Software Design and Development Study Notes

Development and Impact of software solutions

Social and Ethical Issues

Rights and ResponsibilitiesThe Developers of Software solutions have many rights, which they own and

owe towards the users of their software. These rights and responsibilities are: Authorship

A developer has the rights to own the ideas and software that they develop The developer has a responsibility to protect their interests in the

development of the software and the rights of the people who are involved in the development of the product

The right of authorship is known as copyright Future developers must respect copyright issues if they wish to use new

ideas or modules in their software. Copyright means that people cannot use any items in the product

Reliability Reliability refers to the guarantee of the product to run as advertised and

according to the manual for a certain period of time Under the reliability issues the software developer has the responsibility to

provide service updates for any faults in original product for at least the duration of the warranty

The software must be able to function with acceptable response time, and fail to crash or une

Quality The software must fulfil software standards Quality ties in closely with reliability. The quality of the product must be

satisfactory so that it is able to be reliable under general circumstances The software must be consistent within the program and compared to other

programs performing similar function. It must also be consistent with the typical design interface of the operating system on which the program runs

The program must have quality documentation available to the user. The quality of the documentation is defined by how well it helps the user perform the basic tasks of the program. How the documentation deals with common troubleshooting problems. Finally how easy the user manual is to understand relative to the experience of the users of the program

Response to problems The developer has the responsibility to provide adequate response to

problems users of the software encounter They must attempt to rectify all security issues especially in software

accessing the internet or running over a network Developers must implement problems identified in the program as quickly as

possible Code of Conduct

The developer has the responsibility to make sure that all aspects of their software cohere to all legal issues such as intellectual property and copyright

They must acknowledge all people who contributed to the production of their software

Adhere to privacy laws and rights- 1 -

Use of appropriate prompts and language used in both internal and external documentation such that it is not racist, offensive or in any way degrades any persons of society, especially the users of the software

Viruses Developers must make sure that their software does not pose any problems

to the functioning of their computer. The software must not carry any viruses Developers must ensure that viruses cannot be spread or created by the use

of their software

Piracy and copyrightSoftware piracy is the theft of computer programs from the developers.

Such piracy can include the illegal installation of files on one machine or a group of machines that is outside the terms of the license agreement of the software. It is also the illegal sale and distribution of copyrighted software. Either of these actions results in an increase in the price of the product for ethical users of the software as the company is not receiving the profits necessary to develop the software further. Two aspects of piracy are intellectual property and plagiarism

Intellectual property - is the personal ownership of the creative ideas that develop from an individual’s mind or intellect. Types of property include patents, trademarks, designs and confidential business information. However in today’s computer world determining intellectual property is a hard task as many people will create software based on specific ideas. This is why copyright and plagiarism laws have been put in place to protect this intellectual copyright

Plagiarism – is the theft of the ideas and expressions of another person. Often this includes the steeling of code and design in programs. To prevent plagiarism and protect intellectual property license agreements and copyright laws have come of place as outlined below

License AgreementsLicence agreements give the user different rights according to the conditions

of the use and purchase of the software. The three main types of agreements are shareware, freeware and public domain software

Freeware – gives the user complete access to the program without having to pay any money. However any of the code cannot be copied or modified. However the program can be freely distributed

Shareware – is distributed software for trial purposes before purchase. It can be freely distributed, but after the trial period is up the person user must pay an amount of money – generally less than the cost of commercial products directly to the developer. The code again cannot be copied or modified

Public domain software – are any programs that are freely available for copying and modification. Such software comes about because the owner has forfeited copyright or has been dead for over 50 years. Such software are good tools for new developers.

Networks be coming increasing common so many programs have evolved to encompass network use. This is done is one of two ways. The program either has centralised software where a single copy is run from a central computer. The software license then needs to cover the each machine that uses the software. The second method is distributed software where each computer has a copy of the program on the machine but runs the program from a central database of information.

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EULA – End User License Agreements are used to prevent the illegal re-distribution of software. There are three types of EULA agreements.

Single Use licences – allow the purchaser to install one copy of the software on one computer only

Multi-use licences – provide one copy of the software to be distributed on a specified number of machines

Network licences – provide the use of the software across a network with a specific number of computers

CopyrightCopyright is the legal protection of computer programs against illegal

plagiarism or piracy. It provides the developer legal right to control the use of their product. The protection given by copyright does not usually protect the idea behind the program, but the way in which the idea is expressed. Current copyright laws allow the user to:

Make or have backup copies of the original program in case the original software is damaged

Use a copy of the program for research or study purposes. Ie look at the code and layout of the software to see how such programs interact. However the code cannot be modified, copied or changed

Reverse EngineeringReverse engineering is the process of reading source code and translating it

to an algorithm. Reverse engineering is only illegal if it has been carried out by a person who does not own the program and then redistributed the code in another language or different format.

National/International views to piracy and copyrightThere are many current day events that effect the issues of piracy and

copyright. Some examples are highlighted below: In Indonesia in 2005 to prevent the use of pirated software which was a

major problem. To overcome this issues Microsoft charged people in Indonesia about $1.50AU to legally own the software and reduce the rates of piracy in the country.

Application of software development approachesThere are four different types of approaches to software development. The

four different types are Structured, Prototyping, Rapid Application (RAD) and End User (EUD). Below is a summary table of the of each types of approach

Approach

Advantages Disadvantages

Structured

Thoroughly testedShould meet the exact requirements of usersUses a range of experts

CostlyTime consumingRequired a wide range of different people with different skills

Prototyping

Relatively fast developmentModels a larger project, thus allows easier modification and visualisation of the end product

Many be difficult to implement as a full working program

RAD Fast development (RAD)Relatively cheap

Many not meet exact program requirements

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Uses considerable amount of existing reusable code

Many involve copyright and intellectual property of others. (Developers must be careful not to break laws)

End-user Should meet exact user requirementsQuick and cheap

Limited to simple project and limitations of application programs

Structured ApproachThe structured approach follows

the software development cycle. It considers the program on a whole and takes logical steps to arrive at the end product. The process is time consuming and costly and necessary and suitable to tackle a large program.

Because the process is long a complex often a team of people is required to tackle the problem. Some of the people include: system analyst, designers including software engineers, programmers, graphic designers and consultants, managers, trainers and users. The software analyst is the person who is generally given control of the management of the project and is the first level of communication between the management and development team.

In development the structured approach follows the development cycle as on the right. Each step is explained in more detail below:

Phase 1: Defining the problemThis step is used to help the team thoroughly understand and define the

problem itself. If the problem is not properly understood the program may end up solving a different problem than the one that needs to be solved. If this step is not properly sorted out, it will take considerable time and cost to fix the problem later on. Management is also completely involved in this process

Phase 2: Planning the solutionThis step involves a further understanding of the needs and requirements of

the end users. This step also looks at the choice and methods of how the problem will be solved. To get the needs of the end user four main tools are used: written documents, questionaries/surveys, interviews and observations.

