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Question 1. In the Karel world, which coordinate pair represents the intersection of Street 3 and Avenue 5? A) (3,5) B) (5,3) C) (3,‑5) D) (5,‑3) Answer: A Explanation: Streets are the vertical axis (y‑coordinate) and Avenues are the horizontal axis (x‑coordinate); thus Street 3, Avenue 5 is (3,5). Question 2. Which primitive command makes Karel turn 90° to the left? A) turnRight() B) turnAround() C) turnLeft() D) move() Answer: C Explanation: turnLeft() rotates Karel 90° counter‑clockwise; the other commands do not exist in the basic set. Question 3. What is the purpose of the run() method in a Karel program? A) To declare global variables B) To serve as the entry point where execution begins C) To define custom functions D) To stop the program Answer: B
Explanation: run() is automatically called when the program starts and contains the sequential commands Karel will execute. Question 4. Which of the following statements is a syntax error in Java‑based Karel? A) move(); B) turnLeft() C) putBeeper(); D) while(frontIsClear()) { } Answer: B Explanation: All statements must end with a semicolon; missing it makes the line a syntax error. Question 5. In Python‑based Karel, which line correctly defines a function that places a beeper? A) def placeBeeper(): B) function placeBeeper() { } C) void placeBeeper() { } D) placeBeeper() = void; Answer: A Explanation: Python uses the def keyword and a colon to start a function block. Question 6. Which loop structure is best when the exact number of repetitions is known beforehand? A) while loop B) do‑while loop C) for loop D) if statement
D) false when Karel is not facing east Answer: C Explanation: The NOT operator (!) inverts the boolean result; thus it is true when Karel is NOT facing east. Question 10. Which of the following best describes a fencepost error? A) Using the wrong sensor method B) Forgetting a semicolon C) Off‑by‑one mistake in loop boundaries D) Declaring a variable twice Answer: C Explanation: Fencepost errors occur when loop counters cause one extra or one missing iteration. Question 11. When defining a helper function in Java‑based Karel, which access modifier is most appropriate for a routine used only inside the class? A) public B) protected C) private D) static Answer: C Explanation: private limits visibility to the defining class, matching the typical use of helper functions. Question 12. Which pair of functions would most logically decompose a checkerboard‑painting task? A) paintSquare() and turnRight()
B) fillRow() and reposition() C) moveToWall() and turnAround() D) pickBeeper() and putBeeper() Answer: B Explanation: fillRow() can paint a single row, while reposition() moves Karel to the start of the next row—common decomposition for checkerboards. Question 13. What should be the postcondition of a function called moveToCorner() that places Karel in the southwest corner of the world? A) Karel is facing north B) Karel’s bag is empty C) Karel’s coordinates are (1,1) and facing any direction D) Karel has placed a beeper at the corner Answer: C Explanation: The postcondition describes the world state after the function; (1,1) is the southwest corner, orientation may be unspecified. Question 14. Which comment style is valid in a Java‑based Karel program? A) # This is a comment B) // Move forward C) D) /* Comment /; Answer: B Explanation: // starts a single‑line comment in Java; # is for Python, is HTML, and / */ must not be followed by a semicolon.
