apcsp codehs stuff

What is **data abstraction**?

The process of simplifying complicated data into manageable chunks

Which of the following are examples of **encoding** information?

All of the above (Representing fast food meals as numbers on the menu. For example a number 1 represents a hamburger, Assigning a numeric value to every area of a region, for example zip codes in the United States, Assigning a number to every character of the alphabet so we can represent sentences as series of simple digits)

What is the **number base** of the binary number system?

2

In the binary value 1002, what is the place value of the **1**?

4s place

What is the value of 1410 in binary?

1110

How many bits are used to encode a character according to the ASCII encoding scheme?

8 bits \n (ex: 0100 0001 encodes ‘A’)

How many possible values can be created with only 2 bits?

4

What is a pixel?

A single tiny dot, or square, of color in a digital image.

What is the value of F16 in decimal?

15

What is the value of 9F16 in binary?

1001 1111

What are the 3 color channels that make up a pixel according to the RGB color scheme?

Red, Green, and Blue

What is the range of values (expressed in decimal) that each color channel can have?

0 - 255

Which of the following pixels has a color value of #ff0000 (expressed in hexadecimal)

Red

We want to write a brightness filter that brightens a given pixel.

R = min(R + 50, 255) G = min(G + 50, 255) B = min(B + 50, 255)

Which of the following describes the instructions for a general image filter?

Given an image: for every (x, y) coordinate in the image Get the current pixel at (x, y) Modify the pixel according to a function Update image at (x, y) with this modified pixel

Which of the following filter functions properly removes all green and blue from a pixel and returns the modified color tuple?

RED = 0 GREEN = 1 BLUE = 2 def remove_green_and_blue(pixel): new_green = 0 new_blue = 0 return (pixel\[RED\], new_green, new_blue)

Why do we compress data?

All of the above (To save memory space on devices, To speed up the time it takes to send a file over the internet, The computation it takes to decompress data is cheaper than the storage space required to store uncompressed data)

Which of the following is true about lossless data compression?

The compressed data can be restored back to its original state

We are going to compress this text using the Run Length Encoding compression algorithm:

WWWWWWHAAAAAAT??

Which of the following would be the proper compressed text?

W6H1A6T1?2

What types of data should be compressed with the Run Length Encoding algorithm? What types of data does the algorithm perform well with?

Text with many repeated characters

Which of the following is true about lossy compression?

All of the above (Lossy compression can compress data down to significantly less bits than lossless compression can, Data compressed with lossy compression cannot be restored back to its original state, Lossy compression throws away a lot of the original data, but humans can’t even tell anything is missing)

Which of the following are true about Public Key Encryption?

**I**: It requires all senders and receivers to have their own public key and their own private key \n **II**: A message encrypted with a person’s public key can only be decrypted with the same person’s private key \n **III**: A public key can be shared with anyone \n **IV**: Public key encryption is the most common form of encryption for internet communication

**I**, **II**, **III**, and **IV**

Which of the following are true about Symmetric Key Encryption?

**I**: The same key is used for both encryption and decryption \n **II**: The sender and receiver must exchange a shared key in private before using symmeric key encryption to communicate \n **III**: Symmetric key encryption is the most common form of encryption for internet communication

**I** and **II** only

Which of the following statements are true about Caesar’s Cipher?

**I**: Caesar’s Cipher is a form of Symmetric Encryption \n **II**: Caesar’s Cipher is a “hard” encryption to crack

**I** only

Which number system is used to store information digitally in a computer?

Binary (base 2)

\
How many different digits are used in the Hexadecimal number system?

16

\
What is the decimal value of 1101(2)?

13

How many different values can be represented using 4 bits?

16 different values

Suppose the ESPN website uses 8-bit unsigned integers to store how many points a team has scored in an NBA game. \n For example: \n 0000 0010 represents 2 points \n 0000 1000 represents 8 points

What is the highest possible score the ESPN website could display?

255(10)

A news website uses 32-bit integers to count the number of times an article has been viewed.

The website is becoming more popular, and expects some of the articles to exceed the number of views that can be represented with 32 bits. In anticipation of this, the website is planning to change to 64-bit integers for the view counter.

Which of the following best describes the result of using 64-bit integers instead of 32-bit integers?

2^32 times as many values can be represented

ASCII characters can also be represented by hexadecimal (base 16) numbers. According to the ASCII character encoding, which of the following characters is represented by the hexadecimal (base 16) number 6E(16)

n

Which ASCII character is represented by the decimal (base 10) number 72?

H

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.

A student is transferring photos from her camera to her computer. The student notices that the saved photos on her computer are lower quality than the original raw photo on her camera.

Which of the following could be a possible explanation for the difference in image quality?

The saved image files were compressed with a lossy compression technique.

Consider the following numbers:

* The decimal value 1010
* The binary value 10012
* Hexadecimal value C16

Which of the following lists the numbers in order from least to greatest?

1001(2), 10(10), C(16)

An online store uses 8-bit binary values to identify each unique item for sale. The store plans to increase number of items it sells and is considering changing to 9-bit binary values.

Which of the following best describes the result of using 9-bit values instead of 8-bit values?

2 times as many items can be uniquely identified

A computer program uses 3 bits to represent integers. When the program adds the decimal (base 10) numbers 6 and 2, the result is 0. Which of the following is the best explanation for this result?

An overflow error occurred.

The RGB encoding scheme encodes a color using 24 bit sequences. The first 8 bits encode the amount of red in the color, the next 8 bits encode the amount of green in the color, and the last 8 bits encode the amount of blue in the color.

Which of the following is a true statement about the color encoded by this binary sequence:

1110 1001 0111 1100 0000 1111

This color is mostly red.

RED = 0 GREEN = 1 BLUE = 2 def filter(pixel): pixel\[RED\] = 255 - pixel\[RED\]; pixel\[GREEN\] = 255 - pixel\[GREEN\]; pixel\[BLUE\] = 255 - pixel\[BLUE\]; return (pixel\[RED\], pixel\[GREEN\], pixel\[BLUE\])

Which of the following best describes the result of applying this filter to every pixel in the image?

The image will be inverted, bright pixels will become dark and dark pixels will become bright.

What is the range of numbers for the ASCII Code Chart?

65 - 122

How many non letter characters are in between the upper case and lower case ASCII Code Chart characters?

6 (90 - 96)

Does upper case or lower case come first in the ASCII Code Chart?

Upper case

How do you convert from decimal to binary?

Write it out, write out the bases of 2s for the binary system up until it exceeds the amount in decimal form, subtract by each, put a 1 if it can be put a 0 if it can’t be.

How do you convert from binary to decimal?

Write it out, write out the bases of 2s for the binary system under it, multiply the 1s by the number under them, add them together

How do you convert from hexadecimal to decimal?

Write it out, write the bases of 16s for the hexadecimal system (1, 16, 256, etc.), multiply the number/letter by the number under it, add them together

What are the numbers in the hexadecimal system?

0, 1, 2, 3, 4, 5, 6, 7, 8, 9, A, B, C, D, E, F