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SESK: Stuff Everyone Should Know · sesk.info/tech-ascii-seven-bits

How many bits does standard ASCII use for each character?

7 bits, which gives 128 characters.

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  1. 7 bits ✔
  2. 8 bits
  3. 16 bits

Why: ASCII is a 7-bit code, so it has 128 codes covering English letters, digits, punctuation and control codes. It is usually stored in an 8-bit byte with the top bit set to 0.

Huh, didn't know that: RFC 20, published in October 1969, proposed 7-bit ASCII inside 8-bit bytes for network interchange.

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Why did the ASCII character go to therapy? It had too many control issues.
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References

Answer: 7 bits. ASCII is a 7-bit code, so it has 128 codes covering English letters, digits, punctuation and control codes. It is usually stored in an 8-bit byte with the top bit set to 0.

  1. RFC 20: ASCII format for Network Interchange www.rfc-editor.org/rfc/rfc20.txt
    we suggest the use of standard 7-bit ASCII embedded in an 8 bit byte whose high order bit is always 0
    Checked 2026-10-10.

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