Explanation: Dynamic solutions avoid fixed numbers, allowing the same program to run in worlds of different dimensions. Question 18. To find the midpoint of a row using beepers, which high‑level strategy is correct? A) Place a beeper at each end, then repeatedly move the outer beepers inward until they meet B) Count the length of the row, divide by two, and move that many steps C) Use the turnAround() command twice D) Randomly drop beepers until the middle is guessed Answer: A Explanation: The classic “beeper‑shrink” method moves markers toward each other, guaranteeing the meeting point is the midpoint. Question 19. Which debugging tool helps you manually track Karel’s coordinates and direction step‑by‑step? A) Trace table B) Compiler warning C) Syntax highlighter D) Memory profiler Answer: A Explanation: A trace table records position and orientation after each command, useful for logical debugging. Question 20. Which of the following is a syntax error in Java‑based Karel? A) if (beepersPresent()) { putBeeper(); } B) while (frontIsClear()) putBeeper();
C) for (int i = 0; i < 5; i++) { move(); } D) int = 3; Answer: D Explanation: “int” is a reserved keyword; a variable name must follow it (e.g., int count = 3;). The other lines are syntactically correct. Question 21. Which condition will cause an infinite loop if Karel never picks up a beeper? A) while(beepersInBag()) { move(); } B) while(!beepersInBag()) { turnLeft(); } C) while(frontIsClear()) { move(); } D) while(beepersPresent()) { pickBeeper(); } Answer: B Explanation: If Karel never acquires a beeper, !beepersInBag() stays true forever, resulting in an infinite loop. Question 22. Which of the following best illustrates proper indentation for nested control structures? A) No indentation at all B) Indent the inner block two spaces more than the outer block C) Indent the inner block the same as the outer block D) Indent the outer block more than the inner block Answer: B Explanation: Consistent increased indentation for inner blocks improves readability and reflects hierarchy.
Answer: D Explanation: Preconditions describe required world state; the function assumes the specific start location and orientation. Question 26. Which loop correctly iterates until Karel reaches a wall on his left side? A) while(leftIsClear()) { move(); } B) while(!leftIsClear()) { move(); } C) while(frontIsClear()) { turnLeft(); } D) while(rightIsClear()) { move(); } Answer: A Explanation: leftIsClear() is true while there is no wall on the left; looping while it is true moves Karel until the wall appears. Question 27. What is the effect of the statement turnLeft(); turnLeft();? A) Karel turns 90° left B) Karel turns 180° (faces opposite direction) C) Karel turns 270° left D) Karel does not change direction Answer: B Explanation: Two consecutive left turns rotate Karel 180°, i.e., faces the opposite direction. Question 28. Which of the following is NOT a primitive command in the standard Karel library? A) putBeeper() B) pickBeeper() C) jump()
D) move() Answer: C Explanation: jump() is not part of the basic Karel command set. Question 29. In a world where streets increase upward and avenues increase to the right, which direction does Karel face when facingSouth() returns true? A) Toward decreasing street numbers B) Toward increasing street numbers C) Toward decreasing avenue numbers D) Toward increasing avenue numbers Answer: A Explanation: South is opposite North; moving south reduces the street coordinate. Question 30. Which statement correctly checks that Karel is NOT standing on a beeper? A) beepersPresent() B) !beepersPresent() C) beepersInBag() D) !beepersInBag() Answer: B Explanation: The NOT operator negates the sensor; !beepersPresent() is true when no beeper is on the current corner. Question 31. When using a for loop to place 15 beepers in a line, which header is correct? A) for (int i = 0; i <= 15; i++) B) for (int i = 0; i < 15; i++)
Question 34. Which of the following best avoids a “off‑by‑one” error when Karel must move exactly 7 steps? A) for (int i = 0; i <= 7; i++) move(); B) for (int i = 1; i <= 7; i++) move(); C) while (i < 7) { move(); i++; } D) move(); repeat 7 times; Answer: B Explanation: Starting i at 1 and looping while i ≤ 7 yields precisely 7 iterations. Option A would iterate 8 times. Question 35. Which sensor method would you use to test whether Karel can turn right without hitting a wall? A) rightIsClear() B) frontIsClear() C) leftIsClear() D) backIsClear() Answer: A Explanation: rightIsClear() directly reports whether the square to Karel’s right is free. Question 36. Which of the following correctly defines a helper function named turnRight() using only primitive commands? A) void turnRight() { turnLeft(); turnLeft(); turnLeft(); } B) void turnRight() { turnLeft(); } C) void turnRight() { turnAround(); } D) void turnRight() { move(); }
