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App Dev Worksheet: Debugging

App development lesson 21: Debugging: find the bug line · Set 191 · 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.🐞 After fixing a bug you should ___. (a) test it again (b) never test (c) release at once (d) delete the test
  2. 2.🐞 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 34
    line 2: stars = stars - 5; // take away 5
    line 3: stars = stars * 2; // double it
    line 4: show(stars); // 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 points = 31; // start at 31
    line 2: points = points - 1; // take away 1
    line 3: points = points - 3; // take away 3
    line 4: points = points + 4; // take away 4
    line 5: show(points); // show it
  4. 4.🐞 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 + 1; // take away 1
    line 4: show(lives); // show it
  5. 5.🐞 This code has a bug. What number does it ACTUALLY show?
    line 1: let score = 38; // start at 36
    line 2: score = score - 3; // take away 3
    line 3: score = score * 2; // double it
    line 4: show(score); // show it
  6. 6.🐞 This code has a bug. What number does it ACTUALLY show?
    line 1: let score = 47; // start at 46
    line 2: score = score - 3; // take away 3
    line 3: score = score + 2; // add 2
    line 4: score = score * 2; // double it
    line 5: show(score); // show it
  7. 7.🐞 A comment in code (after //) is for ___. (a) people reading the code (b) the app store (c) the phone screen (d) the battery
  8. 8.🐞 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 44
    line 2: coins = coins * 2; // double it
    line 3: coins = coins - 8; // take away 5
    line 4: show(coins); // 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 = 45; // start at 43
    line 2: points = points * 2; // double it
    line 3: points = points - 3; // take away 3
    line 4: points = points + 2; // add 2
    line 5: show(points); // show it
  10. 10.🐞 What is a good first step when an app gives a wrong result? (a) buy a new phone (b) find where it goes wrong (c) add more colours (d) delete the app
  11. 11.🐞 This code has a bug. What number SHOULD it show, if every line did what its comment says?
    line 1: let stars = 40; // start at 40
    line 2: stars = stars + 3; // add 2
    line 3: stars = stars + 4; // add 4
    line 4: show(stars); // show it
  12. 12.🐞 What is a bug? (a) a mistake in the code (b) a nice icon (c) a fast phone (d) a new feature
  13. 13.🐞 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 + 6; // add 6
    line 3: score = score + 6; // add 6
    line 4: score = score + 2; // double it
    line 5: show(score); // show it     (a) line 2 (b) line 4 (c) line 1 (d) line 3
  14. 14.🐞 Each comment says what its line SHOULD do. Which line has the bug?
    line 1: let score = 40; // start at 39
    line 2: score = score + 5; // add 5
    line 3: score = score * 2; // double it
    line 4: show(score); // show it     (a) line 3 (b) line 1 (c) line 2
  15. 15.🐞 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 + 5; // add 5
    line 3: lives = lives + 2; // add 2
    line 4: lives = lives - 5; // add 5
    line 5: show(lives); // 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 coins = 42; // start at 42
    line 2: coins = coins + 3; // take away 3
    line 3: coins = coins * 2; // double it
    line 4: show(coins); // show it
  17. 17.🐞 This code has a bug. What number does it ACTUALLY show?
    line 1: let points = 44; // start at 44
    line 2: points = points + 1; // take away 1
    line 3: points = points + 4; // add 4
    line 4: points = points - 2; // take away 2
    line 5: show(points); // show it
  18. 18.🐞 This code has a bug. What number does it ACTUALLY show?
    line 1: let coins = 31; // start at 31
    line 2: coins = coins * 2; // double it
    line 3: coins = coins * 3; // double it
    line 4: show(coins); // show it
  19. 19.🐞 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 44
    line 2: score = score + 5; // add 5
    line 3: score = score - 3; // take away 1
    line 4: show(score); // show it
  20. 20.🐞 Each comment says what its line SHOULD do. Which line has the bug?
    line 1: let points = 43; // start at 41
    line 2: points = points * 2; // double it
    line 3: points = points + 5; // add 5
    line 4: show(points); // show it     (a) line 2 (b) line 1 (c) line 3
  21. 21.🐞 Each comment says what its line SHOULD do. Which line has the bug?
    line 1: let coins = 35; // start at 35
    line 2: coins = coins + 4; // add 3
    line 3: coins = coins + 5; // add 5
    line 4: show(coins); // show it     (a) line 2 (b) line 1 (c) line 3
  22. 22.🐞 This code has a bug. What number does it ACTUALLY show?
    line 1: let stars = 42; // start at 42
    line 2: stars = stars * 2; // double it
    line 3: stars = stars + 3; // add 2
    line 4: stars = stars + 2; // add 2
