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App Dev Worksheet: Debugging

App development lesson 21: Debugging: find the bug line · Set 426 · 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.🐞 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 - 5; // take away 5
    line 3: score = score + 4; // add 4
    line 4: show(score); // show it     (a) line 3 (b) line 1 (c) line 2
  2. 2.🐞 This code has a bug. What number does it ACTUALLY show?
    line 1: let stars = 53; // start at 50
    line 2: stars = stars + 5; // add 5
    line 3: stars = stars - 3; // take away 3
    line 4: show(stars); // show it
  3. 3.🐞 Each comment says what its line SHOULD do. Which line has the bug?
    line 1: let lives = 33; // start at 33
    line 2: lives = lives + 3; // add 3
    line 3: lives = lives + 2; // double it
    line 4: lives = lives + 4; // add 4
    line 5: show(lives); // show it     (a) line 1 (b) line 2 (c) line 3 (d) line 4
  4. 4.🐞 This code has a bug. What number does it ACTUALLY show?
    line 1: let score = 33; // start at 32
    line 2: score = score - 2; // take away 2
    line 3: score = score * 2; // double it
    line 4: show(score); // show it
  5. 5.🐞 What is a bug? (a) a fast phone (b) a new feature (c) a mistake in the code (d) a nice icon
  6. 6.🐞 Each comment says what its line SHOULD do. Which line has the bug?
    line 1: let score = 50; // start at 50
    line 2: score = score * 2; // double it
    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
  7. 7.🐞 This code has a bug. What number does it ACTUALLY show?
    line 1: let score = 46; // start at 46
    line 2: score = score * 2; // double it
    line 3: score = score + 2; // double it
    line 4: show(score); // show it
  8. 8.🐞 This code has a bug. What number does it ACTUALLY show?
    line 1: let coins = 51; // start at 50
    line 2: coins = coins * 2; // double it
    line 3: coins = coins - 4; // take away 4
    line 4: show(coins); // show it
  9. 9.🐞 This code has a bug. What number does it ACTUALLY show?
    line 1: let stars = 31; // start at 31
    line 2: stars = stars + 5; // add 3
    line 3: stars = stars * 2; // double it
    line 4: show(stars); // show it
  10. 10.🐞 This code has a bug. What number does it ACTUALLY show?
    line 1: let coins = 48; // start at 48
    line 2: coins = coins - 1; // take away 1
    line 3: coins = coins - 6; // take away 4
    line 4: show(coins); // show it
  11. 11.🐞 Each comment says what its line SHOULD do. Which line has the bug?
    line 1: let coins = 39; // start at 39
    line 2: coins = coins - 1; // take away 1
    line 3: coins = coins + 4; // add 4
    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
  12. 12.🐞 Each comment says what its line SHOULD do. Which line has the bug?
    line 1: let coins = 36; // start at 36
    line 2: coins = coins - 4; // take away 4
    line 3: coins = coins + 2; // double it
    line 4: show(coins); // show it     (a) line 1 (b) line 3 (c) line 2
  13. 13.🐞 Finding and fixing bugs is called ___. (a) designing (b) downloading (c) debugging (d) decorating
  14. 14.🐞 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 * 2; // double it
    line 3: points = points - 6; // take away 5
    line 4: show(points); // 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 stars = 38; // start at 37
    line 2: stars = stars * 2; // double it
    line 3: stars = stars * 2; // double it
    line 4: stars = stars + 4; // add 4
    line 5: show(stars); // show it
  16. 16.🐞 What is a good first step when an app gives a wrong result? (a) delete the app (b) buy a new phone (c) add more colours (d) find where it goes wrong
  17. 17.🐞 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 36
    line 2: lives = lives * 2; // double it
    line 3: lives = lives * 2; // double it
    line 4: show(lives); // show it
  18. 18.🐞 This code has a bug. What number does it ACTUALLY show?
    line 1: let score = 34; // start at 34
    line 2: score = score * 2; // double it
    line 3: score = score - 2; // take away 1
    line 4: score = score * 2; // double it
    line 5: show(score); // show it
  19. 19.🐞 After fixing a bug you should ___. (a) test it again (b) release at once (c) delete the test (d) never test
  20. 20.🐞 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 35
    line 2: stars = stars * 2; // double it
    line 3: stars = stars + 1; // take away 1
    line 4: show(stars); // show it
  21. 21.🐞 This code has a bug. What number does it ACTUALLY show?
    line 1: let score = 37; // start at 37
    line 2: score = score - 5; // take away 5
    line 3: score = score + 2; // double it
    line 4: score = score - 1; // take away 1
    line 5: show(score); // show it
  22. 22.🐞 This code has a bug. What number does it ACTUALLY show?
    line 1: let coins = 37; // start at 37
    line 2: coins = coins - 7; // take away 5
    line 3: coins = coins * 2; // double it
    line 4: show(coins); // show it
