Hollerith card compatibility. A negative number on a punch card is indicated with a "11-row" overpunch.
Charles -----Original Message----- From: IBM Mainframe Discussion List [mailto:IBM-MAIN@LISTSERV.UA.EDU] On Behalf Of Paul Gilmartin Sent: Friday, August 4, 2017 8:54 AM To: IBM-MAIN@LISTSERV.UA.EDU Subject: "-0" (was: Someone just too smart ...?) On Fri, 4 Aug 2017 17:06:52 +0200, Bernd Oppolzer wrote: > >IMO, the case for the RFE could be >that programs that rely on the initialization of > >DCL SUM DEC FIXED (7) INIT (-0.1); > >with negative zero (X'0000000d') >should be flagged; this is bad practice, and I would like such >initializations to be flagged as ERROR (not only warning) and to be >told by the error message, that the initialization will be POSITIVE >zero from now on. (Losing decimal digits to the right of the decimal >point should only be a warning, IMO). > The designers of S/360 wisely avoided the "-0" silliness for fixed binary by choosing 2's complement ratner than the sign-magnitude used by the 7090. This also avoids the need for a recomplement cycle dependent on the sign of the result. It would have been wiser to make the packed representation 10's complement rather than sign-magnitude for similar reasons: o No "-0". o Five times the range in the same storage. o Never a need for a recomplement cycle. I am not much swayed by the opposing arguments: o FORTRAN II relied on "-0" to indicate a blank input field. o Sign-magnitude is more legible than complement in a dump. o Some theorems in numerical analysis depend on symmetric range. o Possible overflow complementing a numbe is harmful. ---------------------------------------------------------------------- For IBM-MAIN subscribe / signoff / archive access instructions, send email to lists...@listserv.ua.edu with the message: INFO IBM-MAIN
