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App Dev Worksheet: Debugging

App development lesson 21: Debugging: find the bug line · Set 21 · 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.🐞 What is a good first step when an app gives a wrong result? (a) add more colours (b) find where it goes wrong (c) buy a new phone (d) delete the app
  2. 2.🐞 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 + 2; // add 2
    line 3: points = points + 3; // add 3
    line 4: points = points * 3; // double it
    line 5: show(points); // 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 coins = 34; // start at 34
    line 2: coins = coins + 2; // add 2
    line 3: coins = coins + 2; // double it
    line 4: coins = coins + 2; // add 2
    line 5: show(coins); // show it
  4. 4.🐞 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 37
    line 2: points = points * 2; // double it
    line 3: points = points + 2; // add 2
    line 4: points = points - 3; // add 3
    line 5: show(points); // show it
  5. 5.🐞 Finding and fixing bugs is called ___. (a) designing (b) debugging (c) downloading (d) decorating
  6. 6.🐞 Each comment says what its line SHOULD do. Which line has the bug?
    line 1: let points = 49; // start at 47
    line 2: points = points - 4; // take away 4
    line 3: points = points * 2; // double it
    line 4: show(points); // show it     (a) line 3 (b) line 1 (c) line 2
  7. 7.🐞 What is a bug? (a) a mistake in the code (b) a nice icon (c) a new feature (d) a fast phone
  8. 8.🐞 This code has a bug. What number does it ACTUALLY show?
    line 1: let coins = 36; // start at 36
    line 2: coins = coins * 3; // double it
    line 3: coins = coins + 3; // add 3
    line 4: show(coins); // show it
  9. 9.🐞 A comment in code (after //) is for ___. (a) the app store (b) the phone screen (c) the battery (d) people reading the code
  10. 10.🐞 This code has a bug. What number SHOULD it show, if every line did what its comment says?
    line 1: let score = 41; // start at 41
    line 2: score = score - 5; // add 5
    line 3: score = score + 2; // add 2
    line 4: score = score * 2; // double it
    line 5: show(score); // show it
  11. 11.🐞 After fixing a bug you should ___. (a) never test (b) delete the test (c) release at once (d) test it again
  12. 12.🐞 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 39
    line 2: lives = lives - 2; // take away 2
    line 3: lives = lives + 2; // add 2
    line 4: lives = lives + 6; // add 6
    line 5: show(lives); // show it
  13. 13.🐞 This code has a bug. What number does it ACTUALLY show?
    line 1: let score = 46; // start at 44
    line 2: score = score + 3; // add 3
    line 3: score = score + 4; // add 4
    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 score = 51; // start at 50
    line 2: score = score + 6; // add 6
    line 3: score = score * 2; // double it
    line 4: score = score + 5; // add 5
    line 5: show(score); // 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 lives = 38; // start at 37
    line 2: lives = lives - 2; // take away 2
    line 3: lives = lives + 6; // add 6
    line 4: 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 = 33; // start at 33
    line 2: coins = coins * 3; // double it
    line 3: coins = coins * 2; // double it
    line 4: coins = coins + 2; // add 2
    line 5: show(coins); // 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 stars = 33; // start at 33
    line 2: stars = stars - 4; // add 4
    line 3: stars = stars + 4; // add 4
    line 4: show(stars); // show it
  18. 18.🐞 This code has a bug. What number does it ACTUALLY show?
    line 1: let stars = 50; // start at 50
    line 2: stars = stars * 2; // double it
    line 3: stars = stars - 6; // add 6
    line 4: stars = stars * 2; // double it
    line 5: show(stars); // 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 = 41; // start at 39
    line 2: score = score - 3; // take away 3
    line 3: score = score * 2; // double it
    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 = 34; // start at 32
    line 2: points = points * 2; // double it
    line 3: points = points * 2; // double it
    line 4: points = points + 2; // add 2
    line 5: show(points); // show it     (a) line 2 (b) line 4 (c) line 3 (d) line 1
  21. 21.🐞 Each comment says what its line SHOULD do. Which line has the bug?
    line 1: let coins = 52; // start at 49
    line 2: coins = coins * 2; // double it
    line 3: coins = coins * 2; // double it
    line 4: coins = coins * 2; // double it
    line 5: show(coins); // show it     (a) line 1 (b) line 3 (c) line 4 (d) line 2
  22. 22.🐞 Each comment says what its line SHOULD do. Which line has the bug?
    line 1: let lives = 50; // start at 48
    line 2: lives = lives + 5; // add 5
    line 3: lives = lives - 4; // take away 4
    line 4: show(lives); // show it     (a) line 1 (b) line 2 (c) line 3
  23. 23.🐞 This code has a bug. What number does it ACTUALLY show?
    line 1: let score = 45; // start at 45
