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App Dev Worksheet: Debugging

App development lesson 21: Debugging: find the bug line · Set 962 · 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 does it ACTUALLY show?
    line 1: let points = 35; // start at 35
    line 2: points = points + 3; // add 3
    line 3: points = points + 3; // take away 3
    line 4: show(points); // show it
  2. 2.🐞 Each comment says what its line SHOULD do. Which line has the bug?
    line 1: let points = 52; // start at 50
    line 2: points = points - 1; // take away 1
    line 3: points = points - 5; // take away 5
    line 4: show(points); // show it     (a) line 3 (b) line 1 (c) line 2
  3. 3.🐞 What is a bug? (a) a nice icon (b) a fast phone (c) a new feature (d) a mistake in the code
  4. 4.🐞 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 - 4; // add 4
    line 4: show(lives); // show it
  5. 5.🐞 This code has a bug. What number does it ACTUALLY show?
    line 1: let stars = 34; // start at 34
    line 2: stars = stars * 2; // double it
    line 3: stars = stars * 3; // double it
    line 4: stars = stars - 2; // take away 2
    line 5: show(stars); // show it
  6. 6.🐞 A comment in code (after //) is for ___. (a) people reading the code (b) the phone screen (c) the battery (d) the app store
  7. 7.🐞 This code has a bug. What number does it ACTUALLY show?
    line 1: let score = 46; // start at 46
    line 2: score = score + 4; // add 4
    line 3: score = score * 3; // double it
    line 4: score = score * 2; // double it
    line 5: show(score); // show it
  8. 8.🐞 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 + 4; // take away 4
    line 3: points = points - 2; // take away 2
    line 4: show(points); // show it     (a) line 1 (b) line 3 (c) line 2
  9. 9.🐞 This code has a bug. What number SHOULD it show, if every line did what its comment says?
    line 1: let lives = 34; // start at 32
    line 2: lives = lives + 3; // add 3
    line 3: lives = lives + 3; // add 3
    line 4: show(lives); // show it
  10. 10.🐞 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 - 5; // add 5
    line 3: coins = coins - 4; // take away 4
    line 4: coins = coins * 2; // double it
    line 5: show(coins); // show it
  11. 11.🐞 Each comment says what its line SHOULD do. Which line has the bug?
    line 1: let lives = 31; // start at 31
    line 2: lives = lives * 2; // double it
    line 3: lives = lives + 3; // add 2
    line 4: show(lives); // show it     (a) line 2 (b) line 3 (c) line 1
  12. 12.🐞 This code has a bug. What number SHOULD it show, if every line did what its comment says?
    line 1: let stars = 37; // start at 37
    line 2: stars = stars * 2; // double it
    line 3: stars = stars + 3; // take away 3
    line 4: show(stars); // show it
  13. 13.🐞 Each comment says what its line SHOULD do. Which line has the bug?
    line 1: let coins = 42; // start at 42
    line 2: coins = coins + 2; // double it
    line 3: coins = coins - 1; // take away 1
    line 4: show(coins); // show it     (a) line 3 (b) line 2 (c) line 1
  14. 14.🐞 This code has a bug. What number SHOULD it show, if every line did what its comment says?
    line 1: let stars = 34; // start at 33
    line 2: stars = stars * 2; // double it
    line 3: stars = stars * 2; // double it
    line 4: stars = stars * 2; // double it
    line 5: show(stars); // show it
  15. 15.🐞 This code has a bug. What number does it ACTUALLY show?
    line 1: let stars = 36; // start at 35
    line 2: stars = stars + 5; // add 5
    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 points = 35; // start at 32
    line 2: points = points + 5; // add 5
    line 3: points = points - 1; // take away 1
    line 4: points = points - 1; // take away 1
    line 5: show(points); // show it
  17. 17.🐞 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 32
    line 2: lives = lives + 5; // add 5
    line 3: lives = lives - 3; // take away 3
    line 4: show(lives); // show it
  18. 18.🐞 Finding and fixing bugs is called ___. (a) designing (b) debugging (c) downloading (d) decorating
  19. 19.🐞 This code has a bug. What number does it ACTUALLY show?
    line 1: let stars = 43; // start at 42
    line 2: stars = stars * 2; // double it
    line 3: stars = stars * 2; // double it
    line 4: show(stars); // show it
  20. 20.🐞 This code has a bug. What number does it ACTUALLY show?
    line 1: let stars = 32; // start at 30
    line 2: stars = stars - 5; // take away 5
    line 3: stars = stars - 1; // take away 1
    line 4: show(stars); // show it
  21. 21.🐞 This code has a bug. What number does it ACTUALLY show?
    line 1: let lives = 34; // start at 34
    line 2: lives = lives - 2; // take away 2
    line 3: lives = lives * 2; // double it
    line 4: lives = lives * 3; // double it
