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App Dev Worksheet: Debugging

App development lesson 21: Debugging: find the bug line · Set 774 · 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 SHOULD it show, if every line did what its comment says?
    line 1: let stars = 32; // start at 32
    line 2: stars = stars - 5; // take away 3
    line 3: stars = stars + 4; // add 4
    line 4: show(stars); // show it
  2. 2.🐞 What is a good first step when an app gives a wrong result? (a) buy a new phone (b) delete the app (c) add more colours (d) find where it goes wrong
  3. 3.🐞 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; // take away 3
    line 3: coins = coins * 2; // double it
    line 4: show(coins); // 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 = 31; // start at 31
    line 2: lives = lives - 4; // add 4
    line 3: lives = lives * 2; // double it
    line 4: show(lives); // show it
  5. 5.🐞 After fixing a bug you should ___. (a) release at once (b) never test (c) test it again (d) delete the test
  6. 6.🐞 This code has a bug. What number SHOULD it show, if every line did what its comment says?
    line 1: let points = 49; // start at 49
    line 2: points = points + 6; // add 4
    line 3: points = points + 4; // add 4
    line 4: show(points); // show it
  7. 7.🐞 Finding and fixing bugs is called ___. (a) decorating (b) downloading (c) designing (d) debugging
  8. 8.🐞 This code has a bug. What number does it ACTUALLY show?
    line 1: let lives = 48; // start at 48
    line 2: lives = lives - 5; // take away 5
    line 3: lives = lives - 4; // add 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 coins = 45; // start at 43
    line 2: coins = coins + 5; // add 5
    line 3: coins = coins - 3; // take away 3
    line 4: coins = coins + 2; // add 2
    line 5: 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 score = 30; // start at 30
    line 2: score = score + 5; // add 5
    line 3: score = score - 3; // add 3
    line 4: score = score + 5; // add 5
    line 5: show(score); // show it
  11. 11.🐞 What is a bug? (a) a new feature (b) a fast phone (c) a nice icon (d) a mistake in the code
  12. 12.🐞 This code has a bug. What number SHOULD it show, if every line did what its comment says?
    line 1: let stars = 47; // start at 47
    line 2: stars = stars - 5; // take away 5
    line 3: stars = stars - 6; // add 6
    line 4: show(stars); // show it
  13. 13.🐞 This code has a bug. What number does it ACTUALLY show?
    line 1: let coins = 44; // start at 44
    line 2: coins = coins - 1; // take away 1
    line 3: coins = coins - 6; // take away 3
    line 4: coins = coins + 3; // add 3
    line 5: show(coins); // show it
  14. 14.🐞 Each comment says what its line SHOULD do. Which line has the bug?
    line 1: let lives = 31; // start at 30
    line 2: lives = lives + 2; // add 2
    line 3: lives = lives * 2; // double it
    line 4: show(lives); // show it     (a) line 3 (b) line 2 (c) line 1
  15. 15.🐞 This code has a bug. What number does it ACTUALLY show?
    line 1: let coins = 32; // start at 30
    line 2: coins = coins * 2; // double it
    line 3: coins = coins * 2; // double it
    line 4: show(coins); // show it
  16. 16.🐞 Each comment says what its line SHOULD do. Which line has the bug?
    line 1: let points = 33; // start at 33
    line 2: points = points + 2; // add 2
    line 3: points = points + 4; // add 2
    line 4: show(points); // 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 points = 31; // start at 31
    line 2: points = points * 2; // double it
    line 3: points = points - 2; // take away 2
    line 4: points = points * 3; // double it
    line 5: show(points); // show it     (a) line 1 (b) line 2 (c) line 3 (d) line 4
  18. 18.🐞 A comment in code (after //) is for ___. (a) the app store (b) the phone screen (c) the battery (d) people reading the code
  19. 19.🐞 This code has a bug. What number SHOULD it show, if every line did what its comment says?
    line 1: let points = 30; // start at 30
    line 2: points = points * 2; // double it
    line 3: points = points + 2; // double it
    line 4: show(points); // show it
  20. 20.🐞 Each comment says what its line SHOULD do. Which line has the bug?
    line 1: let lives = 44; // start at 42
    line 2: lives = lives + 4; // add 4
    line 3: lives = lives - 1; // take away 1
    line 4: show(lives); // show it     (a) line 3 (b) line 1 (c) line 2
  21. 21.🐞 This code has a bug. What number does it ACTUALLY show?
    line 1: let points = 43; // start at 41
    line 2: points = points + 5; // add 5
    line 3: points = points + 6; // add 6
    line 4: show(points); // show it
  22. 22.🐞 This code has a bug. What number does it ACTUALLY show?
    line 1: let points = 40; // start at 40
    line 2: points = points - 4; // add 4
    line 3: points = points + 2; // add 2
    line 4: points = points + 6; // add 6
    line 5: show(points); // show it
  23. 23.🐞 This code has a bug. What number does it ACTUALLY show?
    line 1: let stars = 37; // start at 35
