DITEC - Software Engineering

DITEC - Software Engineering

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  Diploma in InformationTechnology Module VII: Software Engineering Rasan Samarasinghe ESOFT Computer Studies (pvt) Ltd. No 68/1, Main Street, Pallegama, Embilipitiya.
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  Contents 1. What issoftware? 2. Software classification 3. Attributes of Software 4. What is Software Engineering? 5. Software Process Model 6. Waterfall Model 7. Prototype Model 8. Throw away prototype model 9. Evolutionary prototype model 10. Rapid application development 11. Programming styles 12. Unstructured programming 13. Structured programming 14. Object oriented programming 15. Flow charts 16. Questions 17. Pseudo codes 18. Object oriented programming 19. OOP Concepts 20. Inheritance 21. Polymorphism 22. Encapsulation 23. Generalization/specialization 24. Unified Modeling Language 25. Class Diagrams 26. Use case diagrams 27. Software testing 28. Black box testing 29. White box testing 30. Software documentation
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  What is software? Asoftware is a collection of instructions that enables a user to interact with the computer or have the computer perform special task for them.
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  Software classification • SystemSoftware – Directly controlling the hardware resources and supports the operation of application software. • Application Software – Serves the user requirements in a particular application domain.
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  Software classification • GenericSoftware (off the shelf) – Available on open market to any customer who is able to buy it. • Custom Software (bespoke) – Developed specially for a customer requirement.
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  Generic Software vsCustom Software Less expensive More reliable Immediate installation More user friendly User requirements are not completely satisfied Cannot accommodate future changes More expensive Less reliable Delay due to high development time Less user friendly Completely satisfied Can easily accommodate future changes Generic Software Custom Software
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  Attributes of Software •Maintainability • Dependability • Efficiency • Usability • Security • Reliability • Robustness • Customizability • Scalability • Accessibility • Extensibility
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  What is SoftwareEngineering? Software engineering is concerned with application of theories, methods and tools to develop and maintain software systems that behave reliably and efficiently, are affordable to develop and maintain, and satisfy all the requirements that customers have defined for them.
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  Software Engineering ProcessModelA software process model is a set of predicted procedures or set of stages to be use to develop a fully tested software system timely. Software Process Model
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  • Waterfall model •Prototyping model • Rapid application development model • Spiral model • V-model • Join application development model • Incremental development model Software Process Models
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  Waterfall Model
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  Waterfall Model • Alinear sequential development model. • Because of the cascade form one stage to another it is known as waterfall model. • Divided project activities into isolated stages and each stage should complete before next started. • Concurrent activities are not possible. • Need to wait until end of the life cycle to see the outcome. • Suitable for develop systems which has stable requirements.
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  Waterfall Model Stages Stage1: Requirement Definition • The system services, constraints and goals are established by consulting with the system users. • They are define in a manner which is understandable by both users and the development staff.
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  Waterfall Model Stages Stage2: System and Software designing • Partitions the requirements either hardware or software. • Involves representing the software system functions in a form that may be transformed into executable programs. • Identifying and describing fundamental software system abstraction and there relationships.
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  Waterfall Model Stages Stage3: Implementation and unit testing • Implementation consists of converting the physical designing into set of actual programs and a set of database tables. • The software is realized as a set of programs or program units. • Unit testing involves verifying that each unit meets it’s requirements.
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  Waterfall Model Stages Stage4: integration and system testing • Individual program units are integrated and tested as a complete system. • Ensure the software requirements have been met. • After testing the software system is delivered to the customer.
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  Waterfall Model Stages Stage5: Operation and maintenance • The system installed and put into practical use. • Involved correcting errors which were not discovered in earlier stages. • Improving implementation as new requirements are discovered. • Normally this is the longest life cycle phase.
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  Extended Waterfall Model •Due to the above discussed disadvantages, the waterfall model was modified with the concept of backtracking. • As a result, the Extended Waterfall Model introduced.
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  Extended Waterfall Model
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  Prototype Model Prototype isa working model of the actual System There are two types of prototype model. 1. Throw away prototype model 2. Evolutionary prototype model
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  Throw away prototypemodel
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  Throw away prototypemodel • Prototype is use to gather requirements and there after it will be thrown away. • Further designing, construction and implementation will be done using the normal life cycle stages. • Requirements gathering can be exactly done by using the prototype • Even to develop prototype consumes lot of time and effort , therefore once a prototype is thrown away it’s a waste of time and money.
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  Evolutionary prototype model System Complete System Architecture Identify PrototypeQuick Design Construct And Use The System Revise Prototype Deliver System Yes No
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  Evolutionary prototype model •Prototype is use to gather requirements and it will become the final system. • Both the prototyping process as well as the development process will be combine together. • Prototype will not be thrown away and it is not wasting effort and cost like throw away prototype.
