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App Dev Worksheet: Debugging

App development lesson 21: Debugging: find the bug line · Set 767 · 40 questions
TalentJR

Developer's tip (Compare with the comment): Read each line and its comment (after //): does the code do exactly that? Actual = run the lines as written. Expected = follow every comment. After the fix, test again.

NameDateTime takenScore ___ / 40
  1. 1.🐞 After fixing a bug you should ___. (a) test it again (b) never test (c) release at once (d) delete the test
  2. 2.🐞 This code has a bug. What number does it ACTUALLY show?
    line 1: let lives = 47; // start at 47
    line 2: lives = lives - 6; // add 6
    line 3: lives = lives + 4; // add 4
    line 4: show(lives); // show it
  3. 3.🐞 This code has a bug. What number SHOULD it show, if every line did what its comment says?
    line 1: let lives = 49; // start at 49
    line 2: lives = lives * 2; // double it
    line 3: lives = lives + 9; // add 6
    line 4: show(lives); // show it
  4. 4.🐞 This code has a bug. What number SHOULD it show, if every line did what its comment says?
    line 1: let lives = 46; // start at 44
    line 2: lives = lives + 6; // add 6
    line 3: lives = lives + 4; // add 4
    line 4: lives = lives + 2; // add 2
    line 5: show(lives); // show it
  5. 5.🐞 This code has a bug. What number SHOULD it show, if every line did what its comment says?
    line 1: let score = 45; // start at 45
    line 2: score = score - 3; // add 3
    line 3: score = score * 2; // double it
    line 4: score = score - 1; // take away 1
    line 5: show(score); // show it
  6. 6.🐞 What is a good first step when an app gives a wrong result? (a) delete the app (b) add more colours (c) find where it goes wrong (d) buy a new phone
  7. 7.🐞 This code has a bug. What number does it ACTUALLY show?
    line 1: let score = 51; // start at 48
    line 2: score = score - 5; // take away 5
    line 3: score = score + 2; // add 2
    line 4: show(score); // show it
  8. 8.🐞 This code has a bug. What number does it ACTUALLY show?
    line 1: let lives = 32; // start at 32
    line 2: lives = lives * 2; // double it
    line 3: lives = lives + 4; // take away 4
    line 4: lives = lives * 2; // double it
    line 5: show(lives); // show it
  9. 9.🐞 This code has a bug. What number does it ACTUALLY show?
    line 1: let points = 47; // start at 47
    line 2: points = points - 5; // add 5
    line 3: points = points + 5; // add 5
    line 4: show(points); // show it
  10. 10.🐞 A comment in code (after //) is for ___. (a) the phone screen (b) the app store (c) the battery (d) people reading the code
  11. 11.🐞 This code has a bug. What number does it ACTUALLY show?
    line 1: let lives = 47; // start at 47
    line 2: lives = lives - 2; // take away 1
    line 3: lives = lives * 2; // double it
    line 4: show(lives); // show it
  12. 12.🐞 What is a bug? (a) a mistake in the code (b) a fast phone (c) a new feature (d) a nice icon
  13. 13.🐞 Each comment says what its line SHOULD do. Which line has the bug?
    line 1: let coins = 33; // start at 33
    line 2: coins = coins + 2; // double it
    line 3: coins = coins - 4; // take away 4
    line 4: show(coins); // show it     (a) line 2 (b) line 3 (c) line 1
  14. 14.🐞 Each comment says what its line SHOULD do. Which line has the bug?
    line 1: let coins = 47; // start at 44
    line 2: coins = coins - 2; // take away 2
    line 3: coins = coins - 5; // take away 5
    line 4: coins = coins - 5; // take away 5
    line 5: show(coins); // show it     (a) line 2 (b) line 4 (c) line 3 (d) line 1
  15. 15.🐞 This code has a bug. What number SHOULD it show, if every line did what its comment says?
    line 1: let points = 31; // start at 30
    line 2: points = points * 2; // double it
    line 3: points = points - 4; // take away 4
