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App Dev Worksheet: Debugging

App development lesson 21: Debugging: find the bug line · Set 251 · 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 coins = 44; // start at 44
    line 2: coins = coins + 1; // take away 1
    line 3: coins = coins - 3; // take away 3
    line 4: coins = coins + 2; // add 2
    line 5: show(coins); // show it
  2. 2.🐞 Finding and fixing bugs is called ___. (a) designing (b) decorating (c) downloading (d) debugging
  3. 3.🐞 This code has a bug. What number does it ACTUALLY show?
    line 1: let coins = 42; // start at 42
    line 2: coins = coins + 4; // add 3
    line 3: coins = coins + 4; // add 4
    line 4: show(coins); // show it
  4. 4.🐞 This code has a bug. What number does it ACTUALLY show?
    line 1: let score = 46; // start at 45
    line 2: score = score - 4; // take away 4
    line 3: score = score - 2; // take away 2
    line 4: show(score); // show it
  5. 5.🐞 This code has a bug. What number does it ACTUALLY show?
    line 1: let lives = 47; // start at 47
    line 2: lives = lives + 7; // add 5
    line 3: lives = lives + 6; // add 6
    line 4: lives = lives + 2; // add 2
    line 5: show(lives); // 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 = 47; // start at 47
    line 2: stars = stars + 3; // take away 3
    line 3: stars = stars * 2; // double it
    line 4: stars = stars - 2; // take away 2
    line 5: show(stars); // show it
  7. 7.🐞 This code has a bug. What number does it ACTUALLY show?
    line 1: let coins = 47; // start at 47
    line 2: coins = coins + 6; // add 6
    line 3: coins = coins * 3; // double it
    line 4: coins = coins - 1; // take away 1
    line 5: show(coins); // show it
  8. 8.🐞 What is a bug? (a) a new feature (b) a nice icon (c) a mistake in the code (d) a fast phone
  9. 9.🐞 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 * 2; // double it
    line 4: stars = stars * 2; // double it
    line 5: show(stars); // show it
  10. 10.🐞 After fixing a bug you should ___. (a) delete the test (b) release at once (c) test it again (d) never test
  11. 11.🐞 Each comment says what its line SHOULD do. Which line has the bug?
    line 1: let stars = 53; // start at 50
    line 2: stars = stars * 2; // double it
    line 3: stars = stars - 2; // take away 2
    line 4: stars = stars * 2; // double it
    line 5: show(stars); // show it     (a) line 3 (b) line 2 (c) line 4 (d) line 1
  12. 12.🐞 Each comment says what its line SHOULD do. Which line has the bug?
    line 1: let score = 45; // start at 45
    line 2: score = score + 2; // double it
    line 3: score = score * 2; // double it
    line 4: score = score + 6; // add 6
    line 5: show(score); // show it     (a) line 4 (b) line 1 (c) line 2 (d) line 3
  13. 13.🐞 Each comment says what its line SHOULD do. Which line has the bug?
    line 1: let stars = 42; // start at 42
    line 2: stars = stars - 4; // take away 4
    line 3: stars = stars + 5; // add 5
    line 4: stars = stars - 7; // take away 5
    line 5: show(stars); // show it     (a) line 3 (b) line 4 (c) line 2 (d) line 1
  14. 14.🐞 This code has a bug. What number does it ACTUALLY show?
    line 1: let points = 34; // start at 34
    line 2: points = points * 2; // double it
    line 3: points = points + 2; // add 2
    line 4: points = points - 4; // take away 3
    line 5: show(points); // show it
  15. 15.🐞 This code has a bug. What number does it ACTUALLY show?
    line 1: let coins = 37; // start at 35
    line 2: coins = coins * 2; // double it
    line 3: coins = coins + 2; // add 2
    line 4: show(coins); // show it
  16. 16.🐞 Each comment says what its line SHOULD do. Which line has the bug?
    line 1: let points = 34; // start at 34
    line 2: points = points + 5; // take away 5
    line 3: points = points - 4; // take away 4
    line 4: show(points); // show it     (a) line 1 (b) line 2 (c) line 3
  17. 17.🐞 This code has a bug. What number does it ACTUALLY show?
    line 1: let score = 30; // start at 30
    line 2: score = score - 2; // add 2
    line 3: score = score - 3; // take away 3
    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 stars = 36; // start at 33
    line 2: stars = stars * 2; // double it
    line 3: stars = stars * 2; // double it
    line 4: show(stars); // show it
  19. 19.🐞 This code has a bug. What number does it ACTUALLY show?
    line 1: let score = 33; // start at 33
    line 2: score = score - 3; // add 3
    line 3: score = score - 1; // take away 1
    line 4: 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 = 46; // start at 46
    line 2: coins = coins * 2; // double it
    line 3: coins = coins + 6; // add 6
    line 4: coins = coins + 2; // double it
    line 5: show(coins); // show it
  21. 21.🐞 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
  22. 22.🐞 This code has a bug. What number SHOULD it show, if every line did what its comment says?
    line 1: let stars = 50; // start at 50
    line 2: stars = stars + 3; // add 3
