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App Dev Worksheet: Debugging

App development lesson 21: Debugging: find the bug line · Set 653 · 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 SHOULD it show, if every line did what its comment says?
    line 1: let points = 41; // start at 40
    line 2: points = points + 2; // add 2
    line 3: points = points - 4; // take away 4
    line 4: points = points * 2; // double it
    line 5: show(points); // show it
  2. 2.🐞 What is a bug? (a) a nice icon (b) a fast phone (c) a new feature (d) a mistake in the code
  3. 3.🐞 This code has a bug. What number SHOULD it show, if every line did what its comment says?
    line 1: let lives = 44; // start at 44
    line 2: lives = lives + 2; // double it
    line 3: lives = lives + 3; // add 3
    line 4: show(lives); // 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 = 31; // start at 31
    line 2: score = score - 6; // add 6
    line 3: score = score + 2; // add 2
    line 4: show(score); // show it
  5. 5.🐞 A comment in code (after //) is for ___. (a) the battery (b) the app store (c) people reading the code (d) the phone screen
  6. 6.🐞 This code has a bug. What number does it ACTUALLY show?
    line 1: let score = 42; // start at 39
    line 2: score = score + 5; // add 5
    line 3: score = score * 2; // double it
    line 4: score = score * 2; // double it
    line 5: show(score); // show it
  7. 7.🐞 After fixing a bug you should ___. (a) delete the test (b) release at once (c) test it again (d) never test
  8. 8.🐞 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
  9. 9.🐞 This code has a bug. What number does it ACTUALLY show?
    line 1: let stars = 35; // start at 32
    line 2: stars = stars + 6; // add 6
    line 3: stars = stars - 1; // take away 1
    line 4: stars = stars + 2; // add 2
    line 5: show(stars); // show it
  10. 10.🐞 This code has a bug. What number SHOULD it show, if every line did what its comment says?
    line 1: let lives = 34; // start at 31
    line 2: lives = lives - 1; // take away 1
    line 3: lives = lives + 2; // add 2
    line 4: show(lives); // show it
  11. 11.🐞 Each comment says what its line SHOULD do. Which line has the bug?
    line 1: let score = 42; // start at 39
    line 2: score = score + 6; // add 6
    line 3: score = score * 2; // double it
    line 4: show(score); // show it     (a) line 1 (b) line 3 (c) line 2
  12. 12.🐞 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 * 3; // double it
    line 3: coins = coins + 4; // add 4
    line 4: show(coins); // show it
  13. 13.🐞 This code has a bug. What number does it ACTUALLY show?
    line 1: let score = 35; // start at 35
    line 2: score = score * 2; // double it
    line 3: score = score - 4; // take away 4
    line 4: score = score + 6; // add 4
    line 5: 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 stars = 35; // start at 32
    line 2: stars = stars * 2; // double it
    line 3: stars = stars - 2; // take away 2
    line 4: stars = stars - 3; // take away 3
    line 5: show(stars); // show it
  15. 15.🐞 This code has a bug. What number does it ACTUALLY show?
    line 1: let points = 53; // start at 50
    line 2: points = points + 5; // add 5
    line 3: points = points - 4; // take away 4
    line 4: points = points * 2; // double it
    line 5: show(points); // show it
  16. 16.🐞 This code has a bug. What number does it ACTUALLY show?
    line 1: let lives = 34; // start at 34
    line 2: lives = lives + 4; // add 4
    line 3: lives = lives * 3; // double it
    line 4: show(lives); // 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 score = 40; // start at 40
    line 2: score = score + 7; // add 6
    line 3: score = score + 6; // add 6
    line 4: show(score); // 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 lives = 41; // start at 41
    line 2: lives = lives * 2; // double it
    line 3: lives = lives + 2; // double it
    line 4: show(lives); // show it
  19. 19.🐞 Each comment says what its line SHOULD do. Which line has the bug?
    line 1: let coins = 42; // start at 42
    line 2: coins = coins * 2; // double it
    line 3: coins = coins + 2; // double it
    line 4: show(coins); // show it     (a) line 2 (b) line 1 (c) line 3
  20. 20.🐞 Each comment says what its line SHOULD do. Which line has the bug?
    line 1: let score = 34; // start at 34
    line 2: score = score * 2; // double it
    line 3: score = score - 3; // take away 1
    line 4: score = score + 6; // add 6
    line 5: show(score); // show it     (a) line 3 (b) line 2 (c) line 1 (d) line 4
  21. 21.🐞 Finding and fixing bugs is called ___. (a) downloading (b) debugging (c) designing (d) decorating
  22. 22.🐞 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 + 4; // add 4
    line 3: score = score - 4; // take away 4
    line 4: show(score); // show it
  23. 23.🐞 Each comment says what its line SHOULD do. Which line has the bug?
    line 1: let coins = 43; // start at 43
    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
