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Key points

  • The ASCII character code uses 7 bits giving 128 possible characters. ASCII characters are stored in groups of 8 bits – the extra bit can be used for error checking.
  • ASCII stands for American Standard Code for Information Interchange and has been used as a standard character code by many computers for decades.


ASCII (American Standard Code for Information Interchange) is a binary code that represents the characters of the English alphabet, punctuation and some other symbols as numbers. ASCII is used with many devices - by using the same codes, devices can share and understand data.

Originally, ASCII used 7 bits. This meant there were a possible 128 characters. Since most computers were designed to use groups of 8 bits, the code was often grouped with a parity bit, used to check each character was not corrupt.

Extended ASCII extended the code to use 8 bits, giving 256 characters.

ASCII was superseded by Unicode though the two are compatible. The main reason that ASCII was replaced with Unicode was the use of languages other than English.

The program below converts characters to ASCII codes.

The ASCII code chart


Further information

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