Lecture 1 - 1pp.pdf

8/10/2019 Lecture 1 - 1pp.pdf

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SENG1120/SENG6120

INTRODUCTION TO SOFTWAREENGINEERING 2

Lecturer:

Dr. Alexandre Mendes (Callaghan)

- room ES249 ES Building

- phone 4921 6172

- email [email protected]

Lectures:

Tuesday 3 - 4 pm and Thursday 3 - 5 pm,

room NURSTH

Workshops in ES409 (five possible times).

Assignments:2 assignments, deadlines in course outline.

LATE ASSIGNMENTS will lose 10% per day or part thereof.

Assessment:

Each of assignments is worth 15%. Mid-semester exam is worth 20%.

Final exam is worth 50%.


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Potential Workshop Times

Lab ES409 has been booked for the

following times:

Tue 5pm-7pm

Thu 11am-1pm

Thu 1pm-3pm Fri 9am-11am

Fri 11am-1pm

Lab sessions are not compulsory, but

attendance is highly recommended.

Students who dont attend to the labsand/or do not complete the tasks will NOT

lose marks.


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TEXTBOOKS -

SENG1120/SENG6120

Data Structures & Other Objects UsingC++, 4th edition,Addison Wesley.

Michael Main & Walter Savitch. This book is available at the Bookstore in

the Union Building.


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Teaching Assistants

Three people have agreed to beteaching assistants. They are:

Dr. Cristian Perfumo Mr. Trent Houliston

Mr. David Bell

Laboratories commence in

week 2 of semester Register yourself in any lab

session


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Communication

There are several means by which Icommunicate with you:

Lectures you should attend every one

of them; Laboratory classes you should attend

each of these as well;

Blackboard you should monitor thecourse site regularly. On the site you will

find: The Course Outline

Announcements

Each weeks lecture slide, released week-by-week

Assignments as they are released

Any other materials I provide to assist you withyour studies


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Programming Language

This course is taught using theprogramming language C++

Your previous programming instruction was inJava, so this represents a change of language

You can install public domain C++ onyour home computer. Options include:

Cygwin (www.cygwin.com) whichimplements a Unix emulation environment

for Windows PCs.

Mac users can download the Mac OS XDeveloper Tools from the Apple site. These

include the GNU compiler for C++

In ES409, we will use Cygwin and your

assignment must be Cygwin-compatible.


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Development

Environment Examples provided in class will

comply with GNU C++ and arecompiled using the compiler called

g++ All labs and assignments must be runnable in

gnu C++, which means, NON-STARDARD LIBRARIES SHOULD

NOT BE USED!!!!


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Development

Environment *** Assignments will be marked as per above.

If you use an IDE to do your work, ensure

that your submission is compatible with the

tools that will be used to mark it *** Computers in ES409 have cygwin and Visual

Studio installed. If you develop your codeusing Visual Studio, NetBeans, Eclipse, Borland

C++, etc, just make sure it compiles and runsunder cygwin.

This is VERY important. When marking, if your

code does not compile and runs, you willlikely lose 50% of the marks straightaway,

because we wont be able to test it.

Plagiarism:

The University has a strict policy on copyright andplagiarism (see the Course Outline which includes alink to the Policy)


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What is C++?

A programming language based on

the language C that was

developed by Dennis Richie in 1972.

C++ was created by Bjarne

Stroustrup in 1979.

C++ is not C. It includes modernconstructs that provide support for

object-oriented programming

techniques C++ had a big influence on James

Goslings development of the Java

programming language.