    line 2: stars = stars - 3; // take away 3
    line 3: stars = stars + 4; // add 4
    line 4: show(stars); // show it
  24. 24.🐞 This code has a bug. What number SHOULD it show, if every line did what its comment says?
    line 1: let points = 52; // start at 50
    line 2: points = points + 6; // add 6
    line 3: points = points - 1; // take away 1
    line 4: points = points - 1; // take away 1
    line 5: show(points); // show it
  25. 25.🐞 This code has a bug. What number does it ACTUALLY show?
    line 1: let stars = 49; // start at 49
    line 2: stars = stars + 5; // add 5
    line 3: stars = stars - 3; // add 3
    line 4: show(stars); // show it
  26. 26.🐞 This code has a bug. What number does it ACTUALLY show?
    line 1: let lives = 38; // start at 36
    line 2: lives = lives + 4; // add 4
    line 3: lives = lives - 1; // take away 1
    line 4: lives = lives * 2; // double it
    line 5: show(lives); // 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 score = 49; // start at 49
    line 2: score = score - 2; // take away 2
    line 3: score = score - 4; // take away 2
    line 4: show(score); // show it
  28. 28.🐞 This code has a bug. What number does it ACTUALLY show?
    line 1: let lives = 34; // start at 34
    line 2: lives = lives + 2; // double it
    line 3: lives = lives - 1; // take away 1
    line 4: lives = lives + 2; // add 2
    line 5: show(lives); // show it
  29. 29.🐞 This code has a bug. What number does it ACTUALLY show?
    line 1: let coins = 40; // start at 40
    line 2: coins = coins * 3; // double it
    line 3: coins = coins - 3; // take away 3
    line 4: show(coins); // show it
  30. 30.🐞 This code has a bug. What number does it ACTUALLY show?
    line 1: let coins = 33; // start at 31
    line 2: coins = coins + 4; // add 4
    line 3: coins = coins - 2; // take away 2
    line 4: coins = coins * 2; // double it
    line 5: show(coins); // show it
  31. 31.🐞 Each comment says what its line SHOULD do. Which line has the bug?
    line 1: let score = 32; // start at 32
    line 2: score = score + 4; // add 4
    line 3: score = score - 3; // add 3
    line 4: show(score); // show it     (a) line 1 (b) line 3 (c) line 2
  32. 32.🐞 This code has a bug. What number does it ACTUALLY show?
    line 1: let points = 37; // start at 36
    line 2: points = points * 2; // double it
    line 3: points = points + 2; // add 2
    line 4: show(points); // show it
  33. 33.🐞 This code has a bug. What number does it ACTUALLY show?
    line 1: let coins = 30; // start at 30
    line 2: coins = coins - 3; // add 3
    line 3: coins = coins - 5; // take away 5
    line 4: coins = coins * 2; // double it
    line 5: show(coins); // show it
  34. 34.🐞 This code has a bug. What number SHOULD it show, if every line did what its comment says?
    line 1: let points = 38; // start at 38
    line 2: points = points + 5; // add 5
    line 3: points = points + 2; // add 2
    line 4: points = points - 2; // add 2
    line 5: show(points); // show it
  35. 35.🐞 This code has a bug. What number does it ACTUALLY show?
    line 1: let score = 46; // start at 46
    line 2: score = score + 2; // double it
    line 3: score = score - 2; // take away 2
    line 4: score = score + 6; // add 6
    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 points = 36; // start at 34
    line 2: points = points * 2; // double it
    line 3: points = points * 2; // double it
    line 4: show(points); // show it
  37. 37.🐞 This code has a bug. What number does it ACTUALLY show?
    line 1: let points = 41; // start at 41
    line 2: points = points + 5; // add 5
    line 3: points = points + 2; // take away 2
    line 4: points = points * 2; // double it
    line 5: show(points); // 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 = 36; // start at 35
    line 2: score = score + 3; // add 3
    line 3: score = score - 5; // take away 5
    line 4: score = score - 3; // take away 3
    line 5: show(score); // show it
  39. 39.🐞 Each comment says what its line SHOULD do. Which line has the bug?
    line 1: let lives = 48; // start at 48
    line 2: lives = lives * 2; // double it
    line 3: lives = lives - 1; // take away 1
    line 4: lives = lives - 2; // take away 1
    line 5: show(lives); // show it     (a) line 2 (b) line 4 (c) line 3 (d) line 1
  40. 40.🐞 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 39
    line 2: coins = coins + 3; // add 3
    line 3: coins = coins + 2; // add 2
    line 4: coins = coins + 1; // take away 1
    line 5: show(coins); // show it

Answer key

  1. 33
  2. find where it goes wrong
  3. 86
  4. 70
  5. test it again
  6. 57
  7. debugging
  8. 78
  9. 49
  10. 43
  11. a mistake in the code
  12. 48
  13. 40
  14. line 1
  15. 128
  16. line 3
  17. line 4
  18. people reading the code
  19. 120
  20. line 1
  21. 54
  22. 44
  23. 38
  24. 54
  25. 51
  26. 82
  27. 45
  28. 37
  29. 117
  30. 70
  31. line 3
  32. 76
  33. 44
  34. 47
  35. 52
  36. 136
  37. 96
  38. 30
  39. line 4
  40. 43

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