Computer Science Principles End-of-Year Exam

A student wrote the following code for a guessing game  

While debugging the code, the student realizes that the loop never terminates. The student plans to insert the instruction win←true somewhere in the code.   Where could win←true be inserted so that the code segment works as intended?  

• Between line 6 and line 7

• Between line 9 and line 10

• Between line 20 and 21

• Between line 21 and 22

Participants in a survey were asked how many hours per day they spend reading, how many hours per day they spend using a smartphone, and whether or not they would be interested in a smartphone application that lets users share book reviews. 

The data from the survey are represented in the graph below. Each × represents a survey participant who said he or she was interested in the application, and each O represents a participant who said he or she was not interested.  

Which of the following hypotheses is most consistent with the data in the graph?  

• Participants who read more were generally more likely to say they are interested in the application.

• Participants who read more were generally less likely to say they are interested in the application.

• Participants who use a smartphone more were generally more likely to say they read more.

• Participants who use a smartphone more were generally less likely to say they read more.

A musician is creating a song using audio samples. Which of the following actions will minimize the risk of a copyright violation when creating sample-based music?  

• Using samples found on popular music-streaming sites

• Using samples found on peer-to-peer networks

• Using samples from nondigital sound sources (vinyl records, tapes, etc.)

• Using samples published with a no-rights-reserved Creative Commons license

 The two code segments below are each intended to display the average of the numbers in the list numList. Assume that numList contains more than one value.  

• Code segment I displays the correct average, but code segment II does not.

• Code segment II displays the correct average, but code segment I does not

• Both code segments display the correct average, but code segment I requires more arithmetic operations than code segment II.

• Both code segments display the correct average, but code segment II requires more arithmetic operations than code segment I

 Internet protocol version 4 (IPv4) represents each IP address as a 32-bit binary number. Internet protocol version 6 (IPv6) represents each IP address as a 128-bit binary number. Which of the following best describes the result of using 128-bit addresses instead of 32-bit addresses?  

• 4 times as many addresses are available.

• 96 times as many addresses are available.

• 2(4) times as many addresses are available.

• 2 (96) times as many addresses are available.

 An online retailer uses an algorithm to sort a list of n items by price. The table below shows the approximate number of steps the algorithm takes to sort lists of different sizes.  

• The algorithm runs in reasonable time.

• The algorithm runs, but not in reasonable time.

• The algorithm attempts to solve an undecidable problem.

• The algorithm attempts to find an approximate solution whenever it fails to find an exact solution.

  A computer program uses 4 bits to represent nonnegative integers. Which of the following statements describe a possible result when the program uses this number representation? 

I. The operation 4+8 will result in an overflow error. 

II. The operation 7 + 10 will result in an overflow error. 

III. The operation 12 + 3 will result in an overflow error. 

• I only

• II only

• II and III only

• I, II, and III

 A NAND gate is a type of logic gate that produces an output of false only when both of its two inputs are true. Otherwise, the gate produces an output of true. Which of the following Boolean expressions correctly models a NAND gate with inputs P and Q ?  

• (NOT P) AND (NOT Q)

• (NOT P) AND Q

• NOT (P AND Q)

• NOT (P OR Q)

  A student wants to create an algorithm that can determine, given any program and program input, whether or not the program will go into an infinite loop for that input. 

The problem the student is attempting to solve is considered an undecidable problem. Which of the following is true?   

• a

• b

• c

• d

In public key cryptography, the sender uses the recipient’s public key to encrypt a message. Which of the following is needed to decrypt the message?  

• The sender’s public key

• The sender’s private key

• The recipient’s public key

• The recipient’s private key