Comp Sci Unit 1
Which of the following best explains how an analog audio signal is typically represented by a computer?
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
Which of the following would result in a better digital approximation of an analog black and white image?
Decreasing the size of each sample square, thus increasing the number of samples taken.
Which of the following is a true statement about data compression?
There are trade-offs involved in choosing a compression technique for storing and transmitting data.
The image below shows an encoding for a black and white pixel image. The first two bytes of the data (circled in red) are used to encode the width and height of the image. What is the best term for this type of "data about the data"?
metadata
An artist makes an RGB raster image in which each pixel color is encoded with 12-bits --- 4 bits each for red, green and blue. Which of the following correctly shows the hexadecimal value for Red as a 12-bit representation?
111100000000
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?
2^32 times as many
How many bytes (or bits) are required to encode an image that is 25 pixels wide and 50 pixels tall, if you encode each pixel with 3 bytes (24 bits) of RGB data. (Don't forget to add in the metadata! -- you should assume that we are using the file format used in this lesson with metadata that had 1 byte each for width, height and bits-per-pixel.
3,753 bytes (30,024 bits)
Your computer uses 6 bits to represent decimal numbers (0, 1, 2, 3 and so on) in binary. What is the SMALLEST number for which an overflow error occur?
64
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?
9
Which of the following is an advantage of a lossless compression algorithm over a lossy compression algorithm?
A lossless compression algorithm can guarantee reconstruction of original data, while a lossy compression algorithm cannot.
Which of the following actions is most likely to raise legal or ethical concerns?
A musician creates a song using samples of a copyrighted work and then uses a Creative Commons license to publish the song.
Consider the following numeric values. Binary 1011 Binary 1101 Decimal 5 Decimal 12 Which of the following lists the values in order from least to greatest?
A. Decimal 5, binary 1011, decimal 12, binary 1101
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?
A. The song was saved using fewer bits per second than the original song.
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?
An overflow error will occur because 4 bits is not large enough to represent 29, the sum of 14 and 15.
A user wants to save a data file on an online storage site. The user wants to reduce the size of the file, if possible, and wants to be able to completely restore the file to its original version. Which of the following actions best supports the user's needs?
Compressing the file using a lossless compression algorithm before uploading it
Which of the following best describes the impact of Creative Commons?
Creative Commons gives creators of digital content the ability to indicate how their works can be legally used and distributed, enabling broad access to digital information.
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 enough to store the eight directions.
The author of an e-book publishes the e-book using a no-rights-reserved Creative Commons license. Which of the following best explains the consequences of publishing the book with this type of license?
Individuals can freely distribute or use the contents of the e-book without needing to obtain additional permissions from the author.
A programmer is developing software for a social media platform. The programmer is planning to use compression when users send attachments to other users. Which of the following is a true statement about the use of compression?
Lossy compression of an image file generally provides a greater reduction in transmission time than lossless compression does.
Which statement about analog and digital images is true
Sampling an analog image more frequently produces a digital image with a better representation
Assume your friend just sent you 32 bits of pixel data (just the 0s and 1s for black and white pixels) that were encoded after sampling an image. Choose the two statements that are true
The correct width and height must be input into the pixelation widget to produce the image. The fact that only 32 bits were used to represent the image indicates relatively large sample squares were used. The digital image may vary from the analog image significantly.
What is the most important quality of lossless compression?
The data is transformed to usually make it smaller. It can always be re-constructed back to the origina
The position of a runner in a race is a type of analog data. The runner's position is tracked using sensors. Which of the following best describes how the position of the runner is represented digitally?
The position of the runner is sampled at regular intervals to approximate the real-word position, and a sequence of bits is used to represent each sample.
In a certain computer program, two positive integers are added together, resulting in an overflow error. Which of the following best explains why the error occurs?
The program can only use a fixed number of bits to represent integers; the computed sum is greater than the maximum representable value.
A programmer created a piece of software and wants to publish it using a Creative Commons license. Which of the following is a direct benefit of publishing the software with this type of license?
The programmer can specify the ways that other people are legally allowed to use and distribute the software.
What are true statements about the data that can be represented using binary sequences?
binary sequences can be used to represent strings of characters binary sequences can be used to represent colors binary sequences can be used to represent audio recordings
Each time we add another bit, what happens to the amount of numbers we can make?
it doubles
The colors of the pixels in a digital image are often represented by red, green, and blue values between 0 and 255 (an RGB triplet). A photographer is manipulating a digital image to lighten it because all of the RGB values in the image are less than 100, making it very dark. He does this by adding 20 to the R, G, and B values of each pixel, then overwriting the original image. What type of transformation is the photographer using on the digital image?
lossless
A compression scheme for long strings of bits called run-length encoding is described as follows:Rather than record each 0 and 1 individually, instead record "runs" of bits by storing the number of consecutive 1s and 0s that appear.Since it's binary, any run of 0s must be followed by a run of 1s (even if the run is only 1-bit long) and vice versa. Thus, you can store a list of small numbers that represents the alternating runs of 0s and 1s. Below is an example: To uncompress the data back into its original binary state, you simply reverse the process. This technique is an example of what type of compression?
lossless compression
A raw digital sound file samples a sound wave at some interval and measures the height of the wave at each point. Thus, raw sound is recorded as a list of numbers. In very broad terms the MP3 audio compression algorithm identifies frequencies and volume levels - low and high - that are outside the range of human hearing and removes the data representing these frequencies from the original. This technique results in a smaller audio file that sounds exactly the same to the human ear. This technique is an example of what type of compression?
lossy compression
