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App Dev Worksheet: Debugging

App development lesson 21: Debugging: find the bug line · Set 787 · 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 stars = 45; // start at 45
    line 2: stars = stars - 4; // add 4
    line 3: stars = stars + 6; // add 6
    line 4: show(stars); // show it
  2. 2.🐞 This code has a bug. What number does it ACTUALLY show?
    line 1: let points = 49; // start at 46
    line 2: points = points + 4; // add 4
    line 3: points = points * 2; // double it
    line 4: points = points + 5; // add 5
    line 5: show(points); // show it
  3. 3.🐞 What is a bug? (a) a new feature (b) a fast phone (c) a mistake in the code (d) a nice icon
  4. 4.🐞 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 - 3; // add 3
    line 3: coins = coins + 3; // add 3
    line 4: coins = coins - 4; // take away 4
    line 5: show(coins); // 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 = 39; // start at 38
    line 2: points = points + 4; // add 4
    line 3: points = points * 2; // double it
    line 4: points = points + 6; // add 6
    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 coins = 36; // start at 36
    line 2: coins = coins - 6; // add 6
    line 3: coins = coins + 2; // add 2
    line 4: coins = coins * 2; // double it
    line 5: show(coins); // 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 points = 40; // start at 40
    line 2: points = points * 2; // double it
    line 3: points = points + 2; // double it
    line 4: show(points); // show it
  8. 8.🐞 This code has a bug. What number does it ACTUALLY show?
    line 1: let lives = 41; // start at 41
    line 2: lives = lives + 2; // add 2
    line 3: lives = lives + 8; // add 5
    line 4: lives = lives + 5; // add 5
    line 5: show(lives); // show it
  9. 9.🐞 A comment in code (after //) is for ___. (a) the app store (b) the phone screen (c) people reading the code (d) the battery
  10. 10.🐞 This code has a bug. What number does it ACTUALLY show?
    line 1: let lives = 36; // start at 36
    line 2: lives = lives + 1; // take away 1
    line 3: lives = lives + 5; // add 5
    line 4: show(lives); // 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 score = 38; // start at 38
    line 2: score = score - 6; // add 6
    line 3: score = score * 2; // double it
    line 4: show(score); // show it
  12. 12.🐞 What is a good first step when an app gives a wrong result? (a) add more colours (b) buy a new phone (c) find where it goes wrong (d) delete the app
  13. 13.🐞 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 * 2; // double it
    line 4: stars = stars + 6; // add 6
    line 5: show(stars); // show it
  14. 14.🐞 Each comment says what its line SHOULD do. Which line has the bug?
    line 1: let coins = 34; // start at 34
    line 2: coins = coins + 5; // add 3
    line 3: coins = coins + 2; // add 2
    line 4: coins = coins + 2; // add 2
    line 5: show(coins); // show it     (a) line 4 (b) line 1 (c) line 2 (d) line 3
  15. 15.🐞 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 + 2; // double it
    line 3: lives = lives * 2; // double it
    line 4: show(lives); // show it
  16. 16.🐞 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 + 1; // take away 1
    line 4: score = score + 4; // add 4
    line 5: show(score); // show it     (a) line 3 (b) line 1 (c) line 4 (d) line 2
  17. 17.🐞 This code has a bug. What number does it ACTUALLY show?
    line 1: let score = 51; // start at 48
    line 2: score = score - 3; // take away 3
    line 3: score = score * 2; // double it
    line 4: score = score + 6; // add 6
    line 5: show(score); // show it
  18. 18.🐞 This code has a bug. What number does it ACTUALLY show?
    line 1: let coins = 47; // start at 47
    line 2: coins = coins + 3; // add 2
    line 3: coins = coins + 4; // add 4
    line 4: coins = coins - 4; // take away 4
    line 5: show(coins); // show it
  19. 19.🐞 Each comment says what its line SHOULD do. Which line has the bug?
    line 1: let points = 37; // start at 37
    line 2: points = points - 1; // take away 1
    line 3: points = points - 5; // take away 2
    line 4: points = points * 2; // double it
    line 5: show(points); // show it     (a) line 2 (b) line 4 (c) line 1 (d) line 3
  20. 20.🐞 Each comment says what its line SHOULD do. Which line has the bug?
    line 1: let stars = 47; // start at 47
    line 2: stars = stars + 5; // add 5
    line 3: stars = stars - 2; // take away 1
    line 4: show(stars); // show it     (a) line 3 (b) line 2 (c) line 1
  21. 21.🐞 This code has a bug. What number SHOULD it show, if every line did what its comment says?
    line 1: let stars = 31; // start at 31
    line 2: stars = stars * 2; // double it
    line 3: stars = stars + 2; // double it
    line 4: stars = stars + 5; // add 5
    line 5: show(stars); // show it
  22. 22.🐞 This code has a bug. What number does it ACTUALLY show?
    line 1: let score = 46; // start at 46
    line 2: score = score - 2; // take away 2
    line 3: score = score + 2; // take away 2
    line 4: score = score - 4; // take away 4
