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Chapter one introduction to event driven programming .pptx
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- 2. 2 What is Event-drivenprogramming? • Event-driven programming is a programming paradigm in which the flow of program execution is determined by events - for example a user action such as a mouse click, key press, or a message from the operating system or another program. • An event-driven application is designed to detect events as they occur, and then deal with them using an appropriate event-handling procedure. • Event-driven programs can be written in any programming language, although some languages (Visual Basic and Visual C++ for example) are specifically designed to facilitate event-driven programming, and provide an integrated development environment (IDE) that partially automates the production of code, and provides a comprehensive selection of built-in objects and controls, each of which can respond to a range of events
- 3. 3 What is Event-drivenprogramming? • Virtually all object-oriented and visual languages support event-driven programming. Visual Basic, C#, Visual C++ and Java are examples of such languages. • A visual programming IDE such as VB.Net provides much of the code for detecting events automatically when a new application is created. • The programmer can therefore concentrate on issues such as interface design, which involves adding controls such as command buttons, text boxes, and labels to standard forms (a form represents an application's workspace or window). • Once the user interface is substantially complete, the programmer can add event-handling code to each control as required.
- 4. Dec 9, 2025 Event Driven Programming 4 Introduction to SoftwareDevelopment What is Software? Is a computer program used to perform a certain task. products may be developed for a particular customer or a general market. Software products may be Generic - developed to be sold to a range of different customers. Custom - developed for a single customer according to their specification What is Software Development? Is the process of creating new software solutions or modifying existing software solutions It includes all that is involved between the conception of the desired software through to the final manifestation of the software, ideally in a planned and structured process
- 5. Dec 9, 2025 Event Driven Programming 5 Cont’d… Software Engineering:- is concerned with theories, methods and tools for professional software development. an engineering discipline which is concerned with all aspects of software production. concerned with cost-effective software development. Software engineers should adopt a systematic and organised approach to their work and use appropriate tools and techniques depending on the problem to be solved, the development constraints and the resources available
- 6. Dec 9, 2025 Event Driven Programming 6 Cont’d… Attributes of goodsoftware software should deliver the required functionality and performance to the user and should be maintainable, dependable and usable. Maintainability - must evolve to meet changing needs. Dependability - must be trustworthy. Efficiency - should not make wasteful use of system resources Usability - must be usable by the users for which it was designed.
- 7. Dec 9, 2025 Event Driven Programming 7 Cont’d… What is aSoftware Process (software life cycle)? Coherent sets of activities for specifying, designing, implementing and testing software systems Generic activities in all software processes are: Specification - what the system should do and its development constraints. Development - production of the software system Design and implementation of the software. Validation - checking that the software is what the customer wants To ensure that the software does what the customer requires. Evolution - changing the software in response to changing demands. Adaptation and modification of the software to cope with changing customer and market requirements. Generic activities may be organized in different ways and described in different levels of detail for different types of software
- 8. Dec 9, 2025 Event Driven Programming 8 Software Development Approaches Software can be designed and developed in many different ways. The approach taken to design & develop a software package can vary from the very simple, limited planning approach to a very detailed, formal and structured approach The commonly used approaches are:- Structured Approach JAD Approach Prototyping Approach Rapid Application Development Approach Method:- which approach and language is best? what happens if you get it wrong?
- 9. Dec 9, 2025 Event Driven Programming 9 Cont’d… 1. Structured involvesthe use of the program development cycle: Defining the problem – necessary to understand the problem in as much detail as possible. Planning the solution – involves determining data types, developing algorithms & diagrams, whether ‘start from scratch approach' needed, determine the programming language used Building the solution – converting the specifications and algorithms developed during the planning stage into code. Checking the solution – check that is operates correctly. Modifying the solution – may be necessary if errors are detected, or the users' feedback means that the program doesn't meet their needs, or the underlying processes change, or the existing system changes, etc. Accurate documentation is extremely important because the modifications may be made by programmer who were not part of the original team.