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C++ and Java

C++:

Has as a major design priority

that the same C program should

run as fast when compiled with aC as a C++ compiler

So there is no run-time boundschecking and no garbage collection

Is a compiled language for which

the compiler produces nativecode

Compiled programs are not portable,and different parts of a program

compiled by different compilers maynot be compatible with each other


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C++ and Java

Java:

Implements the most commonly-used C++ techniques when there

are multiple available in C++

Does not implement features thatwere open to abuse in C++

Tries to prevent the execution of

incorrect programs By increasing error checking by the

compiler

By having the Virtual Machine (VM)throw exceptions for run-time faults

Comprises a bytecode compiler and

a VM, resulting in code that can run

on any platform for which a VM isimplemented


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C++ and Java

Speed:

Initially, C++ programs ran muchfaster than Java programs

Improvements in compiler and

virtual machine technology haveclosed the gap

However, the absence of run-time

error checking should result inequally well written C++ code

running faster than the equivalent

Java code


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Some Differences

Some major differences betweenC++ and Java are:

Java does automatic garbage collection.This is not the case for C++, resulting

in the possibilities of memory leaksand existence of pointers to non-existent (or worse still not intended)objects.

Java does array bound checking. C++

does not check array indexes by default,and this has been used by hackers tooverwrite data values and code, and to

obtain data.

All Java variables are initialised on

creation (zero for primitive types andnull for object references). This is not

the case for C++. Additionally nonvoid functions are not checked to

ensure they return something.


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Some Differences

Some major differences betweenC++ and Java are:

Java provides support for multi

threading. C++ does not, thoughlibrary routines exist for many

platforms

Java provides an extensive standardApplication Programming Interface

(API). The C++ API is small, comprisingsome I/O support, a complex numberspackage and the Standard TemplateLibrary (STL) that provides support for

data structures, collections and generic

algorithms. Other C++ libraries arenot specified by a standard and arevendor-specific in content and interface


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Program Template

A simple C++ program is shown below:#include

using namespace std;

int main() {

cout


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Compiling & Running a

Program To compile the previous program,

(assuming it is stored in a file

called test.cpp you would type:

g++ -o test test.cpp

Alternately a Makefile could be used make test or simply make, depending on

the Makefile

This would produce a file called

test.exe (in Windows) or

test.out (in Unix)

The program would be run in theusual way

Though it may be necessary to

provide the path, e.g. ./test


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Makefiles

This can be used as is with the command

make after a simple edit that provides thenames of the input and output files

Or you could use it to make another program,e.g. make add would compile the file add.cpp,producing the object file add.o and theprogram file add.exe

You could also produce only the object fileusing make add.o

Note the use of labels. E.g. the commandmake clean will remove any .o or corefiles produced by previous activities

A sample

Makefile is

provided on

Blackboard

CC=g++CFLAGS=-c -WallLDFLAGS=SOURCES=test.cppOBJECTS=$(SOURCES:.cpp=.o)EXECUTABLE=test

all: $(SOURCES) $(EXECUTABLE)

$(EXECUTABLE): $(OBJECTS)

$(CC) $(LDFLAGS) $(OBJECTS) -o $@

.cpp.o:$(CC) $(CFLAGS) $< -o $@

clean:rm -rf *.o core


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Primitive Types for C++:

Integers, Floating Point

Numbers & Booleans Java provides 8 primitive types with

precise sets of possible values spanning allplatforms

C++ has many primitive types with rangesdependent on the host architecture andOS

Examples of C++ primitive types include:

The basic integer type int for which machine

representation can be 16, 32 or 64 bits,dependent on host architecture. The keywordsshort and long can be added to int, withint never being shorter than a short int(or short) or longer than a long int (orlong).long constants are indicated as, forexample 1000L.

The modifiers signed and unsigned can alsobe added to int and char, extending the rangeof possible values in the case of unsigned int,and forming an 8-bit byte in the case of signedchar


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Integers, Floating Point

Numbers & Booleans Java provides 8 primitive types with

precise sets of possible values spanning allplatforms

C++ has many primitive types with rangesdependent on the host architecture andOS

Examples of C++ primitive types include:

The floating point types float and double. The

standard does not require constants fornegative and positive infinity as it does for Java

The boolean type is bool which has values trueor false. In old C++ the boolean types were

not specified, and zero was interpreted as false,non-zero to true. Dodgy code like:if (i != 0) being replaced by if(i) was the

result!