Answer: A Explanation: Three left turns equal a right turn; the other options do not achieve the intended orientation. Question 37. In a maze where Karel must backtrack when hitting a dead end, which control structure is most suitable? A) for loop B) while loop with a break statement C) do‑while loop without condition D) nested if statements only Answer: B Explanation: A while loop can continue exploring; when a dead end is detected, a break exits the loop to trigger backtracking logic. Question 38. Which comment style correctly documents a function in Java‑based Karel? A) /** Places a beeper and moves forward / B) // Places a beeper and moves forward C) # Places a beeper and moves forward D) Answer: A Explanation: /* ... */ is Javadoc style, suitable for documenting methods in Java. Question 39. Which of the following is a logical error rather than a syntax error? A) Missing semicolon after move() B) Using turnRight() without defining it
Question 42. Which of the following best describes the effect of move(); move(); turnLeft(); on Karel’s position and orientation? A) Two steps forward, then faces north if initially east B) Two steps forward, then faces west if initially east C) Two steps backward, then faces south if initially east D) No movement, only changes direction Answer: B Explanation: Two moves keep the current orientation; a left turn from east results in facing north? Wait: East left turn → North. Actually east → north. So answer should be A. Correction: The correct answer is A. Explanation: Starting east, two moves keep Karel moving east; turnLeft() rotates to north. Question 43. Which sensor method would you use to check whether Karel is at the northern edge of the world? A) frontIsClear() when facing north B) leftIsClear() when facing north C) rightIsClear() when facing north D) frontIsBlocked() when facing north Answer: D Explanation: At the northern edge, there is a wall directly ahead when Karel faces north; frontIsBlocked() returns true. Question 44. In a function that draws a vertical line of beepers, which direction must Karel face before entering the loop? A) East B) West
C) North D) South Answer: C Explanation: Moving north increments the street coordinate, creating a vertical line upward. Question 45. Which of the following statements correctly uses the NOT operator to invert a condition? A) if (frontIsClear() !) { move(); } B) if (!frontIsClear()) { turnLeft(); } C) if (frontIsClear(!)) { move(); } D) if (frontIsClear() == !) { turnLeft(); } Answer: B Explanation: The syntax !condition negates the boolean result; option B follows proper Java/Python style. Question 46. Which of these is the most efficient way to make Karel turn around (180°) using primitive commands? A) turnLeft(); turnLeft(); turnLeft(); turnLeft(); B) turnLeft(); turnLeft(); C) turnRight(); turnRight(); D) move(); move(); turnLeft(); turnLeft(); Answer: B Explanation: Two left turns rotate Karel exactly 180°; option A does four turns (full circle), C assumes turnRight() exists, D adds unnecessary moves.
Explanation: The sensor facingNorth() returns true when Karel’s orientation is north. Question 50. When Karel executes putBeeper(); move(); on a corner where a wall is directly in front, what will happen? A) Karel places a beeper and then crashes into the wall B) Karel places a beeper and then does nothing because move() is illegal C) Karel places a beeper and the program terminates with a runtime error D) Karel places a beeper and turns left automatically Answer: C Explanation: Attempting to move into a wall causes a runtime error; the beeper is placed before the error occurs. Question 51. Which loop structure is most appropriate for “keep moving forward until you encounter a beeper”? A) for (int i = 0; ; i++) { move(); if (beepersPresent()) break; } B) while (!beepersPresent()) { move(); } C) do { move(); } while (beepersPresent()); D) while (beepersPresent()) { move(); } Answer: B Explanation: The loop continues while there is no beeper; when a beeper is found, the condition becomes false and the loop stops. Question 52. Which of the following statements correctly uses a comment to temporarily disable a line of code? A) // move(); B) /* move(); */
C) /** move(); **/ D) # move(); Answer: A Explanation: In Java, // comments out the remainder of the line; option B also works but comments out the line within block comment syntax, which is also valid. However the simplest single‑line comment is A. Question 53. Which sensor method would you combine with ! to test whether there is a wall on Karel’s right side? A) rightIsClear() B) frontIsClear() C) leftIsClear() D) backIsClear() Answer: A Explanation: !rightIsClear() is true when the right side is blocked. Question 54. Which of the following best describes a “precondition” for a function? A) The state that must be true before the function is called B) The value the function returns C) The code that runs after the function finishes D) The number of parameters the function accepts Answer: A Explanation: Preconditions are assumptions about the world before execution.