    line 5: show(score); // show it
  23. 23.🐞 Finding and fixing bugs is called ___. (a) debugging (b) downloading (c) decorating (d) designing
  24. 24.🐞 After fixing a bug you should ___. (a) delete the test (b) release at once (c) never test (d) test it again
  25. 25.🐞 Each comment says what its line SHOULD do. Which line has the bug?
    line 1: let lives = 34; // start at 32
    line 2: lives = lives + 6; // add 6
    line 3: lives = lives + 5; // add 5
    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
  26. 26.🐞 Each comment says what its line SHOULD do. Which line has the bug?
    line 1: let score = 34; // start at 33
    line 2: score = score - 4; // take away 4
    line 3: score = score - 5; // take away 5
    line 4: score = score * 2; // double it
    line 5: show(score); // show it     (a) line 3 (b) line 1 (c) line 4 (d) line 2
  27. 27.🐞 Each comment says what its line SHOULD do. Which line has the bug?
    line 1: let score = 33; // start at 32
    line 2: score = score * 2; // double it
    line 3: score = score + 2; // add 2
    line 4: score = score - 1; // take away 1
    line 5: show(score); // show it     (a) line 4 (b) line 3 (c) line 2 (d) line 1
  28. 28.🐞 Each comment says what its line SHOULD do. Which line has the bug?
    line 1: let stars = 32; // start at 32
    line 2: stars = stars + 3; // add 3
    line 3: stars = stars - 5; // take away 5
    line 4: stars = stars + 2; // double it
    line 5: show(stars); // show it     (a) line 3 (b) line 1 (c) line 4 (d) line 2
  29. 29.🐞 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; // double it
    line 3: score = score - 1; // take away 1
    line 4: score = score - 4; // take away 4
    line 5: show(score); // show it     (a) line 4 (b) line 1 (c) line 3 (d) line 2
  30. 30.🐞 Each comment says what its line SHOULD do. Which line has the bug?
    line 1: let lives = 41; // start at 41
    line 2: lives = lives + 6; // add 6
    line 3: lives = lives - 6; // add 6
    line 4: show(lives); // show it     (a) line 1 (b) line 2 (c) line 3
  31. 31.🐞 Each comment says what its line SHOULD do. Which line has the bug?
    line 1: let coins = 46; // start at 45
    line 2: coins = coins - 3; // take away 3
    line 3: coins = coins + 6; // add 6
    line 4: coins = coins + 4; // add 4
    line 5: show(coins); // show it     (a) line 2 (b) line 4 (c) line 3 (d) line 1
  32. 32.🐞 Each comment says what its line SHOULD do. Which line has the bug?
    line 1: let points = 35; // start at 35
    line 2: points = points - 3; // take away 3
    line 3: points = points - 2; // add 2
    line 4: show(points); // show it     (a) line 1 (b) line 3 (c) line 2
  33. 33.🐞 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 + 5; // add 5
    line 4: score = score - 4; // take away 4
    line 5: show(score); // show it
  34. 34.🐞 Each comment says what its line SHOULD do. Which line has the bug?
    line 1: let points = 48; // start at 46
    line 2: points = points + 2; // add 2
    line 3: points = points + 6; // add 6
    line 4: show(points); // show it     (a) line 1 (b) line 2 (c) line 3
  35. 35.🐞 This code has a bug. What number does it ACTUALLY show?
    line 1: let coins = 48; // start at 47
    line 2: coins = coins * 2; // double it
    line 3: coins = coins - 4; // take away 4
    line 4: coins = coins - 5; // take away 5
    line 5: show(coins); // show it
  36. 36.🐞 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 + 8; // add 5
    line 3: score = score + 4; // add 4
    line 4: show(score); // show it     (a) line 1 (b) line 2 (c) line 3
  37. 37.🐞 This code has a bug. What number does it ACTUALLY show?
    line 1: let stars = 49; // start at 49
    line 2: stars = stars + 3; // add 3
    line 3: stars = stars + 4; // take away 4
    line 4: show(stars); // show it
  38. 38.🐞 Each comment says what its line SHOULD do. Which line has the bug?
    line 1: let points = 32; // start at 30
    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     (a) line 4 (b) line 3 (c) line 1 (d) line 2
  39. 39.🐞 This code has a bug. What number does it ACTUALLY show?
    line 1: let points = 40; // start at 40
    line 2: points = points + 3; // add 2
    line 3: points = points + 3; // add 3
    line 4: points = points + 5; // add 5
    line 5: show(points); // 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 points = 44; // start at 41
    line 2: points = points - 1; // take away 1
    line 3: points = points * 2; // double it
    line 4: points = points + 6; // add 6
    line 5: show(points); // show it

Answer key

  1. 47
  2. 111
  3. a mistake in the code
  4. 46
  5. 90
  6. 88
  7. 160
  8. 56
  9. people reading the code
  10. 42
  11. 88
  12. find where it goes wrong
  13. 110
  14. line 2
  15. 156
  16. line 3
  17. 102
  18. 50
  19. line 3
  20. line 3
  21. 129
  22. 42
  23. debugging
  24. test it again
  25. line 1
  26. line 1
  27. line 1
  28. line 4
  29. line 2
  30. line 3
  31. line 1
  32. line 3
  33. 95
  34. line 1
  35. 87
  36. line 2
  37. 56
  38. line 1
  39. 51
  40. 86

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