COMP SCI Unit 2 #7

An office building has two floors. A computer program is used to control an elevator that travels between the two floors. Physical sensors are used to set the following Boolean variables.

The elevator moves when the door is closed and the elevator is called to the floor that it is not currently on. Which of the following Boolean expressions can be used in a selection statement to cause the elevator to move?

• (onFloor1 AND callTo2) AND (onFloor2 AND callTo1)

• (onFloor1 AND callTo2) OR (onFloor2 AND callTo1)

• (onFloor1 OR callTo2) AND (onFloor2 OR callTo1)

• (onFloor1 OR callTo2) OR (onFloor2 OR callTo1)

Directions: The question or incomplete statement below is followed by four suggested answers or completions. Select the one that is best in each case.

A flowchart is a way to visually represent an algorithm. The flowchart below is used by an apartment rental Web site to set the variable  to  for apartments that meet certain criteria.

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The diagram below shows a circuit composed of two logic gates labeled OR and AND. Each gate takes two inputs and produces a single output.

If the inputs A and C are both true, which of the following best describes the output of the AND gate?

• The output will be true no matter what the value of input B is.

• The output will be false no matter what the value of input B is.

• The output will be true if input B is true; otherwise it will be false.

• The output will be false if input B is true; otherwise it will be true.

Consider the following code segment.

Which of the following initial values of the variable y would result in the variable z being set to 2 after the code segment is executed?

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Three words are stored in the variables word1, word2, and word3. The values of the variables are to be updated as shown in the following table.

Which of the following code segments can be used to update the values of the variables as shown in the table?

• temp ← word1

  word3 ← word1

  word1 ← temp

• temp ← word1

  word1 ← word3

  word3 ← temp

• temp ← word1

  word1 ← word2

  word2 ← word3

  word3 ← temp

• temp ← word3

  word3 ← word2

  word2 ← word1

  word1 ← temp

The following table shows the value of expression based on the values of input1 and input2.

Which of the following expressions are equivalent to the value of expression as shown in the table?

Select two answers.

• (NOT input1) OR (NOT input2)

• (NOT input1) AND (NOT input2)

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  NOT (input1 OR input2)

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  NOT (input1 AND input2)

A programmer wants to determine whether a score is within 10 points of a given target. For example, if the target is 50, then the scores 40, 44, 50, 58, and 60 are all within 10 points of the target, while 38 and 61 are not.

Which of the following Boolean expressions will evaluate to true if and only if score is within 10 points of target ?

• (score ≤ target + 10) AND (target + 10 ≤ score)

• (target + 10 ≤ score) AND (score ≤ target - 10)

• (score ≤ target - 10) AND (score ≤ target + 10)

• (target - 10 ≤ score) AND (score ≤ target + 10)

The code fragment below is intended to display "odd" if the positive number num is odd.

Which of the following can be used to replace <MISSING CONDITION> so that the code fragment will work as intended?

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  (num MOD 1) = 0

• (num MOD 1) = 1

• (num MOD 2) = 0

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  (num MOD 2) = 1

Directions: The question or incomplete statement below is followed by four suggested answers or completions. Select the one that is best in each case.

The diagram below shows a circuit composed of three logic gates. Each gate takes two inputs and produces a single output.

For which of the following input values will the circuit have an output of  ?

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Directions: For the question or incomplete statement below, two of the suggested answers are correct. For this question, you must select both correct choices to earn credit. No partial credit will be earned if only one correct choice is selected. Select the two that are best in each case.

Which of the following Boolean expressions are equivalent to the expression 

num >= ?

Select two answers.

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