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App Dev Worksheet: Debugging

App development lesson 21: Debugging: find the bug line · Set 808 · 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) never test (b) release at once (c) test it again (d) delete the test
  2. 2.🐞 This code has a bug. What number does it ACTUALLY show?
    line 1: let points = 33; // start at 33
    line 2: points = points * 2; // double it
    line 3: points = points + 2; // double it
    line 4: points = points - 3; // take away 3
    line 5: show(points); // show it
  3. 3.🐞 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
  4. 4.🐞 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 49
    line 2: stars = stars * 2; // double it
    line 3: stars = stars - 4; // take away 4
    line 4: stars = stars * 3; // double it
    line 5: show(stars); // show it
  5. 5.🐞 This code has a bug. What number does it ACTUALLY show?
    line 1: let points = 48; // start at 48
    line 2: points = points + 3; // add 3
    line 3: points = points + 8; // add 6
    line 4: points = points - 4; // take away 4
    line 5: 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 = 49; // start at 49
    line 2: stars = stars * 3; // double it
    line 3: stars = stars + 6; // add 6
    line 4: stars = stars + 2; // add 2
    line 5: show(stars); // show it
  7. 7.🐞 This code has a bug. What number SHOULD it show, if every line did what its comment says?
    line 1: let coins = 35; // start at 32
    line 2: coins = coins * 2; // double it
    line 3: coins = coins + 4; // add 4
    line 4: show(coins); // show it
  8. 8.🐞 This code has a bug. What number does it ACTUALLY show?
    line 1: let score = 31; // start at 31
    line 2: score = score - 3; // take away 3
    line 3: score = score * 3; // double it
    line 4: score = score * 2; // double it
    line 5: show(score); // show it
  9. 9.🐞 This code has a bug. What number does it ACTUALLY show?
    line 1: let points = 38; // start at 38
    line 2: points = points + 3; // add 3
    line 3: points = points * 3; // double it
    line 4: points = points * 2; // double it
    line 5: show(points); // show it
  10. 10.🐞 This code has a bug. What number does it ACTUALLY show?
    line 1: let coins = 33; // start at 33
    line 2: coins = coins * 2; // double it
    line 3: coins = coins - 6; // add 6
    line 4: show(coins); // show it
  11. 11.🐞 Finding and fixing bugs is called ___. (a) downloading (b) designing (c) debugging (d) decorating
  12. 12.🐞 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 - 3; // take away 3
    line 3: score = score + 9; // add 6
    line 4: show(score); // show it
  13. 13.🐞 Each comment says what its line SHOULD do. Which line has the bug?
    line 1: let lives = 30; // start at 30
    line 2: lives = lives + 2; // add 2
    line 3: lives = lives + 1; // take away 1
    line 4: show(lives); // show it     (a) line 1 (b) line 3 (c) line 2
  14. 14.🐞 This code has a bug. What number SHOULD it show, if every line did what its comment says?
    line 1: let coins = 38; // start at 37
    line 2: coins = coins + 3; // add 3
    line 3: coins = coins + 4; // add 4
    line 4: coins = coins - 3; // take away 3
    line 5: show(coins); // 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 = 49; // start at 48
    line 2: score = score - 3; // take away 3
    line 3: score = score - 3; // take away 3
    line 4: show(score); // show it
  16. 16.🐞 Each comment says what its line SHOULD do. Which line has the bug?
    line 1: let coins = 31; // start at 30
    line 2: coins = coins + 2; // add 2
    line 3: coins = coins + 4; // add 4
    line 4: show(coins); // show it     (a) line 1 (b) line 2 (c) line 3
  17. 17.🐞 This code has a bug. What number SHOULD it show, if every line did what its comment says?
    line 1: let coins = 35; // start at 35
    line 2: coins = coins * 2; // double it
    line 3: coins = coins + 2; // double it
    line 4: show(coins); // show it
  18. 18.🐞 This code has a bug. What number SHOULD it show, if every line did what its comment says?
    line 1: let stars = 44; // start at 44
    line 2: stars = stars - 4; // take away 4
    line 3: stars = stars - 7; // take away 4
    line 4: stars = stars - 4; // take away 4
    line 5: show(stars); // show it
  19. 19.🐞 This code has a bug. What number does it ACTUALLY show?
    line 1: let score = 36; // start at 36
    line 2: score = score * 2; // double it
    line 3: score = score - 2; // add 2
    line 4: score = score - 5; // take away 5
    line 5: show(score); // show it
  20. 20.🐞 This code has a bug. What number SHOULD it show, if every line did what its comment says?
    line 1: let coins = 34; // start at 32
    line 2: coins = coins + 2; // add 2
    line 3: coins = coins - 2; // take away 2
    line 4: 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 points = 49; // start at 49
    line 2: points = points + 3; // take away 3
    line 3: points = points - 3; // take away 3
    line 4: show(points); // show it
  22. 22.🐞 This code has a bug. What number does it ACTUALLY show?
    line 1: let lives = 44; // start at 42