  23. 23.🐞 This code has a bug. What number does it ACTUALLY show?
    line 1: let lives = 45; // start at 44
    line 2: lives = lives + 4; // add 4
    line 3: lives = lives - 1; // take away 1
    line 4: show(lives); // show it
  24. 24.🐞 This code has a bug. What number does it ACTUALLY show?
    line 1: let stars = 35; // start at 35
    line 2: stars = stars * 2; // double it
    line 3: stars = stars + 4; // add 4
    line 4: stars = stars + 2; // double it
    line 5: show(stars); // show it
  25. 25.🐞 This code has a bug. What number does it ACTUALLY show?
    line 1: let points = 50; // start at 50
    line 2: points = points + 5; // add 5
    line 3: points = points + 2; // double it
    line 4: show(points); // show it
  26. 26.🐞 This code has a bug. What number does it ACTUALLY show?
    line 1: let coins = 42; // start at 42
    line 2: coins = coins + 3; // add 3
    line 3: coins = coins - 4; // add 4
    line 4: show(coins); // show it
  27. 27.🐞 Each comment says what its line SHOULD do. Which line has the bug?
    line 1: let stars = 45; // start at 45
    line 2: stars = stars - 2; // take away 2
    line 3: stars = stars + 3; // add 2
    line 4: show(stars); // show it     (a) line 2 (b) line 3 (c) line 1
  28. 28.🐞 This code has a bug. What number SHOULD it show, if every line did what its comment says?
    line 1: let lives = 50; // start at 50
    line 2: lives = lives + 2; // double it
    line 3: lives = lives + 2; // add 2
    line 4: show(lives); // show it
  29. 29.🐞 This code has a bug. What number does it ACTUALLY show?
    line 1: let coins = 36; // start at 36
    line 2: coins = coins * 3; // double it
    line 3: coins = coins - 4; // take away 4
    line 4: show(coins); // show it
  30. 30.🐞 A comment in code (after //) is for ___. (a) people reading the code (b) the battery (c) the phone screen (d) the app store
  31. 31.🐞 This code has a bug. What number does it ACTUALLY show?
    line 1: let lives = 33; // start at 32
    line 2: lives = lives - 4; // take away 4
    line 3: lives = lives + 4; // add 4
    line 4: lives = lives - 4; // take away 4
    line 5: show(lives); // show it
  32. 32.🐞 Each comment says what its line SHOULD do. Which line has the bug?
    line 1: let points = 33; // start at 33
    line 2: points = points + 2; // double it
    line 3: points = points * 2; // double it
    line 4: points = points + 6; // add 6
    line 5: show(points); // show it     (a) line 2 (b) line 4 (c) line 3 (d) line 1
  33. 33.🐞 Each comment says what its line SHOULD do. Which line has the bug?
    line 1: let lives = 38; // start at 38
    line 2: lives = lives + 7; // add 5
    line 3: lives = lives - 4; // take away 4
    line 4: show(lives); // show it     (a) line 3 (b) line 2 (c) line 1
  34. 34.🐞 Each comment says what its line SHOULD do. Which line has the bug?
    line 1: let points = 39; // start at 39
    line 2: points = points - 3; // take away 3
    line 3: points = points * 3; // double it
    line 4: points = points + 3; // add 3
    line 5: show(points); // show it     (a) line 3 (b) line 4 (c) line 1 (d) 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 score = 47; // start at 47
    line 2: score = score + 5; // add 4
    line 3: score = score - 1; // take away 1
    line 4: score = score * 2; // double it
    line 5: show(score); // 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 = 44; // start at 44
    line 2: score = score + 2; // double it
    line 3: score = score + 2; // add 2
    line 4: score = score * 2; // double it
    line 5: show(score); // show it
  37. 37.🐞 This code has a bug. What number does it ACTUALLY show?
    line 1: let score = 42; // start at 39
    line 2: score = score - 3; // take away 3
    line 3: score = score * 2; // double it
    line 4: score = score - 2; // take away 2
    line 5: show(score); // show it
  38. 38.🐞 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 - 3; // take away 3
    line 3: score = score + 3; // take away 3
    line 4: show(score); // show it     (a) line 2 (b) line 1 (c) line 3
  39. 39.🐞 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 - 4; // take away 4
    line 3: coins = coins - 4; // add 4
    line 4: show(coins); // 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 lives = 43; // start at 42
    line 2: lives = lives * 2; // double it
    line 3: lives = lives - 5; // take away 5
    line 4: show(lives); // show it

Answer key

  1. line 1
  2. 55
  3. line 3
  4. 62
  5. a mistake in the code
  6. line 4
  7. 94
  8. 98
  9. 72
  10. 41
  11. line 4
  12. line 3
  13. debugging
  14. 57
  15. 152
  16. find where it goes wrong
  17. 144
  18. 132
  19. test it again
  20. 69
  21. 33
  22. 60
  23. 48
  24. 76
  25. 57
  26. 41
  27. line 3
  28. 102
  29. 104
  30. people reading the code
  31. 29
  32. line 2
  33. line 2
  34. line 3
  35. 100
  36. 180
  37. 76
  38. line 3
  39. 44
  40. 79

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