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App Dev Worksheet: Debugging

App development lesson 21: Debugging: find the bug line · Set 983 · 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 lives = 36; // start at 36
    line 2: lives = lives - 1; // take away 1
    line 3: lives = lives * 3; // double it
    line 4: lives = lives * 2; // double it
    line 5: show(lives); // show it
  2. 2.🐞 Finding and fixing bugs is called ___. (a) downloading (b) decorating (c) designing (d) debugging
  3. 3.🐞 This code has a bug. What number SHOULD it show, if every line did what its comment says?
    line 1: let points = 34; // start at 31
    line 2: points = points - 2; // take away 2
    line 3: points = points - 4; // take away 4
    line 4: points = points + 4; // add 4
    line 5: show(points); // show it
  4. 4.🐞 Each comment says what its line SHOULD do. Which line has the bug?
    line 1: let score = 46; // start at 45
    line 2: score = score + 2; // add 2
    line 3: score = score + 3; // add 3
    line 4: score = score * 2; // double it
    line 5: show(score); // show it     (a) line 2 (b) line 3 (c) line 4 (d) line 1
  5. 5.🐞 This code has a bug. What number does it ACTUALLY show?
    line 1: let points = 31; // start at 31
    line 2: points = points - 2; // take away 2
    line 3: points = points * 2; // double it
    line 4: points = points + 2; // double it
    line 5: show(points); // show it
  6. 6.🐞 After fixing a bug you should ___. (a) release at once (b) never test (c) delete the test (d) test it again
  7. 7.🐞 This code has a bug. What number SHOULD it show, if every line did what its comment says?
    line 1: let points = 37; // start at 37
    line 2: points = points * 2; // double it
    line 3: points = points - 2; // add 2
    line 4: show(points); // show it
  8. 8.🐞 This code has a bug. What number does it ACTUALLY show?
    line 1: let lives = 49; // start at 48
    line 2: lives = lives - 2; // take away 2
    line 3: lives = lives + 2; // add 2
    line 4: show(lives); // show it
  9. 9.🐞 This code has a bug. What number does it ACTUALLY show?
    line 1: let score = 37; // start at 36
    line 2: score = score + 6; // add 6
    line 3: score = score - 1; // take away 1
    line 4: score = score + 3; // add 3
    line 5: show(score); // show it
  10. 10.🐞 This code has a bug. What number does it ACTUALLY show?
    line 1: let lives = 41; // start at 41
    line 2: lives = lives + 4; // add 2
    line 3: lives = lives * 2; // double it
    line 4: show(lives); // show it
  11. 11.🐞 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; // add 4
    line 4: stars = stars + 3; // add 3
    line 5: show(stars); // 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 = 30; // start at 30
    line 2: score = score - 3; // take away 3
    line 3: score = score * 2; // double it
    line 4: score = score * 3; // double it
    line 5: show(score); // show it
  13. 13.🐞 A comment in code (after //) is for ___. (a) people reading the code (b) the phone screen (c) the app store (d) the battery
  14. 14.🐞 What is a good first step when an app gives a wrong result? (a) buy a new phone (b) add more colours (c) delete the app (d) find where it goes wrong
  15. 15.🐞 This code has a bug. What number does it ACTUALLY show?
    line 1: let lives = 44; // start at 44
    line 2: lives = lives + 6; // add 6
    line 3: lives = lives - 5; // add 5
    line 4: show(lives); // show it
  16. 16.🐞 This code has a bug. What number SHOULD it show, if every line did what its comment says?
    line 1: let stars = 33; // start at 33
    line 2: stars = stars + 2; // take away 2
    line 3: stars = stars * 2; // double it
    line 4: show(stars); // show it
  17. 17.🐞 Each comment says what its line SHOULD do. Which line has the bug?
    line 1: let coins = 30; // start at 30
    line 2: coins = coins + 3; // add 3
    line 3: coins = coins - 4; // take away 1
    line 4: coins = coins * 2; // double it
    line 5: show(coins); // show it     (a) line 2 (b) line 1 (c) line 4 (d) line 3
  18. 18.🐞 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 + 5; // take away 5
    line 3: stars = stars - 5; // take away 5
    line 4: show(stars); // show it     (a) line 3 (b) line 1 (c) line 2
  19. 19.🐞 This code has a bug. What number does it ACTUALLY show?
    line 1: let stars = 35; // start at 32
    line 2: stars = stars * 2; // double it
    line 3: stars = stars + 5; // add 5
    line 4: show(stars); // show it
  20. 20.🐞 Each comment says what its line SHOULD do. Which line has the bug?
    line 1: let lives = 35; // start at 35
    line 2: lives = lives - 8; // take away 5
    line 3: lives = lives * 2; // double it
    line 4: show(lives); // show it     (a) line 1 (b) line 2 (c) line 3
  21. 21.🐞 This code has a bug. What number does it ACTUALLY show?
    line 1: let score = 38; // start at 38
    line 2: score = score * 2; // double it
    line 3: score = score * 3; // double it
    line 4: score = score - 5; // take away 5
    line 5: show(score); // show it
  22. 22.🐞 This code has a bug. What number does it ACTUALLY show?
    line 1: let coins = 46; // start at 44
    line 2: coins = coins * 2; // double it
    line 3: coins = coins + 5; // add 5
