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Week 2 – Basic Constructs 1

Week 2 – Basic Constructs 1. Sequential Conditional branching Looping. Last week. Introduced Stepwise refinement There is often more than one solution to a problem Discussion and working in groups is a useful technique to include in problem-solving. Sequences. Instruction 1

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Week 2 – Basic Constructs 1

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  1. Week 2 – Basic Constructs 1 • Sequential • Conditional branching • Looping

  2. Last week • Introduced • Stepwise refinement • There is often more than one solution to a problem • Discussion and working in groups is a useful technique to include in problem-solving.

  3. Sequences • Instruction 1 • Instruction 2 • Instruction 3

  4. Sequences • The instructions follow on from each other, always the same.

  5. Sequences • Starting at the first and ‘flowing’ down.

  6. Conditional Statements • If test 1 is true then do instruction 1 • If test 2 is true then do instruction 2 if false then do instruction 3

  7. Conditional Statements • The flow of the program can be altered by whether a test is true or not.

  8. Looping • Instruction 1 • Instruction 2 • Go back to instruction 1 • Sometimes we want to repeat a list of instructions.

  9. Looping – with a test • Instruction 1 • Instruction 2 • Go back to instruction 1 while test is true • Repeat a list of instructions, but only if a test is true.

  10. Problem 2.1 • A routine to calculate a tip based on the overall service. • No tip if the service is poor • 10% tip if the service is okay • 15% tip if the service is good or better

  11. Problem 2.1– Problems • What does poor, okay or good mean?

  12. Problem 2.1– Problems • How do we quantify these? • We could use marks out of 10. • <3 for poor • 3<=marks<=8 for okay • >8 for good

  13. Problem 2.1– Problems • What is our tip a percentage of? • We know this is going to be a percentage of the price of the bill.

  14. Analysis • Inputs needed • Price of the meal • Marks for service

  15. Analysis • Outputs • Price + tip

  16. Analysis • Rules • <3 for poor • 3<=marks<=8 for okay • >8 for good

  17. Design • Input the price • Input the marks out of 10 • If marks<3then Tip=0; • If 3<=marks<=8 then Tip =Price*0.1; • If marks>8 then Tip=Price*0.15 • Display Tip • Display Price

  18. Problem 2.2 • What would we have to do to the previous routine if we want it to repeated calculated tips?

  19. Problem 2.2 • One of the basic constructs is the loop. • The next question is what to loop? • In this case all the routine needs to loop.

  20. Start of loop 1 • Input the price • Input the marks out of 10 • If marks<3 • Tip=0; • If 3<=marks<=8 • Tip =Price*0.1; • If marks>8 • Tip=Price*0.15 • Display Tip and price • Go back to start of loop 1

  21. convention • instructions that are the result of a particular conditional statement or loop are indented below it signify they belong to that instruction.

  22. Problem 2.3 • Design a system to make the robots you met last week move towards a wall detect the wall is there and reverse backwards and turn to the right 90 degrees.

  23. Problem 2.3 • Let’s experiment: In small groups use drawings (does need to be neat) to express your ideas while you thinking about this as a group. Then write down your choosen solution as a set of instructions.

  24. Start of one possible solution (needs expanding) • Move the robot forward • Check if the wall is detected • If wall is detected then • Go back wards • Turn to the right 90 degrees • Repeat this whole process

  25. Problem 2.4: • Write down a detailed list of instructions to open a bottle. • Have a go yourselves • Have you thought of all situations?

  26. Problem 2.5 • Wall-following robot • Keeps the wall to its right and follows the contour of the room. • It can touch the wall.

  27. Problem 2.6 • Try problems 2.3 or 2.5 with different sensors.

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