Planning is a complex phase during which each of the following steps will be undertaken:

Planning the data and program structures to be used Designing algorithms Planning the user interface Scheduling the project Choosing a programming languageThe above will be looked at in more detail later on

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Phase 3: Building the solutionThis step requires the full involvement of the development team (analyst,

designers, programmers, users and management). Each member must have a clear understanding of the goals and the overall plan for the project.

The solution to the large program is usually broken down into smaller modules. This process is called step-wise refinement. This makes the program much simpler to tackle. The reasons for refining the problem are:

Greater efficiency as each module can be separately designed and tested All members of the team can be involved at the same time Modules can be separately testes and modified without affecting the

entire project It is easier to debug if one module is tested at a single time Modules can be reused or modified and reused at some other similar point

in the project or in other projects.

Phase 4: Checking the solutionChecking the solution is a continuos part of the cycle. This testing involves

the program using real data and can include acceptance and beta testing. Acceptance testing involves users to test custom software. Beta testing is used in application software development with the potential users of the product. The point of all testing is to make sure the program meets the requirements of the originally defined program. After all testing has been done and errors fixed, the program will be passed to management who will approve and implement the program.

Phase 5: Modifying the solutionOften it is necessary to modify the program after it has been implemented so

it works more efficiently, copes with improvements in hardware and software changes or expansions to cover more tasks. Changes at this stage can be very costly and are only undertaken is they are small or crucial to the operation of the program. Otherwise the analyst will suggest the cycle be started again and a new version of the program released.

Prototyping ApproachThe prototyping approach involves building a working model of the program

that is evaluated by the users. Usually the model is then modified and evaluated further, and may finally become the entire solution. The approach usually involves a small team of programmers and one or more users. Beta testing is often used by such an approach.

Prototyping is used for many reasons including quick development of the program, a clear view of product requirements, to allow trial-and-error testing for new concepts, for demonstration purposes or to use as a substitute for a more expensive program. This approach is also often used a the beginning or planning stages of the structured approach.

Two types of prototypes are used: Concept prototypes – are prototypes developed to gather information to

be used in another program. The program is not intended for a full working program itself. 5GL languages are often used for this approach because they are more dynamic and allow better feedback.

Evolutionary prototypes – are prototypes, which will later become full working programs. A model is produced and then later refined This approach is used is the planning stages do not provide enough information on the requirements of the program.

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Some aspects to note in this approach are that the emphasis of the program is on the menus, windows, input and output processes. Little security or error recovery is considered. There is also reduced documentation compared to the structured approach, which leads to harder maintenance of the system.

RAD approachThe RAD approach is any method of software design that uses tools to

quickly generate a program for a user. The approach uses existing solutions or code, CASE tools and templates. RAD also lacks formal programming stages.

This approach involves a very small team, low budget and minimal time on small-scale projects. It is taken across a range of coding languages.

End user development approachEUD is where the user adapts existing software tools to suit their needs or to

obtain a solution to a problem, which they have. This is an informal program production usually written in 4GL languages. Programs usually written include adding menus to applications for additional functions or repetitive actions, or adding macros to larger programs. One disadvantage is that end users often duplicate the same tasks.

Methods of ImplementationThere are many ways in which a new software solution can be implemented.

These methods are:Direct – the new software takes over from the old software solution from a

particular date onwards

OLD NEW

Phased – the new software solution is gradually introduced into the environment one step or item at a time while the old system is gradually phased out

OLD OLD OLD NEWOLD OLD NEW NEWOLD NEW NEW NEW

Parallel – both new and old systems run at the same time. This is helpful in many ways. If the new system has an error or flaw this can be picked up while the old system is still running, therefore data is not lost. It can also see if the new software solution is appropriate for the environment in which it is running. If the new system is then to be used, the old system is directly removed and the new system takes over, vice versa if the new system does not function properly or does not meet the needs of the user

OLDNEW

NEW

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Pilot – a complete section of the environment or organisation is directly converted to the new system to see if the new system works in the organisation. If the new system is appropriate then the entire organisation is converted to the new system

OLD OLD NEW NEW

OLD NEW NEW NEW

Current Trends in software development

OutsourcingOutsourcing is the process whereby a company needing software services

hires an outside organization to handle all or part of these services. The range of activities performed includes regular maintenance of systems, modifying or installing programs etc. Contracts can range from 1 to 10 years.

The reasons for outsourcing include: New technology is readily available Development time is faster Gaining experts in the field Cheaper Higher quality results Resources not available internally Better response to changeThe advantages of outsourcing include saving of money on as a result of

lower staff numbers and effective use of scarce technological assets. Disadvantages include the difficulty in breaking unsatisfactory contracts; the outsourced company may not understand the ethos of the organization, and the organization can loss control of the system and be unable to fix any minor problems.

Popular approaches Increased ability for EUD Editors and compilers for ‘non-programmers’ to generate simple

programs and websites Greater distribution of code libraries Use of hypermedia – the use of multimedia in which a user can browse a

program at their whim

Popular languages 3GL-5GL languages BASIC/QB/VB C/C++ Prolog SQL Java Cobol

Employment trendsEmployment in the software development field has been increasing over the

last few years since the .com crash. This comes about due to the increase of the - 7 -

use in computer technology in many other areas, rather than just the creation of computers. Science and medical fields are increasingly requiring processor technology, increasing the number of jobs available.

The jobs available also have changed where many programmers work on short contracts with companies, or as consultants. More skilled jobs, and management positions are looking for higher education graduates, simply for the training and skills they have.

NetworkingNetworks in work places are becoming increasingly abundant, so software

developers have developed ways to cope which such systems. These include the development of operating systems specifically run networks or have the inbuilt capability to provide small networks with adequate security. Also application software has been developed to cope with networks and the use of many peripheral devices.

Customised off-the-shelf packagesThese types of products are becoming more readily available, and are often

offered as suites of packages with integration with each other to perform a wide range of tasks. These types of software are often more reliable (being tested in a wide area of applications), reduce costs for the end user, can be available earlier and more easily updated that custom software produced for the company.

