the logical comparison or test operator = = (this is a combination of two equalities)

Assignment statements

You can combine the = operator with other mathematical operators. For example, x++; and ++x; are shorthand for x = x + 1; similarly x += 5; means x = x + 5; this is known as incrementing.

Arithmetic Operations

Arithmetic operators are used in expressions. + addition - subtraction * multiplication / division

modulo

If both arguments are integers, the result is truncated to an integer, otherwise the result is a floating point number.

% modulo - the remainder of the division of two integers.

Order rules

For example: 1 + 2 - 3 * 4 / 5 % 6 1 + 2 - (3*4) / 5 % 6 1 + 2 - 12 / 5 % 6 1 + 2 - (12 / 5) % 6 1 + 2 - 2 % 6 1 + 2 - (2 % 6) 1 + 2 - 2 1

Order rules continued

Also x *= y + 2;means: x = x * (y + 2)