    line 4: points = points + 4; // add 4
    line 5: show(points); // show it
  16. 16.🐞 This code has a bug. What number does it ACTUALLY show?
    line 1: let stars = 34; // start at 34
    line 2: stars = stars + 2; // double it
    line 3: stars = stars * 2; // double it
    line 4: show(stars); // show it
  17. 17.🐞 This code has a bug. What number SHOULD it show, if every line did what its comment says?
    line 1: let score = 41; // start at 41
    line 2: score = score + 3; // add 2
    line 3: score = score * 2; // double it
    line 4: score = score - 5; // take away 5
    line 5: show(score); // show it
  18. 18.🐞 This code has a bug. What number SHOULD it show, if every line did what its comment says?
    line 1: let score = 42; // start at 42
    line 2: score = score - 1; // take away 1
    line 3: score = score - 2; // add 2
    line 4: score = score - 1; // take away 1
    line 5: show(score); // show it
  19. 19.🐞 This code has a bug. What number SHOULD it show, if every line did what its comment says?
    line 1: let coins = 36; // start at 36
    line 2: coins = coins + 3; // add 3
    line 3: coins = coins + 8; // add 6
    line 4: coins = coins + 2; // add 2
    line 5: show(coins); // show it
  20. 20.🐞 This code has a bug. What number SHOULD it show, if every line did what its comment says?
    line 1: let coins = 43; // start at 43
    line 2: coins = coins - 2; // add 2
    line 3: coins = coins * 2; // double it
    line 4: show(coins); // show it
  21. 21.🐞 Each comment says what its line SHOULD do. Which line has the bug?
    line 1: let lives = 31; // start at 31
    line 2: lives = lives + 5; // add 5
    line 3: lives = lives + 5; // take away 5
    line 4: lives = lives + 3; // add 3
    line 5: show(lives); // show it     (a) line 3 (b) line 1 (c) line 4 (d) line 2
  22. 22.🐞 This code has a bug. What number does it ACTUALLY show?
    line 1: let score = 46; // start at 46
    line 2: score = score + 2; // add 2
    line 3: score = score * 3; // double it
    line 4: score = score + 5; // add 5
    line 5: show(score); // show it
  23. 23.🐞 Each comment says what its line SHOULD do. Which line has the bug?
    line 1: let stars = 40; // start at 40
    line 2: stars = stars + 2; // double it
    line 3: stars = stars - 4; // take away 4
    line 4: show(stars); // show it     (a) line 3 (b) line 2 (c) line 1
  24. 24.🐞 Each comment says what its line SHOULD do. Which line has the bug?
    line 1: let score = 49; // start at 49
    line 2: score = score * 2; // double it
    line 3: score = score - 5; // add 5
    line 4: show(score); // show it     (a) line 3 (b) line 1 (c) line 2
  25. 25.🐞 This code has a bug. What number SHOULD it show, if every line did what its comment says?
    line 1: let coins = 32; // start at 31
    line 2: coins = coins + 5; // add 5
    line 3: coins = coins * 2; // double it
    line 4: coins = coins - 5; // take away 5
    line 5: show(coins); // show it
  26. 26.🐞 This code has a bug. What number SHOULD it show, if every line did what its comment says?
    line 1: let score = 34; // start at 34
    line 2: score = score + 4; // add 2
    line 3: score = score - 1; // take away 1
    line 4: show(score); // show it
  27. 27.🐞 Each comment says what its line SHOULD do. Which line has the bug?
    line 1: let score = 40; // start at 40
    line 2: score = score * 2; // double it
    line 3: score = score * 3; // double it
    line 4: score = score * 2; // double it
    line 5: show(score); // show it     (a) line 4 (b) line 1 (c) line 3 (d) line 2
  28. 28.🐞 Finding and fixing bugs is called ___. (a) debugging (b) downloading (c) designing (d) decorating
  29. 29.🐞 This code has a bug. What number SHOULD it show, if every line did what its comment says?
    line 1: let score = 34; // start at 32
    line 2: score = score - 3; // take away 3
