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App Dev Worksheet: Debugging

App development lesson 21: Debugging: find the bug line · Set 597 · 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 = 37; // start at 34
    line 2: points = points + 4; // add 4
    line 3: points = points + 5; // add 5
    line 4: points = points * 2; // double it
    line 5: show(points); // show it
  2. 2.🐞 This code has a bug. What number does it ACTUALLY show?
    line 1: let points = 36; // start at 34
    line 2: points = points - 5; // take away 5
    line 3: points = points * 2; // double it
    line 4: points = points + 6; // add 6
    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 stars = 48; // start at 47
    line 2: stars = stars - 1; // take away 1
    line 3: stars = stars + 5; // add 5
    line 4: stars = stars * 2; // double it
    line 5: show(stars); // 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 score = 39; // start at 39
    line 2: score = score - 5; // take away 2
    line 3: score = score * 2; // double it
    line 4: score = score * 2; // double it
    line 5: show(score); // show it
  5. 5.🐞 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 + 4; // take away 4
    line 3: points = points - 5; // take away 5
    line 4: points = points + 5; // add 5
    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 score = 35; // start at 35
    line 2: score = score - 1; // take away 1
    line 3: score = score - 4; // add 4
    line 4: score = score * 2; // double it
    line 5: show(score); // show it
  7. 7.🐞 This code has a bug. What number does it ACTUALLY show?
    line 1: let points = 50; // start at 50
    line 2: points = points * 2; // double it
    line 3: points = points - 4; // add 4
    line 4: show(points); // show it
  8. 8.🐞 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 48
    line 2: coins = coins + 4; // add 2
    line 3: coins = coins * 2; // double it
    line 4: coins = coins + 3; // add 3
    line 5: show(coins); // show it
  9. 9.🐞 This code has a bug. What number does it ACTUALLY show?
    line 1: let stars = 48; // start at 48
    line 2: stars = stars - 1; // take away 1
    line 3: stars = stars + 2; // take away 2
    line 4: show(stars); // show it
  10. 10.🐞 This code has a bug. What number does it ACTUALLY show?
    line 1: let coins = 42; // start at 39
    line 2: coins = coins - 4; // take away 4
    line 3: coins = coins + 4; // add 4
    line 4: show(coins); // show it
  11. 11.🐞 This code has a bug. What number SHOULD it show, if every line did what its comment says?
    line 1: let coins = 49; // start at 49
    line 2: coins = coins * 3; // double it
    line 3: coins = coins * 2; // double it
    line 4: show(coins); // show it
  12. 12.🐞 Finding and fixing bugs is called ___. (a) downloading (b) debugging (c) decorating (d) designing
  13. 13.🐞 This code has a bug. What number SHOULD it show, if every line did what its comment says?
    line 1: let lives = 45; // start at 43
    line 2: lives = lives - 1; // take away 1
    line 3: lives = lives * 2; // double it
    line 4: lives = lives * 2; // double it
    line 5: show(lives); // 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 lives = 31; // start at 31
    line 2: lives = lives * 2; // double it
    line 3: lives = lives + 2; // take away 2
    line 4: show(lives); // 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 points = 35; // start at 33
    line 2: points = points - 5; // take away 5
    line 3: points = points * 2; // double it
    line 4: show(points); // show it
  16. 16.🐞 This code has a bug. What number does it ACTUALLY show?
    line 1: let coins = 31; // start at 31
    line 2: coins = coins - 2; // take away 1
    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 = 41; // start at 41
    line 2: points = points + 4; // add 2
    line 3: points = points * 2; // double it
    line 4: show(points); // show it
  18. 18.🐞 Each comment says what its line SHOULD do. Which line has the bug?
    line 1: let coins = 44; // start at 44
    line 2: coins = coins + 2; // double it
    line 3: coins = coins + 6; // add 6
    line 4: show(coins); // show it     (a) line 1 (b) line 2 (c) line 3
  19. 19.🐞 This code has a bug. What number does it ACTUALLY show?
    line 1: let score = 31; // start at 31
    line 2: score = score + 2; // double it
    line 3: score = score + 4; // add 4
    line 4: score = score * 2; // double it
    line 5: show(score); // show it
  20. 20.🐞 Each comment says what its line SHOULD do. Which line has the bug?
    line 1: let score = 44; // start at 44
    line 2: score = score - 2; // add 2
    line 3: score = score * 2; // double it
    line 4: score = score - 4; // take away 4
    line 5: show(score); // show it     (a) line 3 (b) line 4 (c) line 2 (d) line 1
  21. 21.🐞 This code has a bug. What number does it ACTUALLY show?
    line 1: let points = 41; // start at 38
    line 2: points = points - 5; // take away 5
