AP Computer Science Principles Scoring Guide
Review for Quiz 1
1. ASCII is a character-encoding scheme that uses 7 bits to represent each character. The decimal (base 10) values 65 through 90 represent the capital letters A through Z, as shown in the table below.
What ASCII character is represented by the binary (base 2) number 1001010 ?
A H
B I
C J
D K
2. What is the best explanation for why digital data is represented in computers in binary?
Copyright © 2017. The College Board. These materials are part of a College Board program. Use or distribution of these materials online or in print beyond your school’s participation in the program is prohibited. Page 1 of 7 AP Computer Science Principles Scoring Guide
Review for Quiz 1
The binary number system is the only system flexible enough to allow for representing A data other than numbers.
It typically takes fewer digits to represent a number in binary when compared to other B number systems (for example, the decimal number system)
It's impossible to build a computing machine that uses anything but binary to represent C numbers
It's easier, cheaper, and more reliable to build machines and devices that only have to D distinguish between binary states.
3. Which best describes a bit?
A binary number, such as 110
A rule governing the exchange or transmission of data between devices.
A single 0 or a 1
Time it takes for a number to travel from its sender to its receiver
4. A student is recording a song on her computer. When the recording is finished, she saves a copy on her computer. The student notices that the saved copy is of lower sound quality than the original recording. Which of the following could be a possible explanation for the difference in sound quality?
Copyright © 2017. The College Board. These materials are part of a College Board program. Use or distribution of these materials online or in print beyond your school’s participation in the program is prohibited. Page 2 of 7 AP Computer Science Principles Scoring Guide
Review for Quiz 1
A The song was saved using fewer bits per second than the original song.
B The song was saved using more bits per second than the original song.
C The song was saved using a lossless compression technique.
Some information is lost every time a file is saved from one location on a computer to D another location.
5. What is the minimum number of bits you would need to encode 51 different colors?
5 bits
6 bits
7 bits
8 bits
6. A video-streaming Web site uses 32-bit integers to count the number of times each video has been played. In anticipation of some videos being played more times than can be represented with 32 bits, the Web site is planning to change to 64-bit integers for the counter. Which of the following best describes the result of using 64-bit integers instead of 32-bit integers?
Copyright © 2017. The College Board. These materials are part of a College Board program. Use or distribution of these materials online or in print beyond your school’s participation in the program is prohibited. Page 3 of 7 AP Computer Science Principles Scoring Guide
Review for Quiz 1
A 2 times as many values can be represented.
B 32 times as many values can be represented.
C 232 times as many values can be represented.
D 322 times as many values can be represented.
7. Which is the best definition for bandwidth?
A set of rules governing the exchange or transmission of data between devices.
Time it takes for a bit to travel from its sender to its receiver.
The number of bits that are conveyed or processed per unit of time. e.g. 8 bits/sec.
Transmission capacity measure by bit rate
8. 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?
Copyright © 2017. The College Board. These materials are part of a College Board program. Use or distribution of these materials online or in print beyond your school’s participation in the program is prohibited. Page 4 of 7 AP Computer Science Principles Scoring Guide
Review for Quiz 1
A 2 more items can be uniquely identified.
B 10 more items can be uniquely identified.
C 2 times as many items can be uniquely identified.
D 10 times as many items can be uniquely identified.
9. Which is the best definition for latency?
A set of rules governing the exchange or transmission of data between devices.
Time it takes for a bit to travel from its sender to its receiver.
the number of bits that are conveyed or processed per unit of time. e.g. 8 bits/sec.
Transmission capacity measure by bit rate
10. Which of the following is NOT an example of a binary question?
When is your birthday?
Which do you prefer: Coke or Pepsi?
Do you want to go to the store today?
Do you like math or history better?
Copyright © 2017. The College Board. These materials are part of a College Board program. Use or distribution of these materials online or in print beyond your school’s participation in the program is prohibited. Page 5 of 7 AP Computer Science Principles Scoring Guide
Review for Quiz 1
11. What is the 5-bit binary number for the decimal number twenty-six (26)?
A 10010
B 11010
C 10110
D 10101
12. Which word best fits the following definition: A set of rules governing the exchange or transmission of data between devices.
Bandwidth
Bit rate
Latency
Protocol
13. Number systems with different bases such as binary (base-2) and decimal (base-10) are all used to view and represent digital data. Which of the following is NOT true about representing digital data?
Copyright © 2017. The College Board. These materials are part of a College Board program. Use or distribution of these materials online or in print beyond your school’s participation in the program is prohibited. Page 6 of 7 AP Computer Science Principles Scoring Guide
Review for Quiz 1
Some large numbers cannot be represented in binary and can only be represented in A decimal.
Groups of bits can be used to represent abstractions, including but not limited to numbers B and characters.
The same value (number) can have a different representation depending on the number C system used to represent it.
At one of the lowest levels of abstraction, all digital data can be represented in binary D using only combinations of the digits zero and one
14. 5 bits is enough to represent 32 different numbers. How many bits do you need to represent twice as many numbers (64)?
6
7
10
11
15. Which is the best definition for bit rate?
A set of rules governing the exchange or transmission of data between devices.
Time it takes for a bit to travel from its sender to its receiver.
the number of bits that are conveyed or processed per unit of time. e.g. 8 bits/sec.
Transmission capacity measure by bit rate
Copyright © 2017. The College Board. These materials are part of a College Board program. Use or distribution of these materials online or in print beyond your school’s participation in the program is prohibited. Page 7 of 7