Representing Text

Question 1

What is a character set?

Answer 1

a list of characters and the codes used to represent each one

Question 2

What does ASCII stand for?

Answer 2

American Standard Code for Information Interchange

Question 3

The original ASCII had how many bits?

Answer 3

7 for 128 unique characters

Question 4

How many control characters are there?

Answer 4

33

Question 5

How many bits does the “later/new” ASCII have?

Answer 5

8

Question 6

The first and last ____ of the ASCII are control characters/hidden characters

Answer 6

32

Question 7

Uppercase letters start when?

Answer 7

65

Question 8

Lowercase letters start when?

Answer 8

97

Question 9

What is the difference between the upper and lower case letters?

Answer 9

32

Question 10

Where is 0-9 coded consecutively?

Answer 10

48-57

Question 11

Where is A-Z coded consecutively?

Answer 11

65-90

Question 12

Where is a-z coded consecutively?

Answer 12

97-122

Question 13

What is Unicode?

Answer 13

superset of ASCII
- bigger character set than ASCII

Question 14

How many bits are in Unicode?

Answer 14

16

Question 15

True or False
In Unicode, 1-127 is the same as ASCII, but 128-255 are symbols and accented letters

Answer 15

True

Question 16

What is data compression?

Answer 16

It is a reduction in the amount of space needed to store a piece of data

Question 17

What is ratio compression?

Answer 17

It is the size of the compressed data divided by the size of the original data

Question 18

What are the 2 techniques for data compression?

Answer 18

1. Lossless
2. Lossy

Question 19

What does Lossless mean?

Answer 19

The data can be retrieved without any loss of the original information

Question 20

What does Lossy mean?

Answer 20

Some information may be lost in the process of compaction

Question 21

What are the 3 examples of techniques for data compression?

Answer 21

1. Keyword encoding
2. Run-length encoding
3. Huffman encoding

Question 22

Is Keyword encoding effective?

Answer 22

No, it is the least effective

Question 23

Which technique is good for compressing data with lots of spaces?

Answer 23

Run-length encoding

Question 24

Which example is the most effective?

Answer 24

Huffman encoding

Question 25

What are examples of Huffman encoding?

Answer 25

JPG, MP3, ZIP

Question 26

What does Keyword encoding refer to?

Answer 26

Words are replaced with a symbol

Question 27

What is the limitation rule to the Keyword encoding?

Answer 27

Symbols used cannot be in the original data

Question 28

What does Run-length encoding refer to?

Answer 28

Words with multiple instances of the same letters beside each other can use a number instead

Question 29

What does Huffman coding refer to?

Answer 29

The idea of Morse code - Only using a few bits to represent characters - Some characters will be represented by 5 bits and others by 6 bits

Question 30

Does the Huffman coding allow for ASCII?

Answer 30

No, it neglects it and uses a different number of bits, not 8

Question 31

What are the 4 steps in Huffman's Algorithm?

Answer 31

1. Count Frequencies 2. Sort in ascending order 3. Start merging the letter and number into a tree diagram 4. Label branches

Question 32

Typically, which branches are labelled with 0 and which are labelled with 1?

Answer 32

Left branch = 0 Right branch = 1

Question 33

For Huffman's Algorithm, what is our input?

Answer 33

symbols and their frequency counts

Question 34

For Huffman's Algorithm, what is our output?

Answer 34

binary code for each symbol

Question 35

For Huffman's Algorithm, what is our property?

Answer 35

optimum compression rate with the prefix property

Question 36

Where would we find the prefix property in the tree diagram?

Answer 36

displayed at the leaf node

Question 37

What is the optimum compression ratio?

Answer 37

merge the least frequent first and the most frequent last

Question 38

What is the compression's bit length?

Answer 38

sum of char-code length x frequency-count

Question 39

What are examples of run-length encoding?

Answer 39

white spaces in faxes