- 10. Dec 9, 2025 Event Driven Programming 10 Cont’d… 1. Structured … Used when there is a high budget, where there is a long time period to complete the project, and is where it is preferable for the project to be completed by teams. It is characterized by distinct stages, with each stage being completed before moving onto the next stage Characteristics Long time periods from start to implementation of the final product (can be many months or even years.) used for large-scale projects, or difficult projects, or new concept projects associated with large budgets and large organizations involves a number of different personnel (analysts, designers, programmers, users and management) Eg. Operating Systems
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- 12. Dec 9, 2025 Event Driven Programming 12 Cont’d… 2. Prototyping Isthe process of designing and building a scaled down version of the desired information system. activity of creating prototypes of software applications, i.e., incomplete versions of the software program being developed. developer makes a small scale model of the proposed program so that users can give feedback and ensure it meets their needs. Prototypes are useful in seeking user reactions, suggestions, innovations, and revision plans before the final version of the system is developed. Involves development of a working model which may then be developed further into a fully functioning solution
- 13. Dec 9, 2025 Event Driven Programming 13 Cont’d… Design Prototy pe Custom er Evaluati on Revie w & Updat e Initial Requireme nts Developme nt Test Maintain Custome r Satisfact ion Prototyping To validatethe user requirements for new software before progressing too far in the development process, prototypes of the software system may be developed. Whether a low-fidelity prototype that illustrates the look-and-feel of the design or a high-fidelity prototype that implements part of the system’s functionality, approval by the customer is required before full system implementation is begun.
- 14. Dec 9, 2025 Event Driven Programming 14 Cont’d… Characteristics Prototypesfocus on what the users interacts with, the input and output requirements only Prototypes are not interested in the code behind the interfaces It encourages end user participation It improves communication between programmer/s and end user/s developer can develop typical screens and then quickly modify them after user feedback quickly create the look and feel for the proposed/final product in comparison to other approaches They typically results in a lower required budget and shorter development time They are a good approach for small scale projects
- 15. Dec 9, 2025 Event Driven Programming 15 Cont’d… Advantages Potential forchanging the system early in its development. Opportunity to stop development on an unworkable system. Possibility of developing a system that closely addresses users' needs and expectations. Disadvantages Managing the prototyping process is difficult because of its rapid, iterative nature. Requires feedback on the prototype. Incomplete prototypes may be regarded as complete systems. E.g.: Multimedia, website’s, online enquiry
- 16. Dec 9, 2025 Event Driven Programming 16 Cont’d… 3. Rapid ApplicationDevelopment (RAD) Is a methodology created to radically decrease the time needed to design and build an information system. Efficient and Cheaper Allows systems developers and end users work together from the beginning Is an object-oriented approach group (team-based) approach, but goes much further. Component based construction approach less emphasis on planning and more on process (Developing instead of planning) lack of pre-planning generally allows software to be written much faster, and makes it easier to change requirements
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- 18. Dec 9, 2025 Event Driven Programming 18 Cont’d… Characteristics Extremelygood approach for small scale projects Reuse of code is encouraged which allowing the program to be developed quickly Automated tools are used to make the software Lacks the formal stages of other approaches Fast development time Relatively cheap to develop; relative to Structured approach incorporate all parts of the development cycle, including project management, requirement gathering, some code generation, test documentation, evaluation, etc Personal (developer & end user)
- 19. Event Driven Programming 19 Cont’d… Advantages Systems canbe developed more quickly with significant cost savings. Disadvantages May try and hurry the project too much. Loosely documented. May not address pressing business problems. Potentially steep learning curve for programmers inexperienced with RAD tools 16-Sep-23
- 20. Dec 9, 2025 Event Driven Programming 20 Cont’d… 4. Joint ApplicationDesign (JAD) Process in which users, managers, and analysts work together for several days in a series of intensive meetings to specify or review system requirements. involves the client or end user in the design and development of an application, through a succession of collaborative workshops called JAD sessions User Involvement Users have a vital stake in an information system, and they should participate fully Successful systems must be user-oriented and users need to be involved JAD participants should be insulated from the distraction of day-to-day operations
- 21. Dec 9, 2025 Event Driven Programming 21 Cont’d… Objective: toanalyze the existing system, obtain user input and expectations, and document user requirements for the new system
- 22. Dec 9, 2025 Event Driven Programming 22 Cont’d… Advantages Allows keyusers to participate effectively. When properly used, JAD can result in a more accurate statement of system requirements, a better understanding of common goals, and a stronger commitment to the success of the new system. Disadvantages More expensive and can be cumbersome if the group is too large relative to the size of the project.
