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App Dev Worksheet: Debugging

App development lesson 21: Debugging: find the bug line · Set 279 · 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 lives = 34; // start at 34
    line 2: lives = lives + 2; // add 2
    line 3: lives = lives - 5; // take away 5
    line 4: lives = lives + 1; // take away 1
    line 5: show(lives); // show it     (a) line 2 (b) line 4 (c) line 1 (d) line 3
  2. 2.🐞 What is a good first step when an app gives a wrong result? (a) buy a new phone (b) find where it goes wrong (c) delete the app (d) add more colours
  3. 3.🐞 This code has a bug. What number does it ACTUALLY show?
    line 1: let score = 48; // start at 48
    line 2: score = score + 2; // double it
    line 3: score = score * 2; // double it
    line 4: score = score + 3; // add 3
    line 5: show(score); // show it
  4. 4.🐞 This code has a bug. What number does it ACTUALLY show?
    line 1: let score = 50; // start at 50
    line 2: score = score + 2; // double it
    line 3: score = score * 2; // double it
    line 4: show(score); // show it
  5. 5.🐞 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 + 4; // take away 4
    line 4: score = score + 4; // add 4
    line 5: show(score); // show it
  6. 6.🐞 Each comment says what its line SHOULD do. Which line has the bug?
    line 1: let score = 38; // start at 37
    line 2: score = score * 2; // double it
    line 3: score = score + 3; // add 3
    line 4: show(score); // show it     (a) line 2 (b) line 1 (c) line 3
  7. 7.🐞 Each comment says what its line SHOULD do. Which line has the bug?
    line 1: let points = 51; // start at 49
    line 2: points = points * 2; // double it
    line 3: points = points - 2; // take away 2
    line 4: show(points); // show it     (a) line 1 (b) line 2 (c) line 3
  8. 8.🐞 This code has a bug. What number does it ACTUALLY show?
    line 1: let stars = 32; // start at 32
    line 2: stars = stars + 5; // add 5
    line 3: stars = stars + 2; // double it
    line 4: show(stars); // show it
  9. 9.🐞 Each comment says what its line SHOULD do. Which line has the bug?
    line 1: let lives = 43; // start at 43
    line 2: lives = lives - 4; // take away 3
    line 3: lives = lives * 2; // double it
    line 4: lives = lives * 2; // double it
    line 5: show(lives); // show it     (a) line 2 (b) line 1 (c) line 3 (d) line 4
  10. 10.🐞 Each comment says what its line SHOULD do. Which line has the bug?
    line 1: let points = 33; // start at 31
    line 2: points = points - 5; // take away 5
    line 3: points = points - 3; // take away 3
    line 4: show(points); // show it     (a) line 2 (b) line 1 (c) line 3
  11. 11.🐞 Each comment says what its line SHOULD do. Which line has the bug?
    line 1: let lives = 51; // start at 50
    line 2: lives = lives + 4; // add 4
    line 3: lives = lives + 3; // add 3
    line 4: lives = lives + 6; // add 6
    line 5: show(lives); // show it     (a) line 4 (b) line 2 (c) line 1 (d) line 3
  12. 12.🐞 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 47
    line 2: score = score - 2; // take away 1
    line 3: score = score + 5; // add 5
    line 4: show(score); // show it
  13. 13.🐞 This code has a bug. What number does it ACTUALLY show?
    line 1: let lives = 37; // start at 37
    line 2: lives = lives * 3; // double it
    line 3: lives = lives + 6; // add 6
    line 4: show(lives); // show it
  14. 14.🐞 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 41
    line 2: points = points + 3; // add 3
    line 3: points = points + 2; // add 2
    line 4: show(points); // show it
  15. 15.🐞 This code has a bug. What number does it ACTUALLY show?
    line 1: let lives = 47; // start at 44
    line 2: lives = lives - 1; // take away 1
    line 3: lives = lives + 3; // add 3
    line 4: show(lives); // show it
  16. 16.🐞 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; // double it
    line 3: points = points - 6; // take away 4
    line 4: points = points - 1; // take away 1
    line 5: show(points); // show it     (a) line 4 (b) line 1 (c) line 2 (d) line 3
  17. 17.🐞 What is a bug? (a) a mistake in the code (b) a nice icon (c) a fast phone (d) a new feature
  18. 18.🐞 This code has a bug. What number SHOULD it show, if every line did what its comment says?
    line 1: let lives = 44; // start at 44
    line 2: lives = lives + 2; // add 2
    line 3: lives = lives - 4; // add 4
    line 4: lives = lives - 3; // take away 3
    line 5: show(lives); // show it
  19. 19.🐞 Each comment says what its line SHOULD do. Which line has the bug?
    line 1: let stars = 32; // start at 31
    line 2: stars = stars + 6; // add 6
    line 3: stars = stars - 1; // take away 1
    line 4: stars = stars - 2; // take away 2
    line 5: show(stars); // show it     (a) line 1 (b) line 4 (c) line 2 (d) line 3
  20. 20.🐞 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; // add 2
    line 3: points = points - 3; // take away 3
    line 4: points = points + 2; // double it
    line 5: show(points); // show it     (a) line 4 (b) line 3 (c) line 1 (d) line 2
  21. 21.🐞 This code has a bug. What number does it ACTUALLY show?
