AP Computer Science Principles Review

Which of the following is NOT a benefit of collaborating to develop a computing innovation?

• Collaboration can decrease the size and complexity of tasks required of individual team members.

• Collaboration can make it easier to find and correct errors during the development process.

• Collaboration eliminates the need to resolve differences of opinion.

• Collaboration facilitates multiple perspectives in developing ideas.

Answer explanation

While effective collaboration often benefits from a diversity of talents and perspectives, collaborators still need to develop strategies to resolve differences of opinion.

In the following procedure, assume that the parameter x is an integer. Which of the following best describes the behavior of the procedure?

• It displays nothing if x is negative and displays true otherwise.

• It displays nothing if x is negative and displays false otherwise.

• It displays true if x is negative and displays nothing otherwise.

• It displays true if x is negative and displays false otherwise.

Answer explanation

When x is negative, y is assigned the value true and the value of y is displayed. When x is not negative, y is assigned the value false and the display statement is never executed.

Directions: The question or incomplete statement below is followed by four suggested answers or completions. Select the one that is best in each case. Which of the following is a true statement about program documentation?

• Program documentation should not be changed after it is first written.

• Program documentation is only needed for programs in development; it is not needed after a program is completed.

• Program documentation is useful when programmers collaborate but not when a programmer works individually on a project.

• Program documentation is useful during initial program development and also when modifications are made to existing programs.

Answer explanation

During initial program development, documentation can allow the writer to organize his or her thinking, state assumptions about input, and explain the path of future development. When modifications are made to existing programs, documentation is used to record the changes or additions to an existing program.

A computer program uses 3 bits to represent integers. When the program adds the decimal (base 10) numbers 5 and 3, the result is 0. Which of the following is the best explanation for the result?

• An overflow error occurred.

• A round-off error occurred.

• The result was affected by lossy data compression.

• The result was approximated by a floating-point representation.

Answer explanation

The binary representations (in 3 bits) of 5 and 3 are 101 and 011, respectively. If these numbers are added, the result would be 1000. Since only 3 bits are used to represent integers in this example, the result would be stored as 000. This is an example of overflow error.

Consider the 4-bit binary numbers 0011, 0110, and 1111. Which of the following decimal values is NOT equal to one of these binary numbers?

• 3

• 6

• 9

• 15

Answer explanation

Binary 0011 is equivalent to 2^1+2^0, or decimal 3. Binary 0110 is equivalent to 2^2+2^1, or decimal 6. Binary 1111 is equivalent to 2^3+2^2+2^1+2^0, or decimal 15. Decimal 9 is not equivalent to any of the given binary numbers.

Which of the following is an advantage of a lossless compression algorithm over a lossy compression algorithm?

• A lossless compression algorithm can guarantee that compressed information is kept secure, while a lossy compression cannot.

• A lossless compression algorithm can guarantee reconstruction of original data, while a lossy compression algorithm cannot.

• A lossless compression algorithm typically allows for faster transmission speeds than does a lossy compression algorithm.

• A lossless compression algorithm typically provides a greater reduction in the number of bits stored or transmitted than does a lossy compression algorithm.

Answer explanation

Lossless compression algorithms are guaranteed to be able to reconstruct the original data, while lossy compression algorithms are not.

A list of binary values (0 or 1) is used to represent a black-and-white image. Which of the following is LEAST likely to be stored as metadata associated with the image?

• Copyright information for the image

• The date and time the image was created

• The dimensions (number of rows and columns of pixels) of the image

• A duplicate copy of the data

Answer explanation

Metadata typically consists of descriptive information about the data, not a copy of the data itself.

The owner of a clothing store records the following information for each transaction made at the store during a 7-day period: the date of the transaction, the method of payment used in the transaction, the number of items purchased in the transaction, and the total amount of the transaction, in dollars. Using only the data collected during the 7-day period, which of the following statements is true?

• The average amount spent per day during the 7-day period can be determined by sorting the data by the total transaction amount, then adding the 7 greatest amounts, and then dividing the sum by 7.

• The method of payment that was used in the greatest number of transactions during the 7-day period can be determined by sorting the data by the method of payment, then adding the number of items purchased for each type of payment method, and then finding the maximum sum.

• The most expensive item purchased on a given date can be determined by searching the data for all items purchased on the given date and then sorting the matching items by item price.

• The total number of items purchased on a given date can be determined by searching the data for all transactions that occurred on the given date and then adding the number of items purchased for each matching transaction.

Answer explanation

For each transaction, the data includes the date of the transaction and the number of items purchased in the transaction. By searching the data to find all transactions that occurred on the given date, and then adding the number of items purchased in each of those transactions, the total number of items purchased on a given date can be determined.

Consider the following code segment. What is the value of r as a result of executing the code segment?

• 10

• 20

• 30

• 40

Answer explanation

The first four statements assign values to the variables. The fifth statement assigns the value of q (which is 20) to p. The sixth statement assigns the value of r (which is 30) to q. The seventh statement assigns the value of q (which is 30) to s. The last statement assigns the value of p (which is 20) to r. Therefore, r has the value 20. After executing the code segment, the value of p is 20, the value of q is 30, the value of r is 20, and the value of s is 30.

Which of the following is a benefit of using a list as a data abstraction in a program?

• Lists often allow their size to be easily updated to hold as many data values as needed.

• Lists convert all elements to strings so that they can be inspected character-by-character.

• Lists prevent duplicate data values from appearing in the list.

• Lists are used to store all input data so that there is a running record of all user input.

Answer explanation

Lists are data abstractions that allow multiple elements to be stored in a single collection. Many programming languages allow programmers to append, insert, or remove data elements, allowing the size of the list to grow or shrink as needed.