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App Dev Worksheet: Debugging

App development lesson 21: Debugging: find the bug line · Set 142 · 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 stars = 49; // start at 49
    line 2: stars = stars + 6; // add 6
    line 3: stars = stars * 2; // double it
    line 4: stars = stars * 3; // double it
    line 5: show(stars); // show it
  2. 2.🐞 Each comment says what its line SHOULD do. Which line has the bug?
    line 1: let coins = 51; // start at 48
    line 2: coins = coins * 2; // double it
    line 3: coins = coins - 1; // take away 1
    line 4: coins = coins + 5; // add 5
    line 5: show(coins); // show it     (a) line 2 (b) line 4 (c) line 1 (d) line 3
  3. 3.🐞 Each comment says what its line SHOULD do. Which line has the bug?
    line 1: let points = 38; // start at 38
    line 2: points = points + 9; // add 6
    line 3: points = points * 2; // double it
    line 4: show(points); // show it     (a) line 3 (b) line 2 (c) line 1
  4. 4.🐞 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 49
    line 2: points = points - 2; // take away 2
    line 3: points = points - 3; // take away 3
    line 4: points = points * 2; // double it
    line 5: show(points); // show it
  5. 5.🐞 Finding and fixing bugs is called ___. (a) downloading (b) designing (c) decorating (d) debugging
  6. 6.🐞 What is a bug? (a) a new feature (b) a fast phone (c) a nice icon (d) a mistake in the code
  7. 7.🐞 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 + 6; // add 4
    line 4: show(score); // show it     (a) line 2 (b) line 3 (c) line 1
  8. 8.🐞 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 + 5; // take away 5
    line 3: lives = lives - 4; // take away 4
    line 4: lives = lives + 4; // add 4
    line 5: show(lives); // show it
  9. 9.🐞 This code has a bug. What number does it ACTUALLY show?
    line 1: let stars = 42; // start at 41
    line 2: stars = stars + 2; // add 2
    line 3: stars = stars * 2; // double it
    line 4: show(stars); // show it
  10. 10.🐞 Each comment says what its line SHOULD do. Which line has the bug?
    line 1: let points = 52; // start at 50
    line 2: points = points + 6; // add 6
    line 3: points = points + 6; // add 6
    line 4: show(points); // show it     (a) line 2 (b) line 3 (c) line 1
  11. 11.🐞 This code has a bug. What number does it ACTUALLY show?
    line 1: let coins = 36; // start at 36
    line 2: coins = coins * 2; // double it
    line 3: coins = coins + 3; // take away 3
    line 4: show(coins); // show it
  12. 12.🐞 After fixing a bug you should ___. (a) never test (b) delete the test (c) test it again (d) release at once
  13. 13.🐞 A comment in code (after //) is for ___. (a) people reading the code (b) the app store (c) the battery (d) the phone screen
  14. 14.🐞 What is a good first step when an app gives a wrong result? (a) find where it goes wrong (b) add more colours (c) buy a new phone (d) delete the app
  15. 15.🐞 This code has a bug. What number does it ACTUALLY show?
    line 1: let stars = 34; // start at 34
    line 2: stars = stars * 2; // double it
    line 3: stars = stars + 3; // add 3
    line 4: stars = stars - 2; // add 2
    line 5: show(stars); // 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 stars = 33; // start at 33
    line 2: stars = stars * 2; // double it
    line 3: stars = stars + 2; // double it
    line 4: show(stars); // 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 = 30; // start at 30
    line 2: score = score * 3; // double it
    line 3: score = score * 2; // double it
    line 4: show(score); // show it
  18. 18.🐞 This code has a bug. What number does it ACTUALLY show?
    line 1: let stars = 31; // start at 31
    line 2: stars = stars * 2; // double it
    line 3: stars = stars - 5; // take away 5
    line 4: stars = stars - 4; // add 4
    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 = 43; // start at 43
    line 2: score = score - 3; // add 3
    line 3: score = score + 3; // add 3
    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 = 31; // start at 30
    line 2: coins = coins + 2; // add 2
    line 3: coins = coins - 1; // take away 1
    line 4: show(coins); // show it
  21. 21.🐞 This code has a bug. What number SHOULD it show, if every line did what its comment says?
    line 1: let coins = 42; // start at 41
    line 2: coins = coins - 1; // take away 1
    line 3: coins = coins * 2; // double it
    line 4: show(coins); // show it
  22. 22.🐞 This code has a bug. What number SHOULD it show, if every line did what its comment says?
    line 1: let lives = 49; // start at 49
    line 2: lives = lives * 2; // double it
    line 3: lives = lives * 3; // double it
    line 4: lives = lives - 5; // take away 5
    line 5: show(lives); // show it
  23. 23.🐞 This code has a bug. What number does it ACTUALLY show?