The use of CASE tools in software developmentCASE Tool stands for (Computer-Assisted Software Engineering). These tools are designed to aid the software developers in the design of their applications and HardwareThe purposes of CASE Tools are:

Problem-tracking tools Data modelling Document generation for the creation of user manuals, installation

instructions and troubleshooting issues Reverse engineering tools to convert existing code into algorithms Tools for structured analysis of design and scripts Simulation tools such as those tools that allow prototypes to be built Help the maintenance team to improve bugs and issues within existing

programs. These include the use of Simulators Debuggers Test drivers Instrumentation

CASE Tools allow and provide the following Show the relationship between global variables and various parts of the

program Identified problems within the program Support for design specifications including the preparation of documents and

their diagram tic forms Produces uniform design across a program Support for software design

Support for design implementation including language-specific editors that provide some support for the coding phase etc…

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The Software Development Cycle

Defining and Understanding the problem

The software development cycles first step is to define the problem that the software needs to be solved. This stage of the cycle involves being able to understand the software being

developed such that the end product is:

Dependable: the program should be reliable, secure and safe Efficient: the program should not waste resources, such as memory Usability: the program should be straight forward for the program to

use Robustness: the program should not fail under normal circumstances

of use or by minor errors made by users Maintainability: the program should be able to evolve to suit the

users changing needs

The defining and understanding the problem stage involves looking at multiple issues involved with the program including the needs, screen design, objectives, boundaries, determining feasibility and social and ethical issues.

NeedsA need is anything that is a necessity for the program. This can include

output being shown as two decimal places, or the requirements of the user to operate the program for extended periods without suffering strain or injury. They are different to Preferences of the user, which are elements of the program that the user would rather work with. Needs are based around the health and safety of the computer user and are essential to the operation of the program

Screen DesignAspects of screen design include the layout of the screen including fields,

button and menu layout. Colour design and aesthetics are also an important issue. Other aspects of screen design are appropriate and concise messages providing useful feedback for the user that does not use technical language beyond the capabilities of the user. The message should also not blame the user for the error. Also appropriate icons and images for shortcut menus or actions should match the outcome of the programming

ObjectivesThe objectives of the program are the aims and outcomes, which the

program must achieve. All objectives should meet the needs of the user. Objectives must

Meet social and ethical issues Use appropriate methods of information display Providing adequate input and output methods Use of relevant data types for information display

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Providing clear and understandable methods of navigation between screens

BoundariesThe boundaries are the limits or borders in which the program can operate.

The borders are determined by what is feasible for the program and what the needs of the users are. The boundaries of the program are also determined by the hardware restrictions the program needs to run on. For example if the program runs over a network. On home computers or on high powered operating systems

FeasibilityFeasibility determines whether the

problem is worth solving and whether a software solution can be adequately developed and fit into the above criteria. There are two issues that must be considered. Can the program actually be developed, and is it worth proceeding with the program depending on the requirements of creating it. The specific issues in feasibility are:

Constraints – these are any restrictions or limitations placed on the production of the software such as money and time

Budgetary feasibility – this determines wether or not the program can be designed, built and put into practice within the budgetary constraints of the project

Operational feasibility – this refers to the skills and resources needed to create the program and maintain it. If the program requires a greater range of skills and resources than can be gathered, the program cannot be built. This skills and resources also refer to those of the user. This asks whether the user has the skills, time, money and resources to firstly run the program, and then maintain it.

Technical feasibility – the availability of hardware and software for the product. Can the program run on the software that the intended users have without having major problems

Scheduling feasibility – refers to the time constraints of the development of the program. This is determined by when the program must be released, or depending on how much money the project has, the cost of employing the programmers, installations and other aspects may constrain how long these people can be employed for, and therefore how long the program can have for it to be constructed

Possible alternatives – this looks at the other options available to solve the problem. This could help in the saving of time, money and effort to make the development of the program easier and quicker. However, each of the other available options must be studied and advantages and disadvantages, to determine whether this program is a better choice than the one currently being studied

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While all of these are areas of feasibility, there are four main areas of feasibility. These areas are Budgetary, Operational, Technical and Scheduling feasibility

Social and Ethical issuesSocial and ethical issues must be taken into consideration. All the issues

should be considered, but the following two should be especially considered in the when defining and understanding the program.

Lifestyle – how the program effects the lifestyle of the end user. If the program drastically alters the lifestyle of the user and their interactions with the world in a way that they do not want, then the program may not be useful. The advantages of the program must outweigh the disadvantages of the program on the impact of the end user’s lifestyle.

Work – how the computer program impacts the work and working opportunities of the end user. As a results of program, jobs are lost through the automation of tasks, but other jobs are created as people are required to use and maintain the new software solutions. Programs can mean that through e-mail the work of a user can be taken with them everywhere, and the entire world is always connected.

The major concern with all the program software in reference to the above two categories is whether the actions and effects on both the lifestyle and work of the end user is unethical. Programs that are written to destroy the jobs of people or create havoc in the home and office are unethical. In a moral sense the issue of cutting jobs by releasing new software must also be considered.

Design SpecificationsDesign specifications involve that data types, data structures, the types of algorithms to be used, and other aspects of software design such as the physical representation of the programs over algorithm are needed to be considered when understanding and defining the program. See the Programming Elements notes for more information on this section.

Data typesThere is a range of data types that include

Data Type Characteristics Example/sInteger Positive or negative whole number -23475Floating point

Real or decimal number 45.994

Character Any letter, number, command, punctuation or symbol

$^&*

String Sequence of characters with a single identity

Hello World!

Boolean Variable with one of two possible outputs True or False

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Data structuresThere are four types of data structures

Data Structure

Characteristics

Array Variables of the same type stored in sequential memory locations

Record Set of related fields storing data of different typesArray of Records

Set of related records stored as one entity

File Set of related data items of various types stored as one entity eg sequential files

AlgorithmsThere are three types of algorithms that can be used: Sequence – a logical order of commands Selection – the carrying out of commands based of a choice Repetition (iteration) – the continual carrying out of commands until a

criteria is met

Data validationThis involves the checking of data to see if it is the correct type and meets

any restrictions imposed by the program. There are two types of checks: Reasonableness check – to check the input against the data type Range check – to check the input data against the boundaries of the data

type. The makes sure no limitations of calculations, output etc. are exceeded

The user’s perspectiveThe important aspects to the user must be considered in the design

specification. These include The appearance of the program and the ease of use – the user interface

must be ‘user friendly’ containing drop down menus, clickable icons and keyboard shortcuts. The interface must be intuitive and have simple navigation

The programs functionality – this refers to the programs ability to carry out the required tasks. This should be designed such that the tasks is carried out in the easiest and simplest way

The programs scope – this refers to the boundaries of the program and the range of tasks carried out. The users would want to know if future needs and any maintenance requirements can be done so in an easy and convenient way.

ModellingA system is a collection of interacting parts working together to achieve a

particular task. Such aspects include, coding, hardware, procedures, raw data and personal. All these actions can be modelled in different ways

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IPO (Input-Process-Output) DiagramsShows the connection between any input, the process to be carried and the

output achieved

Story BoardsShows the designs of the screen of the program and the link between them.

