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App Dev Worksheet: Debugging

App development lesson 21: Debugging: find the bug line · Set 253 · 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 = 47; // start at 47
    line 2: lives = lives * 2; // double it
    line 3: lives = lives * 2; // double it
    line 4: lives = lives - 2; // add 2
    line 5: show(lives); // show it     (a) line 4 (b) line 2 (c) line 1 (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 score = 40; // start at 40
    line 2: score = score * 2; // double it
    line 3: score = score + 2; // double it
    line 4: show(score); // show it
  3. 3.🐞 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 30
    line 2: points = points + 2; // add 2
    line 3: points = points + 5; // add 5
    line 4: show(points); // show it
  4. 4.🐞 What is a bug? (a) a fast phone (b) a mistake in the code (c) a nice icon (d) a new feature
  5. 5.🐞 Each comment says what its line SHOULD do. Which line has the bug?
    line 1: let points = 36; // start at 33
    line 2: points = points - 4; // take away 4
    line 3: points = points * 2; // double it
    line 4: show(points); // show it     (a) line 3 (b) line 1 (c) line 2
  6. 6.🐞 Finding and fixing bugs is called ___. (a) downloading (b) debugging (c) designing (d) decorating
  7. 7.🐞 This code has a bug. What number SHOULD it show, if every line did what its comment says?
    line 1: let coins = 50; // start at 50
    line 2: coins = coins + 3; // add 2
    line 3: coins = coins - 2; // take away 2
    line 4: coins = coins + 3; // add 3
    line 5: show(coins); // show it
  8. 8.🐞 Each comment says what its line SHOULD do. Which line has the bug?
    line 1: let stars = 40; // start at 38
    line 2: stars = stars + 5; // add 5
    line 3: stars = stars - 1; // take away 1
    line 4: show(stars); // show it     (a) line 2 (b) line 3 (c) line 1
  9. 9.🐞 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 * 3; // double it
    line 3: stars = stars * 2; // double it
    line 4: show(stars); // show it
  10. 10.🐞 This code has a bug. What number does it ACTUALLY show?
    line 1: let score = 53; // start at 50
    line 2: score = score + 2; // add 2
    line 3: score = score + 3; // add 3
    line 4: show(score); // show it
  11. 11.🐞 Each comment says what its line SHOULD do. Which line has the bug?
    line 1: let points = 46; // start at 46
    line 2: points = points - 3; // take away 2
    line 3: points = points + 3; // add 3
    line 4: points = points + 3; // add 3
    line 5: show(points); // show it     (a) line 4 (b) line 2 (c) line 1 (d) line 3
  12. 12.🐞 Each comment says what its line SHOULD do. Which line has the bug?
    line 1: let coins = 51; // start at 49
    line 2: coins = coins + 5; // add 5
    line 3: coins = coins + 5; // add 5
    line 4: coins = coins - 4; // take away 4
    line 5: show(coins); // show it     (a) line 1 (b) line 2 (c) line 4 (d) line 3
  13. 13.🐞 This code has a bug. What number SHOULD it show, if every line did what its comment says?
    line 1: let coins = 36; // start at 34
    line 2: coins = coins * 2; // double it
    line 3: coins = coins * 2; // double it
    line 4: show(coins); // show it
  14. 14.🐞 This code has a bug. What number does it ACTUALLY show?
    line 1: let lives = 46; // start at 46
    line 2: lives = lives + 4; // add 2
    line 3: lives = lives + 6; // add 6
    line 4: show(lives); // show it
  15. 15.🐞 What is a good first step when an app gives a wrong result? (a) delete the app (b) buy a new phone (c) add more colours (d) find where it goes wrong
  16. 16.🐞 This code has a bug. What number does it ACTUALLY show?
    line 1: let lives = 47; // start at 47
    line 2: lives = lives - 1; // take away 1
    line 3: lives = lives + 5; // add 5
    line 4: lives = lives - 3; // add 3
    line 5: show(lives); // show it
  17. 17.🐞 A comment in code (after //) is for ___. (a) people reading the code (b) the phone screen (c) the battery (d) the app store
  18. 18.🐞 This code has a bug. What number SHOULD it show, if every line did what its comment says?
    line 1: let lives = 42; // start at 41
    line 2: lives = lives - 1; // take away 1
    line 3: lives = lives * 2; // double it
    line 4: lives = lives * 2; // double it
    line 5: show(lives); // 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 stars = 41; // start at 41
    line 2: stars = stars - 4; // take away 4
    line 3: stars = stars + 2; // double it
    line 4: stars = stars - 4; // take away 4
    line 5: show(stars); // show it
  20. 20.🐞 This code has a bug. What number does it ACTUALLY show?
    line 1: let score = 32; // start at 32
    line 2: score = score + 3; // take away 3
    line 3: score = score - 1; // take away 1
    line 4: score = score + 6; // add 6
    line 5: show(score); // 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 = 39; // start at 36
    line 2: coins = coins * 2; // double it
    line 3: coins = coins + 6; // add 6
    line 4: coins = coins - 1; // take away 1
    line 5: show(coins); // show it