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Characters C++ uses the char type to store

characters.

Most compilers use 8 bits and store

ASCII (c.f. Java, which stores 16-bitUnicode)

A character constant is enclosed bysingle quotes, e.g. a

There are many additional escape

sequences for unprintable characters,quotes, backslashes, the bell, etc

The standard header file cctype

(#include ) provides routinessuch as isupper, islower, isalpha,

toupper, tolower to determine orchange properties of characters


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Software Development

Whether you are a student completingexercises and assignments, or a software

engineer working on a major softwaresystem, you development process should

include the following phases: Task specification

Solution design

Implementation of the solution (coding)

Analysis of the solution

Testing and debugging

Maintenance and evolution

Obsolescence

plus continuous DOCUMENTATION

The phases may be performed together,

and sometimes in a different order.Sometimes you will revisit phases and dothem again.

You are expected to practice these phases

through this course (and beyond)


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Sample Problem

Let us use a simple problem to

demonstrate the stages:

Given an interval set by the user

(e.g. -10, 40), display a table forconverting Celsius temperatures toFahrenheit as displayed below:

CONVERSIONS FROM -10.0 to 40.0C

Celsius Fahrenheit

-10.0C Display degrees

-9.0C F in this column

. after they

. have been

. computed

35.0C

36.0C

37.0C

38.0C

39.0C

40.0C


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The algorithm

This is a set of instructions for solving the

problem

Typically expressed in pseudocode, a mixture of

English and program code

Designing the algorithm involves

decomposing the problem into sub-tasks

Then treating each sub-task as a problem that

can be broken into sub-tasks

Eventually the sub-tasks become trivial

enough to be easily coded

For example, our problem has the sub-

tasks:

Input the temperature range from the user

Convert a temperature from degrees C todegrees F

Print the lines of the conversion table


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Pseudocode The problem solution can be described as:

1. Perform tasks that open and set up the output device(screen, file, etc.)

2. Input the temperature range from the user

3. Display the labels at the top of the table

4. For each line in the table (using variables celsius andfahrenheit:

a. Set celsius appropriately for the new lineb. The variable fahrenheit = the result of

converting the celsius temperature

c. Print the temperatures together with labels on anoutput line

Step 1 provides a good example offunctionality that could be provided usingpre-existing software, i.e. exercising codereuse

It is common for C++ programmers to buildup collections of related functions to formpackages that are re-used in many programs

Component tasks should be performed byfunctions that are truly separate from oneand other

So design of one function can be donewithout concern for internal design of theothers

This approach is termed information hiding


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Pre- and Post-Conditions

It is the most basic documentation for

interface definition.

When we define a function, we specify

howit performs its task When we use a function, we are only

concerned with what it does

Documenting the what for a function

is done using pre and post conditions

A pre-condition states conditions thatmust be true when the function is

called Otherwise it is not guaranteed to perform

correctly

A post-condition states what will betrue when the function call has

completed. Provided the pre-condition was satisfied and the

function is correctly designed and implemented


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Example of Pre and Post

Conditions For our temperature conversion problem we

could state the following:double celsius_to_fahrenheit(double c);

// Precondition: c is a celsius

// temperature that is not less than// absolute zero (-273.15 degrees C)

// Postcondition: The return value is

// the input temperature c converted

// to Fahrenheit degrees

The characters // indicate that the rest of the line

is a comment

The brackets /* followed by */ are also valid

As a first step in designing any function you should

write out its signature (return type, name and

parameter list followed by a semi-colon), then the

pre and post conditions as comments

This may need modification if further developmentshows it is insufficient or incorrect

The use of pre and post conditions is extremely

important in team situations

Because it forms a contract between the user of a

function and its writer


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The STL and Standard

Namespace C++ now has compiler requirements

defined in the ANSI/ISO C++ Standard

(American National Standards

Institute/International Organization forStandardization)

