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App Dev Worksheet: Debugging

App development lesson 21: Debugging: find the bug line · Set 320 · 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 stars = 30; // start at 30
    line 2: stars = stars * 2; // double it
    line 3: stars = stars + 2; // take away 2
    line 4: show(stars); // show it
  2. 2.🐞 A comment in code (after //) is for ___. (a) the phone screen (b) the app store (c) the battery (d) people reading the code
  3. 3.🐞 This code has a bug. What number does it ACTUALLY show?
    line 1: let points = 44; // start at 44
    line 2: points = points * 3; // double it
    line 3: points = points * 2; // double it
    line 4: show(points); // show it
  4. 4.🐞 This code has a bug. What number does it ACTUALLY show?
    line 1: let lives = 38; // start at 38
    line 2: lives = lives * 2; // double it
    line 3: lives = lives + 3; // take away 3
    line 4: show(lives); // show it
  5. 5.🐞 Finding and fixing bugs is called ___. (a) debugging (b) designing (c) downloading (d) decorating
  6. 6.🐞 This code has a bug. What number does it ACTUALLY show?
    line 1: let stars = 42; // start at 42
    line 2: stars = stars + 6; // add 6
    line 3: stars = stars * 2; // double it
    line 4: stars = stars - 5; // take away 3
    line 5: show(stars); // show it
  7. 7.🐞 What is a good first step when an app gives a wrong result? (a) delete the app (b) buy a new phone (c) find where it goes wrong (d) add more colours
  8. 8.🐞 This code has a bug. What number SHOULD it show, if every line did what its comment says?
    line 1: let lives = 33; // start at 32
    line 2: lives = lives * 2; // double it
    line 3: lives = lives + 6; // add 6
    line 4: show(lives); // show it
  9. 9.🐞 This code has a bug. What number SHOULD it show, if every line did what its comment says?
    line 1: let points = 41; // start at 40
    line 2: points = points + 3; // add 3
    line 3: points = points * 2; // double it
    line 4: show(points); // show it
  10. 10.🐞 After fixing a bug you should ___. (a) delete the test (b) never test (c) release at once (d) test it again
  11. 11.🐞 Each comment says what its line SHOULD do. Which line has the bug?
    line 1: let coins = 49; // start at 49
    line 2: coins = coins + 3; // add 3
    line 3: coins = coins - 4; // take away 4
    line 4: coins = coins * 3; // double it
    line 5: show(coins); // show it     (a) line 3 (b) line 1 (c) line 4 (d) line 2
  12. 12.🐞 Each comment says what its line SHOULD do. Which line has the bug?
    line 1: let stars = 37; // start at 37
    line 2: stars = stars - 2; // add 2
    line 3: stars = stars - 1; // take away 1
    line 4: stars = stars * 2; // double it
    line 5: show(stars); // show it     (a) line 1 (b) line 4 (c) line 3 (d) line 2
  13. 13.🐞 What is a bug? (a) a new feature (b) a nice icon (c) a mistake in the code (d) a fast phone
  14. 14.🐞 Each comment says what its line SHOULD do. Which line has the bug?
    line 1: let score = 51; // start at 48
    line 2: score = score + 4; // add 4
    line 3: score = score + 5; // add 5
    line 4: show(score); // show it     (a) line 3 (b) line 2 (c) line 1
  15. 15.🐞 Each comment says what its line SHOULD do. Which line has the bug?
    line 1: let score = 46; // start at 46
    line 2: score = score * 2; // double it
    line 3: score = score * 3; // double it
    line 4: show(score); // show it     (a) line 2 (b) line 1 (c) line 3
  16. 16.🐞 Each comment says what its line SHOULD do. Which line has the bug?
    line 1: let score = 37; // start at 34
    line 2: score = score * 2; // double it
    line 3: score = score - 1; // take away 1
    line 4: show(score); // show it     (a) line 2 (b) line 3 (c) line 1
  17. 17.🐞 This code has a bug. What number SHOULD it show, if every line did what its comment says?
