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App Dev Worksheet: Debugging

App development lesson 21: Debugging: find the bug line · Set 99 · 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.🐞 A comment in code (after //) is for ___. (a) the phone screen (b) the app store (c) the battery (d) people reading the code
  2. 2.🐞 This code has a bug. What number SHOULD it show, if every line did what its comment says?
    line 1: let stars = 49; // start at 46
    line 2: stars = stars * 2; // double it
    line 3: stars = stars + 5; // add 5
    line 4: stars = stars - 3; // take away 3
    line 5: show(stars); // show it
  3. 3.🐞 This code has a bug. What number does it ACTUALLY show?
    line 1: let coins = 40; // start at 40
    line 2: coins = coins + 2; // add 2
    line 3: coins = coins * 3; // double it
    line 4: show(coins); // show it
  4. 4.🐞 This code has a bug. What number does it ACTUALLY show?
    line 1: let points = 47; // start at 47
    line 2: points = points - 6; // add 6
    line 3: points = points * 2; // double it
    line 4: points = points * 2; // double it
    line 5: show(points); // show it
  5. 5.🐞 Finding and fixing bugs is called ___. (a) downloading (b) debugging (c) decorating (d) designing
  6. 6.🐞 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 + 3; // take away 3
    line 3: lives = lives - 4; // take away 4
    line 4: show(lives); // show it
  7. 7.🐞 This code has a bug. What number does it ACTUALLY show?
    line 1: let stars = 36; // start at 36
    line 2: stars = stars + 7; // add 5
    line 3: stars = stars * 2; // double it
    line 4: show(stars); // show it
  8. 8.🐞 This code has a bug. What number does it ACTUALLY show?
    line 1: let points = 45; // start at 45
    line 2: points = points + 2; // take away 2
    line 3: points = points * 2; // double it
    line 4: points = points + 4; // add 4
    line 5: show(points); // show it
  9. 9.🐞 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 - 5; // take away 5
    line 4: stars = stars * 3; // double it
    line 5: show(stars); // show it
  10. 10.🐞 After fixing a bug you should ___. (a) release at once (b) test it again (c) never test (d) delete the test
  11. 11.🐞 Each comment says what its line SHOULD do. Which line has the bug?
    line 1: let points = 48; // start at 45
    line 2: points = points + 2; // add 2
    line 3: points = points + 5; // add 5
    line 4: show(points); // show it     (a) line 3 (b) line 1 (c) line 2
  12. 12.🐞 Each comment says what its line SHOULD do. Which line has the bug?
    line 1: let coins = 30; // start at 30
    line 2: coins = coins - 2; // add 2
    line 3: coins = coins * 2; // double it
    line 4: coins = coins * 2; // double it
    line 5: show(coins); // show it     (a) line 2 (b) line 1 (c) line 4 (d) line 3
  13. 13.🐞 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 - 4; // take away 4
    line 3: score = score + 2; // add 2
    line 4: score = score - 3; // add 3
    line 5: show(score); // show it
  14. 14.🐞 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 - 1; // take away 1
    line 3: coins = coins + 2; // double it
    line 4: coins = coins + 3; // add 3
    line 5: show(coins); // show it     (a) line 1 (b) line 4 (c) line 2 (d) line 3
  15. 15.🐞 What is a bug? (a) a mistake in the code (b) a nice icon (c) a new feature (d) a fast phone
  16. 16.🐞 This code has a bug. What number does it ACTUALLY show?
    line 1: let stars = 38; // start at 35
    line 2: stars = stars * 2; // double it
    line 3: stars = stars * 2; // double it
    line 4: stars = stars - 2; // take away 2
    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 = 45; // start at 45
    line 2: points = points - 2; // take away 2
    line 3: points = points + 6; // add 3
    line 4: points = points + 3; // add 3
    line 5: show(points); // show it     (a) line 1 (b) line 2 (c) line 3 (d) line 4
  18. 18.🐞 Each comment says what its line SHOULD do. Which line has the bug?
    line 1: let coins = 36; // start at 36
    line 2: coins = coins + 4; // add 4
    line 3: coins = coins - 5; // add 5
    line 4: coins = coins + 4; // add 4
    line 5: show(coins); // show it     (a) line 1 (b) line 4 (c) line 3 (d) line 2
  19. 19.🐞 This code has a bug. What number does it ACTUALLY show?
    line 1: let score = 32; // start at 30
    line 2: score = score + 6; // add 6
    line 3: score = score + 4; // add 4
    line 4: score = score - 3; // take away 3
    line 5: show(score); // show it
  20. 20.🐞 Each comment says what its line SHOULD do. Which line has the bug?
    line 1: let lives = 48; // start at 48
    line 2: lives = lives - 5; // take away 5
    line 3: lives = lives - 3; // add 3
    line 4: lives = lives * 2; // double it
    line 5: show(lives); // show it     (a) line 3 (b) line 2 (c) line 4 (d) line 1
  21. 21.🐞 This code has a bug. What number does it ACTUALLY show?
    line 1: let stars = 33; // start at 30