    line 1: let stars = 43; // start at 43
    line 2: stars = stars + 2; // take away 2
    line 3: stars = stars * 2; // double it
    line 4: stars = stars - 5; // take away 5
    line 5: show(stars); // show it
  22. 22.🐞 Finding and fixing bugs is called ___. (a) decorating (b) debugging (c) designing (d) downloading
  23. 23.🐞 This code has a bug. What number SHOULD it show, if every line did what its comment says?
    line 1: let score = 32; // start at 30
    line 2: score = score - 3; // take away 3
    line 3: score = score + 3; // add 3
    line 4: show(score); // 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 = 36; // start at 36
    line 2: points = points + 2; // take away 2
    line 3: points = points + 4; // add 4
    line 4: show(points); // show it
  25. 25.🐞 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 + 2; // add 2
    line 3: points = points + 2; // add 2
    line 4: points = points + 5; // add 5
    line 5: show(points); // show it     (a) line 2 (b) line 3 (c) line 1 (d) line 4
  26. 26.🐞 Each comment says what its line SHOULD do. Which line has the bug?
    line 1: let lives = 43; // start at 43
    line 2: lives = lives - 5; // add 5
    line 3: lives = lives + 5; // add 5
    line 4: show(lives); // show it     (a) line 2 (b) line 1 (c) line 3
  27. 27.🐞 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 47
    line 2: lives = lives - 3; // take away 3
    line 3: lives = lives + 2; // add 2
    line 4: show(lives); // 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 score = 42; // start at 42
    line 2: score = score * 3; // double it
    line 3: score = score - 4; // take away 4
    line 4: score = score - 3; // take away 3
    line 5: show(score); // show it
  29. 29.🐞 This code has a bug. What number does it ACTUALLY show?
    line 1: let stars = 45; // start at 45
    line 2: stars = stars + 9; // add 6
    line 3: stars = stars + 3; // add 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 stars = 42; // start at 42
    line 2: stars = stars * 2; // double it
    line 3: stars = stars + 4; // add 3
    line 4: show(stars); // show it     (a) line 1 (b) line 3 (c) line 2
  31. 31.🐞 Each comment says what its line SHOULD do. Which line has the bug?
    line 1: let score = 32; // start at 31
    line 2: score = score + 4; // add 4
    line 3: score = score + 6; // add 6
    line 4: show(score); // show it     (a) line 1 (b) line 3 (c) line 2
  32. 32.🐞 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 - 3; // take away 3
    line 3: score = score + 5; // take away 5
    line 4: score = score * 2; // double it
    line 5: show(score); // show it     (a) line 3 (b) line 2 (c) line 1 (d) line 4
  33. 33.🐞 After fixing a bug you should ___. (a) delete the test (b) release at once (c) never test (d) test it again
  34. 34.🐞 This code has a bug. What number does it ACTUALLY show?
    line 1: let stars = 50; // start at 49
    line 2: stars = stars * 2; // double it
    line 3: stars = stars * 2; // double it
    line 4: stars = stars - 1; // take away 1
    line 5: show(stars); // show it
  35. 35.🐞 This code has a bug. What number does it ACTUALLY show?
    line 1: let lives = 32; // start at 30
    line 2: lives = lives + 3; // add 3
    line 3: lives = lives - 5; // take away 5
    line 4: show(lives); // 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 = 43; // start at 41
    line 2: points = points + 2; // add 2
    line 3: points = points * 2; // double it
    line 4: points = points - 2; // take away 2
    line 5: show(points); // show it
  37. 37.🐞 Each comment says what its line SHOULD do. Which line has the bug?
    line 1: let points = 44; // start at 43
    line 2: points = points - 5; // take away 5
    line 3: points = points - 4; // take away 4
    line 4: points = points + 3; // add 3
    line 5: show(points); // show it     (a) line 1 (b) line 3 (c) line 2 (d) line 4
  38. 38.🐞 This code has a bug. What number SHOULD it show, if every line did what its comment says?
    line 1: let lives = 49; // start at 48
    line 2: lives = lives + 2; // add 2
    line 3: lives = lives + 4; // add 4
    line 4: show(lives); // show it
  39. 39.🐞 Each comment says what its line SHOULD do. Which line has the bug?
    line 1: let score = 43; // start at 43
    line 2: score = score + 3; // add 3
    line 3: score = score - 2; // take away 1
    line 4: show(score); // 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 score = 39; // start at 39
    line 2: score = score + 5; // add 4
    line 3: score = score + 3; // add 3
    line 4: show(score); // show it     (a) line 3 (b) line 1 (c) line 2

Answer key

  1. line 4
  2. find where it goes wrong
  3. 103
  4. 104
  5. 35
  6. line 1
  7. line 1
  8. 39
  9. line 2
  10. line 1
  11. line 1
  12. 51
  13. 117
  14. 46
  15. 49
  16. line 3
  17. a mistake in the code
  18. 47
  19. line 1
  20. line 4
  21. 85
  22. debugging
  23. 30
  24. 38
  25. line 1
  26. line 2
  27. 46
  28. 77
  29. 57
  30. line 3
  31. line 1
  32. line 3
  33. test it again
  34. 199
  35. 30
  36. 84
  37. line 1
  38. 54
  39. line 3
  40. line 2

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