    line 4: show(coins); // show it
  23. 23.🐞 Each comment says what its line SHOULD do. Which line has the bug?
    line 1: let lives = 38; // start at 35
    line 2: lives = lives * 2; // double it
    line 3: lives = lives - 5; // take away 5
    line 4: show(lives); // show it     (a) line 3 (b) line 1 (c) line 2
  24. 24.🐞 What is a bug? (a) a fast phone (b) a new feature (c) a mistake in the code (d) a nice icon
  25. 25.🐞 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 - 4; // take away 4
    line 3: stars = stars - 5; // take away 5
    line 4: stars = stars + 3; // take away 3
    line 5: show(stars); // show it
  26. 26.🐞 Each comment says what its line SHOULD do. Which line has the bug?
    line 1: let stars = 41; // start at 41
    line 2: stars = stars - 1; // take away 1
    line 3: stars = stars * 2; // double it
    line 4: stars = stars - 5; // take away 2
    line 5: show(stars); // show it     (a) line 1 (b) line 3 (c) line 4 (d) line 2
  27. 27.🐞 This code has a bug. What number SHOULD it show, if every line did what its comment says?
    line 1: let coins = 33; // start at 31
    line 2: coins = coins * 2; // double it
    line 3: coins = coins + 4; // add 4
    line 4: coins = coins * 2; // double it
    line 5: show(coins); // show it
  28. 28.🐞 Each comment says what its line SHOULD do. Which line has the bug?
    line 1: let points = 47; // start at 46
    line 2: points = points + 2; // add 2
    line 3: points = points * 2; // double it
    line 4: show(points); // show it     (a) line 1 (b) line 2 (c) line 3
  29. 29.🐞 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 + 4; // add 4
    line 3: stars = stars + 3; // take away 3
    line 4: show(stars); // show it
  30. 30.🐞 Each comment says what its line SHOULD do. Which line has the bug?
    line 1: let coins = 31; // start at 31
    line 2: coins = coins + 4; // add 4
    line 3: coins = coins * 3; // double it
    line 4: show(coins); // show it     (a) line 2 (b) line 3 (c) line 1
  31. 31.🐞 Each comment says what its line SHOULD do. Which line has the bug?
    line 1: let coins = 49; // start at 48
    line 2: coins = coins - 1; // take away 1
    line 3: coins = coins - 2; // take away 2
    line 4: coins = coins - 1; // take away 1
    line 5: show(coins); // show it     (a) line 2 (b) line 3 (c) line 4 (d) line 1
  32. 32.🐞 Each comment says what its line SHOULD do. Which line has the bug?
    line 1: let coins = 36; // start at 36
    line 2: coins = coins + 6; // add 6
    line 3: coins = coins - 5; // add 5
    line 4: show(coins); // show it     (a) line 2 (b) line 1 (c) line 3
  33. 33.🐞 This code has a bug. What number does it ACTUALLY show?
    line 1: let lives = 46; // start at 46
    line 2: lives = lives - 5; // take away 5
    line 3: lives = lives + 2; // double it
    line 4: show(lives); // show it
  34. 34.🐞 Each comment says what its line SHOULD do. Which line has the bug?
    line 1: let score = 45; // start at 43
    line 2: score = score + 6; // add 6
    line 3: score = score + 5; // add 5
    line 4: show(score); // show it     (a) line 3 (b) line 1 (c) line 2
  35. 35.🐞 Each comment says what its line SHOULD do. Which line has the bug?
    line 1: let points = 34; // start at 31
    line 2: points = points - 5; // take away 5
    line 3: points = points + 6; // add 6
    line 4: show(points); // show it     (a) line 1 (b) line 2 (c) line 3
  36. 36.🐞 This code has a bug. What number does it ACTUALLY show?
    line 1: let score = 40; // start at 39
    line 2: score = score + 3; // add 3
    line 3: score = score * 2; // double it
    line 4: score = score + 4; // add 4
    line 5: show(score); // show it
  37. 37.🐞 Each comment says what its line SHOULD do. Which line has the bug?
    line 1: let points = 40; // start at 38
    line 2: points = points + 6; // add 6
    line 3: points = points + 5; // add 5
    line 4: show(points); // show it     (a) line 1 (b) line 2 (c) line 3
  38. 38.🐞 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 - 2; // take away 2
    line 3: points = points - 3; // take away 3
    line 4: show(points); // 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 coins = 48; // start at 47
    line 2: coins = coins + 3; // add 3
    line 3: coins = coins - 5; // take away 5
    line 4: coins = coins - 5; // take away 5
    line 5: show(coins); // show it     (a) line 3 (b) line 4 (c) line 1 (d) line 2
  40. 40.🐞 This code has a bug. What number does it ACTUALLY show?
    line 1: let points = 38; // start at 35
    line 2: points = points * 2; // double it
    line 3: points = points - 1; // take away 1
    line 4: points = points - 3; // take away 3
    line 5: show(points); // show it

Answer key

  1. 140
  2. debugging
  3. 29
  4. line 1
  5. 60
  6. test it again
  7. 76
  8. 49
  9. 45
  10. 90
  11. 67
  12. 108
  13. people reading the code
  14. find where it goes wrong
  15. 45
  16. 62
  17. line 3
  18. line 2
  19. 75
  20. line 2
  21. 223
  22. 97
  23. line 1
  24. a mistake in the code
  25. 33
  26. line 4
  27. 132
  28. line 1
  29. 48
  30. line 3
  31. line 1
  32. line 3
  33. 43
  34. line 1
  35. line 1
  36. 90
  37. line 1
  38. line 1
  39. line 1
  40. 72

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