    line 2: lives = lives - 1; // take away 1
    line 3: lives = lives - 4; // take away 4
    line 4: lives = lives + 4; // add 4
    line 5: show(lives); // show it
  23. 23.🐞 This code has a bug. What number does it ACTUALLY show?
    line 1: let stars = 45; // start at 43
    line 2: stars = stars + 6; // add 6
    line 3: stars = stars - 4; // take away 4
    line 4: show(stars); // show it
  24. 24.🐞 Each comment says what its line SHOULD do. Which line has the bug?
    line 1: let score = 32; // start at 32
    line 2: score = score * 2; // double it
    line 3: score = score + 4; // take away 4
    line 4: show(score); // show it     (a) line 1 (b) line 3 (c) line 2
  25. 25.🐞 Each comment says what its line SHOULD do. Which line has the bug?
    line 1: let stars = 39; // start at 39
    line 2: stars = stars - 2; // add 2
    line 3: stars = stars * 2; // double it
    line 4: show(stars); // show it     (a) line 3 (b) line 2 (c) line 1
  26. 26.🐞 This code has a bug. What number does it ACTUALLY show?
    line 1: let coins = 38; // start at 36
    line 2: coins = coins + 2; // add 2
    line 3: coins = coins * 2; // double it
    line 4: coins = coins + 6; // add 6
    line 5: show(coins); // show it
  27. 27.🐞 This code has a bug. What number does it ACTUALLY show?
    line 1: let stars = 35; // start at 35
    line 2: stars = stars - 6; // take away 4
    line 3: stars = stars * 2; // double it
    line 4: stars = stars * 2; // double it
    line 5: show(stars); // 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 coins = 48; // start at 46
    line 2: coins = coins * 2; // double it
    line 3: coins = coins - 4; // take away 4
    line 4: show(coins); // show it
  29. 29.🐞 Each comment says what its line SHOULD do. Which line has the bug?
    line 1: let lives = 46; // start at 46
    line 2: lives = lives + 4; // add 4
    line 3: lives = lives + 2; // double it
    line 4: show(lives); // show it     (a) line 2 (b) line 3 (c) line 1
  30. 30.🐞 What is a bug? (a) a new feature (b) a fast phone (c) a mistake in the code (d) a nice icon
  31. 31.🐞 This code has a bug. What number SHOULD it show, if every line did what its comment says?
    line 1: let points = 50; // start at 50
    line 2: points = points + 2; // take away 2
    line 3: points = points * 2; // double it
    line 4: show(points); // show it
  32. 32.🐞 This code has a bug. What number does it ACTUALLY show?
    line 1: let stars = 30; // start at 30
    line 2: stars = stars + 2; // double it
    line 3: stars = stars + 5; // add 5
    line 4: show(stars); // show it
  33. 33.🐞 This code has a bug. What number does it ACTUALLY show?
    line 1: let score = 44; // start at 42
    line 2: score = score + 3; // add 3
    line 3: score = score - 3; // take away 3
    line 4: show(score); // show it
  34. 34.🐞 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 + 4; // add 3
    line 3: lives = lives + 4; // add 4
    line 4: lives = lives - 1; // take away 1
    line 5: show(lives); // show it     (a) line 3 (b) line 2 (c) line 4 (d) line 1
  35. 35.🐞 This code has a bug. What number SHOULD it show, if every line did what its comment says?
    line 1: let lives = 37; // start at 37
    line 2: lives = lives * 2; // double it
    line 3: lives = lives + 2; // take away 2
    line 4: lives = lives * 2; // double it
    line 5: show(lives); // show it
  36. 36.🐞 A comment in code (after //) is for ___. (a) the battery (b) people reading the code (c) the phone screen (d) the app store
  37. 37.🐞 Each comment says what its line SHOULD do. Which line has the bug?
    line 1: let stars = 40; // start at 38
    line 2: stars = stars + 3; // add 3
    line 3: stars = stars + 3; // add 3
    line 4: show(stars); // show it     (a) line 2 (b) line 3 (c) line 1
  38. 38.🐞 Each comment says what its line SHOULD do. Which line has the bug?
    line 1: let coins = 38; // start at 38
    line 2: coins = coins + 6; // add 6
    line 3: coins = coins * 2; // double it
    line 4: coins = coins - 2; // add 2
    line 5: show(coins); // show it     (a) line 1 (b) line 3 (c) line 2 (d) line 4
  39. 39.🐞 This code has a bug. What number does it ACTUALLY show?
    line 1: let score = 42; // start at 42
    line 2: score = score + 3; // add 2
    line 3: score = score * 2; // double it
    line 4: show(score); // show it
  40. 40.🐞 This code has a bug. What number does it ACTUALLY show?
    line 1: let lives = 49; // start at 47
    line 2: lives = lives + 4; // add 4
    line 3: lives = lives * 2; // double it
    line 4: show(lives); // show it

Answer key

  1. test it again
  2. 65
  3. find where it goes wrong
  4. 188
  5. 55
  6. 106
  7. 68
  8. 168
  9. 246
  10. 60
  11. debugging
  12. 38
  13. line 3
  14. 41
  15. 42
  16. line 1
  17. 140
  18. 32
  19. 65
  20. 32
  21. 43
  22. 43
  23. 47
  24. line 3
  25. line 2
  26. 86
  27. 116
  28. 88
  29. line 3
  30. a mistake in the code
  31. 96
  32. 37
  33. 44
  34. line 2
  35. 144
  36. people reading the code
  37. line 1
  38. line 4
  39. 90
  40. 106

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