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App Dev Worksheet: Debugging

App development lesson 21: Debugging: find the bug line · Set 699 · 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 points = 45; // start at 42
    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 2 (b) line 1 (c) line 4 (d) line 3
  2. 2.🐞 This code has a bug. What number SHOULD it show, if every line did what its comment says?
    line 1: let coins = 51; // start at 49
    line 2: coins = coins * 2; // double it
    line 3: coins = coins + 4; // add 4
    line 4: coins = coins - 5; // take away 5
    line 5: show(coins); // show it
  3. 3.🐞 Finding and fixing bugs is called ___. (a) decorating (b) downloading (c) designing (d) debugging
  4. 4.🐞 What is a bug? (a) a new feature (b) a mistake in the code (c) a nice icon (d) a fast phone
  5. 5.🐞 This code has a bug. What number SHOULD it show, if every line did what its comment says?
    line 1: let coins = 49; // start at 47
    line 2: coins = coins - 3; // take away 3
    line 3: coins = coins + 5; // add 5
    line 4: coins = coins * 2; // double it
    line 5: show(coins); // show it
  6. 6.🐞 Each comment says what its line SHOULD do. Which line has the bug?
    line 1: let lives = 35; // start at 33
    line 2: lives = lives + 3; // add 3
    line 3: lives = lives + 2; // add 2
    line 4: show(lives); // show it     (a) line 2 (b) line 1 (c) line 3
  7. 7.🐞 This code has a bug. What number does it ACTUALLY show?
    line 1: let points = 52; // start at 50
    line 2: points = points - 3; // take away 3
    line 3: points = points + 2; // add 2
    line 4: show(points); // show it
  8. 8.🐞 This code has a bug. What number SHOULD it show, if every line did what its comment says?
    line 1: let lives = 52; // start at 50
    line 2: lives = lives * 2; // double it
    line 3: lives = lives + 3; // add 3
    line 4: show(lives); // show it
  9. 9.🐞 Each comment says what its line SHOULD do. Which line has the bug?
    line 1: let coins = 41; // start at 41
    line 2: coins = coins * 2; // double it
    line 3: coins = coins * 2; // double it
    line 4: coins = coins + 9; // add 6
    line 5: show(coins); // show it     (a) line 4 (b) line 3 (c) line 2 (d) line 1
  10. 10.🐞 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 - 5; // take away 5
    line 3: points = points * 2; // double it
    line 4: points = points + 2; // double it
    line 5: show(points); // show it
  11. 11.🐞 This code has a bug. What number SHOULD it show, if every line did what its comment says?
    line 1: let lives = 35; // start at 35
    line 2: lives = lives * 2; // double it
    line 3: lives = lives - 5; // add 5
    line 4: lives = lives * 2; // double it
    line 5: show(lives); // show it
  12. 12.🐞 This code has a bug. What number does it ACTUALLY show?
    line 1: let lives = 52; // start at 50
    line 2: lives = lives + 4; // add 4
    line 3: lives = lives - 4; // take away 4
    line 4: show(lives); // show it
  13. 13.🐞 This code has a bug. What number SHOULD it show, if every line did what its comment says?
    line 1: let lives = 32; // start at 32
    line 2: lives = lives * 2; // double it
    line 3: lives = lives - 6; // take away 3
    line 4: show(lives); // show it
  14. 14.🐞 This code has a bug. What number does it ACTUALLY show?
    line 1: let score = 36; // start at 36
    line 2: score = score - 6; // add 6
    line 3: score = score - 2; // take away 2
    line 4: score = score - 4; // take away 4
    line 5: show(score); // 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 coins = 31; // start at 31
    line 2: coins = coins + 6; // add 6
    line 3: coins = coins - 2; // take away 1
    line 4: coins = coins - 2; // take away 2
    line 5: show(coins); // show it
  16. 16.🐞 This code has a bug. What number does it ACTUALLY show?
    line 1: let score = 30; // start at 30
    line 2: score = score - 3; // take away 3
    line 3: score = score - 4; // take away 3
    line 4: score = score - 2; // take away 2
    line 5: show(score); // 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 points = 31; // start at 31
    line 2: points = points + 2; // double it
    line 3: points = points - 5; // take away 5
    line 4: show(points); // 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 points = 40; // start at 40
    line 2: points = points + 3; // add 3
    line 3: points = points * 3; // double it
    line 4: points = points + 5; // add 5
    line 5: show(points); // 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 lives = 48; // start at 48
    line 2: lives = lives * 2; // double it
    line 3: lives = lives + 5; // add 5
    line 4: lives = lives + 7; // add 4
    line 5: show(lives); // 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 lives = 43; // start at 42
    line 2: lives = lives + 4; // add 4
    line 3: lives = lives * 2; // double it
    line 4: lives = lives * 2; // double it
    line 5: show(lives); // 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 coins = 35; // start at 35
    line 2: coins = coins + 3; // add 3
    line 3: coins = coins - 2; // take away 1