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  Rapid Application Development(RAD)
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  Rapid application developmentmodel (RAD) • This is a software process model which uses to develop applications rather quickly. • The entire system is broken down into several manageable stages and each stage analyzed, designed, developed, tested and implemented simultaneously Rapid Application Development (RAD)
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  Stages in theRAD 1. Business modeling • The information flow among business functions is modeled. • Find answers for the following questions: What information drives the business process? What information is generated? Who generate it? Where does information go? Who process it?
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  Stages in theRAD 2. Data modeling • The information flows are refined into set of data objects. • The attributes of each objects and relationships between these objects defined.
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  Stages in theRAD 3. Process modeling • The data objects are transformed to achieve the information flow necessary to implement the business function. • Processes are created for adding, modifying, deleting and retrieving data objects.
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  Stages in theRAD 4. Application generation • Using fourth generation techniques rather than using conventional third generation programming languages. • In possible cases automated tools/reusable components are use to facilitate construction of the software. (Ex: DB query tools, reports, graphics manipulation, interface designs)
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  Stages in theRAD 5. Testing and turnover • Since the RAD process use many reusable components that have been tested, it reduces the overall testing time. • How ever the new components should be tested.
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  Programming Styles There are3 main programming styles 1. Unstructured Programming 2. Structured Programming 3. Object Oriented Programming
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  Unstructured Programming • Unstructuredprogramming is the historically earliest programming paradigm. • It is a procedural program, the statements are executed in sequence as written. • This type of programming uses the goto statement. A goto statement allows control to be passed to any other place in the program. • Difficult to understand the logic of the program. Ex: Machine language, Cobol
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  Structured Programming • Structuredprogramming is a subset of procedural programming that enforces a logical structure to make it more efficient and easier to understand and modify. • Use of the goto statement is discouraged. • Structured programming using 3 controls constructs: – Sequence – Selection – repetition Ex: C, Pascal, Ada
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  Object Oriented Programming •Object-oriented programming (OOP) is a programming model organized around objects rather than actions and data rather than logic. • It is becoming more popular as a designing technique, because it has an ability to represent complex relationships, data and data processing with suitable notations. Ex: Java, C++, C#
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  Flow Charts A flowchartis a diagrammatic representation of the process involved in arriving at a solution to a problem.
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  Flow Chart Notations Start/ End of the program Input / Output Process Decision / Repetition Flow Connector
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  Flow Charts • Question1: Draw a flowchart to develop a program to input the student index number, name and total marks scored in three modules and display the students index number, name and average marks on the screen.
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  Flow Charts • Question2: Draw a flowchart to develop a program to input student number, name, module 1 marks and module 2 marks and display student number, name, average marks and total marks.
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  Flow Charts • Question3: A student has sat for an exam and following details were entered through the keyboard: student number, name, and average marks. If he average is greater than 50 student will be graded as “Pass” otherwise graded as “Fail”. Draw a flowchart to display the student name, average and grade.
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  Flow Charts • Question4: Draw a flowchart to input two numbers from the keyboard and evaluate and display the maximum value.
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  Flow Charts • Question5: Draw a flowchart to develop a program to input student no, name, module 1 marks and module 2 marks by keyboard. Calculate and display student no, average and the grade. The grading system is as follows. Average > 75 grade is “distinction”, 50 - 75 grade is “credit”, 25 - 50 grade is “Pass” and less than 25 is “Fail”.
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  Flow Charts • Question6: Draw a flowchart to calculate and display the sum of first five natural numbers.
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  Flow Charts • Question7: Draw a flowchart to input a number from keyboard, and there after calculate and display the factorial number.
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  Pseudo Codes Pseudo codeconsists of short, English phrases used to explain specific tasks within a program's algorithm. Pseudo code should not include keywords in any specific computer languages. It should be written as a list of consecutive phrases.
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  Pseudo Codes One ofthe concepts in programming is… PROGRAM = DATA + ALGORITHM Data  Data types: String, Integer, Real  Data usage: Variable, Constant  Data scope: Global data, Local data Algorithm  Sequence  Selection  Repetition
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  Object Oriented Programming •Object-oriented programming (OOP) is a programming language model organized around objects rather than actions and data rather than logic. • Object oriented programming becoming more popular as a designing technique, because it has an ability to represent complex relationships, data and data processing with suitable notations.
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  Object Oriented Programming MaleFemale Son Father Mother Daughter Family system Objects
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  Object and Class Anobject is person, place or thing which consist of data and behaviors. The data of an object is its properties (attributes) and behaviors represent how an object acts and reacts. A class is simply a representation of a type of object. It is the blueprint / template that describe the details of an object. Class is composed of three things: a name, attributes, and operations.
