Standardisation was earlier than that :-) ISO-646 is the 7-bit predecessor to the 8-bit ISO-8859. It dates back to the late 1960s. Like 8859, 646 has several variants, such as ISO-646-DE which has ß where ~ is in ascii. (The trigraphs in C are partly to work around transcoding issues between ISO-646 and EBCDIC variants.)