    line 5: show(lives); // show it
  22. 22.🐞 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
  23. 23.🐞 This code has a bug. What number does it ACTUALLY show?
    line 1: let coins = 38; // start at 38
    line 2: coins = coins - 2; // add 2
    line 3: coins = coins * 2; // double it
    line 4: coins = coins - 1; // take away 1
    line 5: show(coins); // 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 stars = 45; // start at 45
    line 2: stars = stars + 2; // add 2
    line 3: stars = stars + 8; // add 6
    line 4: show(stars); // show it
  25. 25.🐞 This code has a bug. What number SHOULD it show, if every line did what its comment says?
    line 1: let lives = 31; // start at 30
    line 2: lives = lives * 2; // double it
    line 3: lives = lives + 6; // add 6
    line 4: show(lives); // show it
  26. 26.🐞 This code has a bug. What number SHOULD it show, if every line did what its comment says?
    line 1: let lives = 30; // start at 30
    line 2: lives = lives - 5; // add 5
    line 3: lives = lives + 3; // add 3
    line 4: show(lives); // show it
  27. 27.🐞 This code has a bug. What number does it ACTUALLY show?
    line 1: let score = 48; // start at 45
    line 2: score = score - 5; // take away 5
    line 3: score = score * 2; // double it
    line 4: score = score * 2; // double it
    line 5: show(score); // show it
  28. 28.🐞 Each comment says what its line SHOULD do. Which line has the bug?
    line 1: let score = 47; // start at 44
    line 2: score = score - 5; // take away 5
    line 3: score = score + 6; // add 6
    line 4: show(score); // show it     (a) line 1 (b) line 2 (c) line 3
  29. 29.🐞 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; // take away 2
    line 3: score = score + 4; // add 4
    line 4: score = score - 2; // take away 1
    line 5: show(score); // show it
  30. 30.🐞 This code has a bug. What number does it ACTUALLY show?
    line 1: let points = 50; // start at 49
    line 2: points = points + 2; // add 2
    line 3: points = points + 4; // add 4
    line 4: show(points); // show it
  31. 31.🐞 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 + 6; // add 5
    line 3: score = score + 5; // add 5
    line 4: score = score + 5; // add 5
    line 5: show(score); // show it     (a) line 1 (b) line 3 (c) line 4 (d) line 2
  32. 32.🐞 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; // take away 2
    line 3: stars = stars + 3; // add 3
    line 4: stars = stars - 2; // add 2
    line 5: show(stars); // show it     (a) line 3 (b) line 4 (c) line 2 (d) line 1
  33. 33.🐞 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 - 1; // take away 1
    line 3: points = points + 2; // double it
    line 4: 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 score = 30; // start at 30
    line 2: score = score - 4; // add 4
    line 3: score = score + 3; // add 3
    line 4: score = score * 2; // double it
    line 5: show(score); // show it
  35. 35.🐞 This code has a bug. What number does it ACTUALLY show?
    line 1: let coins = 48; // start at 48
    line 2: coins = coins - 1; // take away 1
    line 3: coins = coins - 5; // take away 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 = 45; // start at 45
    line 2: score = score * 2; // double it
    line 3: score = score + 6; // add 4
    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
  37. 37.🐞 After fixing a bug you should ___. (a) delete the test (b) release at once (c) never test (d) test it again
  38. 38.🐞 This code has a bug. What number does it ACTUALLY show?
    line 1: let lives = 37; // start at 36
    line 2: lives = lives - 3; // take away 3
    line 3: lives = lives + 4; // add 4
    line 4: lives = lives * 2; // double it
    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 stars = 43; // start at 40
    line 2: stars = stars * 2; // double it
    line 3: stars = stars - 1; // take away 1
    line 4: stars = stars + 5; // add 5
    line 5: show(stars); // show it
  40. 40.🐞 Each comment says what its line SHOULD do. Which line has the bug?
    line 1: let points = 33; // start at 33
    line 2: points = points + 3; // add 2
    line 3: points = points * 2; // double it
    line 4: show(points); // show it     (a) line 3 (b) line 1 (c) line 2

Answer key

  1. 41
  2. line 1
  3. a mistake in the code
  4. 45
  5. 202
  6. people reading the code
  7. 300
  8. line 2
  9. 38
  10. 96
  11. line 3
  12. 71
  13. line 2
  14. 264
  15. 82
  16. 35
  17. 34
  18. debugging
  19. 172
  20. 26
  21. 192
  22. find where it goes wrong
  23. 71
  24. 53
  25. 66
  26. 38
  27. 172
  28. line 1
  29. 36
  30. 56
  31. line 2
  32. line 4
  33. 60
  34. 74
  35. 39
  36. line 3
  37. test it again
  38. 76
  39. 84
  40. line 2

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