Chapter 9

Question 1

Define character set

Answer 1

A list of binary codes used by a computer to represent characters (eg. Text)

Question 2

What is ASCII and what does it stand for?

Answer 2

A character set
American Standard Code for Information Interchange

Question 3

How many unique characters could the original ASCII represent?

Answer 3

2^7 = 128

Question 4

How many bits were used in the original ASCII?

Answer 4

7

Question 5

What do the first 32 binary codes represent?

Answer 5

Formatting commands

Question 6

How to convert from ASCII to character in python

Answer 6

Chr()

Question 7

How to convert from character to ASCII?

Answer 7

Asc()

Question 8

Why was extended ASCII created and how many bits are used?

Answer 8

8 bits because computers think in a byte and it allows for more characters. - 2^8

Question 9

What is and why was Unicode created.

Answer 9

• Different companies used different character sets so a universal code was needed
• 256 codes were not enough
• Unicode uses 4 bytes and can represent 2^32 characters

Question 10

Why was ASCII created?

Answer 10

To make a universal code so all devices could understand each other.

Question 11

How are pictures stored digitally?

Answer 11

Stored as a bitmap - broken down into pixels. Each pixel colour is encoded into binary

Question 12

What is colour depth?

Answer 12

The number of bits used to encode the amount of red green and blue in each pixel.

Question 13

What is the total no of shades a colour depth can represent?

Answer 13

2^no bits

Question 14

How to find image file size

Answer 14

File size = pixel width x pixel height x colour depth/bits

Question 15

What is Metadata

Answer 15

Extra data about the file such as:

Resolution
Any edits
Owner
Date and time

Question 16

Disadvantages of analogue recordings

Answer 16

Difficult to transport
Can degrade
Hard to edit + copy
Limited storage

Question 17

Advantages of digital recordings

Answer 17

Easy to transport
Does not degrade
Cheap to edit+copy
Thousands of songs can be stored in a hard drive

Question 18

How are audio files recorded?

Answer 18

sound waves amplitude was sampled thousands of times a second and encoded into binary

Question 19

How to increase quality of a audio file?

Answer 19

Increasing the sample rate - the no of samples taken per second
Increasing Bit depth - the no of bits used to represent each sample

Question 20

What is the normal sample rate?

Answer 20

44.1KHZ

Question 21

How to calculate an audio file size

Answer 21

Audio file size = sample rate x bit depth x no. Channels x length/seconds

Question 22

How to increase resolution of an image

Answer 22

Increase no. Pixels

Question 23

Name 2 types of compression

Answer 23

Lossy
Lossless

Question 24

Define lossy compression

Answer 24

Decreasing file size by removing data. The data is not recoverable.

Question 25

Define Lossless compression

Answer 25

Reducing file size by removing redundancies

Question 26

What are redundancies

Answer 26

Repeated data

Question 27

Which type of compression do images and audio files undergo?

Answer 27

They are usually lossily compressed.
Image - reduce colour depth or no. Pixels
Audio - reduce sample rate, bit depth or no. Channels