Providing much better portability of C++

source code than was previously the case

This standard includes the STL

(Standard Template Library) Library facilities can be used after an

include directive has been placed at the

top of the file using the facility

The items in the STL are identified

using names in the standard namespace

or std. Thus


must follow the include directives


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Declared Constants

Declared constants are definedusing the keyword const before the

declaration, e.g.

const double LOWEST_LIMIT = -273.15;

Note the convention that capital lettersare used for the constant names

The value of LOWEST_LIMIT can never

change during program execution

Sometimes code is more readable ifvalues are used in code, for examplereturn (9.0/5.0) * c + 32;

reads better thanconst double FRACTION_PART = 9.0/5.0;

const int ADDED_PART = 32;

return FRACTION_PART * c + ADDED_PART;

Use your common sense in suchsituations!


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Checking Preconditions

In many situations it is desirable that therunning code can check thatpreconditions hold on entry to a function

This is achieved using assert If the precondition is not satisfied, a message

can be printed and the program halted, or someother defined error action can be taken

The appropriate STL facilities must bemade available by#include

then the assertion can be made, e.g.assert(c >= LOWEST_LIMIT);

After testing and debugging is complete,assertions can be turned off by placing the

statement#define NDEBUGimmediately before the programs include

directives


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Feedback to the

Operating System A programs main function should end

with a return statement that informs

the operating system of its exit state

The OS can then take further actionsbased on the returned value, e.g. running asubsequent application or displaying an

error dialogue

Typically the return value 0 (zero)

indicates successful execution This is represented in cstdlib by the

constant EXIT_SUCCESS

For example:#include

return EXIT_SUCCESS;

Exception handling is provided in C++

(as in Java) and is typically used to

handle run-time errors


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Testing & Debugging

Testing:

Involves running a program and

observing what it does

Only verifies program behaviour for theparticular input used

The tester observes correctness of output,and temporal program performance

Should be implemented in a systematic

and planned way When choosing test data you

should:

Know what output a correct programshould produce for that data. This may

involve manual calculation.

Include inputs that are most likely tocause errors


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Test Data

Boundary values should be identified.These are inputs that sit one step awayfrom a different kind of programbehaviour. E.g. for:int time_check(int hour);

// Precondition: hour lies in the// range 0


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Debugging

When test data reveals erroneous

output, the first step is to

understand why the bug happened.

Then correct the known error(s).Finally re-run all the test cases.

DO NOT:

Change suspicious code just hoping

things will get better Assume that even controlled

rectification will not change things that

previously worked properly

It is a truism that it is more important when

performing maintenance to ensure that whatpreviously worked continues to work than it

is to ensure the new feature works properly.


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Exception handling

Similar to Java, but not as flexible

due to the everything goes nature

of C++.

try {

// Try the program flow

}

catch(Argument)

{

// Catch the exception}

You can catch any type in C++. It

will just depend on what you

throw.


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Exception handling

#include


int main()

{

int StudentAge;

cout


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Exception handling

Types of exception:

throw: generic exception; catch()

throw : throws a type

throw 5; catch(int param)

throw error; catch(string param)

throw a; catch(char param)

Handling cin >> exceptions

if (cin.fail()) {throws;}

cin.clear() clears cin so the program

can continue.


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Your first code

In collaboration with the person sitting beside you,

write a pseudo-code for the temperature

transformation problem. Include error checking

procedures.

All elements required for the task are included in

this lecture slides.

Think about the documentation

Pre- and post-conditions

A brief explanation about the variables and

constants

Any limitations

1. Input the temperature range from the user and a

step for displaying intermediate values

2. Perform all error checking procedures

3. Display the labels at the top of the table

4. For each line in the table (start, intermediate and

end temperature values), print the temperature in

Celsius, then calculate its equivalent in Fahrenheit

and print it.

5. Ask the user if he/she wants to repeat the

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