CS605 Quiz

Introduction to Software Engineering

This course is a continuation of the first course on Software Engineering. In order to set the context of our discussion, let us first look at some of the definitions of software engineering.

Software Engineering is the set of processes and tools to develop software. Software Engineering is the combination of all the tools, techniques, and processes that used in software production. Therefore Software Engineering encompasses all those things that are used in software production like:

Programming Language Programming Language Design Software Design Techniques Tools Testing Maintenance Development etc.

So all those thing that are related to software are also related to software engineering.

Some of you might have thought that how programming language design could be related to software engineering. If you look more closely at the software engineering definitions described above then you will definitely see that software engineering is related to all those things that are helpful in software development. So is the case with programming language design. Programming language design is one of the major successes in last fifty years. The design of Ada language was considered as the considerable effort in software engineering.

These days object-oriented programming is widely being used. If programming languages will not support object-orientation then it will be very difficult to implement objectoriented design using object-oriented principles. All these efforts made the basis of software engineering.

Well-Engineered Software

Let’s talk something about what is well-engineered software. Well-engineered software is one that has the following characteristics.

It is reliable It has good user-interface It has acceptable performance It is of good quality It is cost-effective Every company can build software with unlimited resources but well-engineered software is one that conforms to all characteristics listed above.

Software has very close relationship with economics. When ever we talk about engineering systems we always first analyze whether this is economically feasible or not. Therefore you have to engineer all the activities of software development while keeping its economical feasibility intact.

The major challenges for a software engineer is that he has to build software within limited time and budget in a cost-effective way and with good quality

Therefore well-engineered software has the following characteristics.

Provides the required functionality Maintainable Reliable Efficient User-friendly Cost-effective

But most of the times software engineers ends up in conflict among all these goals. It is also a big challenge for a software engineer to resolve all these conflicts.

The Balancing Act!

Software Engineering is actually the balancing act. You have to balance many things like cost, user friendliness, Efficiency, Reliability etc. You have to analyze which one is the more important feature for your software is it reliability, efficiency, user friendliness or something else. There is always a trade-off among all these requirements of software. It may be the case that if you try to make it more user-friendly then the efficiency may suffer. And if you try to make it more cost-effective then reliability may suffer. Therefore there is always a trade-off between these characteristics of software.

These requirements may be conflicting. For example, there may be tension among the following:

Cost vs. Efficiency Cost vs. Reliability Efficiency vs. User-interface

A Software Engineer is required to analyze these conflicting entities and tries to strike a balance.

Challenge is to balance these requirements.

Software Engineers always confront with the challenge to make a good balance of all these tings depending on the requirements of the particular software system at hand. He should analyze how much weight should all these things get such that it will have acceptable quality, acceptable performance and will have acceptable user-interface.

In some software the efficiency is more important and desirable. For example if we talk about a cruise missile or a nuclear reactor controller that are droved by the software systems then performance and reliability is far more important than the cost-effectiveness and user-friendliness. In these cases if your software does not react within a certain amount of time then it may result in the disaster like Chernobyl accident.

Therefore software development is a process of balancing among different characteristics of software described in the previous section. And it is an art to come up with such a good balance and that art can be learned from experience.

Law of diminishing returns

In order to understand this concept lets take a look at an example. Most of you have noticed that if you dissolve sugar in a glass of water then the sweetness of water will increase gradually. But at a certain level of saturation no more sugar will dissolved into water. Therefore at that point of saturation the sweetness of water will not increase even if you add more sugar into it.

The law of diminishing act describes the same phenomenon. Similar is the case with software engineering. Whenever you perform any task like improving the efficiency of the system, try to improve its quality or user friendliness then all these things involves an element of cost. If the quality of your system is not acceptable then with the investment of little money it could be improved to a higher degree. But after reaching at a certain level of quality the return on investment on the system’s quality will become reduced. Meaning that the return on investment on quality of software will be less than the effort or money we invest. Therefore, in most of the cases, after reaching at a reasonable level of quality we do not try to improve the quality of software any further. This phenomenon is shown in the figure below.

benefit · cost · benefit · cost · Software Background