The first version of ECMA-6 had been published in 1965,[4] based on work the ECMA's Technical Committee TC1 had carried out since December 1960.

[5] Since that portion of ISO/IEC 646, that is the invariant character set shared by all countries, specified only those letters used in the ISO basic Latin alphabet, countries using additional letters needed to create national variants of ISO/IEC 646 to be able to use their native scripts.

ISO/IEC 646 and its predecessor ASCII (ASA X3.4) largely endorsed existing practice regarding character encodings in the telecommunications industry.

Among these exercises, ISO 646:1991 IRV (International Reference Version) is explicitly defined and identical to ASCII.

[6] The ISO/IEC 8859 series of standards governing 8-bit character encodings supersede the ISO/IEC 646 international standard and its national variants, by providing 96 additional characters with the additional bit and thus avoiding any substitution of ASCII codes.

The cells with non-white background emphasize the differences from US-ASCII (also the Basic Latin subset of ISO/IEC 10646 and Unicode).

This is attested in the code charts for IRV, GB, FR1, CA, and CA2, which note that "',^ would behave as the diaeresis, acute accent, cedilla, and circumflex (rather than quotation marks, a comma, and an upward arrowhead) when preceded or followed by a backspace.

This encoding method originated in the typewriter/teletype era when use of backspace would overstamp a glyph, and may be considered deprecated.

The National Replacement Character Set (NRCS) is a family of 7-bit encodings introduced in 1983 by DEC with the VT200 series of computer terminals.

[92] Some 7-bit character sets for non-Latin alphabets are derived from the ISO/IEC 646 standard: these do not themselves constitute ISO/IEC 646 due to not following its invariant code points (often replacing the letters of at least one case), due to supporting differing alphabets which the set of national code points provide insufficient encoding space for.