On Wed, 14 Sep 2016 15:34:32 -0500, Bill Woodger wrote: >When IBM decided to use "character" comparisons where possible for numerics, >they had to ban the negative zero.
They also had to enforce the preferred sign. Just as X'0C' and X'0D' would be equal using a CP instruction, they are also equal to X'0F', but they are not when performing a character compare. As to the idea that X'80000000' could be a negative zero, consider what happens when you add 1 to it. You get X'80000001'. Dave may indeed have had a loop that used a binary counter that started out negative and eventually reached X'80000000'. Someone at the time may have looked at and mistakenly thought that it was negative zero, but it would have in fact been the maximum negative number, and subtracting one again would have resulted in overflow. If the overflow was ignored, the value would then be X'7FFFFFFF'. It would take a while for that counter to reach zero. -- Tom Marchant ---------------------------------------------------------------------- For IBM-MAIN subscribe / signoff / archive access instructions, send email to lists...@listserv.ua.edu with the message: INFO IBM-MAIN
