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App Dev Worksheet: Debugging

App development lesson 21: Debugging: find the bug line · Set 752 · 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.🐞 Each comment says what its line SHOULD do. Which line has the bug?
    line 1: let score = 38; // start at 38
    line 2: score = score + 6; // add 3
    line 3: score = score + 5; // add 5
    line 4: score = score + 6; // add 6
    line 5: show(score); // show it     (a) line 1 (b) line 4 (c) line 2 (d) line 3
  2. 2.🐞 What is a bug? (a) a nice icon (b) a mistake in the code (c) a fast phone (d) a new feature
  3. 3.🐞 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 32
    line 2: coins = coins + 6; // add 6
    line 3: coins = coins * 2; // double it
    line 4: coins = coins - 6; // add 6
    line 5: show(coins); // show it
  4. 4.🐞 This code has a bug. What number does it ACTUALLY show?
    line 1: let coins = 46; // start at 46
    line 2: coins = coins - 1; // take away 1
    line 3: coins = coins * 3; // double it
    line 4: coins = coins - 2; // take away 2
    line 5: show(coins); // show it
  5. 5.🐞 This code has a bug. What number does it ACTUALLY show?
    line 1: let stars = 45; // start at 45
    line 2: stars = stars + 2; // add 2
    line 3: stars = stars + 4; // add 4
    line 4: stars = stars * 3; // double it
    line 5: show(stars); // show it
  6. 6.🐞 Finding and fixing bugs is called ___. (a) debugging (b) designing (c) downloading (d) decorating
  7. 7.🐞 A comment in code (after //) is for ___. (a) the phone screen (b) the battery (c) the app store (d) people reading the code
  8. 8.🐞 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 + 2; // add 2
    line 4: score = score - 2; // take away 2
    line 5: show(score); // show it
  9. 9.🐞 This code has a bug. What number does it ACTUALLY show?
    line 1: let points = 48; // start at 47
    line 2: points = points * 2; // double it
    line 3: points = points + 5; // add 5
    line 4: points = points * 2; // double it
    line 5: 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.🐞 This code has a bug. What number SHOULD it show, if every line did what its comment says?
    line 1: let coins = 37; // start at 37
    line 2: coins = coins - 2; // take away 2
    line 3: coins = coins + 6; // add 6
    line 4: coins = coins * 3; // double it
    line 5: show(coins); // show it
  12. 12.🐞 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 + 2; // add 2
    line 3: score = score * 2; // double it
    line 4: score = score + 6; // add 5
    line 5: show(score); // show it
  13. 13.🐞 Each comment says what its line SHOULD do. Which line has the bug?
    line 1: let coins = 32; // start at 32
    line 2: coins = coins + 2; // double it
    line 3: coins = coins * 2; // double it
    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 stars = 39; // start at 39
    line 2: stars = stars - 3; // add 3
    line 3: stars = stars * 2; // double it
    line 4: show(stars); // show it     (a) line 3 (b) line 1 (c) line 2
  15. 15.🐞 Each comment says what its line SHOULD do. Which line has the bug?
    line 1: let coins = 41; // start at 40
    line 2: coins = coins - 2; // take away 2
    line 3: coins = coins * 2; // double it
    line 4: show(coins); // show it     (a) line 3 (b) line 2 (c) line 1
  16. 16.🐞 Each comment says what its line SHOULD do. Which line has the bug?
    line 1: let coins = 48; // start at 47
    line 2: coins = coins * 2; // double it
    line 3: coins = coins - 2; // take away 2
    line 4: show(coins); // show it     (a) line 2 (b) line 1 (c) line 3
  17. 17.🐞 Each comment says what its line SHOULD do. Which line has the bug?
    line 1: let stars = 45; // start at 43
    line 2: stars = stars * 2; // double it
    line 3: stars = stars + 2; // add 2
    line 4: stars = stars * 2; // double it
    line 5: show(stars); // show it     (a) line 3 (b) line 2 (c) line 1 (d) line 4
  18. 18.🐞 What is a good first step when an app gives a wrong result? (a) buy a new phone (b) add more colours (c) find where it goes wrong (d) delete the app
  19. 19.🐞 This code has a bug. What number does it ACTUALLY show?
    line 1: let stars = 35; // start at 33
    line 2: stars = stars + 6; // add 6
    line 3: stars = stars + 3; // add 3
    line 4: show(stars); // show it
  20. 20.🐞 Each comment says what its line SHOULD do. Which line has the bug?
    line 1: let stars = 47; // start at 47
    line 2: stars = stars - 4; // take away 4
    line 3: stars = stars * 2; // double it
    line 4: stars = stars - 6; // take away 5
    line 5: show(stars); // show it     (a) line 1 (b) line 3 (c) line 4 (d) line 2
  21. 21.🐞 This code has a bug. What number does it ACTUALLY show?
    line 1: let points = 32; // start at 32
    line 2: points = points + 3; // add 3
    line 3: points = points * 3; // double it
    line 4: points = points + 4; // add 4
    line 5: show(points); // show it
  22. 22.🐞 This code has a bug. What number SHOULD it show, if every line did what its comment says?
    line 1: let points = 45; // start at 45
    line 2: points = points - 4; // add 4
    line 3: points = points * 2; // double it
    line 4: points = points - 4; // take away 4
    line 5: show(points); // show it
  23. 23.🐞 This code has a bug. What number does it ACTUALLY show?
    line 1: let score = 34; // start at 34
    line 2: score = score - 4; // take away 2
