3 ms·

> ASCII is a character set, it doesn't define the on-disk representation ASCII is an encoding, and sometimes people refer to the ASCII charset as "ASCII" too.

> ASCII is a character set, it doesn't define the on-disk representation ASCII is an encoding, and sometimes people refer to the ASCII charset as "ASCII" too. So it does define on-disk representation. A file with the leading 0s removed is no longer ascii-encoded. Similarly, a gzipped ASCII file is also no longer an ASCII file

mjg59 3y ago
What specification defines ASCII encoding as an 8-bit format?
- LegionMammal978 3y ago
  RFC 20 [0] defines an 8-bit "ASCII Format for Network Interchange". The older documents are careful to call it "network ASCII" or "ASCII-8" (or the related "NVT-ASCII" for TELNET), but some newer documents (e.g., [1], [2], or [3]) abbreviate the name to "ASCII" in the context of network interchange. (Though I don't mean to refute that "ASCII" or "7-bit ASCII" or especially "US-ASCII" can refer to rhe 7-bit codeset, only to note that the unqualified name has been overloaded to refer to 8-bit ASCII as well.) [0] https://www.rfc-editor.org/rfc/rfc20.html https://www.rfc-editor.org/rfc/rfc20.html [1] https://www.rfc-editor.org/rfc/rfc822.html https://www.rfc-editor.org/rfc/rfc822.html [2] https://www.rfc-editor.org/rfc/rfc3797.html#page-6 https://www.rfc-editor.org/rfc/rfc3797.html#page-6 [3] https://www.rfc-editor.org/rfc/rfc7997.html https://www.rfc-editor.org/rfc/rfc7997.html
  - mjg59 3y ago
    I'd argue that the need to provide a specification for ASCII as an 8-bit format is pretty strong evidence of the existence of ASCII in other formats :) Edit: to clarify, there's a spec for ASCII-as-8-bit-with-top-bit-clear, but it came some time after the ASCII spec and if someone needed to define that later it strongly suggests some people were doing it differently
  - SAI_Peregrinus 3y ago
    ASCII is standardized in (latest version) ANSI X3.4-1986, not by an internet RFC. That standard did not define an 8-bit encoding of ASCII, only a 7-bit encoding. That the IETF later called an 8-bit encoding ASCII just causes confusion. IMO they should have called it ISCII, for IETF Standard Code for Information Interchange.
    - LegionMammal978 3y ago
      The 8-bit "ASCII Format for Network Interchange" (generally called "network ASCII" or "net-ASCII" or similar in older RFCs) is defined in the very first paragraph of RFC 20: > For concreteness, we suggest the use of standard 7-bit ASCII embedded in an 8 bit byte whose high order bit is always 0. Meanwhile, ANSI X3.4-1986 defines the "7-Bit American National Standard Code for Information Interchange (7-Bit ASCII)". Even the older standard calls it the "USA Standard Code for Information Interchange", i.e., "US-ASCII". None of these standards define "ASCII". It's up to us to interpret "ASCII" as "7-bit ASCII" or "US-ASCII" or "network ASCII" or any other form of ASCII according to context; there is no monopoly on the unqualified term.

mjg59 3y ago

What specification defines ASCII encoding as an 8-bit format?

LegionMammal978 3y ago
RFC 20 [0] defines an 8-bit "ASCII Format for Network Interchange". The older documents are careful to call it "network ASCII" or "ASCII-8" (or the related "NVT-ASCII" for TELNET), but some newer documents (e.g., [1], [2], or [3]) abbreviate the name to "ASCII" in the context of network interchange. (Though I don't mean to refute that "ASCII" or "7-bit ASCII" or especially "US-ASCII" can refer to rhe 7-bit codeset, only to note that the unqualified name has been overloaded to refer to 8-bit ASCII as well.) [0] https://www.rfc-editor.org/rfc/rfc20.html https://www.rfc-editor.org/rfc/rfc20.html [1] https://www.rfc-editor.org/rfc/rfc822.html https://www.rfc-editor.org/rfc/rfc822.html [2] https://www.rfc-editor.org/rfc/rfc3797.html#page-6 https://www.rfc-editor.org/rfc/rfc3797.html#page-6 [3] https://www.rfc-editor.org/rfc/rfc7997.html https://www.rfc-editor.org/rfc/rfc7997.html
- mjg59 3y ago
  I'd argue that the need to provide a specification for ASCII as an 8-bit format is pretty strong evidence of the existence of ASCII in other formats :) Edit: to clarify, there's a spec for ASCII-as-8-bit-with-top-bit-clear, but it came some time after the ASCII spec and if someone needed to define that later it strongly suggests some people were doing it differently
- SAI_Peregrinus 3y ago
  ASCII is standardized in (latest version) ANSI X3.4-1986, not by an internet RFC. That standard did not define an 8-bit encoding of ASCII, only a 7-bit encoding. That the IETF later called an 8-bit encoding ASCII just causes confusion. IMO they should have called it ISCII, for IETF Standard Code for Information Interchange.
  - LegionMammal978 3y ago
    The 8-bit "ASCII Format for Network Interchange" (generally called "network ASCII" or "net-ASCII" or similar in older RFCs) is defined in the very first paragraph of RFC 20: > For concreteness, we suggest the use of standard 7-bit ASCII embedded in an 8 bit byte whose high order bit is always 0. Meanwhile, ANSI X3.4-1986 defines the "7-Bit American National Standard Code for Information Interchange (7-Bit ASCII)". Even the older standard calls it the "USA Standard Code for Information Interchange", i.e., "US-ASCII". None of these standards define "ASCII". It's up to us to interpret "ASCII" as "7-bit ASCII" or "US-ASCII" or "network ASCII" or any other form of ASCII according to context; there is no monopoly on the unqualified term.