WHAT IS THE NEED OF SOFTWARE ENGINEERING

Scalability-
 is the ability of a system, network, or process to handle a growing amount of work in a capable manner or its ability to be enlarged to accommodate that growth.

Q-WHAT IS A SCLABLE   IN TERM OF SOFTWARE  -
ANS -
1- It is the ability of a computer application or product (hardware or software) to continue to function well when it (or its context) is changed in size or volume in order to meet a user need. Typically, the rescaling is to a larger size or volume. The rescaling can be of the product itself (for example, a line of computer systems of different sizes in terms of storage, RAM, and so forth) or in the scalable object's movement to a new context (for example, a new operating system).

An example: John Young in his book Exploring IBM's New-Age Mainframesdescribes the RS/6000 SP operating system as one that delivers scalability ("the ability to retain performance levels when adding additional processors"). Another example: In printing, scalable fonts are fonts that can be resized smaller or larger using software without losing quality.

2) It is the ability not only to function well in the rescaled situation, but to actually take full advantage of it. For example, an application program would be scalable if it could be moved from a smaller to a larger operating systemand take full advantage of the larger operating system in terms ofperformance (user response time and so forth) and the larger number of users that could be handled.

It is usually easier to have scalability upward rather than downward since developers often must make full use of a system's resources (for example, the amount of disk storage available) when an application is initially coded. Scaling a product downward may mean trying to achieve the same results in a more constrained environment.

Q- WHAT IS A  RELIABLE SOFTWARE ?

ANS

1.The ability of an apparatus, machine, or system to consistently perform its intended or required function or mission, on demand and without degradation or failure.

2.Manufacturing: The probability of failure-free performance over an item's useful life, or a specified timeframe, under specified environmental and duty-cycle conditions. Often expressed as mean time between failures (MTBF) or reliability coefficient. Also called quality over time. See also availability.

OR

Software Reliability is the probability of failure-free software operation for a specified period of time in a specified environment. Software Reliability is also an important factor affecting system reliability. It differs from hardware reliability in that it reflects the design perfection, rather than manufacturing perfection. The high complexity of software is the major contributing factor of Software Reliability problems. Software Reliability is not a function of time - although researchers have come up with models relating the two. The modeling technique for Software Reliability is reaching its prosperity, but before using the technique, we must carefully select the appropriate model that can best suit our case. Measurement in software is still in its infancy. No good quantitative methods have been developed to represent Software Reliability without excessive limitations. Various approaches can be used to improve the reliability of software, however, it is hard to balance development time and budget with software reliability.

Q - acceptable software .

 software which  full fill requirements of a user .

Q - FEASIBILITY  STUDY .

As the name implies, a feasibility study is an analysis of the viability of an idea. The feasibility study focuses on helping answer the essential question of “should we proceed with the proposed project idea?” All activities of the study are directed toward helping answer this question.

An analysis and evaluation of a proposed project to determine if it (1) is technically feasible, (2) is feasible within the estimated cost, and (3) will be profitable. Feasibility studies are almost always conducted where large sums are at stake. Also called feasibility analysis. See also cost benefit analysis.

                           NEED OF SOFTWARE ENGINEERING 

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.

Characteristics 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

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.