    line 3: points = points + 2; // add 2
    line 4: points = points - 4; // take away 4
    line 5: show(points); // show it
  22. 22.🐞 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 + 3; // add 3
    line 4: points = points * 2; // double it
    line 5: show(points); // show it     (a) line 4 (b) line 3 (c) line 2 (d) line 1
  23. 23.🐞 Each comment says what its line SHOULD do. Which line has the bug?
    line 1: let points = 46; // start at 46
    line 2: points = points - 3; // add 3
    line 3: points = points * 2; // double it
    line 4: points = points * 2; // double it
    line 5: show(points); // show it     (a) line 3 (b) line 4 (c) line 1 (d) line 2
  24. 24.🐞 Each comment says what its line SHOULD do. Which line has the bug?
    line 1: let score = 47; // start at 47
    line 2: score = score * 2; // double it
    line 3: score = score + 6; // add 6
    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
  25. 25.🐞 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 35
    line 2: lives = lives * 2; // double it
    line 3: lives = lives + 2; // double it
    line 4: lives = lives - 5; // take away 5
    line 5: 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 score = 39; // start at 39
    line 2: score = score * 2; // double it
    line 3: score = score + 4; // add 4
    line 4: score = score - 6; // add 6
    line 5: show(score); // 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 score = 48; // start at 48
    line 2: score = score * 2; // double it
    line 3: score = score + 1; // take away 1
    line 4: show(score); // show it
  28. 28.🐞 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
  29. 29.🐞 This code has a bug. What number does it ACTUALLY show?
    line 1: let stars = 37; // start at 36
    line 2: stars = stars - 4; // take away 4
    line 3: stars = stars - 4; // take away 4
    line 4: stars = stars + 6; // add 6
    line 5: show(stars); // show it
  30. 30.🐞 A comment in code (after //) is for ___. (a) the battery (b) the app store (c) people reading the code (d) the phone screen
  31. 31.🐞 Each comment says what its line SHOULD do. Which line has the bug?
    line 1: let points = 32; // start at 32
    line 2: points = points + 3; // add 3
    line 3: points = points + 3; // take away 3
    line 4: show(points); // show it     (a) line 2 (b) line 1 (c) line 3
  32. 32.🐞 This code has a bug. What number SHOULD it show, if every line did what its comment says?
    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
  33. 33.🐞 This code has a bug. What number SHOULD it show, if every line did what its comment says?
    line 1: let coins = 49; // start at 49
    line 2: coins = coins - 4; // add 4
    line 3: coins = coins - 4; // take away 4
    line 4: show(coins); // 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 stars = 46; // start at 46
    line 2: stars = stars * 2; // double it
    line 3: stars = stars + 6; // add 3
    line 4: show(stars); // 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 coins = 36; // start at 34
    line 2: coins = coins * 2; // double it
    line 3: coins = coins * 2; // double it
    line 4: show(coins); // show it
  36. 36.🐞 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 45
    line 2: score = score - 2; // take away 2
    line 3: score = score - 4; // take away 4
    line 4: score = score + 2; // add 2
    line 5: show(score); // show it
  37. 37.🐞 This code has a bug. What number does it ACTUALLY show?
    line 1: let coins = 49; // start at 48
    line 2: coins = coins - 2; // take away 2
    line 3: coins = coins - 1; // take away 1
    line 4: show(coins); // show it
  38. 38.🐞 This code has a bug. What number SHOULD it show, if every line did what its comment says?
    line 1: let points = 40; // start at 40
    line 2: points = points + 5; // add 2
    line 3: points = points * 2; // double it
    line 4: points = points * 2; // double it
    line 5: show(points); // 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 score = 33; // start at 30
    line 2: score = score + 4; // add 4
    line 3: score = score + 4; // add 4
    line 4: show(score); // show it
  40. 40.🐞 This code has a bug. What number SHOULD it show, if every line did what its comment says?
    line 1: let score = 38; // start at 37
    line 2: score = score - 3; // take away 3
    line 3: score = score + 4; // add 4
    line 4: score = score * 2; // double it
    line 5: show(score); // show it

Answer key

  1. 92
  2. 68
  3. 102
  4. 148
  5. 46
  6. 76
  7. 96
  8. 103
  9. 49
  10. 42
  11. 196
  12. debugging
  13. 168
  14. 60
  15. 56
  16. 58
  17. 90
  18. line 2
  19. 74
  20. line 2
  21. 34
  22. line 1
  23. line 2
  24. line 4
  25. 135
  26. 88
  27. 95
  28. find where it goes wrong
  29. 35
  30. people reading the code
  31. line 3
  32. 160
  33. 49
  34. 95
  35. 136
  36. 41
  37. 46
  38. 168
  39. 38
  40. 76

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