    line 3: stars = stars * 2; // double it
    line 4: stars = stars + 2; // double it
    line 5: show(stars); // show it
  23. 23.🐞 This code has a bug. What number SHOULD it show, if every line did what its comment says?
    line 1: let coins = 32; // start at 30
    line 2: coins = coins - 1; // take away 1
    line 3: coins = coins - 4; // take away 4
    line 4: show(coins); // show it
  24. 24.🐞 This code has a bug. What number does it ACTUALLY show?
    line 1: let score = 34; // start at 32
    line 2: score = score + 2; // add 2
    line 3: score = score + 4; // add 4
    line 4: show(score); // show it
  25. 25.🐞 This code has a bug. What number SHOULD it show, if every line did what its comment says?
    line 1: let score = 30; // start at 30
    line 2: score = score + 2; // take away 2
    line 3: score = score * 2; // double it
    line 4: score = score + 4; // add 4
    line 5: show(score); // 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 points = 46; // start at 46
    line 2: points = points - 1; // take away 1
    line 3: points = points + 5; // add 4
    line 4: show(points); // 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 = 31; // start at 31
    line 2: score = score - 4; // add 4
    line 3: score = score * 2; // double it
    line 4: score = score + 2; // add 2
    line 5: show(score); // show it
  28. 28.🐞 A comment in code (after //) is for ___. (a) people reading the code (b) the phone screen (c) the app store (d) the battery
  29. 29.🐞 This code has a bug. What number does it ACTUALLY show?
    line 1: let points = 39; // start at 36
    line 2: points = points - 1; // take away 1
    line 3: points = points + 2; // add 2
    line 4: show(points); // show it
  30. 30.🐞 This code has a bug. What number SHOULD it show, if every line did what its comment says?
    line 1: let stars = 37; // start at 37
    line 2: stars = stars + 4; // take away 4
    line 3: stars = stars + 6; // add 6
    line 4: show(stars); // show it
  31. 31.🐞 This code has a bug. What number does it ACTUALLY show?
    line 1: let score = 37; // start at 37
    line 2: score = score * 2; // double it
    line 3: score = score - 7; // take away 4
    line 4: score = score + 4; // add 4
    line 5: show(score); // 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 lives = 34; // start at 34
    line 2: lives = lives - 4; // add 4
    line 3: lives = lives - 1; // take away 1
    line 4: show(lives); // show it
  33. 33.🐞 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 * 2; // double it
    line 3: score = score * 2; // double it
    line 4: show(score); // show it     (a) line 2 (b) line 3 (c) line 1
  34. 34.🐞 Each comment says what its line SHOULD do. Which line has the bug?
    line 1: let points = 43; // start at 41
    line 2: points = points + 3; // add 3
    line 3: points = points * 2; // double it
    line 4: show(points); // show it     (a) line 1 (b) line 3 (c) line 2
  35. 35.🐞 This code has a bug. What number SHOULD it show, if every line did what its comment says?
    line 1: let points = 46; // start at 46
    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
  36. 36.🐞 Each comment says what its line SHOULD do. Which line has the bug?
    line 1: let coins = 44; // start at 43
    line 2: coins = coins - 4; // take away 4
    line 3: coins = coins * 2; // double it
    line 4: coins = coins + 6; // add 6
    line 5: show(coins); // show it     (a) line 4 (b) line 3 (c) line 2 (d) line 1
  37. 37.🐞 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 31
    line 2: coins = coins * 2; // double it
    line 3: coins = coins * 2; // double it
    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 lives = 32; // start at 31
    line 2: lives = lives + 3; // add 3
    line 3: lives = lives + 5; // add 5
    line 4: lives = lives - 1; // take away 1
    line 5: show(lives); // show it
  39. 39.🐞 Each comment says what its line SHOULD do. Which line has the bug?
    line 1: let points = 49; // start at 46
    line 2: points = points - 5; // take away 5
    line 3: points = points + 5; // add 5
    line 4: points = points + 4; // add 4
    line 5: show(points); // show it     (a) line 4 (b) line 3 (c) line 2 (d) line 1
  40. 40.🐞 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; // double it
    line 3: stars = stars - 5; // take away 4
    line 4: stars = stars - 5; // take away 5
    line 5: show(stars); // show it     (a) line 4 (b) line 3 (c) line 2 (d) line 1

Answer key

  1. 42
  2. debugging
  3. 50
  4. 40
  5. 62
  6. 86
  7. 158
  8. a mistake in the code
  9. 164
  10. test it again
  11. line 1
  12. line 2
  13. line 4
  14. 66
  15. 76
  16. line 2
  17. 25
  18. 132
  19. 29
  20. 196
  21. find where it goes wrong
  22. 212
  23. 25
  24. 40
  25. 60
  26. 49
  27. 72
  28. people reading the code
  29. 40
  30. 39
  31. 71
  32. 37
  33. line 1
  34. line 1
  35. 186
  36. line 1
  37. 124
  38. 38
  39. line 1
  40. line 3

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