Chapter 9 - Binary Representations

Question 1

Why was ASCII invented?

Answer 1

All companies before ASCII sent data using different codes

Question 2

What is a character set?

Answer 2

A list of binary codes that can be recognised by computers as being useable characters

Question 3

How to convert between character to its ASCII code in python?

Answer 3

Print(ord(‘d’)

Question 4

How to convert between ASCII to character in python

Answer 4

Print(chr(67))

Question 5

How many bits was the original ASCII character set?

Answer 5

7-bit or 2**7

Question 6

How many bits was the extended ASCII character set?

Answer 6

8-bit or 2**8

Question 7

Why was UNICODE invented?

Answer 7

Different companies created different extended ASCII charcetr sets and 256 codes (2**8) wasn’t enough

Question 8

What is UNICODE

Answer 8

A character set incorporating ASCII, extended ASCII and, with 4 bytes per code, enough for 2**32 = 4.3 billion characters

Question 9

What does a digital camera do with a snapshot?

Answer 9

breaks it down into pixels (picture elements)

Question 10

What is the formula for the total number of pixels

Answer 10

total number of pixels = width x height

Question 11

What does the higher resolution of a camera do?

Answer 11

Makes the image clearer

Question 12

What is each pixels colour encoded into binary dependant on?

Answer 12

the colour depth

Question 13

What is colour depth?

Answer 13

The number of bits used to encode the amount of Red, Green and Blue in a pixels colour

Question 14

What is a common colour depth?

Answer 14

3 bytes ( 1 for red, 1 for green and 1 for blue)

Question 15

What is the total number of shades a particular colour depth can represent?

Answer 15

2**number of bits

Question 16

What is the calculation for total graphic file size?

Answer 16

Total graphic file size = pixel width x pixel height x colour depth

Question 17

What is metadata?

Answer 17

Data about data

Question 18

Give examples of metadata

Answer 18

Data & time photo was taken
The make, model, etc. of the camera
Location where photo taken
Any edits done to photo
Owner of photo

Question 19

What are some disadvantages of analogue recordings

Answer 19

Bulky, degraded, hard to edit, limited storage capacity and hard to copy

Question 20

What does bulky mean?

Answer 20

the cassette or record was large and cumbersome to transport

Question 21

What does degraded mean?

Answer 21

if handled poorly, record could scratch and cassettes could be wiped by magnets

Question 22

What does hard to edit mean?

Answer 22

Without expensive equipment, people couldn’t edit music or create musicL

Question 23

What does limited storage capacity mean?

Answer 23

A record could store around 40 minutes of audio and a cassette could store about 80 minutes

Question 24

What does hard to copy mean?

Answer 24

Only expensive equipment could do that

Question 25

How do you work our audio file size?

Answer 25

Audio file size = song duration in seconds x sampling frequency x bit depth x number of channels

Question 26

What is a low sample rate?

Answer 26

20kHz or sample rate of 20,000 times a second

Question 27

What is a high sample rate?

Answer 27

40kHz or sample rate of 40,000 times a second

Question 28

What is normal audio recording sample rate?

Answer 28

44.1kHz

Question 29

What frequencies can the human ear hear up to?

Answer 29

20kHz

Question 30

What frequencies can a 20kHz sample rate capture

Answer 30

10kHz

Question 31

What frequencies can a 40kHz sample rate capture

Answer 31

20kHz

Question 32

What are the advantages of digital audio?

Answer 32

-Easy to transport digital audio
-Cheap to edit n copy
-Doesn’t degrade
-Thousands of songs stored on a hard drive or cloud
-Easy for artists to get their music “out there”

Question 33

What are the two ways of reducing the size of a file

Answer 33

Lossy compression & Lossless compression

Question 34

What does Lossy compression do?

Answer 34

Decreases the file size by removing some of the data, the original graphic or audio file can never be reconstituted from a loosily compressed file

Question 35

What does lossless compression do?

Answer 35

it decreases the file size by removing redundancies

Question 36

What is a redundancy?

Answer 36

Data in a file that is repeated (e.g. blocks of colour in a graphic, or repeated words in a text file.” Text files are never compressed with lossy compression otherwise letter or formatting would be lost and text wouldn’t make sense. Text file sizes can be reduced with lossless compression by creating a look up table and keys