1.2 Part 2 (Characters, Images, Sound, Compression)

Question 1

Character set

Answer 1

A defined list of characters recognised by a computer hardware/software, with each character being represented by a binary code

they are agreed standards

Question 2

What is each character represented by?

Answer 2

A unique binary number

Question 3

What are some well-known character sets?

Answer 3

ASCII, Extended ASCII, Unicode

Question 4

What is the formula for the number of unique binary combinations?

Answer 4

2 to the power of n, whereas n is the number of bits per character, and 2 are the 0s and 1s in binary

Question 5

How many bits does ASCII have per character?

Answer 5

n = 7, 128 characters

Question 6

How many bits does Extended ASCII have per character?

Answer 6

n = 8, 256 characters

Question 7

How many bits does Unicode have per character?

Answer 7

n = 24, >16 million characters

Question 8

Which number of ASCII started showing the recognisable part of the character set?

Answer 8

32

Question 9

What is the need for Unicode?

Answer 9

We want a fully international and multilingual character set that includes thousands of characters and special symbols

Question 10

What is the limitation of writing binary in Unicode?

Answer 10

Writing in 24 bits is slow, cumbersome and error prone, so hexadecimal is used as an alternative

Question 11

What affects the overall quality of a digitally converted sound wave and its file size?

Answer 11

The sample rate and the bit depth

Question 12

What is the sample rate?

Answer 12

How often you record the amplitude of a sound wave

How often per second we are sampling the original analogue sound

The more often you record a sample the smoother the playback will sound

Question 13

What is the bit depth?

Answer 13

The amount of detail we’re capturing with each sample

Question 14

What is the formula for calculating the file size of a sound file?

Answer 14

sample rate (Number of samples per second) x bit depth (Number of bits in sample) x duration (Length of sample in seconds)

Question 15

What is the sound file size represented in?

Answer 15

Bits

Question 16

What are the 2 ways of storing images in binary?

Answer 16

Bitmaps and Vectors

Question 17

How do bitmaps represent images?

Answer 17

Different coloured squares, with each square having a unique binary value

Question 18

How do vectors represent images?

Answer 18

The mathematics to store

Question 19

What images are appropriate to be stored as bitmaps/vectors?

Answer 19

Bitmaps: images not made of simple shapes
Vectors: Technical drawings, clip art, and logos

Question 20

What is metadata and what are some of its examples?

Answer 20

Additional data stored with the image to define information such as:
Height of image
Width of image
Color depth

Question 21

What is color depth?

Answer 21

Number of bits needed to store each pixel

Question 22

How many bits per pixel is used in modern color depth?

The modern color depth is at an agreed standard

Answer 22

24 bits, so over 16 million colors, as many as the human eye can see

Question 23

What is the limitation of representing colors using binary in the modern color depth?

Answer 23

Representing these 24-bit colors can be cumbersome and error prone, so a 6 digit hexadecimal representation is used

Question 24

What is the need for compression?

Answer 24

Compression reduces the size of a file so it takes up less space
It maximises the amount you can store on a device
Smaller file sizes are quicker to download and stream over networks

Question 25

What is lossy compression?

Answer 25

Storing a lower number of colors or storing bigger areas of pixels as 1 color (JPEG & GIF)

Question 26

What are the effects of lossy compression?

Answer 26

Loss of quality is not too noticable
An acceptable compromise of quality vs file size and download time

Question 27

What is lossless compression?

Answer 27

Allows the original data to be perfectly reconstructed from the compressed data with no loss of data.

Question 28

What do lossy and lossless compression work well on?

Answer 28

Lossy: images, sound and videos
Lossless: documents, code and images with repeating colors