  22. 22.🐞 After fixing a bug you should ___. (a) delete the test (b) release at once (c) never test (d) test it again
  23. 23.🐞 This code has a bug. What number does it ACTUALLY show?
    line 1: let score = 33; // start at 32
    line 2: score = score * 2; // double it
    line 3: score = score + 2; // add 2
    line 4: score = score - 4; // take away 4
    line 5: show(score); // show it
  24. 24.🐞 This code has a bug. What number does it ACTUALLY show?
    line 1: let lives = 46; // start at 46
    line 2: lives = lives - 4; // take away 3
    line 3: lives = lives - 2; // take away 2
    line 4: show(lives); // show it
  25. 25.🐞 Each comment says what its line SHOULD do. Which line has the bug?
    line 1: let coins = 49; // start at 49
    line 2: coins = coins - 4; // take away 3
    line 3: coins = coins - 4; // take away 4
    line 4: show(coins); // show it     (a) line 3 (b) line 1 (c) line 2
  26. 26.🐞 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 * 2; // double it
    line 3: score = score - 2; // add 2
    line 4: show(score); // show it     (a) line 1 (b) line 2 (c) line 3
  27. 27.🐞 Each comment says what its line SHOULD do. Which line has the bug?
    line 1: let score = 42; // start at 42
    line 2: score = score - 4; // take away 1
    line 3: score = score * 2; // double it
    line 4: show(score); // show it     (a) line 3 (b) line 1 (c) line 2
  28. 28.🐞 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 35
    line 2: lives = lives + 6; // add 6
    line 3: lives = lives + 3; // add 3
    line 4: lives = lives - 1; // take away 1
    line 5: show(lives); // show it
  29. 29.🐞 Each comment says what its line SHOULD do. Which line has the bug?
    line 1: let score = 41; // start at 41
    line 2: score = score + 3; // add 3
    line 3: score = score - 4; // add 4
    line 4: score = score + 3; // add 3
    line 5: show(score); // show it     (a) line 1 (b) line 2 (c) line 3 (d) line 4
  30. 30.🐞 Each comment says what its line SHOULD do. Which line has the bug?
    line 1: let coins = 34; // start at 34
    line 2: coins = coins * 2; // double it
    line 3: coins = coins * 3; // double it
    line 4: coins = coins + 6; // add 6
    line 5: show(coins); // show it     (a) line 1 (b) line 2 (c) line 3 (d) line 4
  31. 31.🐞 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: points = points + 5; // add 5
    line 5: show(points); // show it
  32. 32.🐞 Each comment says what its line SHOULD do. Which line has the bug?
    line 1: let score = 49; // start at 48
    line 2: score = score - 4; // take away 4
    line 3: score = score - 3; // take away 3
    line 4: score = score + 4; // add 4
    line 5: show(score); // show it     (a) line 3 (b) line 4 (c) line 2 (d) line 1
  33. 33.🐞 Each comment says what its line SHOULD do. Which line has the bug?
    line 1: let score = 33; // start at 33
    line 2: score = score - 3; // take away 3
    line 3: score = score + 1; // take away 1
    line 4: show(score); // show it     (a) line 1 (b) line 2 (c) line 3
  34. 34.🐞 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 - 2; // take away 2
    line 4: show(points); // show it     (a) line 3 (b) line 1 (c) line 2
  35. 35.🐞 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 32
    line 2: score = score - 2; // take away 2
    line 3: score = score * 2; // double it
    line 4: score = score - 2; // add 2
    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 score = 42; // start at 42
    line 2: score = score + 2; // double it
    line 3: score = score - 5; // take away 5
    line 4: show(score); // show it
  37. 37.🐞 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 + 5; // take away 5
    line 3: lives = lives * 2; // double it
    line 4: show(lives); // show it
  38. 38.🐞 Each comment says what its line SHOULD do. Which line has the bug?
    line 1: let score = 48; // start at 48
    line 2: score = score * 2; // double it
    line 3: score = score + 3; // take away 3
    line 4: show(score); // 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 = 39; // start at 37
    line 2: stars = stars + 2; // add 2
    line 3: stars = stars * 2; // double it
    line 4: stars = stars * 2; // double it
    line 5: show(stars); // show it     (a) line 1 (b) line 3 (c) line 2 (d) line 4
  40. 40.🐞 This code has a bug. What number SHOULD it show, if every line did what its comment says?
    line 1: let lives = 37; // start at 37
    line 2: lives = lives + 6; // add 6
    line 3: lives = lives - 2; // take away 2
    line 4: lives = lives + 2; // double it
    line 5: show(lives); // show it

Answer key

  1. line 4
  2. 160
  3. 37
  4. a mistake in the code
  5. line 1
  6. debugging
  7. 53
  8. line 1
  9. 128
  10. 58
  11. line 2
  12. line 1
  13. 136
  14. 56
  15. find where it goes wrong
  16. 48
  17. people reading the code
  18. 160
  19. 70
  20. 40
  21. 77
  22. test it again
  23. 64
  24. 40
  25. line 2
  26. line 3
  27. line 2
  28. 43
  29. line 3
  30. line 3
  31. 125
  32. line 1
  33. line 3
  34. line 2
  35. 62
  36. 79
  37. 60
  38. line 3
  39. line 1
  40. 82

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