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App Dev Worksheet: Debugging

App development lesson 21: Debugging: find the bug line · Set 46 · 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 points = 42; // start at 42
    line 2: points = points * 2; // double it
    line 3: points = points - 2; // add 2
    line 4: show(points); // show it     (a) line 1 (b) line 2 (c) line 3
  2. 2.🐞 This code has a bug. What number does it ACTUALLY show?
    line 1: let coins = 48; // start at 48
    line 2: coins = coins - 4; // add 4
    line 3: coins = coins + 3; // add 3
    line 4: show(coins); // 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 score = 32; // start at 32
    line 2: score = score + 2; // double it
    line 3: score = score + 4; // add 4
    line 4: show(score); // show it
  4. 4.🐞 Each comment says what its line SHOULD do. Which line has the bug?
    line 1: let stars = 47; // start at 47
    line 2: stars = stars - 2; // take away 2
    line 3: stars = stars + 1; // take away 1
    line 4: show(stars); // show it     (a) line 2 (b) line 1 (c) line 3
  5. 5.🐞 This code has a bug. What number does it ACTUALLY show?
    line 1: let points = 39; // start at 39
    line 2: points = points + 3; // add 3
    line 3: points = points * 2; // double it
    line 4: points = points + 2; // double it
    line 5: show(points); // show it
  6. 6.🐞 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 * 2; // double it
    line 3: score = score - 2; // take away 2
    line 4: show(score); // show it     (a) line 3 (b) line 2 (c) line 1
  7. 7.🐞 After fixing a bug you should ___. (a) never test (b) release at once (c) delete the test (d) test it again
  8. 8.🐞 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 48
    line 2: points = points + 3; // add 3
    line 3: points = points * 2; // double it
    line 4: points = points * 2; // double it
    line 5: show(points); // show it
  9. 9.🐞 This code has a bug. What number does it ACTUALLY show?
    line 1: let score = 38; // start at 37
    line 2: score = score + 2; // add 2
    line 3: score = score + 5; // add 5
    line 4: score = score - 2; // take away 2
    line 5: show(score); // show it
  10. 10.🐞 Each comment says what its line SHOULD do. Which line has the bug?
    line 1: let coins = 50; // start at 50
    line 2: coins = coins + 5; // add 5
    line 3: coins = coins + 1; // take away 1
    line 4: coins = coins + 6; // add 6
    line 5: show(coins); // show it     (a) line 1 (b) line 4 (c) line 3 (d) line 2
  11. 11.🐞 This code has a bug. What number does it ACTUALLY show?
    line 1: let score = 33; // start at 32
    line 2: score = score + 6; // add 6
    line 3: score = score + 5; // add 5
    line 4: show(score); // show it
  12. 12.🐞 This code has a bug. What number does it ACTUALLY show?
    line 1: let lives = 46; // start at 46
    line 2: lives = lives - 1; // take away 1
    line 3: lives = lives + 4; // add 4
    line 4: lives = lives + 9; // add 6
    line 5: show(lives); // show it
  13. 13.🐞 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 - 2; // take away 2
    line 3: score = score * 3; // double it
    line 4: show(score); // show it
  14. 14.🐞 Each comment says what its line SHOULD do. Which line has the bug?
    line 1: let points = 34; // start at 32
    line 2: points = points + 4; // add 4
    line 3: points = points + 4; // add 4
    line 4: points = points * 2; // double it
    line 5: show(points); // show it     (a) line 2 (b) line 4 (c) line 3 (d) line 1
  15. 15.🐞 Each comment says what its line SHOULD do. Which line has the bug?
    line 1: let coins = 35; // start at 34
    line 2: coins = coins + 3; // add 3
    line 3: coins = coins * 2; // double it
    line 4: show(coins); // show it     (a) line 2 (b) line 1 (c) line 3
  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 - 3; // take away 3
    line 3: points = points + 3; // take away 3
    line 4: points = points + 6; // add 6
    line 5: show(points); // show it     (a) line 2 (b) line 4 (c) line 3 (d) line 1
  17. 17.🐞 This code has a bug. What number SHOULD it show, if every line did what its comment says?
    line 1: let score = 44; // start at 41
    line 2: score = score + 2; // add 2
    line 3: score = score - 1; // take away 1
    line 4: score = score + 4; // add 4
    line 5: show(score); // 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 = 50; // start at 50
    line 2: coins = coins - 1; // take away 1
    line 3: coins = coins * 3; // double it
    line 4: show(coins); // show it
  19. 19.🐞 This code has a bug. What number does it ACTUALLY show?
    line 1: let coins = 40; // start at 40
    line 2: coins = coins + 3; // add 3
    line 3: coins = coins - 4; // take away 4
    line 4: coins = coins - 7; // take away 4
    line 5: show(coins); // show it
  20. 20.🐞 Each comment says what its line SHOULD do. Which line has the bug?
    line 1: let coins = 39; // start at 39
    line 2: coins = coins + 6; // add 6
    line 3: coins = coins + 5; // add 2
    line 4: coins = coins + 5; // add 5
    line 5: show(coins); // show it     (a) line 4 (b) line 1 (c) line 2 (d) line 3
  21. 21.🐞 This code has a bug. What number does it ACTUALLY show?
