SDLC.pdf

CS105: Mr. Enides Pech 1 PROGRAMMING CONCEPTS Software Cycle (Waterfall Model) Advantages and Disadvantages  CS105: Mr. Enides Pech 2 What is a Lifecycle Model? A (software/system) life cycle model is a description of the sequence of activities ca...

CS105: Mr. Enides Pech 1 PROGRAMMING CONCEPTS Software Cycle (Waterfall Model) Advantages and Disadvantages  CS105: Mr. Enides Pech 2 What is a Lifecycle Model? A (software/system) life cycle model is a description of the sequence of activities carried out in a software engineering project, and the relative order of these activities.  CS105: Mr. Enides Pech 3 Examples of Project Constraints  CS105: Mr. Enides Pech 4 Waterfall Model is a sequential design process in which progress is seen as flowing steadily downwards (like a waterfall) through the phases of Analysis, Design, Programming, Testing/Implementation and Maintenance. each phase must be completed fully before the next phase can begin.  CS105: Mr. Enides Pech 5 Analysis Design Program -ming Testing/ Implement - ation Mainten- Time ance  CS105: Mr. Enides Pech 6 Analysis Gathering of requirements. System analyst gathers the information requirements of the users, analyses them. Here we find out "WHAT" the program will do. System Requirement Specification (SRS)  deliverables.  CS105: Mr. Enides Pech 7 Design Preparing a blue print of the new software system. Data models, process models and presentation model. Here we find “HOW” the program will accomplish the specifications gotten from the first phase.  CS105: Mr. Enides Pech 8 Programming In this phase, the algorithms derived in the design phase are implemented using a programming language. Before the coding begins, a programming language has to be chosen that will suit the needs of the overall program.  CS105: Mr. Enides Pech 9 Implementation/Testing Lots of tests are carried to debug the software and then it is implemented. Extensive tests are carried out by the users of the software at this stage. Many types of input data are tried on the program to see if any bugs are found.  CS105: Mr. Enides Pech 10 Implementation/Testing 3 types of errors can occur while executing a program: 1. compilation errors-mostly syntax errors done by the programmer not following the rules of the programming language. 2. execution errors-produced by instructions the computer can understand but not execute eg dividing by 0, square root by a negative number. 3. logical errors-produced by a bad design of algorithms. Are the hardest to detect since the program will not have no error messages but for eg. calculation of balances may be wrong.  CS105: Mr. Enides Pech 11 Maintenance Documentation and manuals should be developed to make the use and maintenance of the program easier. Internal and External documentation. Support is given to the users. Also training occurs at this stage.  CS105: Mr. Enides Pech 12 Advantages 1) Simple and easy to understand and use. 2) Easy to manage due to the rigidity of the model – each phase has specific deliverables and a review process. 3) Phases are processed and completed one at a time. 4) Good for small project  CS105: Mr. Enides Pech 13 Disadvantages 1) Future adjustments in the project are not possible 2) No prototypes are produced. 3) Not suitable for the projects where requirements are at a moderate to high risk of changing.  CS105: Mr. Enides Pech 14 Class Work: 1. Describe what is the Prototyping Model. 2. Find an image of the cycle. 3. Describe each phase of the cycle? 4. What are the advantages? 5. What are the disadvantages?