    line 2: score = score - 2; // take away 2
    line 3: score = score * 3; // double it
    line 4: score = score + 5; // add 5
    line 5: show(score); // show it
  24. 24.🐞 This code has a bug. What number does it ACTUALLY show?
    line 1: let coins = 35; // start at 35
    line 2: coins = coins * 2; // double it
    line 3: coins = coins + 5; // add 3
    line 4: show(coins); // show it
  25. 25.🐞 Each comment says what its line SHOULD do. Which line has the bug?
    line 1: let points = 40; // start at 40
    line 2: points = points * 3; // double it
    line 3: points = points * 2; // double it
    line 4: show(points); // show it     (a) line 3 (b) line 1 (c) line 2
  26. 26.🐞 This code has a bug. What number does it ACTUALLY show?
    line 1: let coins = 48; // start at 48
    line 2: coins = coins - 3; // take away 3
    line 3: coins = coins * 3; // double it
    line 4: show(coins); // show it
  27. 27.🐞 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 + 5; // add 5
    line 3: points = points - 4; // take away 4
    line 4: points = points + 1; // take away 1
    line 5: show(points); // show it     (a) line 1 (b) line 4 (c) line 2 (d) line 3
  28. 28.🐞 Each comment says what its line SHOULD do. Which line has the bug?
    line 1: let score = 37; // start at 37
    line 2: score = score + 2; // add 2
    line 3: score = score * 3; // double it
    line 4: show(score); // show it     (a) line 3 (b) line 1 (c) line 2
  29. 29.🐞 This code has a bug. What number SHOULD it show, if every line did what its comment says?
    line 1: let lives = 32; // start at 32
    line 2: lives = lives + 6; // add 4
    line 3: lives = lives + 5; // add 5
    line 4: lives = lives - 4; // take away 4
    line 5: show(lives); // show it
  30. 30.🐞 This code has a bug. What number does it ACTUALLY show?
    line 1: let score = 49; // start at 49
    line 2: score = score + 2; // double it
    line 3: score = score + 3; // add 3
    line 4: score = score * 2; // double it
    line 5: show(score); // 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 lives = 43; // start at 43
    line 2: lives = lives * 2; // double it
    line 3: lives = lives * 3; // double it
    line 4: show(lives); // show it
  32. 32.🐞 This code has a bug. What number SHOULD it show, if every line did what its comment says?
    line 1: let points = 52; // start at 49
    line 2: points = points + 3; // add 3
    line 3: points = points - 5; // take away 5
    line 4: show(points); // show it
  33. 33.🐞 This code has a bug. What number does it ACTUALLY show?
    line 1: let stars = 44; // start at 44
    line 2: stars = stars + 7; // add 6
    line 3: stars = stars + 5; // add 5
    line 4: show(stars); // show it
  34. 34.🐞 Each comment says what its line SHOULD do. Which line has the bug?
    line 1: let score = 33; // start at 33
    line 2: score = score + 2; // add 2
    line 3: score = score + 1; // take away 1
    line 4: score = score * 2; // double it
    line 5: show(score); // show it     (a) line 4 (b) line 1 (c) line 2 (d) line 3
  35. 35.🐞 This code has a bug. What number SHOULD it show, if every line did what its comment says?
    line 1: let coins = 30; // start at 30
    line 2: coins = coins + 4; // add 4
    line 3: coins = coins - 5; // take away 2
    line 4: show(coins); // show it
  36. 36.🐞 This code has a bug. What number does it ACTUALLY show?
    line 1: let lives = 39; // start at 39
    line 2: lives = lives * 2; // double it
    line 3: lives = lives - 5; // add 5
    line 4: show(lives); // show it
  37. 37.🐞 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 48
    line 2: stars = stars + 4; // add 4
    line 3: stars = stars - 4; // take away 4
    line 4: stars = stars + 1; // take away 1
    line 5: show(stars); // show it
  38. 38.🐞 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 - 1; // take away 1
    line 3: lives = lives + 3; // take away 3
    line 4: show(lives); // show it     (a) line 1 (b) line 2 (c) line 3
  39. 39.🐞 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 + 5; // add 5
    line 3: score = score + 3; // take away 3
    line 4: score = score - 5; // take away 5
    line 5: show(score); // show it     (a) line 4 (b) line 2 (c) line 3 (d) line 1
  40. 40.🐞 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 31
    line 2: lives = lives - 5; // take away 5
    line 3: lives = lives + 3; // take away 3
    line 4: show(lives); // show it

Answer key

  1. find where it goes wrong
  2. 108
  3. 74
  4. 79
  5. debugging
  6. line 1
  7. a mistake in the code
  8. 111
  9. people reading the code
  10. 96
  11. test it again
  12. 45
  13. 53
  14. 117
  15. 41
  16. 134
  17. 41
  18. 188
  19. 72
  20. line 1
  21. line 1
  22. line 1
  23. 134
  24. 75
  25. line 2
  26. 135
  27. line 4
  28. line 3
  29. 37
  30. 108
  31. 172
  32. 47
  33. 56
  34. line 3
  35. 32
  36. 73
  37. 47
  38. line 3
  39. line 3
  40. 23

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