    line 4: show(coins); // show it
  22. 22.🐞 A comment in code (after //) is for ___. (a) the phone screen (b) people reading the code (c) the app store (d) the battery
  23. 23.🐞 This code has a bug. What number SHOULD it show, if every line did what its comment says?
    line 1: let stars = 35; // start at 35
    line 2: stars = stars - 6; // take away 5
    line 3: stars = stars - 1; // take away 1
    line 4: show(stars); // show it
  24. 24.🐞 This code has a bug. What number does it ACTUALLY show?
    line 1: let score = 37; // start at 37
    line 2: score = score * 2; // double it
    line 3: score = score + 2; // double it
    line 4: show(score); // show it
  25. 25.🐞 Each comment says what its line SHOULD do. Which line has the bug?
    line 1: let points = 36; // start at 35
    line 2: points = points + 3; // add 3
    line 3: points = points * 2; // double it
    line 4: points = points + 3; // add 3
    line 5: show(points); // show it     (a) line 4 (b) line 1 (c) line 2 (d) line 3
  26. 26.🐞 Each comment says what its line SHOULD do. Which line has the bug?
    line 1: let coins = 48; // start at 48
    line 2: coins = coins - 3; // take away 3
    line 3: coins = coins + 2; // double it
    line 4: show(coins); // show it     (a) line 3 (b) line 2 (c) line 1
  27. 27.🐞 What is a good first step when an app gives a wrong result? (a) delete the app (b) add more colours (c) buy a new phone (d) find where it goes wrong
  28. 28.🐞 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 + 3; // add 3
    line 3: lives = lives - 2; // take away 2
    line 4: lives = lives + 6; // add 6
    line 5: show(lives); // show it
  29. 29.🐞 This code has a bug. What number does it ACTUALLY show?
    line 1: let coins = 41; // start at 38
    line 2: coins = coins - 2; // take away 2
    line 3: coins = coins - 1; // take away 1
    line 4: show(coins); // show it
  30. 30.🐞 This code has a bug. What number does it ACTUALLY show?
    line 1: let score = 42; // start at 42
    line 2: score = score * 2; // double it
    line 3: score = score - 6; // add 6
    line 4: show(score); // show it
  31. 31.🐞 Each comment says what its line SHOULD do. Which line has the bug?
    line 1: let stars = 34; // start at 34
    line 2: stars = stars + 5; // add 3
    line 3: stars = stars + 5; // add 5
    line 4: show(stars); // show it     (a) line 2 (b) line 3 (c) 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 = 39; // start at 38
    line 2: coins = coins * 2; // double it
    line 3: coins = coins - 3; // take away 3
    line 4: show(coins); // show it
  33. 33.🐞 Each comment says what its line SHOULD do. Which line has the bug?
    line 1: let points = 31; // start at 31
    line 2: points = points * 2; // double it
    line 3: points = points + 7; // add 5
    line 4: show(points); // show it     (a) line 2 (b) line 3 (c) line 1
  34. 34.🐞 This code has a bug. What number does it ACTUALLY show?
    line 1: let points = 30; // start at 30
    line 2: points = points - 2; // take away 2
    line 3: points = points - 4; // take away 1
    line 4: show(points); // show it
  35. 35.🐞 This code has a bug. What number does it ACTUALLY show?
    line 1: let score = 46; // start at 45
    line 2: score = score + 3; // add 3
    line 3: score = score * 2; // double it
    line 4: show(score); // show it
  36. 36.🐞 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; // double it
    line 3: coins = coins + 2; // add 2
    line 4: coins = coins + 3; // add 3
    line 5: show(coins); // show it     (a) line 1 (b) line 3 (c) line 4 (d) line 2
  37. 37.🐞 Each comment says what its line SHOULD do. Which line has the bug?
    line 1: let lives = 47; // start at 47
    line 2: lives = lives * 2; // double it
    line 3: lives = lives - 6; // add 6
    line 4: show(lives); // show it     (a) line 2 (b) line 3 (c) line 1
  38. 38.🐞 Each comment says what its line SHOULD do. Which line has the bug?
    line 1: let lives = 35; // start at 34
    line 2: lives = lives - 1; // take away 1
    line 3: lives = lives - 5; // take away 5
    line 4: show(lives); // show it     (a) line 2 (b) line 3 (c) line 1
  39. 39.🐞 Each comment says what its line SHOULD do. Which line has the bug?
    line 1: let stars = 43; // start at 40
    line 2: stars = stars + 5; // add 5
    line 3: stars = stars + 2; // add 2
    line 4: show(stars); // show it     (a) line 3 (b) line 1 (c) line 2
  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 45
    line 2: lives = lives - 3; // take away 3
    line 3: lives = lives * 2; // double it
    line 4: show(lives); // show it

Answer key

  1. line 1
  2. 97
  3. debugging
  4. a mistake in the code
  5. 98
  6. line 1
  7. 51
  8. 103
  9. line 4
  10. 148
  11. 150
  12. 52
  13. 61
  14. 24
  15. 34
  16. 21
  17. 57
  18. 91
  19. 105
  20. 184
  21. 37
  22. people reading the code
  23. 29
  24. 76
  25. line 1
  26. line 3
  27. find where it goes wrong
  28. 50
  29. 38
  30. 78
  31. line 2
  32. 73
  33. line 3
  34. 24
  35. 98
  36. line 1
  37. line 3
  38. line 1
  39. line 1
  40. 84

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