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App Dev Worksheet: Debugging

App development lesson 21: Debugging: find the bug line · Set 509 · 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.🐞 This code has a bug. What number does it ACTUALLY show?
    line 1: let lives = 46; // start at 46
    line 2: lives = lives * 2; // double it
    line 3: lives = lives - 4; // take away 1
    line 4: show(lives); // show it
  2. 2.🐞 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 + 4; // take away 4
    line 4: show(stars); // 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 stars = 39; // start at 37
    line 2: stars = stars + 3; // add 3
    line 3: stars = stars + 4; // add 4
    line 4: stars = stars - 1; // take away 1
    line 5: show(stars); // show it
  4. 4.🐞 Each comment says what its line SHOULD do. Which line has the bug?
    line 1: let coins = 44; // start at 41
    line 2: coins = coins + 6; // add 6
    line 3: coins = coins * 2; // double it
    line 4: coins = coins - 5; // take away 5
    line 5: show(coins); // show it     (a) line 2 (b) line 3 (c) line 1 (d) line 4
  5. 5.🐞 This code has a bug. What number does it ACTUALLY show?
    line 1: let coins = 41; // start at 41
    line 2: coins = coins + 3; // take away 3
    line 3: coins = coins - 3; // take away 3
    line 4: coins = coins * 2; // double it
    line 5: show(coins); // show it
  6. 6.🐞 This code has a bug. What number SHOULD it show, if every line did what its comment says?
    line 1: let points = 36; // start at 36
    line 2: points = points - 5; // add 5
    line 3: points = points * 2; // double it
    line 4: show(points); // show it
  7. 7.🐞 A comment in code (after //) is for ___. (a) the app store (b) the battery (c) people reading the code (d) the phone screen
  8. 8.🐞 This code has a bug. What number does it ACTUALLY show?
    line 1: let lives = 33; // start at 30
    line 2: lives = lives + 4; // add 4
    line 3: lives = lives + 3; // add 3
    line 4: show(lives); // show it
  9. 9.🐞 This code has a bug. What number does it ACTUALLY show?
    line 1: let coins = 34; // start at 34
    line 2: coins = coins - 4; // take away 2
    line 3: coins = coins * 2; // double it
    line 4: show(coins); // show it
  10. 10.🐞 This code has a bug. What number SHOULD it show, if every line did what its comment says?
    line 1: let coins = 46; // start at 46
    line 2: coins = coins + 6; // add 4
    line 3: coins = coins + 3; // add 3
    line 4: coins = coins + 5; // add 5
    line 5: show(coins); // show it
  11. 11.🐞 Each comment says what its line SHOULD do. Which line has the bug?
    line 1: let points = 42; // start at 42
    line 2: points = points * 2; // double it
    line 3: points = points + 4; // add 3
    line 4: show(points); // show it     (a) line 2 (b) line 3 (c) line 1
  12. 12.🐞 Each comment says what its line SHOULD do. Which line has the bug?
    line 1: let points = 40; // start at 40
    line 2: points = points - 5; // add 5
    line 3: points = points + 6; // add 6
    line 4: points = points + 4; // add 4
    line 5: show(points); // show it     (a) line 2 (b) line 3 (c) line 1 (d) line 4
  13. 13.🐞 This code has a bug. What number does it ACTUALLY show?
    line 1: let points = 33; // start at 33
    line 2: points = points * 2; // double it
    line 3: points = points - 2; // add 2
    line 4: points = points * 2; // double it
    line 5: show(points); // show it
  14. 14.🐞 This code has a bug. What number SHOULD it show, if every line did what its comment says?
    line 1: let stars = 48; // start at 48
    line 2: stars = stars * 2; // double it
    line 3: stars = stars + 2; // double it
    line 4: stars = stars + 5; // add 5
    line 5: show(stars); // show it
  15. 15.🐞 This code has a bug. What number SHOULD it show, if every line did what its comment says?
    line 1: let score = 36; // start at 35
    line 2: score = score + 6; // add 6
    line 3: score = score - 1; // take away 1
    line 4: show(score); // show it
  16. 16.🐞 This code has a bug. What number does it ACTUALLY show?
    line 1: let points = 34; // start at 33
    line 2: points = points * 2; // double it
    line 3: points = points * 2; // double it
    line 4: show(points); // show it
  17. 17.🐞 After fixing a bug you should ___. (a) release at once (b) never test (c) test it again (d) delete the test
  18. 18.🐞 This code has a bug. What number does it ACTUALLY show?
    line 1: let coins = 49; // start at 49
    line 2: coins = coins + 2; // add 2
    line 3: coins = coins + 3; // add 3
    line 4: coins = coins + 8; // add 5
    line 5: show(coins); // 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 = 42; // start at 42
    line 2: coins = coins + 5; // add 5
    line 3: coins = coins + 2; // take away 2
    line 4: coins = coins - 2; // take away 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 = 40; // start at 40
    line 2: coins = coins - 7; // take away 5
    line 3: coins = coins - 3; // take away 3
    line 4: show(coins); // show it
  21. 21.🐞 This code has a bug. What number SHOULD it show, if every line did what its comment says?
    line 1: let points = 36; // start at 33
    line 2: points = points - 5; // take away 5
    line 3: points = points - 4; // take away 4
    line 4: points = points + 2; // add 2
    line 5: show(points); // show it
