Digital Information #1 (AP CSP)

A video game character can face toward one of four directions: north, south, east, and west. Each direction is stored in memory as a sequence of four bits. A new version of the game is created in which the character can face toward one of eight directions, adding northwest, northeast, southwest, and southeast to the original four possibilities. Which of the following statements is true about how the eight directions must be stored in memory?

• Four bits are not enough to store the eight directions. Five bits are needed for the new version of the game.

• Four bits are not enough to store the eight directions. Eight bits are needed for the new version of the game.

• Four bits are not enough to store the eight directions. Sixteen bits are needed for the new version of the game.

• Four bits are enough to store the eight directions.

Which of the following are true statements about the data that can be represented using binary sequences?

1. 1. Binary sequences can be used to represent strings of characters.

2. 2. Binary sequences can be used to represent colors.

3. 3. Binary sequences can be used to represent audio recordings.

• 1 only

• 1 and 2 only

• 2 and 3 only

• 1, 2, and 3

The player controls in a particular video game are represented by numbers. The controls and their corresponding binary values are shown in the following table.

The numeric values for the controls can also be represented in decimal (base 10).

What is the decimal value for the jump control?

• 3

• 12

• 24

• 48

The player controls in a particular video game are represented by numbers. The controls and their corresponding binary values are shown in the following table.

The numeric values for the controls can also be represented in decimal (base 10).

What control is represented by the decimal value 15 ?

• ←

• ↑

• →

• ↓

A certain programming language uses 4-bit binary sequences to represent nonnegative integers. For example, the binary sequence 0101 represents the corresponding decimal value 5. Using this programming language, a programmer attempts to add the decimal values 14 and 15 and assign the sum to the variable total. Which of the following best describes the result of this operation?

• The correct sum of 29 will be assigned to the variable total.

• An overflow error will occur because 4 bits is not large enough to represent either of the values 14 or 15.

• An overflow error will occur because 4 bits is not large enough to represent 29, the sum of 14 and 15.

• A round-off error will occur because the decimal values 14 and 15 are represented as approximations due to the fixed number of bits used to represent numbers.

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.

An online store uses 6-bit binary sequences to identify each unique item for sale. The store plans to increase the number of items it sells and is considering using 7-bit binary sequences. Which of the following best describes the result of using 7-bit sequences instead of 6-bit sequences?

• 2 more items can be uniquely identified.

• 10 more items can be uniquely identified.

• 2 times as many items can be uniquely identified.

• 10 times as many items can be uniquely identified.

Which of the following best explains how an analog audio signal is typically represented by a computer?

• An analog audio signal is measured as input parameters to a program or procedure. The inputs are represented at the lowest level as a collection of variables.

• An analog audio signal is measured at regular intervals. Each measurement is stored as a sample, which is represented at the lowest level as a sequence of bits.

• An analog audio signal is measured as a sequence of operations that describe how the sound can be reproduced.

• An analog audio signal is measured as text that describes the attributes of the sound. The text is represented at the lowest level as a string.

A binary number is to be transformed by appending three Os to the end of the number. For example, 11101 is transformed to 11101000. Which of the following correctly describes the relationship between the transformed number and the original number?

• The transformed number is 3 times the value of the original number.

• The transformed number is 4 times the value of the original number.

• The transformed number is 8 times the value of the original number.

• The transformed number is 1,000 times the value of the original number.

Some programming languages use constants, which are variables that are initialized at the beginning of a program and never changed. Which of the following are good uses for a constant?

1. 1. To represent the mathematical value π (pi) as 3.14

2. 2. To represent the current score in a game

3. 3. To represent a known value such as the number of days in a week

• 1 only

• 1 and 3 only

• 2 and 3 only

• 1, 2, and 3