Lecture on Top-Down Design and Decomposition

Introduction

• Functions in programming help break down code
  • Avoid code repetition
  • Improve readability
• Strategy for deciding necessary functions is top-down design

Top-Down Design

• A problem-solving strategy
• Break a big problem into smaller, manageable problems
• Continue breaking problems until they are simple and solvable
• Makes code manageable and solution clear

Example: Movie Production

• Large task broken into smaller tasks:
  • Write a script
  • Hire cast
  • Film movie
  • Edit movie
• Each task can be further broken down (e.g., filming scenes)
• Tasks simplified to be solved by individual functions

Decomposition

• Breaking program into small, easy parts
• Decompose large, complex functions into small, simple ones
• Improves program readability
• Example: Karel's task broken into smaller functions

Benefits of Top-Down Design

1. Solve large, complicated problems by breaking into small chunks
2. Increases code readability
   • Easier to understand smaller functions
3. Facilitates collaboration
   • Splitting problem into subproblems allows team members to work independently

Example: Karel's Task

• Task: Karel to jump hurdles and run to finish line
• Process:
  • Define function run_to_hurdle
  • Define function jump_hurdle
  • Define function run_to_finish
• Each task is straightforward
• Functions need to be defined to solve each task

Defining Functions

1. Run to Hurdle Function
   • Karel moves three times
2. Jump Hurdle Function
   • Turn left, move, turn right, move
   • Repeat turning and moving to clear hurdle
3. Turn Right Function
   • Defined using three left turns

Completing the Task

• run_to_finish function defined as moving four times
• Demonstrates reusing functions without redefining
• Resets and tests code to ensure functionality

Conclusion

• Created a simple program using top-down design
• Solved smaller pieces to address the main problem
• Code is straightforward and easy to read
• Encouragement to practice top-down design