They can be linear or non-linear

Data flow diagramsThese diagrams provide detail to the handling of data in the program. There

are four symbols used and these are as follows

A Process An external entity

Data flow Data Storage

Context diagrams

A Process An external entity

Data flow

System FlowchartIs a diagrammatic way of representing the flow of both data and logic

through a system. This is the primary tool for documenting systems. There are many different symbols that can be used, but below are the main ones

Input/Output

Manual Operation

Paper Document

Direct access storage device

Online display Decision

Online Input

Telecommunications link

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Process Magnetic Tape Output

Structured diagramsThis models the hierarchy and sequence of processes to be carried out

Communication Issues

The need to empower the userThe user needs to be consulted on a regular basis so that the user feels ‘in

control’ of the software development. Ideas from the user should be included in the software, or where ideas have been left out, reasoning for this should be explained to the user. Further users should be provided with a choice of functional option within the final product. Satisfaction with the end design is decided by the user.

The need to acknowledge the user’s perspectiveThe user does not need to know the technical information about the

software, however they will be the ones using the software. Therefore specific requirements set by the users that will make the program function better for them should be taken into consideration

Enabling and accepting feedbackFeedback should be encouraged, as it is cheaper and easier to solve

problems early on in the development cycle. Prototypes are effective ways of noting user reaction and help clarify development needs.

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Planning and design of software solutions

Processing strings

Extraction of data from a stringThis process removes a string or set of characters from a string to use in

another. This is equivalent to the copy command. The original characters are left in the stringBEGIN ExtractString(start, length, data)

Temp() is an empty arrayIndex = StartCharacters = 0WHILE Characters < Length

Temp(Characters) = Data(index)Increment indexIncrement Characters

END WHILEData = temp

END ExtractString

Insertion of data into a stringThis is the process of placing strings or characters into a string. This is

equivalent to the paste command, where the characters are inserted into the correct position in the existing string. This process often involved multiple stepsBEGIN InsertString

Last = number of items in array – 1Start = index of location where strings are to be insertedExtractString2(start, last)InsertNewReplaceString

END

BEGIN ExtractString2(Start, last)Index = startCounter = 0WHILE index <= last

Temp(counter) = array(index)Increment counterIncrement index

END WHILEEND ExtractString2

BEGIN InsertNew(Start)Index = startcounter = 0last2 = number of items in arrayinsert – 1WHILE index <= last2

Array(index) = arrayinsert(counter)Increment counterIncrement index

END WHILEStart = index //returns the value of start via the parameters

END InsertNew- 15 -

BEGIN ReplaceString(Start)Index = startLast3 = number of items in array Temp – 1Counter = 0WHILE count <=last3

Array(index) = Temp(counter)Increment indexIncrement counter

END WHILEEND ReplaceString

Deletion of data from a stringThis is the process of removing certain values from a string. This process

generally creates a second array to place the new string in minus the characters that are to be removed

BEGIN DeleteString(Start, Length)READ DataLast = number of items in array – 1Index = 0WHILE index < Start

NewArray(index) = Array(index)Increment index

END WHILENewIndex = indexIndex = index + LengthWHILE index <= last

NewArray(NewIndex) = Array(index)Increment NewIndexIncrement Index

END WHILEEND DeleteString

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Standard searching algorithms

Linear SearchBEGIN

First = 0Last = number of items in array –1Index = firstREAD targetValueWHILE index <= last

IF array(index) = targetValue THEN**insert code depending on actions of finding value

END IFIncrement index

END WHILEEND

Binary SearchBEGIN BINARY SEARCH

BEGIN INITIALISA TION set Lower to first positionset Upper to last positionset Foundlt to FALSEget the Target name END INITIALISATION

REPEAT

set Middle to (Upper + Lower) divided by 2 set Middle to integer part of Middle

IF Target = data at Middle position THEN set Foundlt to TRUE set PositionFound to Middle ELSE

IF Target < data at Middle position THEN set Upper to Middle - 1

ELSE set Lower to Middle + 2

ENDIF ENDIF

UNTIL Foundlt OR Lowe r> Upper

IF Foundlt THEN report PositionFound ELSE report Target not present'

ENDIF

END BINARY SEARCH

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Sorting Algorithms

Bubble SortBEGIN BUBBLE SORT

BEGININITIALISATION set End to last position END INITIALISATION

WHILE End > first position set Current to first position

WHILE Current is less than End

IF data at Current > data at (Current + 1) THEN Temp = Current + 1Current + 1 = CurrentCurrent = Temp

ENDIF increment Current

ENDWHILE

decrement End ENDWHILE END BUBBLE SORT

Selection SortBEGIN SELECTION SORTINITIALISA TION set EndUnsorted to last position END INITIALISATION

WHILE EndUnsorted > first position set Current to first position set Largest to data at Current set PositionOfLargest to Current

WHILE Current < EndUnsorted increment Current

IF data at Current> Largest THEN set Largest to data at Current set PositionOfLargest to Current

ENDIF ENDWHILE

Temp = PositionOfLargestPositionOfLargest = EndUnsortedEndUnsorted = Tempdecrement EndUnsorted ENDWHILE END SELECTION SORT

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Insertion SortBEGIN INSERTION SORTINITIALISA TION set First to first position set Last to last position set PositionOfNext to Last - 1 ENDINITIALISA TION

WHILE PositionOfNext >= First set Next to data at PositionOfNext set Current to Position Of Next

WHILE (Current < Last) AND (Next > data at (Current + 1)) increment Current set data at (Current - 1) to data at Current

ENDWHILE

set data at Current to Next decrement PositionOfNext

ENDWHILE END INSERTION SORT

Customised-design logic used in software solutionsThis section includes identification of inputs, processes and outputs,

representation as an algorithm, definition of required data structures and thorough testing. These areas are described elsewhere. The below two sections are specific issues

Access the data structures – specifically filesThere are two ways through which data can be accessed. These are: Sequential – the search starts at the beginning of the file and goes

through all the data in order until the required data is located Random – in this context is direct access to the storage location of the

data. Such location is difficult, so hashing is used, whereby the number of data storage elements needed is set before the data is stored. The addresses have a range of values and the data is located within this range. This access is also relative access.

Using random numbersRandom numbers are very important for many programs that rely on chance

or random events. Most languages have a simple syntax used for generating random numbers. Care must sometimes be taken when programs generate random numbers. Sometimes these numbers occur in the same sequence.

Standard modules (library routines) used in software solutionsStandard modules are very useful especially for commonly done tasks.

However when creating a library routine, certain elements must be considered.

