IBM 1620 invalid character symbol

Philippe Verdy via Unicode unicode at
Tue Sep 26 13:24:21 CDT 2017

The doc designate those characters as negative digits. They are used during
numeric processing as well and then refered to as "-1".. "-9" and explcitly
says it is a negative sign

2017-09-26 17:53 GMT+02:00 Ken Whistler <kenwhistler at>:

> Philippe,
> Those aren't negative digits, per se. The usage in the manual is with an
> overline (or macron) to indicate the flag bit. It does occur over a zero,
> and in explanation in the text of floating point operations, it is also
> shown over letters (X, M, E) representing digits of the exponent and
> mantissa. See p. 27 (31 of the pdf) in that same manual, for an extensive
> discussion with lots of examples in the text:
> CPU_Model_1_Jul65.pdf
> The Unicode representation of the text material printed on that page would
> best be done with a combining macron, I think.
> --Ken
> On 9/26/2017 6:34 AM, Philippe Verdy via Unicode wrote:
> But what is interesting is the use of negative digits (-1 to -9, with the
> minus sign above the digit; I've not seen a case of minus 0, not needed
> apparently by the described operations)
> How do you encode these negative decimal digits in Unicode ? with a macron
> diacritic ?
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