- 23. Dec 9, 2025 Event Driven Programming 23 Rapid Application Development a development life cycle designed to give much faster development and higher quality results than those achieved with the traditional life cycle. Because of rapidly changing business environments, businesses have to respond to new opportunities and competition. RAD objective is to cut development time and expense by: Involving the users in the development process. Using integrated CASE (computer-aided software engineering) tools. Using faster software development techniques. RAD relies on: Extensive user involvement Joint application design session Prototyping Integrated CASE tools, Code generators
- 24. Dec 9, 2025 Event Driven Programming 24 RAD Principles &Phases RAD Principles To delay producing detailed system design documents until often user requirements are clear. To enable quality products to be developed faster, saving valuable resources. To compresses the step by step development of conventional methods into an iterative process to develop a quality software RAD Phases - There are three broad phases to RAD: Requirements planning RAD design workshop Implementation (construction)
- 25. Dec 9, 2025 Event Driven Programming 25 RAD Phases • RequirementsPlanning Phase Users and analysts meet to identify objectives of the application or system Oriented toward solving business problems • RAD Design Workshop Design and refine phase Use group decision support systems to help users agree on designs Programmers and analysts can build and show visual representations of the designs and workflow to users Users respond to actual working prototypes Analysts refine designed modules based on user responses • Implementation Phase As the systems are built and refined, the new systems or partial systems are tested and introduced to the organization When creating new systems, there is no need to run old systems in parallel
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- 28. Dec 9, 2025 Event Driven Programming 28 When to UseRAD RAD is used when Reasonably well-known requirements User involved throughout the life cycle Project can be time-boxed Functionality delivered in increments High performance not required Low technical risks System can be modularized programmers and analysts who are experienced There are pressing reasons for speeding up application development The project involves a novel ecommerce application and needs quick results Users are sophisticated and highly engaged with the goals of the company
- 29. Dec 9, 2025 Event Driven Programming 29 Software Development Principles 1st Principle:The Reason It All Exists A software system exists for one reason: to provide value to its users. Before anything else ask yourself questions such as: "Does this add real VALUE to the system?" If the answer is "no", don't do it. All other principles support this one. 2nd Principle: KISS (Keep It Simple, Stupid!) Software design is not a haphazard process. There are many factors to consider in any design effort. All design should be as simple as possible, but no simpler. This facilitates having a more easily understood, and easily maintained system. Note: - This is not to say that features, even internal features, should be discarded in the name of simplicity. - Indeed, the more elegant designs(well-designed) are usually the more simple ones. - Simple also does not mean "quick and dirty."
- 30. Dec 9, 2025 Event Driven Programming 30 Cont’d… 3rd Principle: Maintain theVision clear vision is essential to the success of a software project Without conceptual integrity, a system threatens to become a patchwork of incompatible designs, held together by the wrong kind of screws. Conceptual integrity is the most important consideration in system design. Compromising the architectural vision of a software system weakens and will eventually break even the most well designed systems. Having an empowered Architect who can hold the vision and enforce compliance helps ensure a very successful software project.
- 31. Dec 9, 2025 Event Driven Programming 31 Cont’d… 4th Principle: What YouProduce, Others Will Consume Seldom is an industrial-strength software system constructed and used in a vacuum. In some way or other, someone else will use, maintain, document, or otherwise depend on being able to understand your system. always specify, design, & implement knowing someone else will have to understand what you are doing. audience for any product of software development is potentially large. Specify with an eye to the users. Design, keeping the implementers in mind. Code with concern for those that must maintain and extend the system. Someone may have to debug the code you write, and that makes them a user of your code. Making their job easier adds value to the system.
- 32. Dec 9, 2025 Event Driven Programming 32 Cont’d… 5th Principle: Be Opento the Future A system with a long lifetime has more value. True "industrial-strength" software systems must endure far longer. To do this successfully, these systems must be ready to adapt future changes. Systems that do this successfully are those that have been designed this way from the start. Never design yourself into a corner.
- 33. Dec 9, 2025 Event Driven Programming 33 Cont’d… 6th Principle: Plan Aheadfor Reuse Reusing saves time and effort. Achieving a high level of reuse is arguably the hardest goal to accomplish in developing a software system. reuse of code and designs has been proclaimed as a major benefit of using object-oriented technologies. To leverage the reuse possibilities that OO programming provides requires forethought and planning. Planning ahead for reuse reduces the cost and increases the value of both the reusable components and the systems into which they are incorporated.
- 34. Dec 9, 2025 Event Driven Programming 34 Cont’d… 7th Principle: Think! Thislast principle is probably the most overlooked. Placing clear, complete thought before action almost always produces better results. When clear thought has gone into a system, value comes out. Applying the first six principles requires intense thought, for which the potential rewards are enormous.
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