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App Dev Worksheet: Debugging

App development lesson 21: Debugging: find the bug line · Set 703 · 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 = 44; // start at 44
    line 2: lives = lives - 1; // take away 1
    line 3: lives = lives * 2; // double it
    line 4: lives = lives - 3; // take away 1
    line 5: show(lives); // show it     (a) line 3 (b) line 1 (c) line 2 (d) line 4
  2. 2.🐞 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 46
    line 2: score = score * 2; // double it
    line 3: score = score * 2; // double it
    line 4: score = score + 5; // add 5
    line 5: show(score); // show it
  3. 3.🐞 This code has a bug. What number does it ACTUALLY show?
    line 1: let coins = 40; // start at 38
    line 2: coins = coins - 5; // take away 5
    line 3: coins = coins + 4; // add 4
    line 4: show(coins); // show it
  4. 4.🐞 After fixing a bug you should ___. (a) never test (b) test it again (c) delete the test (d) release at once
  5. 5.🐞 This code has a bug. What number SHOULD it show, if every line did what its comment says?
    line 1: let points = 46; // start at 43
    line 2: points = points + 2; // add 2
    line 3: points = points + 3; // add 3
    line 4: show(points); // show it
  6. 6.🐞 This code has a bug. What number SHOULD it show, if every line did what its comment says?
    line 1: let stars = 46; // start at 46
    line 2: stars = stars - 2; // add 2
    line 3: stars = stars - 1; // take away 1
    line 4: stars = stars * 2; // double it
    line 5: show(stars); // show it
  7. 7.🐞 Each comment says what its line SHOULD do. Which line has the bug?
    line 1: let score = 33; // start at 32
    line 2: score = score + 2; // add 2
    line 3: score = score + 5; // add 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
  8. 8.🐞 This code has a bug. What number does it ACTUALLY show?
    line 1: let score = 41; // start at 39
    line 2: score = score + 6; // add 6
    line 3: score = score + 6; // add 6
    line 4: show(score); // show it
  9. 9.🐞 This code has a bug. What number does it ACTUALLY show?
    line 1: let coins = 30; // start at 30
    line 2: coins = coins * 2; // double it
    line 3: coins = coins + 2; // add 2
    line 4: coins = coins + 2; // double it
    line 5: show(coins); // show it
  10. 10.🐞 What is a bug? (a) a fast phone (b) a mistake in the code (c) a new feature (d) a nice icon
  11. 11.🐞 This code has a bug. What number SHOULD it show, if every line did what its comment says?
    line 1: let score = 34; // start at 34
    line 2: score = score - 7; // take away 5
    line 3: score = score * 2; // double it
    line 4: 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 points = 31; // start at 31
    line 2: points = points - 4; // take away 4
    line 3: points = points - 4; // add 4
    line 4: show(points); // show it
  13. 13.🐞 This code has a bug. What number does it ACTUALLY show?
    line 1: let score = 39; // start at 39
    line 2: score = score + 8; // add 6
    line 3: score = score + 6; // add 6
    line 4: 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 points = 37; // start at 36
    line 2: points = points - 1; // take away 1
    line 3: points = points - 2; // take away 2
    line 4: 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 stars = 35; // start at 33
    line 2: stars = stars - 3; // take away 3
    line 3: stars = stars * 2; // double it
    line 4: show(stars); // show it
  16. 16.🐞 This code has a bug. What number SHOULD it show, if every line did what its comment says?
    line 1: let stars = 47; // start at 47
    line 2: stars = stars + 2; // add 2
    line 3: stars = stars + 2; // double it
    line 4: stars = stars + 6; // add 6
    line 5: show(stars); // show it
  17. 17.🐞 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; // add 2
    line 3: points = points + 5; // add 3
    line 4: show(points); // show it     (a) line 3 (b) line 1 (c) line 2
  18. 18.🐞 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 2
    line 3: stars = stars + 8; // add 5
    line 4: show(stars); // show it
  19. 19.🐞 Each comment says what its line SHOULD do. Which line has the bug?
    line 1: let lives = 40; // start at 40
    line 2: lives = lives + 2; // double it
    line 3: lives = lives - 4; // take away 4
    line 4: show(lives); // show it     (a) line 1 (b) line 3 (c) line 2
  20. 20.🐞 This code has a bug. What number SHOULD it show, if every line did what its comment says?
    line 1: let coins = 41; // start at 41
    line 2: coins = coins - 4; // take away 4
    line 3: coins = coins - 6; // take away 4
    line 4: coins = coins - 3; // take away 3