    line 3: score = score * 2; // double it
    line 4: show(score); // show it
  24. 24.🐞 This code has a bug. What number does it ACTUALLY show?
    line 1: let stars = 33; // start at 30
    line 2: stars = stars - 3; // take away 3
    line 3: stars = stars - 4; // take away 4
    line 4: show(stars); // show it
  25. 25.🐞 This code has a bug. What number SHOULD it show, if every line did what its comment says?
    line 1: let score = 47; // start at 45
    line 2: score = score * 2; // double it
    line 3: score = score * 2; // double it
    line 4: show(score); // show it
  26. 26.🐞 This code has a bug. What number does it ACTUALLY show?
    line 1: let stars = 37; // start at 37
    line 2: stars = stars - 2; // take away 2
    line 3: stars = stars + 3; // add 2
    line 4: stars = stars * 2; // double it
    line 5: show(stars); // show it
  27. 27.🐞 This code has a bug. What number SHOULD it show, if every line did what its comment says?
    line 1: let stars = 45; // start at 45
    line 2: stars = stars + 3; // add 3
    line 3: stars = stars - 3; // take away 2
    line 4: show(stars); // 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 stars = 36; // start at 34
    line 2: stars = stars + 2; // add 2
    line 3: stars = stars - 3; // take away 3
    line 4: stars = stars + 5; // add 5
    line 5: show(stars); // show it
  29. 29.🐞 This code has a bug. What number does it ACTUALLY show?
    line 1: let lives = 30; // start at 30
    line 2: lives = lives * 2; // double it
    line 3: lives = lives - 5; // take away 3
    line 4: lives = lives - 2; // take away 2
    line 5: show(lives); // show it
  30. 30.🐞 Each comment says what its line SHOULD do. Which line has the bug?
    line 1: let points = 38; // start at 38
    line 2: points = points + 2; // double it
    line 3: points = points + 5; // add 5
    line 4: show(points); // show it     (a) line 2 (b) line 1 (c) line 3
  31. 31.🐞 Each comment says what its line SHOULD do. Which line has the bug?
    line 1: let lives = 37; // start at 35
    line 2: lives = lives + 6; // add 6
    line 3: lives = lives + 2; // add 2
    line 4: show(lives); // show it     (a) line 3 (b) line 1 (c) line 2
  32. 32.🐞 Each comment says what its line SHOULD do. Which line has the bug?
    line 1: let score = 39; // start at 39
    line 2: score = score + 4; // add 4
    line 3: score = score + 6; // add 6
    line 4: score = score + 4; // add 3
    line 5: show(score); // show it     (a) line 3 (b) line 2 (c) line 1 (d) line 4
  33. 33.🐞 Each comment says what its line SHOULD do. Which line has the bug?
    line 1: let points = 41; // start at 41
    line 2: points = points - 2; // take away 2
    line 3: points = points - 4; // take away 4
    line 4: points = points + 3; // take away 3
    line 5: show(points); // show it     (a) line 4 (b) line 1 (c) line 2 (d) line 3
  34. 34.🐞 This code has a bug. What number does it ACTUALLY show?
    line 1: let lives = 38; // start at 37
    line 2: lives = lives * 2; // double it
    line 3: lives = lives - 3; // take away 3
    line 4: show(lives); // show it
  35. 35.🐞 Each comment says what its line SHOULD do. Which line has the bug?
    line 1: let coins = 47; // start at 47
    line 2: coins = coins * 3; // double it
    line 3: coins = coins - 4; // take away 4
    line 4: coins = coins * 2; // double it
    line 5: show(coins); // show it     (a) line 1 (b) line 3 (c) line 4 (d) line 2
  36. 36.🐞 Each comment says what its line SHOULD do. Which line has the bug?
    line 1: let coins = 44; // start at 44
    line 2: coins = coins + 6; // add 6
    line 3: coins = coins + 5; // add 3
    line 4: show(coins); // show it     (a) line 2 (b) line 1 (c) line 3
  37. 37.🐞 This code has a bug. What number does it ACTUALLY show?
    line 1: let coins = 40; // start at 40
    line 2: coins = coins + 2; // double it
    line 3: coins = coins + 3; // add 3
    line 4: show(coins); // show it
  38. 38.🐞 Each comment says what its line SHOULD do. Which line has the bug?
    line 1: let coins = 41; // start at 40
    line 2: coins = coins + 2; // add 2
    line 3: coins = coins + 3; // add 3
    line 4: coins = coins - 2; // take away 2
    line 5: show(coins); // show it     (a) line 4 (b) line 3 (c) line 2 (d) line 1
  39. 39.🐞 Each comment says what its line SHOULD do. Which line has the bug?
    line 1: let lives = 32; // start at 31
    line 2: lives = lives + 2; // add 2
    line 3: lives = lives + 6; // add 6
    line 4: show(lives); // show it     (a) line 1 (b) line 3 (c) line 2
  40. 40.🐞 Each comment says what its line SHOULD do. Which line has the bug?
    line 1: let stars = 44; // start at 44
    line 2: stars = stars - 2; // add 2
    line 3: stars = stars - 2; // take away 2
    line 4: show(stars); // show it     (a) line 3 (b) line 1 (c) line 2

Answer key

  1. line 2
  2. a mistake in the code
  3. 82
  4. 133
  5. 153
  6. debugging
  7. people reading the code
  8. 51
  9. 202
  10. test it again
  11. 82
  12. 71
  13. line 2
  14. line 2
  15. line 1
  16. line 1
  17. line 1
  18. find where it goes wrong
  19. 44
  20. line 4
  21. 109
  22. 94
  23. 60
  24. 26
  25. 180
  26. 76
  27. 46
  28. 38
  29. 53
  30. line 2
  31. line 1
  32. line 4
  33. line 4
  34. 73
  35. line 2
  36. line 3
  37. 45
  38. line 1
  39. line 1
  40. line 2

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