Representing Characters Edexcel

7-Bit ASCII

What is a character set?

• A character set is a defined list of characters that can be understood by a computer 

• Each character is given a unique binary code

• Character sets are ordered logically, the code for ‘B’ is one more than the code for ‘A’

• A character set provides a standard for computers to communicate and send/receive information

• Without a character set, one system might interpret 01000001 differently from another

• The number of characters that can be represented is determined by the number of bits used by the character set

• Two common character sets are:

  • American Standard Code for Information Interchange (ASCII)

  • Universal Character Encoding (UNICODE)

What is ASCII?

• ASCII is a character set and was an accepted standard for information interchange

• ASCII uses 7 bits, providing 2⁷ unique codes (128) or a maximum of 128 characters it can represent

• ASCII only represents basic characters needed for English, limiting its use for other languages

Limitations of ASCII

• ASCII has a limited number of characters which means it can only represent the English alphabet, numbers and some special characters

  • A, B, C, ………, Z

  • a, b, c ,………….,z

  • 0, 1, 2,…….., 9

  • !, @, #, …..

• ASCII cannot represent characters from languages other than English

• ASCII does not include modern symbols or emojis common in today’s digital communication

What is UNICODE?

• UNICODE is a character set and was created as a solution to the limitations of ASCII

• UNICODE uses a minimum of 16 bits, providing 2¹⁶ unique codes (65,536) or a minimum of 65,536 characters it can represent

• UNICODE can represent characters from all the major languages around the world