Identification of appropriate modulesFactors that determine whether modules can be reused include: Choice of language for implementation Type of interface, since some modules may be adapted better for different

methods of display- 19 -

Social and ethical issues such as intellectual property and copyright The specific task being performed Standard methods of construction of modules so other programmers can

understand them

Consideration of local and global variables and parametersThe use of global and local variables must be carefully considered as to

whether the data contained within the variables will be required to other aspects of the program. Also depending on the amount of times the variable is required, the use of parameters may be considered to pass this value and reduce the overall size of the memory required for the program

Appropriate testing using driversA driver is a special subprogram that is used as a temporary code to test the

execution of a module. A driver allows a module to be tested without the mainline of the program. The driver passes values to the module and provides a target for it to return its values

Customisation of existing software solutionsCommercial packages and software are increasingly providing the means for

end users to create customised software for their particular problems. Many programmers are choosing to use off the shelf customisable packages since they are cheaper and easier to use than creating the software from scratch. Providing the intellectual property and copyright laws are not broken, this is often a viable alternative

Selection of language to be usedWhen writing a program the development team must decide which language

and language type they will use. One of the considerations is how the program operates on a whole. The two options are

Sequential – a language where the programmer defines the order in which modules are executed. Some examples include Qbasic, C, C++

Event Driven – these languages are where the operator of the program determines the order in which modules are executed. As the name says code is executed based on the events of the program determined by the user. Examples include Visual Basic, Prolog

Selecting a language will have ramifications for the hardware required to run the program. Some examples in how the language effect hardware include:

Amount of memory that is required for the program to run The processor speed of the computer depending on the operations the

program is performing. Such as high speeds for graphics or design work compared to lower speeds for word processing

The size of the hard drive which the computer has to store the necessary data for the program on the machine

Documentation of software solutionThe documentation includes the representation of the software solution. This

section includes the other diagrams as above in the notes. Also data dictionaries are includes, as described below

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Data DictionaryThe data dictionary can be used to show the information and type of

variables or in showing the information in a database. An example of the data dictionary is below. There are four fields that are Field Name, Data Type, Size and Description

Field Name

Data Type

Size Description

User Name

String 8 Stores the user name of the user

Password String 8 Stores the password of the userAdministrator

Boolean 3 Stores whether the person is an administrator or not

Implementation of Software Solutions

Interface design in software solutions

Identification of data requiredThe type of data required to be input into the program initially influences

screen design. Graphics, text, sound and mouse movement all need to be handled differently. Once this data is determined it can be easier to design the layout of the screen, and also the style of programming to be used (sequential or even-driven)

Current popular approachesPopular approaches often influence screen design. GUI systems are the most

common at present, therefore new software will need to have a interface that will be able to cope with such an environment. Other designs change if the system is implemented on a microwave or other microchip device. Other issues include the location of menus (eg the File menu is located at the top left and always contains the save, open and new commands). Other trends include the use of highlights to show which menu item the mouse is over, the use of keyboards shortcuts to menus and the implementation of hierarchical menus.

Design of help screensAll interfaces require a help system. The design of the help system should

consider the following: Non-intrusive – operational only when requested by the user Flexible sizing Consistency – always appearing in the same location, with similar colours

and layout Navigation – ease of moving around the help application with links,

buttons and tabs Simplicity – providing basic explanations of solution to a problem Contextual – help is structured to the task being performed Style – help should be positive and provide actions of course.There are also a variety of ways in which help can be provided to the user Context help – small assistants within the program when a specific

problem is encountered Browser help – large help screens and a database of information, often

with a search function Procedural help – screens that take users step by step through a problem Tutorials

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Error messages

Audience identificationThe interface also depends upon the audience who will use the program.

Factors include Age Level of expertise Language level (use of jargon) Disabilities Level of human interaction

Consistency in approachAt all times the interface must be consistence within the program. This

includes adhering to traditional methods of use and design, such as Command-S and a disk icon for Save. Also consistency with colour, font, and background are important

Language syntax required for software solutions

Meta Languages: BNF (Backus Naur/Normal Format) and EBNF

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Meta Languages: Railroad Diagrams

The Role of the CPUThere are many sections of the CPU, which are used when procedures are

carried out. These sections are listed below along with an outline of their function ALU (Arithmetic logic unit)

This performs the arithmetic calculations, logic operations and controls the speed of operations

Registers Temporary storage holding areas. The register stores the address locations

for instructions, results of calculations and flags which indicate the results of comparisons

Accumulator A special register which holds the result of the last computation carried out

by the CPU Buses

Pathways that join components of the computer

The CPU also must deal with the instruction, which are given to it. The instruction is given in machine code (object code). Each character in the code is represented by a byte (a group of 8 bits). The Computer Word is the number of bits that a can be processed at one time

The CPU operates on the commands that are sent to it. The CPU follows the same process each time a new command is received. This process is called the Fetch-Execute cycle. The cycle is outlined below Fetch

The instruction is retrieved from the main memory. The program counter register stores the memory address of the next

instruction to be carried out Decode

The type of instruction to be carried out needs to be decoded The Opcode is a set of binary digits which tell the CPU what process to carry

out The two Operands are the data which needs to be processed

Execute

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This stage carries out the instructions Store

The stores the result of the instruction carried out in the accumulator. The data in the accumulator is then copied to the RAM or registers

During the operation of a program, it may call upon subprograms contained within the CPU to perform specific tasks they different types of subprogram are Subprograms written by the programmer as part of the program Subprograms included in the development structures of the programming

language. These generally form part of a library. An example includes producing a random number

Subprograms built into the operating system. An example would be the print command.

DLL’s are common files used in modern programs to reduce the need for multiple subprograms DLLs can be called from any application and a simple ways of performing common tasks, especially within the operating system.

The Translation ProcessThe process of converting source code into object code is called translation.