  22. 22.🐞 This code has a bug. What number does it ACTUALLY show?
    line 1: let score = 41; // start at 41
    line 2: score = score + 3; // take away 3
    line 3: score = score * 2; // double it
    line 4: show(score); // show it
  23. 23.🐞 What is a good first step when an app gives a wrong result? (a) add more colours (b) find where it goes wrong (c) delete the app (d) buy a new phone
  24. 24.🐞 This code has a bug. What number SHOULD it show, if every line did what its comment says?
    line 1: let stars = 34; // start at 34
    line 2: stars = stars - 4; // take away 3
    line 3: stars = stars - 2; // take away 2
    line 4: stars = stars + 2; // add 2
    line 5: show(stars); // show it
  25. 25.🐞 Each comment says what its line SHOULD do. Which line has the bug?
    line 1: let coins = 42; // start at 40
    line 2: coins = coins - 1; // take away 1
    line 3: coins = coins + 3; // add 3
    line 4: show(coins); // show it     (a) line 3 (b) line 1 (c) line 2
  26. 26.🐞 This code has a bug. What number SHOULD it show, if every line did what its comment says?
    line 1: let lives = 37; // start at 37
    line 2: lives = lives + 3; // add 3
    line 3: lives = lives + 3; // add 2
    line 4: lives = lives + 4; // add 4
    line 5: show(lives); // show it
  27. 27.🐞 This code has a bug. What number does it ACTUALLY show?
    line 1: let coins = 37; // start at 37
    line 2: coins = coins - 3; // take away 3
    line 3: coins = coins - 6; // add 6
    line 4: coins = coins - 4; // take away 4
    line 5: show(coins); // show it
  28. 28.🐞 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 36
    line 2: score = score * 2; // double it
    line 3: score = score - 5; // take away 5
    line 4: show(score); // show it
  29. 29.🐞 This code has a bug. What number does it ACTUALLY show?
    line 1: let lives = 45; // start at 45
    line 2: lives = lives + 2; // double it
    line 3: lives = lives - 5; // take away 5
    line 4: show(lives); // show it
  30. 30.🐞 This code has a bug. What number does it ACTUALLY show?
    line 1: let stars = 41; // start at 41
    line 2: stars = stars + 3; // add 2
    line 3: stars = stars * 2; // double it
    line 4: stars = stars * 2; // double it
    line 5: show(stars); // show it
  31. 31.🐞 This code has a bug. What number does it ACTUALLY show?
    line 1: let coins = 36; // start at 36
    line 2: coins = coins + 2; // double it
    line 3: coins = coins - 5; // take away 5
    line 4: coins = coins + 2; // add 2
    line 5: show(coins); // show it
  32. 32.🐞 This code has a bug. What number does it ACTUALLY show?
    line 1: let coins = 34; // start at 34
    line 2: coins = coins - 3; // take away 3
    line 3: coins = coins + 7; // add 5
    line 4: coins = coins + 6; // add 6
    line 5: show(coins); // show it
  33. 33.🐞 Each comment says what its line SHOULD do. Which line has the bug?
    line 1: let coins = 37; // start at 37
    line 2: coins = coins * 2; // double it
    line 3: coins = coins + 2; // double it
    line 4: coins = coins - 4; // take away 4
    line 5: show(coins); // show it     (a) line 1 (b) line 3 (c) line 4 (d) line 2
  34. 34.🐞 This code has a bug. What number does it ACTUALLY show?
    line 1: let coins = 43; // start at 40
    line 2: coins = coins + 4; // add 4
    line 3: coins = coins + 2; // add 2
    line 4: show(coins); // show it
  35. 35.🐞 What is a bug? (a) a nice icon (b) a fast phone (c) a new feature (d) a mistake in the code
  36. 36.🐞 Each comment says what its line SHOULD do. Which line has the bug?
    line 1: let points = 42; // start at 39
    line 2: points = points * 2; // double it
    line 3: points = points * 2; // double it
    line 4: points = points * 2; // double it
    line 5: show(points); // show it     (a) line 1 (b) line 2 (c) line 4 (d) line 3
  37. 37.🐞 This code has a bug. What number SHOULD it show, if every line did what its comment says?
    line 1: let stars = 49; // start at 49
    line 2: stars = stars + 9; // add 6
    line 3: stars = stars * 2; // double it
    line 4: show(stars); // show it
  38. 38.🐞 This code has a bug. What number does it ACTUALLY show?
    line 1: let lives = 35; // start at 35
    line 2: lives = lives + 2; // double it
    line 3: lives = lives * 2; // double it
    line 4: show(lives); // show it
  39. 39.🐞 This code has a bug. What number does it ACTUALLY show?
    line 1: let score = 33; // start at 30
    line 2: score = score - 4; // take away 4
    line 3: score = score + 4; // add 4
    line 4: score = score * 2; // double it
    line 5: show(score); // 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 score = 30; // start at 30
    line 2: score = score * 2; // double it
    line 3: score = score + 4; // add 3
    line 4: score = score - 5; // take away 5
    line 5: show(score); // show it

Answer key

  1. 88
  2. 72
  3. 43
  4. line 1
  5. 82
  6. 82
  7. people reading the code
  8. 40
  9. 60
  10. 58
  11. line 3
  12. line 2
  13. 128
  14. 197
  15. 40
  16. 136
  17. test it again
  18. 62
  19. 43
  20. 32
  21. 26
  22. 88
  23. find where it goes wrong
  24. 31
  25. line 1
  26. 46
  27. 24
  28. 67
  29. 42
  30. 176
  31. 35
  32. 44
  33. line 3
  34. 49
  35. a mistake in the code
  36. line 1
  37. 110
  38. 74
  39. 66
  40. 58

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