    line 1: let coins = 31; // start at 31
    line 2: coins = coins * 2; // double it
    line 3: coins = coins - 4; // take away 2
    line 4: show(coins); // 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 = 41; // start at 41
    line 2: score = score * 2; // double it
    line 3: score = score + 1; // take away 1
    line 4: score = score * 2; // double it
    line 5: show(score); // show it
  19. 19.🐞 This code has a bug. What number does it ACTUALLY show?
    line 1: let score = 43; // start at 41
    line 2: score = score - 5; // take away 5
    line 3: score = score * 2; // double it
    line 4: show(score); // show it
  20. 20.🐞 Each comment says what its line SHOULD do. Which line has the bug?
    line 1: let score = 36; // start at 35
    line 2: score = score + 5; // add 5
    line 3: score = score - 3; // take away 3
    line 4: show(score); // show it     (a) line 2 (b) line 3 (c) line 1
  21. 21.🐞 Each comment says what its line SHOULD do. Which line has the bug?
    line 1: let score = 34; // start at 34
    line 2: score = score - 2; // take away 2
    line 3: score = score + 2; // double it
    line 4: show(score); // show it     (a) line 2 (b) line 1 (c) line 3
  22. 22.🐞 This code has a bug. What number SHOULD it show, if every line did what its comment says?
    line 1: let stars = 40; // start at 40
    line 2: stars = stars + 5; // add 5
    line 3: stars = stars * 3; // double it
    line 4: show(stars); // show it
  23. 23.🐞 Each comment says what its line SHOULD do. Which line has the bug?
    line 1: let coins = 43; // start at 43
    line 2: coins = coins * 2; // double it
    line 3: coins = coins + 1; // take away 1
    line 4: show(coins); // show it     (a) line 2 (b) line 1 (c) line 3
  24. 24.🐞 Each comment says what its line SHOULD do. Which line has the bug?
    line 1: let points = 35; // start at 34
    line 2: points = points + 2; // add 2
    line 3: points = points * 2; // double it
    line 4: points = points + 4; // add 4
    line 5: show(points); // show it     (a) line 2 (b) line 1 (c) line 3 (d) line 4
  25. 25.🐞 This code has a bug. What number SHOULD it show, if every line did what its comment says?
    line 1: let points = 51; // start at 48
    line 2: points = points + 2; // add 2
    line 3: points = points + 3; // add 3
    line 4: points = points * 2; // double it
    line 5: show(points); // show it
  26. 26.🐞 Each comment says what its line SHOULD do. Which line has the bug?
    line 1: let lives = 41; // start at 41
    line 2: lives = lives + 2; // add 2
    line 3: lives = lives * 3; // double it
    line 4: lives = lives + 4; // add 4
    line 5: show(lives); // show it     (a) line 2 (b) line 1 (c) line 3 (d) line 4
  27. 27.🐞 Each comment says what its line SHOULD do. Which line has the bug?
    line 1: let coins = 31; // start at 30
    line 2: coins = coins + 2; // add 2
    line 3: coins = coins + 5; // add 5
    line 4: coins = coins * 2; // double it
    line 5: show(coins); // show it     (a) line 4 (b) line 2 (c) line 3 (d) line 1
  28. 28.🐞 This code has a bug. What number does it ACTUALLY show?
    line 1: let points = 41; // start at 41
    line 2: points = points - 4; // take away 4
    line 3: points = points * 3; // double it
    line 4: show(points); // show it
  29. 29.🐞 Each comment says what its line SHOULD do. Which line has the bug?
    line 1: let stars = 51; // start at 50
    line 2: stars = stars + 6; // add 6
    line 3: stars = stars - 1; // take away 1
    line 4: show(stars); // show it     (a) line 1 (b) line 2 (c) line 3
  30. 30.🐞 This code has a bug. What number does it ACTUALLY show?
