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App Dev Worksheet: Debugging

App development lesson 21: Debugging: find the bug line · Set 580 · 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 points = 33; // start at 33
    line 2: points = points * 2; // double it
    line 3: points = points + 1; // take away 1
    line 4: show(points); // show it
  2. 2.🐞 This code has a bug. What number does it ACTUALLY show?
    line 1: let stars = 49; // start at 46
    line 2: stars = stars + 3; // add 3
    line 3: stars = stars - 1; // take away 1
    line 4: show(stars); // show it
  3. 3.🐞 What is a good first step when an app gives a wrong result? (a) delete the app (b) add more colours (c) find where it goes wrong (d) buy a new phone
  4. 4.🐞 A comment in code (after //) is for ___. (a) the phone screen (b) the app store (c) the battery (d) people reading the code
  5. 5.🐞 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 * 2; // double it
    line 3: lives = lives - 5; // take away 5
    line 4: lives = lives + 4; // take away 4
    line 5: show(lives); // show it
  6. 6.🐞 What is a bug? (a) a nice icon (b) a new feature (c) a mistake in the code (d) a fast phone
  7. 7.🐞 After fixing a bug you should ___. (a) test it again (b) release at once (c) never test (d) delete the test
  8. 8.🐞 This code has a bug. What number SHOULD it show, if every line did what its comment says?
    line 1: let stars = 35; // start at 35
    line 2: stars = stars + 2; // double it
    line 3: stars = stars - 3; // take away 3
    line 4: stars = stars + 6; // add 6
    line 5: show(stars); // show it
  9. 9.🐞 This code has a bug. What number does it ACTUALLY show?
    line 1: let lives = 37; // start at 34
    line 2: lives = lives + 4; // add 4
    line 3: lives = lives - 4; // take away 4
    line 4: show(lives); // show it
  10. 10.🐞 This code has a bug. What number does it ACTUALLY show?
    line 1: let lives = 45; // start at 45
    line 2: lives = lives - 5; // take away 5
    line 3: lives = lives + 3; // add 3
    line 4: lives = lives + 5; // add 4
    line 5: show(lives); // show it
  11. 11.🐞 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 + 3; // add 3
    line 4: score = score - 2; // take away 2
    line 5: show(score); // 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 = 45; // start at 45
    line 2: score = score + 5; // add 5
    line 3: score = score - 6; // take away 5
    line 4: score = score + 4; // add 4
    line 5: show(score); // 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 = 48; // start at 48
    line 2: score = score + 2; // double it
    line 3: score = score * 2; // double it
    line 4: score = score - 3; // take away 3
    line 5: show(score); // 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 lives = 49; // start at 49
    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
  15. 15.🐞 This code has a bug. What number SHOULD it show, if every line did what its comment says?
    line 1: let score = 45; // start at 45
    line 2: score = score + 6; // add 3
    line 3: score = score + 3; // add 3
    line 4: show(score); // show it
  16. 16.🐞 This code has a bug. What number does it ACTUALLY show?
    line 1: let lives = 34; // start at 34
    line 2: lives = lives + 3; // take away 3
    line 3: lives = lives + 3; // add 3
    line 4: show(lives); // show it
  17. 17.🐞 Finding and fixing bugs is called ___. (a) downloading (b) debugging (c) decorating (d) designing
  18. 18.🐞 This code has a bug. What number does it ACTUALLY show?
    line 1: let lives = 39; // start at 37
    line 2: lives = lives + 6; // add 6
    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 does it ACTUALLY show?
    line 1: let points = 43; // start at 43
    line 2: points = points + 2; // double it
    line 3: points = points + 3; // add 3
    line 4: show(points); // show it
  20. 20.🐞 Each comment says what its line SHOULD do. Which line has the bug?
    line 1: let lives = 45; // start at 45
    line 2: lives = lives + 7; // add 5
    line 3: lives = lives + 4; // add 4
    line 4: show(lives); // show it     (a) line 3 (b) line 2 (c) line 1
  21. 21.🐞 Each comment says what its line SHOULD do. Which line has the bug?
    line 1: let score = 36; // start at 36
    line 2: score = score + 5; // add 5
    line 3: score = score + 5; // add 5
    line 4: score = score - 3; // take away 2
    line 5: show(score); // show it     (a) line 4 (b) line 3 (c) line 1 (d) line 2
  22. 22.🐞 This code has a bug. What number SHOULD it show, if every line did what its comment says?
    line 1: let coins = 48; // start at 45
    line 2: coins = coins - 4; // take away 4
    line 3: coins = coins * 2; // double it
    line 4: coins = coins + 4; // add 4
