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App Dev Worksheet: Debugging

App development lesson 21: Debugging: find the bug line · Set 757 · 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 = 41; // start at 41
    line 2: lives = lives - 3; // take away 1
    line 3: lives = lives + 6; // add 6
    line 4: show(lives); // show it
  2. 2.🐞 What is a bug? (a) a nice icon (b) a mistake in the code (c) a fast phone (d) a new feature
  3. 3.🐞 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 + 3; // take away 3
    line 3: coins = coins + 3; // add 3
    line 4: show(coins); // show it     (a) line 1 (b) line 2 (c) line 3
  4. 4.🐞 This code has a bug. What number does it ACTUALLY show?
    line 1: let coins = 44; // start at 44
    line 2: coins = coins + 2; // double it
    line 3: coins = coins * 2; // double it
    line 4: coins = coins * 2; // double it
    line 5: show(coins); // show it
  5. 5.🐞 This code has a bug. What number does it ACTUALLY show?
    line 1: let coins = 47; // start at 47
    line 2: coins = coins * 2; // double it
    line 3: coins = coins + 5; // add 2
    line 4: show(coins); // show it
  6. 6.🐞 This code has a bug. What number does it ACTUALLY show?
    line 1: let stars = 41; // start at 41
    line 2: stars = stars + 3; // add 3
    line 3: stars = stars + 2; // double it
    line 4: stars = stars * 2; // double it
    line 5: show(stars); // show it
  7. 7.🐞 After fixing a bug you should ___. (a) never test (b) release at once (c) test it again (d) delete the test
  8. 8.🐞 This code has a bug. What number does it ACTUALLY show?
    line 1: let stars = 38; // start at 38
    line 2: stars = stars + 2; // add 2
    line 3: stars = stars + 4; // take away 4
    line 4: show(stars); // show it
  9. 9.🐞 This code has a bug. What number SHOULD it show, if every line did what its comment says?
    line 1: let points = 39; // start at 39
    line 2: points = points - 4; // take away 4
    line 3: points = points + 4; // take away 4
    line 4: points = points * 2; // double it
    line 5: show(points); // show it
  10. 10.🐞 This code has a bug. What number does it ACTUALLY show?
    line 1: let coins = 41; // start at 41
    line 2: coins = coins * 2; // double it
    line 3: coins = coins - 6; // add 6
    line 4: show(coins); // show it
  11. 11.🐞 Finding and fixing bugs is called ___. (a) downloading (b) designing (c) decorating (d) debugging
  12. 12.🐞 A comment in code (after //) is for ___. (a) the app store (b) the battery (c) the phone screen (d) people reading the code
  13. 13.🐞 This code has a bug. What number does it ACTUALLY show?
    line 1: let coins = 48; // start at 48
    line 2: coins = coins + 3; // add 3
    line 3: coins = coins - 6; // take away 3
    line 4: coins = coins - 3; // take away 3
    line 5: show(coins); // show it
  14. 14.🐞 This code has a bug. What number does it ACTUALLY show?
    line 1: let points = 30; // start at 30
    line 2: points = points + 5; // add 5
    line 3: points = points + 4; // add 4
    line 4: points = points + 2; // take away 2
    line 5: show(points); // 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 = 39; // start at 37
    line 2: coins = coins - 3; // take away 3
    line 3: coins = coins - 2; // take away 2
    line 4: show(coins); // show it
  16. 16.🐞 This code has a bug. What number does it ACTUALLY show?
    line 1: let coins = 39; // start at 38
    line 2: coins = coins - 5; // take away 5
    line 3: coins = coins - 1; // take away 1
    line 4: coins = coins - 2; // take away 2
    line 5: show(coins); // show it
  17. 17.🐞 This code has a bug. What number does it ACTUALLY show?
    line 1: let points = 37; // start at 37
    line 2: points = points - 2; // take away 1
    line 3: points = points * 2; // double it
    line 4: points = points - 5; // take away 5
    line 5: 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 coins = 44; // start at 41
    line 2: coins = coins - 2; // take away 2
    line 3: coins = coins + 2; // add 2
    line 4: show(coins); // show it
  19. 19.🐞 Each comment says what its line SHOULD do. Which line has the bug?
    line 1: let stars = 35; // start at 35
    line 2: stars = stars - 4; // take away 4
    line 3: stars = stars + 2; // add 2
    line 4: stars = stars + 5; // add 3
    line 5: show(stars); // show it     (a) line 1 (b) line 2 (c) line 3 (d) line 4
  20. 20.🐞 Each comment says what its line SHOULD do. Which line has the bug?
    line 1: let lives = 37; // start at 37
    line 2: lives = lives - 3; // add 3
    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 SHOULD it show, if every line did what its comment says?
    line 1: let coins = 47; // start at 47
    line 2: coins = coins * 2; // double it
    line 3: coins = coins + 3; // take away 3
    line 4: show(coins); // show it
  22. 22.🐞 This code has a bug. What number SHOULD it show, if every line did what its comment says?
    line 1: let score = 39; // start at 39
    line 2: score = score * 2; // double it