    line 1: let score = 53; // start at 50
    line 2: score = score - 2; // take away 2
    line 3: score = score + 5; // add 5
    line 4: show(score); // show it
  31. 31.🐞 Each comment says what its line SHOULD do. Which line has the bug?
    line 1: let points = 35; // start at 34
    line 2: points = points - 2; // take away 2
    line 3: points = points + 6; // add 6
    line 4: points = points + 3; // add 3
    line 5: show(points); // show it     (a) line 2 (b) line 4 (c) line 3 (d) line 1
  32. 32.🐞 This code has a bug. What number SHOULD it show, if every line did what its comment says?
    line 1: let coins = 48; // start at 47
    line 2: coins = coins + 6; // add 6
    line 3: coins = coins + 5; // add 5
    line 4: show(coins); // show it
  33. 33.🐞 This code has a bug. What number SHOULD it show, if every line did what its comment says?
    line 1: let coins = 50; // start at 49
    line 2: coins = coins + 3; // add 3
    line 3: coins = coins * 2; // double it
    line 4: show(coins); // show it
  34. 34.🐞 This code has a bug. What number does it ACTUALLY show?
    line 1: let lives = 39; // start at 39
    line 2: lives = lives - 5; // add 5
    line 3: lives = lives + 3; // add 3
    line 4: show(lives); // show it
  35. 35.🐞 This code has a bug. What number does it ACTUALLY show?
    line 1: let score = 42; // start at 42
    line 2: score = score + 3; // add 3
    line 3: score = score - 2; // take away 1
    line 4: score = score * 2; // double it
    line 5: show(score); // show it
  36. 36.🐞 This code has a bug. What number SHOULD it show, if every line did what its comment says?
    line 1: let stars = 44; // start at 44
    line 2: stars = stars + 5; // add 2
    line 3: stars = stars + 4; // add 4
    line 4: stars = stars + 2; // add 2
    line 5: show(stars); // show it
  37. 37.🐞 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 + 4; // add 4
    line 3: points = points + 7; // add 6
    line 4: points = points - 3; // take away 3
    line 5: show(points); // show it
  38. 38.🐞 Each comment says what its line SHOULD do. Which line has the bug?
    line 1: let coins = 50; // start at 50
    line 2: coins = coins - 5; // add 5
    line 3: coins = coins - 2; // take away 2
    line 4: coins = coins - 4; // take away 4
    line 5: show(coins); // show it     (a) line 4 (b) line 3 (c) line 1 (d) line 2
  39. 39.🐞 This code has a bug. What number SHOULD it show, if every line did what its comment says?
    line 1: let points = 42; // start at 42
    line 2: points = points * 3; // double it
    line 3: points = points + 2; // add 2
    line 4: show(points); // show it
  40. 40.🐞 Each comment says what its line SHOULD do. Which line has the bug?
    line 1: let coins = 50; // start at 50
    line 2: coins = coins * 2; // double it
    line 3: coins = coins - 3; // add 3
    line 4: coins = coins - 1; // take away 1
    line 5: show(coins); // show it     (a) line 1 (b) line 3 (c) line 4 (d) line 2

Answer key

  1. 62
  2. people reading the code
  3. 264
  4. 79
  5. debugging
  6. 91
  7. find where it goes wrong
  8. 70
  9. 86
  10. test it again
  11. line 4
  12. line 2
  13. a mistake in the code
  14. line 1
  15. line 3
  16. line 1
  17. 60
  18. 162
  19. 76
  20. line 1
  21. line 3
  22. 90
  23. line 3
  24. line 1
  25. 106
  26. line 3
  27. line 1
  28. 111
  29. line 1
  30. 56
  31. line 1
  32. 58
  33. 104
  34. 37
  35. 86
  36. 52
  37. 43
  38. line 2
  39. 86
  40. line 3

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