1. ASCII
American Standard Code for Information Interchange
o The ASCII system was introduced to ensure that all computers use the same binary
patterns to represent the computers character set.
o ASCII gives each character a unique number that can easily be changed into a binary
pattern.
 e.g. A = 65 = 1000001
o The ASCII system standardises text files making them more compatible with a wider
range of computer systems.
o ASCII is a 7-bit system which enables 128 binary patterns to be available to represent
128 different characters.
o 32 of these binary patterns are set aside for control characters, e.g. cursor keys.
Extended ASCII
o This system is an 8-bit system and allows the system to store up to 256 different
characters.
Unicode
Unicode is a 16-bit system, supporting 65,636 different characters.
Unicode is used in countries like Japan, because of the number of characters in their
alphabet.
Advantages of Unicode
Unicode is a 16-bit system which can support many more characters than ASCII.
The first 128 characters are the same as the ASCII system making it compatable.
There are 6400 characters set aside for the user or software.
There are still characters which have not been defined yet, future-proofing the
system.
Disadvantage of Unicode
Unicode files are very large because it takes 2 bytes to store each character.