    line 1: let points = 36; // start at 36
    line 2: points = points * 3; // double it
    line 3: points = points - 1; // take away 1
    line 4: show(points); // show it
  24. 24.🐞 Each comment says what its line SHOULD do. Which line has the bug?
    line 1: let score = 52; // start at 50
    line 2: score = score - 2; // take away 2
    line 3: score = score - 4; // take away 4
    line 4: show(score); // show it     (a) line 2 (b) line 1 (c) line 3
  25. 25.🐞 Each comment says what its line SHOULD do. Which line has the bug?
    line 1: let points = 50; // start at 50
    line 2: points = points + 4; // add 4
    line 3: points = points + 5; // take away 5
    line 4: points = points * 2; // double it
    line 5: show(points); // show it     (a) line 2 (b) line 3 (c) line 1 (d) line 4
  26. 26.🐞 Each comment says what its line SHOULD do. Which line has the bug?
    line 1: let points = 36; // start at 35
    line 2: points = points * 2; // double it
    line 3: points = points + 4; // add 4
    line 4: show(points); // show it     (a) line 3 (b) line 1 (c) line 2
  27. 27.🐞 This code has a bug. What number does it ACTUALLY show?
    line 1: let score = 45; // start at 45
    line 2: score = score * 2; // double it
    line 3: score = score - 4; // take away 2
    line 4: show(score); // show it
  28. 28.🐞 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
  29. 29.🐞 This code has a bug. What number does it ACTUALLY show?
    line 1: let stars = 37; // start at 34
    line 2: stars = stars * 2; // double it
    line 3: stars = stars * 2; // double it
    line 4: stars = stars - 4; // take away 4
    line 5: show(stars); // show it
  30. 30.🐞 This code has a bug. What number does it ACTUALLY show?
    line 1: let coins = 40; // start at 37
    line 2: coins = coins + 2; // add 2
    line 3: coins = coins * 2; // double it
    line 4: show(coins); // show it
  31. 31.🐞 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 * 2; // double it
    line 3: stars = stars - 2; // add 2
    line 4: show(stars); // show it     (a) line 1 (b) line 3 (c) line 2
  32. 32.🐞 This code has a bug. What number SHOULD it show, if every line did what its comment says?
    line 1: let stars = 42; // start at 42
    line 2: stars = stars - 2; // take away 2
    line 3: stars = stars - 4; // take away 4
    line 4: stars = stars * 3; // double it
    line 5: show(stars); // show it
  33. 33.🐞 This code has a bug. What number does it ACTUALLY show?
    line 1: let stars = 33; // start at 31
    line 2: stars = stars * 2; // double it
    line 3: stars = stars * 2; // double it
    line 4: stars = stars - 1; // take away 1
    line 5: show(stars); // show it
  34. 34.🐞 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 - 4; // take away 1
    line 3: points = points * 2; // double it
    line 4: show(points); // show it     (a) line 3 (b) line 1 (c) line 2
  35. 35.🐞 This code has a bug. What number does it ACTUALLY show?
    line 1: let lives = 48; // start at 48
    line 2: lives = lives - 5; // take away 2
    line 3: lives = lives * 2; // double it
    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 score = 36; // start at 36
    line 2: score = score + 6; // add 5
    line 3: score = score - 2; // take away 2
    line 4: show(score); // show it     (a) line 2 (b) line 1 (c) line 3
  37. 37.🐞 This code has a bug. What number does it ACTUALLY show?
    line 1: let coins = 35; // start at 35
    line 2: coins = coins * 3; // double it
    line 3: coins = coins - 3; // take away 3
    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 score = 32; // start at 32
    line 2: score = score + 3; // add 3
    line 3: score = score + 9; // add 6
    line 4: score = score - 3; // take away 3
    line 5: show(score); // show it
  39. 39.🐞 This code has a bug. What number does it ACTUALLY show?
    line 1: let stars = 38; // start at 38
    line 2: stars = stars - 4; // take away 4
    line 3: stars = stars * 3; // double it
    line 4: stars = stars - 4; // take away 4
    line 5: show(stars); // show it
  40. 40.🐞 This code has a bug. What number does it ACTUALLY show?
    line 1: let stars = 47; // start at 47
    line 2: stars = stars + 2; // double it
    line 3: stars = stars + 4; // add 4
    line 4: show(stars); // show it

Answer key

  1. 220
  2. line 1
  3. line 2
  4. 88
  5. debugging
  6. a mistake in the code
  7. line 3
  8. 30
  9. 88
  10. line 1
  11. 75
  12. test it again
  13. people reading the code
  14. find where it goes wrong
  15. 69
  16. 132
  17. 120
  18. 53
  19. 49
  20. 31
  21. 80
  22. 191
  23. 107
  24. line 1
  25. line 3
  26. line 1
  27. 86
  28. 136
  29. 144
  30. 84
  31. line 3
  32. 72
  33. 131
  34. line 2
  35. 172
  36. line 2
  37. 102
  38. 38
  39. 98
  40. 53

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