AP - Computer Science Principles:: Data

What is a BIT, the most fundamental unit of digital information?

- **A)** A group of exactly 8 binary digits
- **B)** A single binary digit that can hold exactly one of two possible values: 0 or 1
- **C)** A synonym for an entire computer program
- **D)** A unit that can hold any one of 10 possible values (0-9)

What is a BYTE?

- **A)** A single binary digit (0 or 1)
- **B)** A group of exactly 1,000 bits
- **C)** A synonym for a pixel
- **D)** A group of 8 bits, commonly used as a standard unit for measuring data size

Why do computers represent ALL data (numbers, text, images, sound, video) using BINARY (0s and 1s), rather than some other number system?

- **A)** Computers are physically incapable of representing more than two total pieces of information ever
- **B)** Binary can only be used for representing whole numbers, never any other kind of data
- **C)** Digital electronic circuits can most easily and reliably distinguish between just two physical states (e.g., 'on/off' or 'high voltage/low voltage'), making binary a natural and robust fit for digital hardware
- **D)** Binary was chosen purely by historical accident and has no technical advantage over other systems

How many DIFFERENT values can be represented using a group of \(n\) bits?

- **A)** Exactly \(n\) different values
- **B)** \(2^n\) different values
- **C)** \(n^2\) different values
- **D)** \(10^n\) different values

How many different values can be represented using exactly 1 BYTE (8 bits)?

- **A)** \(8\)
- **B)** \(64\)
- **C)** \(16\)
- **D)** \(256\)

What is DATA COMPRESSION?

- **A)** Encoding data using FEWER bits than its original representation, in order to reduce file size for storage or transmission
- **B)** A process that always increases a file's total size
- **C)** A technique that only applies to text files, never to images, audio, or video
- **D)** A synonym for encryption

What is the difference between LOSSLESS and LOSSY data compression?

- **A)** LOSSLESS compression allows the original data to be perfectly reconstructed with NO information lost, while LOSSY compression permanently discards SOME information to achieve smaller file sizes, meaning the original cannot be perfectly recovered
- **B)** Lossless compression can only ever be applied to image files, never to any other data type
- **C)** Lossless and lossy compression always produce identical results with no meaningful difference
- **D)** Lossy compression always produces LARGER files than the original, uncompressed data

Why might LOSSY compression be considered ACCEPTABLE for a photograph, but generally NOT acceptable for a text document or computer program's source code?

- **A)** A photograph can often lose some fine visual detail while still looking acceptable to the human eye, but text or program code requires every single character to be EXACTLY correct -- even one incorrect character could change a word's meaning or make code fail to run
- **B)** Text documents are physically impossible to compress using any method
- **C)** Lossy compression is always equally acceptable for every single type of data, with no meaningful difference
- **D)** Photographs can never be compressed using any lossy technique