There are three types of translation outlined below Interpretation

Each line of the code is translated and the immediately executed. (Line by line translation)

The advantages are: Errors are quickly identified and corrected Syntax errors and runtime errors can be checked for line by line and

identified immediately Flags and the debugging output statements to check for correct outputs is

easier The disadvantages are

Program execution is slower Code can be stolen by other people much easier Interpreted code usually takes up more space

Compilation All code is translated before program execution Advantages:

Programs are executed quicker Complied code is usually smaller than source code The program can be easily distributed

Disadvantages: Code is harder to modify during runtime Error can only be detected after compilation Any code changes require the program to be re-compiled Testing can be a longer process due to re-compilation

Incremental interpretation/compilation Program statements/modules are compiled and stored as they are written

and then the whole code is executed Advantages:

Commonly executed modules are complied and stored The mainline of the program is all that needs interpretation Execution can be faster for short testing of program sections

Disadvantages: Interpreted sections of code can still be easily stolen

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Any modules which have been changed still need to be recompiled

The translation process involves a series of stages before object code is produced. These stages and the elements of them are outlined below Lexical Analysis

This is the first stage and involves the reading of the code. The code is read character by character according to the syntax rules of the programming language. White space is omitted

Other elements of the code are given tokens according to the type of characters they are; language elements, syntax, constants, operators, variables

Each statement is identified and separated for the next stage of translation Syntactical analysis

This stage arranges the tokens in a way which can be understood by the processor

Parsing (the use of a parse tree) creates a hierarchy of each section (token) of the code so that it can be interpreted in the same way each time

Type checking is then carried out. Each of the data types in a statement are passed to the translator. Each statement is checked to make sure the operations being performed are valid according to the data type. Error messages are returned to confliction occurs

Traversing then generates the code by moving from the top left of the parse tree down from left to right. Each token in the tree is subsequently converted to machine code

The translation process is a very complicated one. High-level languages contain feature that help in this process. These elements are outline below Linker

The linker creates links between the mainline to other processes, such as calling the operating system, linking to other modules or to library routines

The link is placed in the mainline of the program where the other operation would be placed

Loader This calls a small program called a load module. The load module sets the

memory locations to run from main memory. This allows relative address to be used rather than absolute addresses.

The loader id held in the main memory at the start of execution. It allocated memory locations for code to be executed and prevents memory addresses interfering with each other

Optimiser This is used to reduce redundant code and improve overall runtime This feature is not found on an interpreter, but is used in compliers

Hardware environment to enable the implementation of software solutionsThere is a range of issues concerning hardware that must be addressed

before the implementation of a software solution. Some of the requirements include:

Platform – The specific operating system to be used Configuration – the processor, clock seed and RAM of the intended

platform Memory Peripherals Communications – access to the internet or other network systems

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When creating a software solution, the developer needs to state to the user the minimum system requirements for the program to operate efficiently. This does not mean the software will run on systems with lower standards, but the developer does no guarantee the software to operate efficiently

Some software also requires the presence of additional hardware such as peripheral devices or video cards. The developer may also include drivers and extensions with the software package that talk between the program and the operating system. This allows the software to effectively operate on other systems.

Testing and Evaluation of Software SolutionThere is a range of tests, which can be performed to determine if each item

specified in the design specifications has been achieved, and performs as expected. Testing is usually done incrementally by modules or procedures before integrating them into the program. Testing involves generating relevant test data, benchmarking and quality assurance

Generating Test DataComplex solution involve many variables that is can be impossible to test

every aspect. For this reason two main testing techniques are used to isolate and identify most errors Black-box testing

This checks the inputs of each modules with the expected and actual outputs It is not concerned with the procedures themselves Types of checks which occur include

Range checking – data respective to the upper and lower ends of legal values are tested

Critical value checking – values which determine results are considered critical

Equivalence partitioning – data is sorted according to its type and then a suitable combination of test data is taken from each group

This testing is also called functional testing If after this testing no discrepancies occur then tests may proceed no

further, otherwise they move onto the next stage of testing White-box testing

This checks the procedures within each module to determine their correctness

This is also called structural testing The types of tests which are performed include

Statement coverage testing – test data is chosen so that each statement in a module is executed during the test procedure

Decision condition testing – test data is selected to test each decision within the module

Levels of TestingComplex solutions are tested at various levels before the final product is

released. These levels are explained below starting from the lowest of the three levels and working upwards Unit or module testing

Each module is tested separately to make sure it works correctly This level uses both black and white box testing Drivers can also be used at this stage to substitute for the mainline of the

program Program testing

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This testing ensures that the modules work well together and the mainline of the program performs correctly. It can also use black and white box testing.

This testing can be done in two different ways Bottom-up testing – incorporates each module into the program one step

at a time from the lowest modules to the higher level modules. This makes it easier to detect lower level modules which conflict with other modules. The main program is the last to be tested

Top down testing – this starts with the main program and uses stubs for some modules as it links each module to the mainline. The main program is tested first and each module in turn. Any problems are then likely to occur with recent additions and can be rectified easily. This can be more useful is libraries of common routines already exist

System testing This stage is the checking of the system in environments outside the

development environment. It can involve testing on different processors and different hardware types It is often done by people outside the development team and is sometimes

called acceptance testing Alpha testing is done where the program is tested under controlled situations

and conditions Beta testing is the second stage and is conducted with volunteers and

conditions are open and not regulated. This testing will be wider for off-the-shelf software compared to custom software

Benchmarking and Quality assuranceBenchmarking is the comparison of a program against a set of established

standards. These can include quality of the product and performance. In-house standards are those set by the development company

Quality assurance is a part of benchmarking and attempts to assure the quality of a product. There is a range of quality factors listed below Consistency – the program carries out its operations in the same way each time Documentation – all internal, external and user documentation if available Independence – ability of the program to function on the full range of

processors for which it was designed Integrity – ability for the program to protect itself against corruption, security

breaches or power spikes Interaction with other software – the program can interact with common

software without conflict Maintenance coverage – the program can be easily kept up to date and

debugged when problems are encountered Memory requirements Performance – speed of processing and response time to meet user

requirements is acceptable Recovery – the ability of the program to recover from a failure Stress resistance – ability of the program to handle larger than expected

processing demands User response – program is easy to learn and answers the users needs

regarding functionality Validity – measures the ability of the program to meet user specifications

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Evolution of Programming LanguagesHistorical reasons for the development of the different paradigms

The need for greater productivityAs the popularity of computers began to grow, there was demand for ability

of the software on the computers to increase. This includes an increase in productivity to allow computers to be involved in many of the mundane jobs. This need led to development of many different types of programming languages that could handle the new tasks. The programming languages are divided into five generations of lanugaes. These are outlined below

Low-Level LanguagesLow-level languages are the two earliest forms of languages for a computer.

There are two generations of low-level languages. These are 1GL and 2GL.A 1GL is the most basic language used by a computer. The features of a 1GL

are: Binary/Machine Code (1s and 0s) Can be immediately decoded by a processor Machine/processor specific

A 2GL language is slightly more advanced language than 1GL. It has some simple commands that can be used and interpreted by programmes. The features of a 2GL language are:

Assembler – used to translate the object code into machine code Used symbolic words (mnemonics)- abstraction. (eg using LD to stand for

Load from register/memory etc…) Machine/processor specificRequire some form of translator to convert simple words into machine code.

