Characteristics of an Algorithm

While designing an algorithm as a solution to a given problem, we must take care of the following five important characteristics of an algorithm: 1. Finiteness An algorithm must terminate after a finite number of steps and further each step must be executable in finite amount of time. In order to establish a sequence of steps as an algorithm, it should be established that it terminates (in finite number of steps) on all allowed inputs. 2. Definiteness (no ambiguity)Each step of an algorithm must be precisely defined; the action to be carried...

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Difference between Problems and Instances

The difference between the two concepts viz., ‘problem’ and ‘instance’, can be understood in terms of the following example. An instance of a problem is also called a question. We know that the roots of a general quadratic equation  (1) are given by the equation  (2) where a, b, c may be any real numbers except the restriction that a ≠ 0. Now, if we take a = 3, b = 4 and c = 1, we get the particular equation  (3) Using (2), the...

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Euclid’s Algorithm for Finding G.C.D. of two Natural Numbers m & n

E1. {Find Remainder}. Divide m by n and let r be the (new) remainder {r have 0≤r<n} E2. {Is r zero?} If r = 0, the algorithm terminates and n is the answer. Otherwise, E3. {Interchange}. Let the new value of m be the current value of n and the new value of n be the current value of r. Go back to Step E1. The termination of the above method is guaranteed, as m and n must reduce in each iteration and r must become zero in finite number of repetitions of steps E1, E2 and E3. The great Greek mathematician Euclid sometimes between fourth and third...

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Notation for expressing algorithms

This issue of notation for representations of algorithms will be discussed in some detail, later. However, mainly, some combinations of mathematical symbols, English phrases and sentences, and some sort of pseudo-high-level language notations, shall be used for the purpose. Particularly, the symbol ‘←’ is used for assignment. For example, x←y + 3, means that 3 is added to the value of the variable y and the resultant value becomes the new value of the variable x. However, the value of y remains unchanged. If in an algorithm, more than one variables...

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Capability Maturity Models, Maturity Levels & their Key Process Areas

The process models are based on various software development phases whereas the capability models have an entirely different basis of development. They are based upon the capabilities of software. It was developed by Software Engineering Institute (SEI). In this model, significant emphasis is given to the techniques to improve the “software quality” and “process maturity”. In this model a strategy for improving Software process is devised. It is...

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Spiral Model - Software Development Models

This model can be considered as the model, which combines the strengths of various other models. Conventional software development processes do not take uncertainties into account. Important software projects have failed because of unforeseen risks. The other models view the software process as a linear activity whereas this model considers it as a spiral process. This is made by representing the iterative development cycle as an expanding spiral. The...

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Prototyping Model - Software Development Models

In Prototyping Model, a working model of actual software is developed initially. The prototype is just like sample software having lesser functional capabilities and low reliability and it does not undergo through the rigorous testing phase. Developing a working prototype in the first phase overcomes the disadvantage of the waterfall model where the reporting about serious errors is possible only after completion of software development. The working...

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Iterative Enhancement Model - Software Development Models

Iterative Enhancement Model was developed to remove the shortcomings of waterfall model. In this model, the phases of software development remain the same, but the construction and delivery is done in the iterative mode. In the first iteration, a less capable product is developed and delivered for use. This product satisfies only a subset of the requirements. In the next iteration, a product with incremental features is developed. Every iteration...

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Waterfall Model - Software Development Model

It is the simplest, oldest and most widely used process model. In this model, each phase of the life cycle is completed before the start of a new phase. It is actually the first engineering approach of software development. Figure 1 depicts Water Fall Model. Figure 1 : Waterfall model The functions of various phases are discussed in software process technology. The waterfall model provides a systematic and sequential approach to software development...

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Importance of Software Engineering

As the application domains of software are becoming complicated and design of big software without a systematic approach is virtually impossible, the field of software engineering is increasingly gaining importance. It is now developing like an industry. Thus, the industry has to answer following or similar queries of clients: What is the best approach to design of software? Why the cost of software is too high? Why can’t we find all errors? Why is there always some gap between claimed performance and actual performance? To answer...

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