    line 5: show(coins); // 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 = 43; // start at 43
    line 2: score = score + 5; // add 2
    line 3: score = score + 4; // add 4
    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 coins = 49; // start at 48
    line 2: coins = coins + 4; // add 4
    line 3: coins = coins + 5; // add 5
    line 4: coins = coins - 4; // take away 4
    line 5: show(coins); // show it
  25. 25.🐞 Each comment says what its line SHOULD do. Which line has the bug?
    line 1: let coins = 46; // start at 46
    line 2: coins = coins + 1; // take away 1
    line 3: coins = coins * 2; // double it
    line 4: show(coins); // show it     (a) line 2 (b) line 1 (c) line 3
  26. 26.🐞 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 * 3; // double it
    line 3: points = points * 2; // double it
    line 4: show(points); // show it
  27. 27.🐞 This code has a bug. What number does it ACTUALLY show?
    line 1: let coins = 33; // start at 33
    line 2: coins = coins + 3; // take away 3
    line 3: coins = coins - 2; // take away 2
    line 4: show(coins); // show it
  28. 28.🐞 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 + 9; // add 6
    line 3: score = score - 3; // take away 3
    line 4: show(score); // show it     (a) line 1 (b) line 2 (c) line 3
  29. 29.🐞 This code has a bug. What number does it ACTUALLY show?
    line 1: let coins = 48; // start at 48
    line 2: coins = coins * 2; // double it
    line 3: coins = coins + 5; // take away 5
    line 4: show(coins); // show it
  30. 30.🐞 This code has a bug. What number SHOULD it show, if every line did what its comment says?
    line 1: let coins = 42; // start at 39
    line 2: coins = coins * 2; // double it
    line 3: coins = coins + 5; // add 5
    line 4: coins = coins * 2; // double it
    line 5: 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 coins = 43; // start at 40
    line 2: coins = coins + 4; // add 4
    line 3: coins = coins + 3; // add 3
    line 4: show(coins); // show it
  32. 32.🐞 This code has a bug. What number does it ACTUALLY show?
    line 1: let stars = 49; // start at 49
    line 2: stars = stars - 5; // add 5
    line 3: stars = stars + 5; // add 5
    line 4: show(stars); // show it
  33. 33.🐞 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 - 2; // take away 1
    line 3: stars = stars + 4; // add 4
    line 4: stars = stars + 5; // add 5
    line 5: show(stars); // show it
  34. 34.🐞 This code has a bug. What number does it ACTUALLY show?
    line 1: let score = 51; // start at 50
    line 2: score = score * 2; // double it
    line 3: score = score + 6; // add 6
    line 4: show(score); // show it
  35. 35.🐞 This code has a bug. What number SHOULD it show, if every line did what its comment says?
    line 1: let coins = 30; // start at 30
    line 2: coins = coins * 3; // double it
    line 3: coins = coins + 5; // add 5
    line 4: coins = coins + 3; // add 3
    line 5: show(coins); // show it
  36. 36.🐞 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 - 1; // take away 1
    line 3: score = score * 2; // double it
    line 4: score = score + 2; // double it
    line 5: show(score); // show it     (a) line 3 (b) line 4 (c) line 1 (d) line 2
  37. 37.🐞 This code has a bug. What number does it ACTUALLY show?
    line 1: let lives = 33; // start at 33
    line 2: lives = lives + 1; // take away 1
    line 3: lives = lives - 4; // take away 4
    line 4: show(lives); // show it
  38. 38.🐞 This code has a bug. What number SHOULD it show, if every line did what its comment says?
    line 1: let stars = 39; // start at 39
    line 2: stars = stars * 2; // double it
    line 3: stars = stars - 6; // take away 3
    line 4: show(stars); // 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 score = 42; // start at 41
    line 2: score = score + 2; // add 2
    line 3: score = score + 2; // add 2
    line 4: show(score); // show it
  40. 40.🐞 This code has a bug. What number does it ACTUALLY show?
    line 1: let score = 36; // start at 36
    line 2: score = score - 3; // add 3
    line 3: score = score + 6; // add 6
    line 4: score = score + 6; // add 6
    line 5: show(score); // show it

Answer key

  1. 65
  2. 51
  3. find where it goes wrong
  4. people reading the code
  5. 73
  6. a mistake in the code
  7. test it again
  8. 73
  9. 37
  10. 48
  11. 61
  12. 49
  13. 189
  14. 192
  15. 51
  16. 40
  17. debugging
  18. 180
  19. 48
  20. line 2
  21. line 4
  22. 86
  23. 49
  24. 53
  25. line 2
  26. 168
  27. 34
  28. line 2
  29. 101
  30. 166
  31. 47
  32. 49
  33. 53
  34. 108
  35. 68
  36. line 4
  37. 30
  38. 75
  39. 45
  40. 45

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