NEEDS 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.