1. Lesson Objectives Aims You should be able to:
Explain the use of binary to represent characters
Explain the term “Character set”
Describe the relationship between number of bits per character and amount of characters that can be represented
ASCII
Unicode

2. We know that computers work in binary
Therefore, computers don’t understand text
So it needs encoding – turning in to another form.

3. Text
All text, symbols, numbers, emoji’s (yes even those) are encoded
They form part of a “Character set”
A character set is simply a standard way of representing characters as numbers
E.g. A = 1, B = 2, C = 3….

4. Character sets
There are two main character sets you need to know for your exam:
ASCII (American Standard Code for Information Interchange)
Unicode
A character set means a computer can represent/display all recognised characters and symbols in that set

5. ASCII Binary Decimal Hexadecimal Character 110 0001 97 61 a 110 001098 62 b 99 63 c
100 64 d
101 65 e
102 66 f
103 67 g
104 68 h
105 69 i
106 6A j
107 6B k
108 6C l
109 6D m
110 6E n
111 6F o
112 70 p
113 71 q
114 72 r
115 73 s
116 74 t
117 75 u
118 76 v
119 77 w
120 78 x
121 79 y
122 7A z

6. 7 bit encoding (8th bit is parity) Advantages:
ASCII
7 bit encoding (8th bit is parity)
Advantages:
A standard method of communicating
Needs only 8 bits per character (1 byte)
Disadvantages
Can only represent 128 characters
Does not cater for other languages
Does not encode many symbols

7. A world wide standard for encoding characters
Unicode
A world wide standard for encoding characters
Designed to cover ALL languages and symbols in a standard way
Latest version (9) of Unicode contains:
More than 128,000 characters
135 languages and symbol sets

8. Unicode Advantages Disadvantages
Able to encode every possible character, number and symbol in any language past or present
16 bit (loosely, its actually 8 bit pairings (up to 32 bit) depending on standard used, but OCR keep saying 16 bit) vs 8 for ASCII
UTF 8 and UTF ,112,064 possible characters
UTF 8 fully compatible with ASCII
A unified, standard method of communication
Disadvantages
Requires more storage (bytes) per character than ASCII

9. January 2013 Q8b

12. January 2011 Q10