    line 3: score = score + 5; // add 5
    line 4: score = score + 2; // double it
    line 5: show(score); // show it
  23. 23.🐞 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 * 2; // double it
    line 3: score = score + 5; // take away 5
    line 4: score = score + 3; // add 3
    line 5: show(score); // show it
  24. 24.🐞 Each comment says what its line SHOULD do. Which line has the bug?
    line 1: let lives = 30; // start at 30
    line 2: lives = lives * 2; // double it
    line 3: lives = lives + 7; // add 6
    line 4: show(lives); // show it     (a) line 2 (b) line 1 (c) line 3
  25. 25.🐞 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 + 6; // add 6
    line 3: points = points + 2; // take away 2
    line 4: show(points); // show it     (a) line 1 (b) line 2 (c) line 3
  26. 26.🐞 What is a good first step when an app gives a wrong result? (a) buy a new phone (b) add more colours (c) find where it goes wrong (d) delete the app
  27. 27.🐞 This code has a bug. What number does it ACTUALLY show?
    line 1: let stars = 48; // start at 48
    line 2: stars = stars + 2; // double it
    line 3: stars = stars - 3; // take away 3
    line 4: show(stars); // show it
  28. 28.🐞 Each comment says what its line SHOULD do. Which line has the bug?
    line 1: let points = 45; // start at 45
    line 2: points = points + 2; // double it
    line 3: points = points - 1; // take away 1
    line 4: points = points * 2; // double it
    line 5: show(points); // show it     (a) line 2 (b) line 4 (c) line 1 (d) line 3
  29. 29.🐞 This code has a bug. What number does it ACTUALLY show?
    line 1: let score = 48; // start at 45
    line 2: score = score + 2; // add 2
    line 3: score = score - 1; // take away 1
    line 4: score = score * 2; // double it
    line 5: show(score); // show it
  30. 30.🐞 This code has a bug. What number does it ACTUALLY show?
    line 1: let coins = 36; // start at 36
    line 2: coins = coins * 2; // double it
    line 3: coins = coins + 6; // add 3
    line 4: show(coins); // show it
  31. 31.🐞 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 43
    line 2: lives = lives - 2; // take away 2
    line 3: lives = lives + 2; // add 2
    line 4: lives = lives * 3; // double it
    line 5: show(lives); // show it
  32. 32.🐞 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 * 3; // double it
    line 3: coins = coins + 4; // add 4
    line 4: coins = coins * 2; // double it
    line 5: show(coins); // show it     (a) line 4 (b) line 3 (c) line 1 (d) line 2
  33. 33.🐞 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 * 2; // double it
    line 3: points = points * 2; // double it
    line 4: points = points * 3; // double it
    line 5: show(points); // 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 stars = 38; // start at 38
    line 2: stars = stars - 4; // add 4
    line 3: stars = stars + 5; // add 5
    line 4: stars = stars - 5; // take away 5
    line 5: show(stars); // show it
  35. 35.🐞 Each comment says what its line SHOULD do. Which line has the bug?
    line 1: let score = 34; // start at 34
    line 2: score = score + 4; // add 4
    line 3: score = score + 5; // add 3
    line 4: score = score * 2; // double it
    line 5: show(score); // show it     (a) line 1 (b) line 4 (c) line 2 (d) line 3
  36. 36.🐞 This code has a bug. What number SHOULD it show, if every line did what its comment says?
    line 1: let score = 39; // start at 39
    line 2: score = score + 6; // add 5
    line 3: score = score - 4; // take away 4
    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 score = 46; // start at 46
    line 2: score = score * 3; // double it
    line 3: score = score - 2; // take away 2
    line 4: show(score); // show it
  38. 38.🐞 This code has a bug. What number does it ACTUALLY show?
    line 1: let lives = 43; // start at 40
    line 2: lives = lives * 2; // double it
    line 3: lives = lives + 5; // add 5
    line 4: lives = lives + 6; // add 6
    line 5: show(lives); // show it
  39. 39.🐞 This code has a bug. What number SHOULD it show, if every line did what its comment says?
    line 1: let coins = 47; // start at 47
    line 2: coins = coins - 3; // add 3
    line 3: coins = coins - 1; // take away 1
    line 4: show(coins); // show it
  40. 40.🐞 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 - 6; // add 6
    line 3: points = points * 2; // double it
    line 4: show(points); // show it     (a) line 2 (b) line 3 (c) line 1

Answer key

  1. 46
  2. a mistake in the code
  3. line 2
  4. 184
  5. 99
  6. 92
  7. test it again
  8. 44
  9. 62
  10. 76
  11. debugging
  12. people reading the code
  13. 42
  14. 41
  15. 32
  16. 31
  17. 65
  18. 41
  19. line 4
  20. line 2
  21. 91
  22. 166
  23. 58
  24. line 3
  25. line 3
  26. find where it goes wrong
  27. 47
  28. line 2
  29. 98
  30. 78
  31. 86
  32. line 2
  33. 336
  34. 42
  35. line 3
  36. 40
  37. 90
  38. 97
  39. 49
  40. line 2

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