    line 3: score = score + 4; // add 4
    line 4: show(score); // show it
  30. 30.🐞 Each comment says what its line SHOULD do. Which line has the bug?
    line 1: let points = 32; // start at 31
    line 2: points = points - 1; // take away 1
    line 3: points = points + 2; // add 2
    line 4: points = points * 2; // double it
    line 5: show(points); // show it     (a) line 2 (b) line 4 (c) line 3 (d) line 1
  31. 31.🐞 This code has a bug. What number SHOULD it show, if every line did what its comment says?
    line 1: let coins = 41; // start at 41
    line 2: coins = coins - 5; // take away 5
    line 3: coins = coins - 4; // take away 4
    line 4: coins = coins * 3; // double it
    line 5: show(coins); // show it
  32. 32.🐞 This code has a bug. What number SHOULD it show, if every line did what its comment says?
    line 1: let score = 38; // start at 38
    line 2: score = score * 3; // double it
    line 3: score = score * 2; // double it
    line 4: show(score); // show it
  33. 33.🐞 Each comment says what its line SHOULD do. Which line has the bug?
    line 1: let coins = 36; // start at 36
    line 2: coins = coins - 6; // add 6
    line 3: coins = coins - 2; // take away 2
    line 4: show(coins); // show it     (a) line 3 (b) line 1 (c) line 2
  34. 34.🐞 Each comment says what its line SHOULD do. Which line has the bug?
    line 1: let score = 44; // start at 41
    line 2: score = score + 5; // add 5
    line 3: score = score + 2; // add 2
    line 4: show(score); // show it     (a) line 1 (b) line 3 (c) line 2
  35. 35.🐞 This code has a bug. What number SHOULD it show, if every line did what its comment says?
    line 1: let lives = 48; // start at 46
    line 2: lives = lives * 2; // double it
    line 3: lives = lives + 6; // add 6
    line 4: show(lives); // show it
  36. 36.🐞 Each comment says what its line SHOULD do. Which line has the bug?
    line 1: let lives = 37; // start at 37
    line 2: lives = lives - 6; // add 6
    line 3: lives = lives + 3; // add 3
    line 4: lives = lives + 4; // add 4
    line 5: show(lives); // show it     (a) line 1 (b) line 3 (c) line 2 (d) line 4
  37. 37.🐞 This code has a bug. What number SHOULD it show, if every line did what its comment says?
    line 1: let lives = 46; // start at 43
    line 2: lives = lives + 4; // add 4
    line 3: lives = lives * 2; // double it
    line 4: lives = lives + 4; // add 4
    line 5: show(lives); // show it
  38. 38.🐞 This code has a bug. What number SHOULD it show, if every line did what its comment says?
    line 1: let score = 31; // start at 31
    line 2: score = score - 1; // take away 1
    line 3: score = score - 3; // add 3
    line 4: show(score); // show it
  39. 39.🐞 This code has a bug. What number does it ACTUALLY show?
    line 1: let points = 41; // start at 39
    line 2: points = points - 2; // take away 2
    line 3: points = points + 3; // add 3
    line 4: points = points + 4; // add 4
    line 5: show(points); // show it
  40. 40.🐞 This code has a bug. What number SHOULD it show, if every line did what its comment says?
    line 1: let lives = 47; // start at 44
    line 2: lives = lives - 3; // take away 3
    line 3: lives = lives - 4; // take away 4
    line 4: lives = lives - 1; // take away 1
    line 5: show(lives); // show it

Answer key

  1. test it again
  2. 45
  3. 104
  4. 56
  5. 95
  6. find where it goes wrong
  7. 48
  8. 136
  9. 47
  10. people reading the code
  11. 90
  12. a mistake in the code
  13. line 2
  14. line 1
  15. 60
  16. 72
  17. 81
  18. 42
  19. 47
  20. 90
  21. line 3
  22. 149
  23. line 2
  24. line 3
  25. 67
  26. 35
  27. line 3
  28. debugging
  29. 33
  30. line 1
  31. 64
  32. 152
  33. line 2
  34. line 1
  35. 98
  36. line 2
  37. 98
  38. 33
  39. 46
  40. 36

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