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  Object Instance Object instanceis uniquely identified occurrence of an object Book Book_id Title Author Lending Reservation Reading Book 001 – A Science Peter Lending Reservation Reading Object instance
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  Object Oriented ProgrammingConcepts  Inheritance  Polymorphism  Encapsulation  Generalization  Specialization
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  Inheritance Inheritance is sharingof attributes and operations among classes based on a hierarchical relationship. Vehicle v-no Model color Drive Stop Bus v-no Model color Drive Stop Car v-no Model color Drive Stop Super class operations and attributes are inherited to the sub classes
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  Polymorphism • Polymorphism issimply the ability for an object behaves differently depending on its type. • Ex: both cat and dog are animals which has the same method called makeNoise(). But they are making noise in different ways.
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  Polymorphism
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  Encapsulation • According toencapsulation attributes and operations are encapsulated (hidden) within the object. • The outside world know what the object can do but don’t know how it does or where data is stored. These features are hidden from the user.
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  Generalization / Specialization Generalizationand specialization both refer to inheritance but the approach in which they are implemented are different. If many similar existing classes are combined to form a super class to do common job of its subclass, then it is known as Generalization. If some new subclasses are created from an existing super class to do specific job of the super class, then it is known as Specialization.
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  Generalization / Specialization Vehicle v-no Model Color Drive Stop Motorbike v-no Model color Drive Stop Car v-no Model Color Airbag Drive Stop Reverse Specialization Generalization Carand Motorbike specialize Vehicle to their own sub-type. Vehicle Generalize what is common between Car and Motorbike
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  Unified Modeling Language(UML) • UML is a general purpose visual modeling language to visualize, specify and document software systems. • The most important goal for developing UML is to define some general purpose modeling language which all modelers can use and it also needs to be simple to understand and use.
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  Unified Modeling Language(UML) • Class Diagrams • Use Case Diagrams
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  Class Diagrams • Aclass diagram shows the static structure of an object oriented model. • Also it shows object classes and their internal structures (attributes and operations) and their relationships.
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  Class Diagrams Student Name Address Phone Display Add Edit Delete Class Name Attributes Operations Structureof a Class
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  Relationships • Association • Aggregation •Composition • Generalization
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  Association • An associationis a relationship among classes or objects. • Ex: Student follows Course, Lecturer teaches Student, Manager manages company. manager company
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  Aggregation • When anobject has an another object, then you have got an aggregation between them. • Ex: Library has Students Student Library
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  Composition • When anobject contains the other object, if the contained object cannot exist without the existence of container object, then it is called composition. • Ex: University consist from Buildings, Shirt consist from Collar, buttons, etc.
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  Generalization Person Employer Customer
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  Multiplicity Multiplicity indicates thenumber of instance of one class linked to instance of another class. One to One 1 1 One to Many 1 * Many to Many * *
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  A Sample ClassDiagram A sample class diagram
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  Use Case Diagrams Ause case diagram is a graphical representation of a user's interaction with the system. The purpose of use case diagram is to capture the dynamic aspect of a system.
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  Use Case DiagramNotations Actor Use Case Communication Extend/include System Boundary
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  A Sample UseCase Diagram
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  A Sample UseCase Diagram
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  Software Testing • Theobjective of testing is uncover errors in a program as much as possible • In testing a series of steps such as – Unit Testing – Integration Testing – Validation Testing – System Testing Are planned and executed…
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  Unit Testing Unit Testingfocuses verification effort of the smallest unit of the software component or module.
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  Integration Testing Verifies theincorporation of components into a program structure.
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  Validation Testing Validation Testingis testing traceability to the software requirements.
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  System Testing Validates softwareonce it has been incorporated into a large system. (hardware, people, information)
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  Testing Approaches There aretwo main testing approaches 1. Black Box Testing 2. White Box Testing
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  Black Box Testing •The program is considered as a black box which the internal logic is cannot seen by the testers. • The expected output is checking against the input given to the program.
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  White Box Testing •Program is assumed as a transparent box where the internal logic is seen by the testers. • The flows of every logical pathway are tested in a systematic approach.
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  Software Documentation Documentation aretwo types 1. Documents for programmers 2. Documents for users
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  Documents for Programmers •Internal Used in coding – Meaningful names for variables – Comments – Using standard style and format • External These are the documents which carried out by designers, analysts and programmers to communicate – Requirements Specification – Design Specification – Feasibility Report
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  Documents for Users Thereare user manuals which is giving instructions and support for end users for using the software systems. Explaining the purpose of the system Detailed, descriptions and examples by screen shots. Step by step guide for operating the system Troubleshooting support
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  The End http://twitter.com/rasansmn