Data storage: The term ‘character set’

The idea

A character set is a defined list of characters and the unique binary code assigned to each one. It allows a computer to convert between binary and text. For example, in ASCII the character A is code 65, which is 01000001 in 8-bit binary. The character set must be known by both the sender and receiver; otherwise the same binary code may be displayed as a different character. ASCII is a small character set, while Unicode is a much larger character set that includes characters from many languages and many symbols. The size of a character set affects how many bits are needed for each code.

What earns the marks

• A character set is a defined list of characters and their binary codes.
• Each character in a character set has a unique binary code.
• A character set is used to encode text into binary and decode binary back into text.
• ASCII is an example of a character set that uses 7 or 8 bits per character.
• Unicode is an example of a larger character set that uses more bits and can represent many more characters.
• If the wrong character set is used, the decoded text may contain incorrect characters.

Common mistakes and how to put them right

• Defining a character set as just a list of letters.

  Put it right: A character set includes letters, digits, punctuation and other symbols, each with a unique binary code.

• Thinking that a character set is the same as a font.

  Put it right: A character set defines binary codes for characters, while a font defines their visual appearance.

• Believing that ASCII and Unicode are the same.

  Put it right: ASCII is a smaller character set, while Unicode is a larger character set that can represent many more characters.

Exam tips

• Give a clear definition of character set and then give one example such as ASCII or Unicode.
• When explaining why a character set is needed, refer to encoding and decoding text.
• Use the term unique binary code when describing the code for each character.