The ASCII standard has nothing to say about backspace overstriking - that would be something defined by a terminal, file format, or wire specification. In a more common example, ASCII has nothing to say about how you move the cursor to the start of a new line. Some terminal standards will do so on an LF, others just move the cursor down on LF; file and wire specs need to take a position on how they want to represent a line break; and now we get to the point where CRLF is a magic sequence needed to trigger a line break in some formats and it is completely unrelated to how a particular terminal behaves.