High-Level LanguagesHigh-Level languages came later in history with one main difference. The

code syntax that was used was more like normal human language. A translator was required to convert the object code into machine code. This was a major leap in terms in the evolution of languages. However, from a technical point of view the most significance difference between low and high level languages, was that high-level languages are not processor specific. This means that the program can be run on all different processor chips – ie Intel, AMD etc… The limitation of the language is that they are operating system specific. There are three generations of high-level languages, which are 3GL to 5GL

A 3GL language was the major leap in development from 2GL in terms of the above information. The main aspects of a 3GL language are:

Commands and syntax structures are look much more like ‘normal’ language

Programming is easier as operations can be easier seen Not processor specific – operating system specific The level of operations is the same as 2GL, but the abilities the language

could perform were expanded because the program could be spanned over multiple computers, thus incentive programs was increased. Also since the language was easier to discern, more complex structures could be created easier than before.

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Examples of 3GL include – Visual Basic, Qbasic. COBOL, Pascal, C/C++, FORTRAN

A 4GL language takes the abilities of a 3GL language further. The main difference and advance of 4GL languages is that language focuses more on what the program needs to accomplish rather than the process of how the program must accomplish a task. Therefore the coding syntax is very similar to human speech where the task the processor must accomplish is given to the processor, not where how the processor must accomplish is given to the processor. A 4GL is a non-procedural language. These languages are also generally written to solve a particular problem, or perform a particular task such as a database program, or printer descriptions.

4GL simply the development of programs for the end user. This is because the end user does not need to have an advanced understanding of a programming language to be able to customise the application. The features of 4GL languages are:

Concentrates on What rather than How Task specific – these languages are created to carry out one specific role.

Eg SQL is solely used for working with databases. Postscript is specific to sending data to a printer.

Still have some functions and arguments which the program carries out Examples include LISP, SQL, Postscript, Hypertalk

A 5GL language is the pinnacle of modern day languages in terms of what they are able to accomplish and how these tasks are accomplished. These languages use a programming logical called declarative. They concentrate on the outcomes and leave the processor to determine how to achieve this within a set of given specifications. The features of a 5GL language are:

Have levels of Artificial Intelligence Uses Natural language/speech Examples include Prolog

Recognition of repetitive standard programming tasksWhen computers were first created, the tasks that were being carried out

where simple and requires few repetitive steps. It was just as simple for the programmer to exactly instruct the machine how to handle all data, such as the processing required for an input statement (this includes reading the information, loading it into the accumulator, and storing the input data in memory locations)

As computer began to handle more complex tasks, the programmers realised that common tasks were required in many circumstances, and it was a hassle to tell the computer how to do every single step. As a result the concept of abstraction was introduced. This is a system where single key words are used to represent a series of computer commands, such as the INPUT statement. As higher-level languages were created, process abstraction increased in use, saving the programmers time and allowing more complex tasks to be handled and created in a smaller time frame

Desire to solve different types of problems (eg AI)The original types of programming languages were procedural languages

where the programmer defined the order in which the program was to carry out a series of tasks. Also in procedural languages the programmer told the computer how to carry out every task, such as sorting a list of number

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As greater and more complex problems arose, and with the development of GUI’s, the ability of the computer to handle multiple tasks and figure tasks out for itself became an issue. The ability of the computer was hampered where the programmer had to describe and instruct the computer how to carry out each individual task.

The fourth and fifth generation languages that are non-procedural solved this problem. In other words, in these languages the programmer only gives the computer the data and gives a description of the end result. The computer figures out which steps are required to meet the result. This gives the program more flexibility in operation, and also enables the programs not to have a defined sequence of instructions. Non-procedural languages rely on logic and inference to achieve a result.

In a way, by allowing the computer to calculate the operation required, primitive forms of artificial intelligence are used.

The recognition of a range of different basic building blocksAs the uses of computers expanded, a variety of different methods were used

to solve particular problems. These methods formed the four main types of programming paradigms. Specific languages were then developed to suit each of the programming paradigms. They are summarised in the below table, and expanded upon in later sections

Programming paradigm

Examples

Imperative Pascal, BASIC, C, FORTRAN, COBOL

Functional LISP, APL, Scheme, MLLogic Prolog, SQLObject-oriented Smalltalk, C++, Java, VB

Emerging technologiesEven though the high level languages are non-procedural, in the end the

object code must be translated into sequential machine code for the computer to execute. Emerging technologies provide a hope for more efficient processing of programs. These technologies are summarised below

Parallel processing/computingThis technology uses multiple processors that share out processing tasks.

This enables a set of instruction to be carried out quicker. However, only speed in processing is gained since sequential machine code is still required to enable the programs to run. Some of applications of parallel computing include

Real-time simulations – this includes the modelling of events that exists in the real word in current time. This can be used to analyse the impacts of events and find solution to them such as gaining insight into a volcanic eruption while planning how to minimise the impact of it on humans

Neural networking – this is where computers are able to simulate the workings of the human mind. Multiple processors are linked together each containing their own memory storage. Each processor handles a specific type of data. The computer can be trained in how to respond to certain situations. This has also enabled research into computer learning and AI

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Quantum processingThis is hopefully being used to overcome many of the sequential machine

code issues. It relies heavily on the quantum theory atomic model, where electron, protons and photons would represent the 1s and 0s of the computer. Also since each atom can exist in many quantum states, it is hoped that these computers would efficiently be able to handle parallel computing.

Molecular computing/DNA computingThis research is in its infancy, but the idea is that molecules would be used

to store data and greatly increase the storage capacity of computers by a million times their current ability. Further molecules could be used to carry out particular tasks, increase speed.

Through the implementation of DNA technology it could be possible to use a base-8 system instead of just the normal base-2. This increase speed in processing and reduces the storage space of data.

Visual programming languagesThese are object-oriented programming languages where by the programmer

uses a visual interface and drag and drop techniques to create a screen design layout. It has opened the programming industry to novice programmers who are able to generate programs that carry out simple tasks without having to have a great understanding of computers or programming.

Basic building blocks of programming languagesBefore the basic building blocks of the programming paradigms can be

discussed, the below table summarises the features of each of the paradigms.Paradig

mExamples Format Feature

Imperative

PascalBASICCOBOLFORTRAN

Uses a sequence of operations to produce a result. A procedural sequential language

Specifies a list of operations. Has a defined start and end. Program is a sequence of actions in a fixed order (often defined by line numbers of labels). Uses variables to store data. Programs are procedural

Logical (declarative)

PrologSQL

Specifies outputs in terms of facts and goals

A program consists of declarations of facts, rules and goals. Non-procedural, as the solution is given but the process is not

Functional

LISPAPL

Basic construct is the definition of functions

Does not use variables or assignment statements. A program consists of function definitions and applications of these functions. May use recursion

Object- orientated

SmalltalkC++Java

Consists of interacting objects, each with its own programming. An object’s internal structure is hidden

An object is a list of attributes and procedures or methods. Objects communicate by message passing. A class is a collection of objects which share common attributes and methods. Data and methods are encapsulated within objects

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Imperative paradigm – Variables and control structuresThe basic building blocks of the imperative paradigm are variables and

control structures. Since the imperative structure uses a sequential flow of data, data is handled using variables and assignment statements. Since choices often need to be made, the imperative paradigm also incorporates three control structures; selection, repetition and subprograms

Identifiers are also used. These are descriptive names given for a location in the computer’s memory

Functional paradigm - FunctionsAs its name suggests the functional paradigm uses functions as its basic

building block. This paradigm is one where the instructions are provided as a series of function definitions. They are written as a set of statements where each subsequent statement relies upon the previous statement. Function can handle any types of data and can return a single character (called an atom) or a complete list. Recursion is used for repetition.