    line 2: stars = stars + 5; // add 5
    line 3: stars = stars - 4; // take away 4
    line 4: show(stars); // show it
  22. 22.🐞 This code has a bug. What number does it ACTUALLY show?
    line 1: let coins = 40; // start at 40
    line 2: coins = coins + 7; // add 5
    line 3: coins = coins - 4; // take away 4
    line 4: coins = coins - 4; // take away 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 lives = 46; // start at 45
    line 2: lives = lives * 2; // double it
    line 3: lives = lives - 2; // take away 2
    line 4: 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 coins = 41; // start at 39
    line 2: coins = coins + 5; // add 5
    line 3: coins = coins - 2; // take away 2
    line 4: show(coins); // show it
  25. 25.🐞 This code has a bug. What number does it ACTUALLY show?
    line 1: let lives = 31; // start at 31
    line 2: lives = lives - 3; // take away 3
    line 3: lives = lives - 2; // take away 2
    line 4: lives = lives + 6; // add 3
    line 5: show(lives); // show it
  26. 26.🐞 Each comment says what its line SHOULD do. Which line has the bug?
    line 1: let points = 45; // start at 45
    line 2: points = points + 2; // add 2
    line 3: points = points - 6; // take away 3
    line 4: points = points + 2; // add 2
    line 5: show(points); // show it     (a) line 1 (b) line 2 (c) line 4 (d) line 3
  27. 27.🐞 This code has a bug. What number does it ACTUALLY show?
    line 1: let score = 53; // start at 50
    line 2: score = score * 2; // 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 lives = 50; // start at 48
    line 2: lives = lives - 2; // take away 2
    line 3: lives = lives - 3; // take away 3
    line 4: show(lives); // show it
  29. 29.🐞 What is a good first step when an app gives a wrong result? (a) add more colours (b) delete the app (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 lives = 37; // start at 36
    line 2: lives = lives + 6; // add 6
    line 3: lives = lives - 2; // take away 2
    line 4: show(lives); // show it
  31. 31.🐞 Each comment says what its line SHOULD do. Which line has the bug?
    line 1: let stars = 50; // start at 50
    line 2: stars = stars * 2; // double it
    line 3: stars = stars + 1; // take away 1
    line 4: show(stars); // show it     (a) line 3 (b) line 1 (c) line 2
  32. 32.🐞 This code has a bug. What number does it ACTUALLY show?
    line 1: let score = 44; // start at 42
    line 2: score = score + 4; // add 4
    line 3: score = score - 2; // take away 2
    line 4: show(score); // 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 = 36; // start at 36
    line 2: stars = stars * 2; // double it
    line 3: stars = stars + 2; // double it
    line 4: stars = stars - 3; // take away 3
    line 5: 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 = 47; // start at 47
    line 2: score = score + 8; // add 5
    line 3: score = score * 2; // double it
    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 points = 30; // start at 30
    line 2: points = points * 2; // double it
    line 3: points = points - 6; // take away 3
    line 4: show(points); // show it
  36. 36.🐞 Each comment says what its line SHOULD do. Which line has the bug?
    line 1: let stars = 33; // start at 33
    line 2: stars = stars * 3; // double it
    line 3: stars = stars - 4; // take away 4
    line 4: show(stars); // show it     (a) line 3 (b) line 2 (c) line 1
  37. 37.🐞 This code has a bug. What number does it ACTUALLY show?
    line 1: let stars = 51; // start at 50
    line 2: stars = stars - 3; // take away 3
    line 3: stars = stars - 1; // take away 1
    line 4: stars = stars - 5; // take away 5
    line 5: show(stars); // show it
  38. 38.🐞 This code has a bug. What number does it ACTUALLY show?
    line 1: let score = 45; // start at 45
    line 2: score = score + 2; // double it
    line 3: score = score * 2; // double it
    line 4: score = score - 2; // take away 2
    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 stars = 45; // start at 45
    line 2: stars = stars + 3; // add 3
    line 3: stars = stars - 3; // add 3
    line 4: show(stars); // show it
  40. 40.🐞 This code has a bug. What number does it ACTUALLY show?
    line 1: let score = 33; // start at 33
    line 2: score = score * 2; // double it
    line 3: score = score - 5; // take away 2
    line 4: show(score); // show it

Answer key

  1. people reading the code
  2. 94
  3. 126
  4. 164
  5. debugging
  6. 32
  7. 86
  8. 98
  9. 231
  10. test it again
  11. line 1
  12. line 2
  13. 41
  14. line 3
  15. a mistake in the code
  16. 150
  17. line 3
  18. line 3
  19. 39
  20. line 3
  21. 34
  22. 39
  23. 88
  24. 42
  25. 32
  26. line 3
  27. 212
  28. 45
  29. find where it goes wrong
  30. 41
  31. line 3
  32. 46
  33. 141
  34. 104
  35. 57
  36. line 2
  37. 42
  38. 92
  39. 51
  40. 61

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