    line 5: show(stars); // show it
  23. 23.🐞 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 - 4; // take away 3
    line 3: score = score * 2; // double it
    line 4: score = score * 2; // double it
    line 5: show(score); // show it     (a) line 4 (b) line 3 (c) line 2 (d) line 1
  24. 24.🐞 This code has a bug. What number SHOULD it show, if every line did what its comment says?
    line 1: let coins = 31; // start at 31
    line 2: coins = coins + 2; // add 2
    line 3: coins = coins + 8; // add 6
    line 4: show(coins); // show it
  25. 25.🐞 This code has a bug. What number does it ACTUALLY show?
    line 1: let stars = 41; // start at 41
    line 2: stars = stars * 2; // double it
    line 3: stars = stars - 8; // take away 5
    line 4: show(stars); // show it
  26. 26.🐞 This code has a bug. What number does it ACTUALLY show?
    line 1: let lives = 33; // start at 33
    line 2: lives = lives * 2; // double it
    line 3: lives = lives * 2; // double it
    line 4: lives = lives - 4; // take away 1
    line 5: show(lives); // 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 coins = 32; // start at 30
    line 2: coins = coins - 4; // take away 4
    line 3: coins = coins * 2; // double it
    line 4: show(coins); // show it
  28. 28.🐞 This code has a bug. What number SHOULD it show, if every line did what its comment says?
    line 1: let score = 47; // start at 47
    line 2: score = score * 3; // double it
    line 3: score = score - 3; // take away 3
    line 4: score = score + 6; // add 6
    line 5: show(score); // 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 score = 46; // start at 46
    line 2: score = score - 4; // take away 2
    line 3: score = score - 5; // take away 5
    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 score = 33; // start at 33
    line 2: score = score - 1; // take away 1
    line 3: score = score * 2; // double it
    line 4: score = score - 6; // take away 4
    line 5: show(score); // show it
  31. 31.🐞 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 + 5; // add 5
    line 3: score = score * 3; // double it
    line 4: show(score); // show it     (a) line 1 (b) line 3 (c) line 2
  32. 32.🐞 This code has a bug. What number does it ACTUALLY show?
    line 1: let points = 46; // start at 46
    line 2: points = points - 3; // add 3
    line 3: points = points - 3; // take away 3
    line 4: points = points + 4; // add 4
    line 5: 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 points = 30; // start at 30
    line 2: points = points - 2; // take away 2
    line 3: points = points - 2; // add 2
    line 4: points = points - 4; // take away 4
    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 lives = 43; // start at 43
    line 2: lives = lives - 3; // take away 3
    line 3: lives = lives * 3; // double it
    line 4: show(lives); // show it
  35. 35.🐞 Each comment says what its line SHOULD do. Which line has the bug?
    line 1: let score = 49; // start at 46
    line 2: score = score - 3; // take away 3
    line 3: score = score + 6; // add 6
    line 4: show(score); // show it     (a) line 2 (b) line 3 (c) line 1
  36. 36.🐞 This code has a bug. What number SHOULD it show, if every line did what its comment says?
    line 1: let stars = 48; // start at 47
    line 2: stars = stars * 2; // double it
    line 3: stars = stars * 2; // double it
    line 4: show(stars); // show it
  37. 37.🐞 Each comment says what its line SHOULD do. Which line has the bug?
    line 1: let coins = 47; // start at 47
    line 2: coins = coins + 2; // add 2
    line 3: coins = coins - 4; // add 4
    line 4: show(coins); // show it     (a) line 3 (b) line 1 (c) line 2
  38. 38.🐞 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 33
    line 2: lives = lives - 2; // take away 2
    line 3: lives = lives - 3; // take away 3
    line 4: lives = lives - 4; // take away 4
    line 5: show(lives); // show it
  39. 39.🐞 This code has a bug. What number does it ACTUALLY show?
    line 1: let stars = 38; // start at 38
    line 2: stars = stars * 2; // double it
    line 3: stars = stars + 7; // add 5
    line 4: show(stars); // show it
  40. 40.🐞 This code has a bug. What number does it ACTUALLY show?
    line 1: let score = 40; // start at 40
    line 2: score = score + 2; // add 2
    line 3: score = score - 4; // take away 1
    line 4: show(score); // show it

Answer key

  1. test it again
  2. 58
  3. 23
  4. 33
  5. 70
  6. 92
  7. people reading the code
  8. 83
  9. 85
  10. find where it goes wrong
  11. 46
  12. a mistake in the code
  13. line 4
  14. line 1
  15. 53
  16. 78
  17. 47
  18. 186
  19. 48
  20. line 1
  21. line 2
  22. 89
  23. line 2
  24. 39
  25. 74
  26. 128
  27. 52
  28. 97
  29. 78
  30. 58
  31. line 3
  32. 44
  33. 26
  34. 80
  35. line 1
  36. 188
  37. line 3
  38. 24
  39. 83
  40. 38

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