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# Top Down and Bottom Up Design Model

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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 and Bottom Up Design Model

1. 1. Top Down & Bottom Up Design Model Abdul Rahman Sherzad
2. 2. 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. 2 https://www.facebook.com/Oxus20
3. 3. 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 topdown 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 https://www.facebook.com/Oxus20
4. 4. Top Down Design 4 https://www.facebook.com/Oxus20
5. 5. Top Down Design 5 https://www.facebook.com/Oxus20
6. 6. 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. 6 https://www.facebook.com/Oxus20
7. 7. Example » Problem: outline of the house chimney » Write a program that draws this picture of a house. Windows Door 7 https://www.facebook.com/Oxus20
8. 8. The Top Level » » » » Draw the outline of the house Draw the chimney Draw the door Draw the windows Main Draw Outline Draw Chimney Draw Door Draw Windows 8 https://www.facebook.com/Oxus20
9. 9. Observation » The door has both a frame and knob. We could break this into two steps. Main Draw Outline Draw Chimney Draw Door Frame Draw Door Draw Windows Draw Knob 9 https://www.facebook.com/Oxus20
10. 10. 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. 10 https://www.facebook.com/Oxus20
11. 11. Bottom up Design 11 https://www.facebook.com/Oxus20