    line 1: let score = 51; // start at 50
    line 2: score = score - 1; // take away 1
    line 3: score = score - 1; // take away 1
    line 4: show(score); // show it
  22. 22.🐞 A comment in code (after //) is for ___. (a) the phone screen (b) the battery (c) the app store (d) people reading the code
  23. 23.🐞 This code has a bug. What number does it ACTUALLY show?
    line 1: let lives = 32; // start at 32
    line 2: lives = lives + 2; // double it
    line 3: lives = lives + 4; // add 4
    line 4: lives = lives - 1; // take away 1
    line 5: show(lives); // 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 score = 44; // start at 41
    line 2: score = score - 5; // take away 5
    line 3: score = score + 6; // add 6
    line 4: show(score); // show it
  25. 25.🐞 What is a bug? (a) a fast phone (b) a nice icon (c) a mistake in the code (d) a new feature
  26. 26.🐞 This code has a bug. What number SHOULD it show, if every line did what its comment says?
    line 1: let score = 31; // start at 31
    line 2: score = score * 2; // double it
    line 3: score = score - 4; // take away 1
    line 4: score = score + 3; // add 3
    line 5: show(score); // show it
  27. 27.🐞 This code has a bug. What number does it ACTUALLY show?
    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 + 7; // add 5
    line 5: show(points); // show it
  28. 28.🐞 This code has a bug. What number does it ACTUALLY show?
    line 1: let lives = 42; // start at 42
    line 2: lives = lives + 5; // add 5
    line 3: lives = lives - 3; // take away 2
    line 4: show(lives); // show it
  29. 29.🐞 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 + 4; // add 4
    line 3: coins = coins * 2; // double it
    line 4: coins = coins * 2; // double it
    line 5: show(coins); // show it
  30. 30.🐞 This code has a bug. What number does it ACTUALLY show?
    line 1: let points = 47; // start at 46
    line 2: points = points - 3; // take away 3
    line 3: points = points + 6; // add 6
    line 4: show(points); // show it
  31. 31.🐞 Each comment says what its line SHOULD do. Which line has the bug?
    line 1: let coins = 40; // start at 40
    line 2: coins = coins - 3; // add 3
    line 3: coins = coins + 5; // add 5
    line 4: show(coins); // show it     (a) line 2 (b) line 3 (c) line 1
  32. 32.🐞 Each comment says what its line SHOULD do. Which line has the bug?
    line 1: let lives = 42; // start at 42
    line 2: lives = lives * 2; // double it
    line 3: lives = lives + 7; // add 5
    line 4: show(lives); // show it     (a) line 3 (b) line 2 (c) line 1
  33. 33.🐞 This code has a bug. What number does it ACTUALLY show?
    line 1: let points = 41; // start at 41
    line 2: points = points - 3; // add 3
    line 3: points = points * 2; // double it
    line 4: points = points * 2; // double it
    line 5: show(points); // show it
  34. 34.🐞 Each comment says what its line SHOULD do. Which line has the bug?
    line 1: let lives = 48; // start at 46
    line 2: lives = lives - 1; // take away 1
    line 3: lives = lives + 3; // add 3
    line 4: lives = lives - 4; // take away 4
    line 5: show(lives); // show it     (a) line 1 (b) line 2 (c) line 4 (d) line 3
  35. 35.🐞 This code has a bug. What number SHOULD it show, if every line did what its comment says?
    line 1: let points = 33; // start at 33
    line 2: points = points - 3; // add 3
    line 3: points = points + 2; // add 2
    line 4: show(points); // show it
  36. 36.🐞 Each comment says what its line SHOULD do. Which line has the bug?
    line 1: let coins = 49; // start at 46
    line 2: coins = coins + 2; // add 2
    line 3: coins = coins * 2; // double it
    line 4: show(coins); // show it     (a) line 1 (b) line 2 (c) line 3
  37. 37.🐞 This code has a bug. What number SHOULD it show, if every line did what its comment says?
    line 1: let score = 50; // start at 50
    line 2: score = score + 2; // add 2
    line 3: score = score + 4; // add 4
    line 4: score = score * 3; // double it
    line 5: show(score); // show it
  38. 38.🐞 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 + 2; // double it
    line 3: score = score + 2; // add 2
    line 4: show(score); // show it     (a) line 2 (b) line 1 (c) line 3
  39. 39.🐞 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 * 3; // double it
    line 3: score = score - 2; // take away 2
    line 4: show(score); // show it     (a) line 2 (b) line 3 (c) 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 score = 35; // start at 35
    line 2: score = score + 2; // double it
    line 3: score = score + 5; // add 5
    line 4: show(score); // show it

Answer key

  1. line 3
  2. 47
  3. 68
  4. line 3
  5. 86
  6. line 1
  7. test it again
  8. 204
  9. 43
  10. line 3
  11. 44
  12. 58
  13. 88
  14. line 1
  15. line 1
  16. line 3
  17. 46
  18. 98
  19. 32
  20. line 3
  21. 49
  22. people reading the code
  23. 37
  24. 42
  25. a mistake in the code
  26. 64
  27. 175
  28. 44
  29. 152
  30. 50
  31. line 2
  32. line 3
  33. 152
  34. line 1
  35. 38
  36. line 1
  37. 112
  38. line 2
  39. line 2
  40. 75

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