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App Dev Worksheet: Debugging

App development lesson 21: Debugging: find the bug line · Set 864 · 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 = 33; // start at 33
    line 2: stars = stars - 2; // add 2
    line 3: stars = stars * 2; // double it
    line 4: stars = stars + 4; // add 4
    line 5: show(stars); // show it
  2. 2.🐞 This code has a bug. What number does it ACTUALLY show?
    line 1: let lives = 43; // start at 43
    line 2: lives = lives + 5; // add 5
    line 3: lives = lives - 3; // add 3
    line 4: lives = lives * 2; // double it
    line 5: show(lives); // show it
  3. 3.🐞 This code has a bug. What number does it ACTUALLY show?
    line 1: let stars = 42; // start at 39
    line 2: stars = stars + 4; // add 4
    line 3: stars = stars - 1; // take away 1
    line 4: show(stars); // show it
  4. 4.🐞 After fixing a bug you should ___. (a) test it again (b) release at once (c) delete the test (d) never test
  5. 5.🐞 This code has a bug. What number does it ACTUALLY show?
    line 1: let lives = 52; // start at 50
    line 2: lives = lives * 2; // double it
    line 3: lives = lives * 2; // double it
    line 4: lives = lives - 2; // take away 2
    line 5: show(lives); // show it
  6. 6.🐞 This code has a bug. What number does it ACTUALLY show?
    line 1: let stars = 50; // start at 47
    line 2: stars = stars * 2; // double it
    line 3: stars = stars + 6; // add 6
    line 4: stars = stars * 2; // double it
    line 5: show(stars); // show it
  7. 7.🐞 What is a good first step when an app gives a wrong result? (a) buy a new phone (b) delete the app (c) find where it goes wrong (d) add more colours
  8. 8.🐞 This code has a bug. What number does it ACTUALLY show?
    line 1: let points = 43; // start at 43
    line 2: points = points * 3; // double it
    line 3: points = points * 2; // double it
    line 4: points = points - 3; // take away 3
    line 5: show(points); // show it
  9. 9.🐞 This code has a bug. What number does it ACTUALLY show?
    line 1: let coins = 44; // start at 43
    line 2: coins = coins + 2; // add 2
    line 3: coins = coins + 6; // add 6
    line 4: show(coins); // show it
  10. 10.🐞 Finding and fixing bugs is called ___. (a) designing (b) debugging (c) decorating (d) downloading
  11. 11.🐞 This code has a bug. What number does it ACTUALLY show?
    line 1: let coins = 45; // start at 45
    line 2: coins = coins + 4; // take away 4
    line 3: coins = coins + 4; // add 4
    line 4: show(coins); // show it
  12. 12.🐞 Each comment says what its line SHOULD do. Which line has the bug?
    line 1: let coins = 48; // start at 48
    line 2: coins = coins - 4; // take away 4
    line 3: coins = coins - 3; // take away 3
    line 4: coins = coins + 4; // take away 4
    line 5: show(coins); // show it     (a) line 2 (b) line 1 (c) line 4 (d) line 3
  13. 13.🐞 This code has a bug. What number does it ACTUALLY show?
    line 1: let score = 30; // start at 30
    line 2: score = score * 2; // double it
    line 3: score = score - 5; // add 5
    line 4: score = score * 2; // double it
    line 5: show(score); // show it
  14. 14.🐞 This code has a bug. What number does it ACTUALLY show?
    line 1: let points = 42; // start at 42
    line 2: points = points - 4; // take away 1
    line 3: points = points - 4; // take away 4
    line 4: points = points + 5; // add 5
    line 5: show(points); // show it
  15. 15.🐞 This code has a bug. What number does it ACTUALLY show?
    line 1: let score = 39; // start at 39
    line 2: score = score - 3; // take away 3
    line 3: score = score + 4; // add 3
    line 4: show(score); // 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 coins = 47; // start at 47
    line 2: coins = coins * 2; // double it
    line 3: coins = coins - 5; // take away 5
    line 4: coins = coins - 6; // take away 3
    line 5: show(coins); // show it
  17. 17.🐞 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 - 3; // take away 3
    line 3: stars = stars + 3; // take away 3
    line 4: show(stars); // show it     (a) line 2 (b) line 3 (c) line 1
  18. 18.🐞 What is a bug? (a) a nice icon (b) a fast phone (c) a mistake in the code (d) a new feature
  19. 19.🐞 This code has a bug. What number SHOULD it show, if every line did what its comment says?
    line 1: let coins = 43; // start at 43
    line 2: coins = coins + 1; // take away 1
    line 3: coins = coins + 3; // add 3
    line 4: show(coins); // show it
  20. 20.🐞 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 * 2; // double it
    line 3: lives = lives + 2; // double it
    line 4: lives = lives + 3; // add 3
    line 5: show(lives); // show it     (a) line 1 (b) line 4 (c) line 2 (d) line 3
  21. 21.🐞 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 - 5; // take away 5
    line 3: lives = lives * 2; // double it
    line 4: lives = lives * 3; // double it
    line 5: show(lives); // show it     (a) line 4 (b) line 1 (c) line 3 (d) line 2
  22. 22.🐞 Each comment says what its line SHOULD do. Which line has the bug?
    line 1: let stars = 51; // start at 50
