← Debugging: find the bug line lesson New set →

App Dev Worksheet: Debugging

App development lesson 21: Debugging: find the bug line · Set 805 · 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 does it ACTUALLY show?
    line 1: let stars = 33; // start at 33
    line 2: stars = stars - 7; // take away 4
    line 3: stars = stars * 2; // double it
    line 4: show(stars); // show it
  2. 2.🐞 After fixing a bug you should ___. (a) release at once (b) test it again (c) delete the test (d) never test
  3. 3.🐞 What is a good first step when an app gives a wrong result? (a) find where it goes wrong (b) add more colours (c) delete the app (d) buy a new phone
  4. 4.🐞 This code has a bug. What number does it ACTUALLY show?
    line 1: let score = 43; // start at 43
    line 2: score = score + 2; // double it
    line 3: score = score * 2; // double it
    line 4: show(score); // show it
  5. 5.🐞 This code has a bug. What number does it ACTUALLY show?
    line 1: let score = 33; // start at 33
    line 2: score = score - 4; // take away 4
    line 3: score = score - 2; // take away 2
    line 4: score = score * 3; // double it
    line 5: show(score); // show it
  6. 6.🐞 This code has a bug. What number does it ACTUALLY show?
    line 1: let stars = 34; // start at 32
    line 2: stars = stars - 2; // take away 2
    line 3: stars = stars * 2; // double it
    line 4: stars = stars + 4; // add 4
    line 5: show(stars); // show it
  7. 7.🐞 Each comment says what its line SHOULD do. Which line has the bug?
    line 1: let lives = 32; // start at 32
    line 2: lives = lives * 2; // double it
    line 3: lives = lives * 2; // double it
    line 4: lives = lives - 7; // take away 4
    line 5: show(lives); // show it     (a) line 3 (b) line 2 (c) line 4 (d) line 1
  8. 8.🐞 Each comment says what its line SHOULD do. Which line has the bug?
    line 1: let points = 35; // start at 33
    line 2: points = points * 2; // double it
    line 3: points = points + 3; // add 3
    line 4: show(points); // show it     (a) line 1 (b) line 2 (c) line 3
  9. 9.🐞 Finding and fixing bugs is called ___. (a) debugging (b) downloading (c) designing (d) decorating
  10. 10.🐞 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 46
    line 2: score = score + 6; // add 3
    line 3: score = score + 3; // add 3
    line 4: score = score * 2; // double it
    line 5: show(score); // show it
  11. 11.🐞 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; // add 3
    line 3: stars = stars * 2; // double it
    line 4: show(stars); // show it     (a) line 2 (b) line 1 (c) line 3
  12. 12.🐞 This code has a bug. What number does it ACTUALLY show?
    line 1: let coins = 36; // start at 36
    line 2: coins = coins + 2; // take away 2
    line 3: coins = coins + 4; // add 4
    line 4: show(coins); // show it
  13. 13.🐞 This code has a bug. What number SHOULD it show, if every line did what its comment says?
    line 1: let coins = 39; // start at 39
    line 2: coins = coins * 3; // double it
    line 3: coins = coins * 2; // double it
    line 4: coins = coins * 2; // double it
    line 5: show(coins); // 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 coins = 48; // start at 45
    line 2: coins = coins - 3; // take away 3
    line 3: coins = coins - 5; // take away 5
    line 4: coins = coins + 3; // add 3
    line 5: show(coins); // 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 coins = 48; // start at 46
    line 2: coins = coins + 2; // add 2
    line 3: coins = coins - 3; // take away 3
    line 4: show(coins); // show it
  16. 16.🐞 This code has a bug. What number does it ACTUALLY show?
    line 1: let points = 36; // start at 36
    line 2: points = points * 2; // double it
    line 3: points = points - 4; // add 4
    line 4: points = points - 2; // take away 2
    line 5: show(points); // 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 lives = 36; // start at 36
    line 2: lives = lives * 2; // double it
    line 3: lives = lives + 2; // double it
    line 4: lives = lives + 6; // add 6
    line 5: show(lives); // show it
  18. 18.🐞 This code has a bug. What number does it ACTUALLY show?
    line 1: let score = 43; // start at 43
    line 2: score = score - 1; // take away 1
    line 3: score = score - 5; // add 5
    line 4: score = score - 1; // take away 1
    line 5: show(score); // show it
  19. 19.🐞 This code has a bug. What number does it ACTUALLY show?
    line 1: let score = 32; // start at 32
    line 2: score = score - 1; // take away 1
    line 3: score = score - 3; // add 3
    line 4: score = score - 1; // take away 1
    line 5: 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 lives = 42; // start at 42
    line 2: lives = lives * 3; // double it
    line 3: lives = lives * 2; // double it
    line 4: show(lives); // show it
  21. 21.🐞 Each comment says what its line SHOULD do. Which line has the bug?
    line 1: let points = 45; // start at 45
    line 2: points = points - 5; // take away 5
    line 3: points = points + 3; // add 2
    line 4: show(points); // show it     (a) line 2 (b) line 1 (c) line 3