    line 5: show(coins); // 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 39
    line 2: coins = coins * 2; // double it
    line 3: coins = coins * 3; // double it
    line 4: show(coins); // show it
  22. 22.🐞 Finding and fixing bugs is called ___. (a) downloading (b) debugging (c) designing (d) decorating
  23. 23.🐞 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 31
    line 2: points = points + 2; // double it
    line 3: points = points + 4; // add 4
    line 4: show(points); // show it
  24. 24.🐞 This code has a bug. What number does it ACTUALLY show?
    line 1: let coins = 50; // start at 50
    line 2: coins = coins - 4; // take away 1
    line 3: coins = coins - 4; // take away 4
    line 4: show(coins); // show it
  25. 25.🐞 A comment in code (after //) is for ___. (a) people reading the code (b) the phone screen (c) the battery (d) the app store
  26. 26.🐞 This code has a bug. What number does it ACTUALLY show?
    line 1: let stars = 38; // start at 38
    line 2: stars = stars + 5; // add 5
    line 3: stars = stars * 3; // double it
    line 4: stars = stars + 5; // add 5
    line 5: show(stars); // show it
  27. 27.🐞 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 * 3; // double it
    line 3: score = score * 2; // double it
    line 4: show(score); // show it
  28. 28.🐞 This code has a bug. What number does it ACTUALLY show?
    line 1: let score = 43; // start at 43
    line 2: score = score * 2; // double it
    line 3: score = score + 6; // add 6
    line 4: score = score + 6; // add 4
    line 5: show(score); // show it
  29. 29.🐞 What is a good first step when an app gives a wrong result? (a) delete the app (b) add more colours (c) buy a new phone (d) find where it goes wrong
  30. 30.🐞 This code has a bug. What number does it ACTUALLY show?
    line 1: let stars = 51; // start at 48
    line 2: stars = stars - 3; // take away 3
    line 3: stars = stars + 4; // add 4
    line 4: show(stars); // 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 43
    line 2: coins = coins - 5; // add 5
    line 3: coins = coins - 1; // take away 1
    line 4: show(coins); // show it
  32. 32.🐞 This code has a bug. What number does it ACTUALLY show?
    line 1: let points = 48; // start at 48
    line 2: points = points * 3; // double it
    line 3: points = points + 5; // add 5
    line 4: show(points); // 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 = 47; // start at 44
    line 2: stars = stars - 1; // take away 1
    line 3: stars = stars + 2; // add 2
    line 4: show(stars); // 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 score = 48; // start at 48
    line 2: score = score + 4; // add 4
    line 3: score = score + 2; // double it
    line 4: score = score * 2; // double it
    line 5: 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 stars = 38; // start at 38
    line 2: stars = stars * 3; // double it
    line 3: stars = stars * 2; // double it
    line 4: show(stars); // show it
  36. 36.🐞 Each comment says what its line SHOULD do. Which line has the bug?
    line 1: let stars = 45; // start at 45
    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
  37. 37.🐞 This code has a bug. What number does it ACTUALLY show?
    line 1: let score = 34; // start at 34
    line 2: score = score + 5; // add 5
    line 3: score = score + 4; // add 2
    line 4: score = score - 4; // take away 4
    line 5: show(score); // 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 score = 38; // start at 38
    line 2: score = score - 1; // take away 1
    line 3: score = score - 4; // take away 3
    line 4: score = score - 1; // take away 1
    line 5: show(score); // 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 lives = 39; // start at 39
    line 2: lives = lives * 2; // double it
    line 3: lives = lives * 3; // double it
    line 4: show(lives); // show it
  40. 40.🐞 This code has a bug. What number does it ACTUALLY show?
    line 1: let stars = 45; // start at 43
    line 2: stars = stars * 2; // double it
    line 3: stars = stars * 2; // double it
    line 4: stars = stars + 4; // add 4
    line 5: show(stars); // show it

Answer key

  1. line 4
  2. 189
  3. 39
  4. test it again
  5. 48
  6. 94
  7. line 1
  8. 53
  9. 64
  10. a mistake in the code
  11. 58
  12. 31
  13. 53
  14. 33
  15. 60
  16. 104
  17. line 3
  18. 48
  19. line 2
  20. 30
  21. 156
  22. debugging
  23. 66
  24. 42
  25. people reading the code
  26. 134
  27. 160
  28. 98
  29. find where it goes wrong
  30. 52
  31. 47
  32. 149
  33. 45
  34. 208
  35. 152
  36. line 2
  37. 39
  38. 33
  39. 156
  40. 184

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