    line 2: stars = stars + 5; // add 5
    line 3: stars = stars - 1; // take away 1
    line 4: show(stars); // show it     (a) line 3 (b) line 2 (c) line 1
  23. 23.🐞 This code has a bug. What number SHOULD it show, if every line did what its comment says?
    line 1: let coins = 47; // start at 47
    line 2: coins = coins - 2; // add 2
    line 3: coins = coins - 5; // take away 5
    line 4: show(coins); // show it
  24. 24.🐞 This code has a bug. What number SHOULD it show, if every line did what its comment says?
    line 1: let coins = 34; // start at 34
    line 2: coins = coins - 5; // add 5
    line 3: coins = coins + 4; // add 4
    line 4: show(coins); // show it
  25. 25.🐞 Each comment says what its line SHOULD do. Which line has the bug?
    line 1: let score = 48; // start at 48
    line 2: score = score - 4; // add 4
    line 3: score = score + 4; // add 4
    line 4: show(score); // show it     (a) line 3 (b) line 1 (c) line 2
  26. 26.🐞 Each comment says what its line SHOULD do. Which line has the bug?
    line 1: let lives = 37; // start at 37
    line 2: lives = lives + 9; // add 6
    line 3: lives = lives - 4; // take away 4
    line 4: lives = lives * 2; // double it
    line 5: show(lives); // show it     (a) line 1 (b) line 3 (c) line 2 (d) line 4
  27. 27.🐞 This code has a bug. What number does it ACTUALLY show?
    line 1: let lives = 49; // start at 49
    line 2: lives = lives * 2; // double it
    line 3: lives = lives * 2; // double it
    line 4: lives = lives - 6; // take away 3
    line 5: show(lives); // show it
  28. 28.🐞 This code has a bug. What number does it ACTUALLY show?
    line 1: let stars = 33; // start at 30
    line 2: stars = stars + 2; // add 2
    line 3: stars = stars + 5; // add 5
    line 4: show(stars); // 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 coins = 32; // start at 32
    line 2: coins = coins - 1; // take away 1
    line 3: coins = coins + 6; // add 6
    line 4: coins = coins - 2; // add 2
    line 5: show(coins); // show it
  30. 30.🐞 A comment in code (after //) is for ___. (a) the app store (b) the battery (c) the phone screen (d) people reading the code
  31. 31.🐞 Each comment says what its line SHOULD do. Which line has the bug?
    line 1: let points = 38; // start at 36
    line 2: points = points + 2; // add 2
    line 3: points = points * 2; // double it
    line 4: show(points); // show it     (a) line 3 (b) line 2 (c) line 1
  32. 32.🐞 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 - 3; // take away 3
    line 3: lives = lives + 3; // add 3
    line 4: lives = lives + 6; // add 6
    line 5: show(lives); // show it     (a) line 1 (b) line 4 (c) line 3 (d) line 2
  33. 33.🐞 Each comment says what its line SHOULD do. Which line has the bug?
    line 1: let lives = 47; // start at 47
    line 2: lives = lives - 1; // take away 1
    line 3: lives = lives + 6; // add 3
    line 4: show(lives); // show it     (a) line 2 (b) line 3 (c) line 1
  34. 34.🐞 This code has a bug. What number does it ACTUALLY show?
    line 1: let points = 33; // start at 33
    line 2: points = points - 5; // add 5
    line 3: points = points - 3; // take away 3
    line 4: show(points); // show it
  35. 35.🐞 Each comment says what its line SHOULD do. Which line has the bug?
    line 1: let lives = 39; // start at 36
    line 2: lives = lives * 2; // double it
    line 3: lives = lives + 5; // add 5
    line 4: show(lives); // show it     (a) line 3 (b) line 1 (c) line 2
  36. 36.🐞 This code has a bug. What number does it ACTUALLY show?
    line 1: let points = 40; // start at 40
    line 2: points = points - 4; // take away 4
    line 3: points = points - 6; // take away 3
    line 4: points = points * 2; // double it
    line 5: show(points); // show it
  37. 37.🐞 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 43
    line 2: points = points * 2; // double it
    line 3: points = points * 2; // double it
    line 4: show(points); // show it
  38. 38.🐞 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; // add 4
    line 3: stars = stars - 2; // take away 2
    line 4: show(stars); // show it     (a) line 3 (b) line 2 (c) line 1
  39. 39.🐞 This code has a bug. What number does it ACTUALLY show?
    line 1: let coins = 46; // start at 43
    line 2: coins = coins + 4; // add 4
    line 3: coins = coins + 4; // add 4
    line 4: show(coins); // show it
  40. 40.🐞 Each comment says what its line SHOULD do. Which line has the bug?
    line 1: let points = 36; // start at 36
    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 2 (c) line 3

Answer key

  1. 74
  2. 90
  3. 45
  4. test it again
  5. 206
  6. 212
  7. find where it goes wrong
  8. 255
  9. 52
  10. debugging
  11. 53
  12. line 4
  13. 110
  14. 39
  15. 40
  16. 86
  17. line 3
  18. a mistake in the code
  19. 45
  20. line 3
  21. line 4
  22. line 1
  23. 44
  24. 43
  25. line 2
  26. line 2
  27. 190
  28. 40
  29. 39
  30. people reading the code
  31. line 1
  32. line 1
  33. line 3
  34. 25
  35. line 1
  36. 60
  37. 172
  38. line 2
  39. 54
  40. line 3

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