  22. 22.🐞 Each comment says what its line SHOULD do. Which line has the bug?
    line 1: let coins = 34; // start at 34
    line 2: coins = coins + 2; // double it
    line 3: coins = coins + 2; // add 2
    line 4: show(coins); // show it     (a) line 1 (b) line 2 (c) line 3
  23. 23.🐞 Each comment says what its line SHOULD do. Which line has the bug?
    line 1: let score = 35; // start at 35
    line 2: score = score - 5; // take away 5
    line 3: score = score + 6; // add 4
    line 4: show(score); // show it     (a) line 1 (b) line 2 (c) line 3
  24. 24.🐞 This code has a bug. What number SHOULD it show, if every line did what its comment says?
    line 1: let points = 43; // start at 43
    line 2: points = points - 5; // take away 5
    line 3: points = points * 3; // double it
    line 4: show(points); // show it
  25. 25.🐞 This code has a bug. What number does it ACTUALLY show?
    line 1: let coins = 51; // start at 50
    line 2: coins = coins + 5; // add 5
    line 3: coins = coins * 2; // double it
    line 4: coins = coins * 2; // double it
    line 5: show(coins); // show it
  26. 26.🐞 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 + 7; // add 6
    line 4: show(lives); // show it     (a) line 1 (b) line 3 (c) line 2
  27. 27.🐞 This code has a bug. What number SHOULD it show, if every line did what its comment says?
    line 1: let points = 47; // start at 47
    line 2: points = points - 2; // add 2
    line 3: points = points * 2; // double it
    line 4: show(points); // show it
  28. 28.🐞 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 + 4; // add 3
    line 4: show(coins); // show it     (a) line 2 (b) line 3 (c) line 1
  29. 29.🐞 This code has a bug. What number SHOULD it show, if every line did what its comment says?
    line 1: let score = 35; // start at 33
    line 2: score = score * 2; // double it
    line 3: score = score * 2; // double it
    line 4: show(score); // 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 coins = 48; // start at 48
    line 2: coins = coins + 2; // add 2
    line 3: coins = coins + 3; // add 2
    line 4: coins = coins * 2; // double it
    line 5: show(coins); // show it
  31. 31.🐞 Each comment says what its line SHOULD do. Which line has the bug?
    line 1: let score = 49; // start at 49
    line 2: score = score + 4; // take away 4
    line 3: score = score * 2; // double it
    line 4: show(score); // 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 points = 34; // start at 34
    line 2: points = points * 3; // double it
    line 3: points = points * 2; // double it
    line 4: show(points); // show it     (a) line 1 (b) line 2 (c) line 3
  33. 33.🐞 Each comment says what its line SHOULD do. Which line has the bug?
    line 1: let stars = 47; // start at 47
    line 2: stars = stars * 2; // double it
    line 3: stars = stars * 2; // double it
    line 4: stars = stars * 3; // double it
    line 5: show(stars); // show it     (a) line 4 (b) line 3 (c) line 1 (d) line 2
  34. 34.🐞 This code has a bug. What number does it ACTUALLY show?
    line 1: let lives = 32; // start at 32
    line 2: lives = lives + 2; // double it
    line 3: lives = lives - 1; // take away 1
    line 4: show(lives); // show it
  35. 35.🐞 This code has a bug. What number SHOULD it show, if every line did what its comment says?
    line 1: let points = 37; // start at 37
    line 2: points = points + 6; // add 4
    line 3: points = points + 6; // add 6
    line 4: points = points + 5; // add 5
    line 5: show(points); // show it
  36. 36.🐞 This code has a bug. What number does it ACTUALLY show?
    line 1: let points = 41; // start at 39
    line 2: points = points + 4; // add 4
    line 3: points = points - 1; // take away 1
    line 4: 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 stars = 31; // start at 31
    line 2: stars = stars + 2; // add 2
    line 3: stars = stars - 4; // take away 1
    line 4: stars = stars + 6; // add 6
    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 = 38; // start at 35
    line 2: score = score - 2; // take away 2
    line 3: score = score * 2; // double it
    line 4: show(score); // show it     (a) line 1 (b) line 2 (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 points = 48; // start at 45
    line 2: points = points + 2; // add 2
    line 3: points = points * 2; // double it
    line 4: show(points); // show it
  40. 40.🐞 A comment in code (after //) is for ___. (a) people reading the code (b) the phone screen (c) the battery (d) the app store

Answer key

  1. 52
  2. test it again
  3. find where it goes wrong
  4. 90
  5. 81
  6. 68
  7. line 4
  8. line 1
  9. debugging
  10. 104
  11. line 2
  12. 42
  13. 312
  14. 40
  15. 45
  16. 66
  17. 150
  18. 36
  19. 27
  20. 168
  21. line 3
  22. line 2
  23. line 3
  24. 76
  25. 224
  26. line 3
  27. 98
  28. line 3
  29. 132
  30. 104
  31. line 2
  32. line 2
  33. line 4
  34. 33
  35. 52
  36. 44
  37. 38
  38. line 1
  39. 94
  40. people reading the code

Free app development lessons, practice and worksheets at talentjr.in/app-development-for-students