  24. 24.🐞 Each comment says what its line SHOULD do. Which line has the bug?
    line 1: let stars = 35; // start at 35
    line 2: stars = stars + 4; // add 4
    line 3: stars = stars - 2; // add 2
    line 4: stars = stars - 5; // take away 5
    line 5: show(stars); // show it     (a) line 1 (b) line 2 (c) line 4 (d) line 3
  25. 25.🐞 Each comment says what its line SHOULD do. Which line has the bug?
    line 1: let coins = 46; // start at 46
    line 2: coins = coins + 1; // take away 1
    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 3 (d) line 4
  26. 26.🐞 This code has a bug. What number does it ACTUALLY show?
    line 1: let points = 48; // start at 48
    line 2: points = points + 5; // add 2
    line 3: points = points * 2; // double it
    line 4: show(points); // show it
  27. 27.🐞 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 - 2; // add 2
    line 4: show(score); // show it     (a) line 1 (b) line 2 (c) line 3
  28. 28.🐞 This code has a bug. What number does it ACTUALLY show?
    line 1: let points = 49; // start at 49
    line 2: points = points + 2; // add 2
    line 3: points = points + 8; // add 5
    line 4: points = points * 2; // double it
    line 5: show(points); // show it
  29. 29.🐞 This code has a bug. What number SHOULD it show, if every line did what its comment says?
    line 1: let points = 31; // start at 31
    line 2: points = points - 4; // take away 4
    line 3: points = points * 3; // double it
    line 4: show(points); // show it
  30. 30.🐞 Each comment says what its line SHOULD do. Which line has the bug?
    line 1: let stars = 31; // start at 31
    line 2: stars = stars * 3; // double it
    line 3: stars = stars * 2; // double it
    line 4: stars = stars * 2; // double it
    line 5: show(stars); // show it     (a) line 1 (b) line 4 (c) line 3 (d) line 2
  31. 31.🐞 This code has a bug. What number does it ACTUALLY show?
    line 1: let stars = 46; // start at 44
    line 2: stars = stars * 2; // double it
    line 3: stars = stars - 4; // take away 4
    line 4: show(stars); // show it
  32. 32.🐞 This code has a bug. What number does it ACTUALLY show?
    line 1: let coins = 38; // start at 38
    line 2: coins = coins - 4; // take away 4
    line 3: coins = coins + 3; // take away 3
    line 4: coins = coins * 2; // double it
    line 5: show(coins); // 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 lives = 39; // start at 37
    line 2: lives = lives - 4; // take away 4
    line 3: lives = lives - 5; // take away 5
    line 4: lives = lives * 2; // double it
    line 5: show(lives); // 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 = 46; // start at 45
    line 2: score = score * 2; // double it
    line 3: score = score + 4; // add 4
    line 4: show(score); // show it
  35. 35.🐞 This code has a bug. What number does it ACTUALLY show?
    line 1: let lives = 37; // start at 37
    line 2: lives = lives * 2; // double it
    line 3: lives = lives + 6; // add 5
    line 4: lives = lives * 2; // double it
    line 5: show(lives); // show it
  36. 36.🐞 Each comment says what its line SHOULD do. Which line has the bug?
    line 1: let points = 47; // start at 47
    line 2: points = points + 4; // add 4
    line 3: points = points - 2; // take away 2
    line 4: points = points + 2; // double it
    line 5: show(points); // show it     (a) line 2 (b) line 1 (c) line 4 (d) line 3
  37. 37.🐞 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 * 2; // double it
    line 3: stars = stars - 4; // take away 4
    line 4: stars = stars - 4; // add 4
    line 5: show(stars); // show it
  38. 38.🐞 Each comment says what its line SHOULD do. Which line has the bug?
    line 1: let score = 48; // start at 46
    line 2: score = score + 3; // add 3
    line 3: score = score + 2; // add 2
    line 4: score = score * 2; // double it
    line 5: show(score); // show it     (a) line 1 (b) line 2 (c) line 3 (d) line 4
  39. 39.🐞 This code has a bug. What number does it ACTUALLY show?
    line 1: let score = 49; // start at 49
    line 2: score = score * 3; // double it
    line 3: score = score * 2; // double it
    line 4: score = score - 1; // take away 1
    line 5: show(score); // show it
  40. 40.🐞 Each comment says what its line SHOULD do. Which line has the bug?
    line 1: let lives = 38; // start at 36
    line 2: lives = lives - 1; // take away 1
    line 3: lives = lives + 6; // add 6
    line 4: show(lives); // show it     (a) line 2 (b) line 3 (c) line 1

Answer key

  1. 76
  2. a mistake in the code
  3. 91
  4. 39
  5. people reading the code
  6. 188
  7. test it again
  8. find where it goes wrong
  9. 42
  10. 32
  11. line 1
  12. 100
  13. 72
  14. 59
  15. 108
  16. 114
  17. 52
  18. 164
  19. line 3
  20. line 3
  21. debugging
  22. 45
  23. line 2
  24. line 3
  25. line 2
  26. 106
  27. line 3
  28. 118
  29. 54
  30. line 2
  31. 88
  32. 74
  33. 56
  34. 94
  35. 160
  36. line 4
  37. 66
  38. line 1
  39. 293
  40. line 1

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