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Complex problems can be solved using Top-down design model, also known as Step-wise refinement, where we break the problem into parts and then break the parts into sub parts and finally soon, each of the parts will be easy to code and accomplish…
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Top Down Design Model
» In top-down model, an overview of the system is
formulated, without going into detail for any part of
it.
» Each part of the system is then refined in more
details.
» Each new part may then be refined again, defining
it in yet more details until the entire specification is
detailed enough to validate the model.
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Top Down Concept in Problem Solving
» If we look at a problem as a whole, it may seem impossible to solve because it is so complex. Examples: ˃ writing a University System program
˃ writing a word processor
» Complex problems can be solved using top-down design, also known as stepwise refinement, where ˃ We break the problem into parts
˃ Then break the parts into parts
˃ Soon, each of the parts will be easy to do 3
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Top Down Design
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Top Down Design
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Advantages of Top-Down Design
» Breaking the problem into parts helps us to clarify what
needs to be done.
» At each step of refinement, the new parts become less
complicated and, therefore, easier to figure out.
» Parts of the solution may turn out to be reusable.
» Breaking the problem into parts allows more than one
person to work on the solution.
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Example
» Problem:
» Write a program that
draws this picture of a
house.
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outline of the house
chimney
Windows Door
The Top Level
» Draw the outline of the house
» Draw the chimney
» Draw the door
» Draw the windows
Main
Draw Chimney
Draw Door
Draw Windows
Draw Outline
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Observation
» The door has both a frame and knob. We could break this into two steps.
Main
Draw Chimney
Draw Door
Draw Windows
Draw Outline
Draw Door Frame
Draw Knob
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Bottom-up Design
» In bottom-up design individual parts of the system
are specified in details.
» The parts are then linked together to form larger
components, which are in turn linked until a
complete system is formed.
» Object-oriented languages such as C++ or JAVA use
bottom-up approach where each object is
identified first.
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Bottom up Design
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END
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