Difference between Top-Down Approach and Bottom-Up Approach

Sep 26, 2011 by

What is difference between Top-Down Approach and Bottom-Up Approach

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  1. daniel

    In designing, there are two approaches that you could possibly use and they are known as bottom-up and top-down approaches. Very few individuals comprehend the distinctions between these major approaches. This article attempts to highlight key features found in both approaches, thus helping readers to distinguish them.

    1. Function

    The top-down form normally begins with top level modules and then continues downwards to lower level modules. However, in reality, no system uses this method strictly and designers normally bounce between bottom-up and top-down to complete their designs. Conversely bottom-up starts from lowest subsystems to the greatest modules or subsystems. For this particular approach, the structure chart is needed for determining the actual steps for execution. Furthermore, drivers are also need for completing this kind of design.

    2. Use

    Whereas top down begins from an abstract point and then it moves to attain a concrete design, the bottom-up is simply the reverse because it starts with the solid design so as to obtain an abstract entity. In consequence, a brand new system is best designed through using the top-down approach. Conversely, bottom-up is used in reverse engineering and when it the aim to is to comprehend another design.

    3. Advantages

    The advantages of using both approaches also differ. For example, top-down has several benefits that include making it simpler to visualize the design and it also offers a feeling of completeness. Moreover, it is also simple to test the progress of the design at any specific stage. Equally, bottom-up has various benefits including its ease of making changes and managing them and also the capability of writing great unit tests.

    Both approaches also have demerits as top-down style creates the possibility of unnecessary business logics. Similarly, bottom-down is disadvantageous as lots of effort will be needed for writing test cases. Also, progress is not easily verifiable during mid stage like when using top down style.

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