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Wednesday 26 June 2019

Introduction to Software Engineering

Software is a program or set of programs containing instructions which provide desired functionality
·        Computer programs
·        Data structure
·        Documentation
Engineering is the processes of designing and building something that serves a particular purpose and find a cost effective solution to problems.
Software Engineering is a systematic approach to the design, development, operation, and maintenance of a software system.
                                                              or
Software engineering is an engineering branch associated with development of software product using well-defined scientific principles, methods and procedures. The outcome of software engineering is an efficient and reliable software product

Software Evolution

The process of developing a software product using software engineering principles and methods is referred to as software evolution. This includes the initial development of software and its maintenance and updates, till desired software product is developed, which satisfies the expected requirements.
Evolution starts from the requirement gathering process. After which developers create a prototype of the intended software and show it to the users to get their feedback at the early stage of software product development. The users suggest changes, on which several consecutive updates and maintenance keep on changing too. This process changes to the original software, till the desired software is accomplished.

Software Evolution Laws
Lehman has given laws for software evolution. He divided the software into three different categories:

S-type (static-type) - This is a software, which works strictly according to defined specifications and solutions. The solution and the method to achieve it, both are immediately understood before coding. The s-type software is least subjected to changes hence this is the simplest of all. For example, calculator program for mathematical computation.

P-type (practical-type) - This is a software with a collection of procedures. This is defined by exactly what procedures can do. In this software, the specifications can be described but the solution is not obvious instantly. For example, gaming software.

E-type (embedded-type) - This software works closely as the requirement of real-world environment. This software has a high degree of evolution as there are various changes in laws, taxes etc. in the real world situations. For example, Online trading software.


Objectives of Software Engineering:
1.Maintainability –It should be feasible for the software to evolve to meet changing requirements.
2.Correctness –A software product is correct, if the different requirements as specified in the SRS document have been correctly implemented.
3.Reusability –A software product has good reusability, if the different modules of the product can easily be reused to develop new products.
4.Testability –Here software facilitates both the establishment of test criteria and the evaluation of the software with respect to those criteria.
5.Reliability –It is an attribute of software quality. The extent to which a program can be expected to perform its desired function, over an arbitrary time period.
6.Portability –In this case, software can be transferred from one computer system or environment to another.
7.Adaptability –In this case, software allows differing system constraints and user needs to be satisfied by making changes to the software.

Software Paradigms
Software paradigms refer to the methods and steps, which are taken while designing the software. There are many methods proposed and are in work today, but we need to see where in the software engineering these paradigms stand. These can be combined into various categories, though each of them is contained in one another:

Programming paradigm is a subset of Software design paradigm which is further a subset of Software development paradigm.


Software Development Paradigm:
This Paradigm is known as software engineering paradigms where all the engineering concepts pertaining to the development of software are applied. It includes various researches and requirement gathering which helps the software product to build.
It consists of
  1. ·      Requirement gathering
  2. ·      Software design
  3. ·      Programming


Software Design Paradigm:
This paradigm is a part of Software Development and it includes –
  1. ·      Design
  2. ·      Maintenance
  3. ·      Programming

Programming Paradigm:
This paradigm is related closely to programming aspect of software development. This includes –
  1. ·      Coding
  2. ·      Testing
  3. ·      Integration


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 he 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 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.

Goals of software engineering
To develop a software that satisfies user requirements
To develop a software within the budget
To develop a software within time limit
To improve overall quality of the software
To control and execute the cost of software
To produce reliable and efficient software
To produce proper document along with a software

To develop a software that is to maintain ,modify and debug 

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