These languages are ideal for parallel processors since they are not sequential and allow the processors to perform many aspects of the program at the same time

Logical (Declarative) paradigm – Facts and RulesFacts and rules are the basic building block of the logical paradigm. Facts

are statements that can be proved true or false and rules are a set of procedures that must be followed or accomplished. The programmer simply tells the computer what facts are to be used and the rules that must be followed. Also the results of the processes are described. The computer then decides where to start solving the problem, how each rule and fact is applied and in what order tasks are carried out.

Object-Oriented paradigm – Objects, with data and methods or operationsObjects are the basic building blocks of the object-orientated paradigm.

Objects are independent of other code, and other objects may call or access the information encapsulated in another object. Each object has a set of properties that define the characteristics of that object. Objects are often set up into classes where the objects of each class inherit the characteristics of the class.

Effect on Programmer’s productivityThe choice of the programming language has major effects upon the

requirements of the programmer. This can range from the work load to the time required to properly developed and test the new product. These aspects are discussed below

Speed of code generationA high-level language usually allows a shorter time for development since

even though the levels of complexities required are the same. This arises from the fact that a programmer can ignore the memory location and storage of data as required in low level languages. Further less code needs to be written due to abstraction. Finally aspects such as objects, classes and reusable function tend to lead to a shorter development time, and lend themselves to RAD.

Approach to testingTesting of a program is often a long, exhausting and costly period in software

development, and often the market forces reduce the amount of testing that can be

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accomplished. Therefore, programming languages which reduce the amount of testing which is required and also suits the purpose of the testing influences the choice of language and the productivity of the programmer. The main types of testing are explained below

Structured testing – each algorithm, unit or module if tested as the program code is written. This helps reduce the amount of errors which occur within the system as a whole

Program testing – testing of the product is left until the product is completed. It may reduce the amount of testing required, but also can increase costs and often results in poor quality programs with many bugs

Automated testing – the use of CASE tools, which is expensive but can also prevent many bugs being carried forward further into development.

Each of the different paradigms effect the testing required and these effects are outlined below

Functional – likelihood of syntax errors is minimal since the syntax is simple. It is often easier for programmers to find and fix errors

Object-orientated – modules can be tested independently by using drivers. It is simpler to test small portions of the code first

Imperative – have a logical structure and subprograms are usually tested independently

Logical – involve less code and therefore there is less code to test and maintain

Effect on maintenanceProponents of Prolog say the since it is logical maintenance is reduced.Modular programs are simpler to maintain since when problems occurs only

the specific modules need to be altered, and not the entire program

Efficiency of solution once codedPrograms vary in efficiency when they are executed. Machine code is by far

the quickest in execution, but takes the longest time to develop. High-level languages are quicker to develop but take a longer time to execute. The advantages of each of the paradigms are outlined below

Imperative – run efficiently as they work closely with the hardware Functional – are ideal for parallel processor computers since the programs can

be broken down into different parts. Logical– can have an inefficient execution since they computer may have to

perform many different permutation when determining a correct solution to a problem. Quantum computing would allow this style to be more efficient

Object-oriented – they allow for easy development, but due to the classes which need to be created and the storage of the properties of each object, execution may not be as efficient as other paradigms.

Learning Curve (training required)Different languages and paradigms required different levels of knowledge

and expertise. Also it takes time for programmers to master the individual languages. Languages can often by chosen based on the knowledge the members of the software development team have. Each of the knowledge required for the different programming paradigms is outlined below

Imperative – often used to introduce students to programming. They have a clearly defined syntax and process tasks in a logical order

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Logical – it can be easier to teach a logical program to a beginner than a trained programmer. Logical programming required logical reasoning and is based on mathematical principles. Since the semantics of the program are easier to understand, beginners can often find this paradigm easier to use

Object-oriented – they mimic they way people think by classifying items into separate objects

Paradigm specific concepts

Logic paradigmThe following concepts are specific to the logic paradigm

Heuristics Are a ‘rule of thumb’ A general principle for deciding a course of action Uses Fuzzy logic that enables decision to be made according to the

probability of the decision being true. It enables AI systems to operate when things are not always false or true

Goal These are statements which the program will determine using the rules and

facts The desired output

Inference Engine Uses a knowledge base A system of bringing relevant items of knowledge to bear on a particular

problem Backward/forward chaining

Backward chaining starts with a goal and works backwards to try and prove and validity of each statement in the goal.

Working backwards to prove a goal true or false Forward chaining starts with the facts and then reaches a goal

Object-Orientated paradigmThe following concepts are specific to the object-orientated paradigm

Inheritance Objects that share many of the same properties are shared Can be created from an ancestor It often uses classes to define the properties which elements defined by the

class will then share. Each element of the class can be further defined and carry other properties

This can reduce the complexity of a program as similar interfaces can be commanded by shared controlling code

Encapsulation It is the process of including all the attributions and procedures that an

object needs within the object itself For example this includes holding the scripts which are associated with

buttons, objects, forms and other elements in a program ActiveX controls have this feature as the code contained by the control must

be included when it is imported into a program and used Classes often use encapsulation

Methods A piece of code which is exclusively associated with either a particular class

or object Is consists of a set of statements which perform a particular action

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It can also use parameters and can also output a result Classes

A class of objects share some common characteristics and perform similar procedures

A collection of types of encapsulated variables, methods and objects It is a set of metadata, which is then used to, created and defines other

objects. Abstraction

It involves representing a complex task in a simple or symbolic way This can include the use of abstraction with data and methods It allows the programmer to concentrate on the program structure It allows the programmer to generalise rather than concentrate on the

specifics when creating a new method Polymorphism

This is the idea of allowing the same segment of code to be used by different classes

They can be encapsulated within a class of objects.

Functional paradigmThe concept for the functional paradigm is:

Function Not restricted by the type of data that can be returned by the function Can return a single element (atom) or an entire list Suited to processing type of data used in AI Use recursion Modern functional languages allow the uses of variables and a range of data

structures

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