(Extra Notes) Introduction to Software Engineering.pdf

MODULE 1 LECTURE NOTE 1 INTRODUCTION TO SOFTWARE ENGINEERING The term software engineering is composed of two words, software and eng...

MODULE 1 LECTURE NOTE 1 INTRODUCTION TO SOFTWARE ENGINEERING The term software engineering is composed of two words, software and engineering. Software is more than just a program code. A program is an executable code, which serves some computational purpose. Software is considered to be a collection of executable programming code, associated libraries and documentations. Software, when made for a specific requirement is called software product. Engineering on the other hand, is all about developing products, using well-defined, scientific principles and methods. So, we can define software engineering as an engineering branch associated with the development of software product using well-defined scientific principles, methods and procedures. The outcome of software engineering is an efficient and reliable software product. IEEE defines software engineering as: The application of a systematic, disciplined, quantifiable approach to the development, operation and maintenance of software. We can alternatively view it as a systematic collection of past experience. The experience is arranged in the form of methodologies and guidelines. A small program can be written without using software engineering principles. But if one wants to develop a large software product, then software engineering principles are absolutely necessary to achieve a good quality software cost effectively. Without using software engineering principles it would be difficult to develop large programs. In industry it is usually needed to develop large programs to accommodate multiple functions. A problem with developing such large commercial programs is that the complexity and difficulty levels of the programs increase exponentially with their sizes. Software engineering helps to reduce this programming complexity. Software engineering principles use two important techniques to reduce problem complexity: abstraction and decomposition. The principle of abstraction implies that a problem can be simplified by omitting irrelevant details. In other words, the main purpose of abstraction is to consider only those aspects of the problem that are relevant for certain purpose and suppress other aspects that are not relevant for the given purpose. Once the simpler problem is solved, then the omitted details can be taken into consideration to solve the next lower level abstraction, and so on. Abstraction is a powerful way of reducing the complexity of the problem. The other approach to tackle problem complexity is DEPT OF CSE & IT VSSUT, Burla decomposition. In this technique, a complex problem is divided into several smaller problems and then the smaller problems are solved one by one. However, in this technique any random decomposition of a problem into smaller parts will not help. The problem has to be decomposed such that each component of the decomposed problem can be solved independently and then the solution of the different components can be combined to get the full solution. A good decomposition of a problem should minimize interactions among various components. If the different subcomponents are interrelated, then the different components cannot be solved separately and the desired reduction in complexity will not be realized. NEED OF SOFTWARE ENGINEERING The need of software engineering arises because of higher rate of change in user requirements and environment on which the software is working. Large software - It is easier to build a wall than to a house or building, likewise, as the size of software become large engineering has to step to give it a scientific process. Scalability- If the software process were not based on scientific and engineering concepts, it would be easier to re-create new software than to scale an existing one. Cost- As hardware industry has shown its skills and huge manufacturing has lower down the price of computer and electronic hardware. But the cost of software remains high if proper process is not adapted. Dynamic Nature- The always growing and adapting nature of software hugely depends upon the environment in which the user works. If the nature of software is always changing, new enhancements need to be done in the existing one. This is where software engineering plays a good role. Quality Management- Better process of software development provides better and quality software product. CHARACTERESTICS OF GOOD SOFTWARE A software product can be judged by what it offers and how well it can be used. This software must satisfy on the following grounds: Operational Transitional Maintenance DEPT OF CSE & IT VSSUT, Burla Well-engineered and crafted software is expected to have the following characteristics: Operational This tells us how well software works in operations. It can be measured on: Budget Usability Efficiency Correctness Functionality Dependability Security Safety Transitional This aspect is important when the software is moved from one platform to another: Portability Interoperability Reusability Adaptability Maintenance This aspect briefs about how well a software has the capabilities to maintain itself in the ever- changing environment: Modularity Maintainability Flexibility Scalability In short, Software engineering is a branch of computer science, which uses well-defined engineering concepts required to produce efficient, durable, scalable, in-budget and on-time software products DEPT OF CSE & IT VSSUT, Burla