That rule would be compiler specific, while the FACE / BD is Pack Decimal specific (mainframe / ?other?).
On Mon, Apr 28, 2025 at 11:41 AM Phil Smith III <[email protected]> wrote: > Ah, so the "unsigned" thing is COBOL-specific? That would explain the > confusion/varied answers! > > Heh, "FACE positive, B&D negative" sounds more like something from a NSFW > discussion...(it's Friday, right? Somewhere?) > > -----Original Message----- > From: IBM Mainframe Discussion List <[email protected]> On Behalf > Of Schmitt, Michael > Sent: Monday, April 28, 2025 12:33 PM > To: [email protected] > Subject: Re: Packed decimal sign nibbles > > Same here: F A C E are positive, B & D are negative. > > The machine doesn't have an "unsigned" packed sign nybble. It is either > positive or negative. So "F" is positive as a sign nybble, or it is the > "zone" in other positions in a zoned decimal number. > > "F" is unsigned, however, in IBM Enterprise COBOL for z/OS: when you > compile with NUMPROC(PFD) it is *very* strict: there are only three valid > signs: > > C: positive > D: negative > F: unsigned > > If all your code has preferred signs then it can generate more efficient > code, by using CLC and MVC for example instead of packed decimal > instructions. > > > -----Original Message----- > From: IBM Mainframe Discussion List <[email protected]> On Behalf > Of Phil Smith III > Sent: Monday, April 28, 2025 11:26 AM > To: [email protected] > Subject: Re: Packed decimal sign nibbles > > Ok, well, in 1975 I was still in high school and playing games on VM over > dialup, didn't start my mainframe career until 1980. But the question > stands: what's with these "unpreferred" values? Why would they even > exist/be valid? > > -----Original Message----- > From: IBM Mainframe Discussion List <[email protected]> On Behalf > Of Lennie Bradshaw > Sent: Monday, April 28, 2025 12:21 PM > To: [email protected] > Subject: Re: Packed decimal sign nibbles > > That's exactly as I was taught in about 1975. > Lennie > > -----Original Message----- > From: IBM Mainframe Discussion List <[email protected]> On Behalf > Of Phil Smith III > Sent: 28 April 2025 17:17 > To: [email protected] > Subject: Packed decimal sign nibbles > > A friend asked me about packed decimal sign nibbles, specifically x'0F'. I > said "Unsigned" was what I'd always been told. He said he was finding > varied answers, and then pointed me at SA22-7832-03 (PofOp, but an old > version from 2004) where, on page 8-2 (PDF page 1150) is the following > table. It displays correctly in monospace font, so hopefully you can read > it: > > Recognized As > Code > (Binary) Digit Sign > -------- ------- ------- > 0000 0 Invalid > 0001 1 Invalid > 0010 2 Invalid > 0011 3 Invalid > 0100 4 Invalid > 0101 5 Invalid > 0110 6 Invalid > 0111 7 Invalid > 1000 8 Invalid > 1001 9 Invalid > 1010 Invalid Plus > 1011 Invalid Minus > 1100 Invalid Plus (preferred) > 1101 Invalid Minus (preferred) > 1110 Invalid Plus > 1111 Invalid Plus (zone) > > X'0A'? X'0B'?? X'0E'??? I'd only ever heard of x'0C', x'0D', and sometimes > x'0F'. Is it just me? I certainly don't claim to be Mr. Packed Decimal, but > I have encountered it off and on over the last 45 years, so I was very > surprised. > > I do see the discussion of "zones" in that section of the book, but that > doesn't clarify for me because zones have always been a mystery to > me--never needed to grok them. And it still doesn't explain the other > values. > > ---------------------------------------------------------------------- > For IBM-MAIN subscribe / signoff / archive access instructions, send email > to [email protected] with the message: INFO IBM-MAIN > > ---------------------------------------------------------------------- > For IBM-MAIN subscribe / signoff / archive access instructions, send email > to [email protected] with the message: INFO IBM-MAIN > > ---------------------------------------------------------------------- > For IBM-MAIN subscribe / signoff / archive access instructions, send email > to [email protected] with the message: INFO IBM-MAIN > > ---------------------------------------------------------------------- > For IBM-MAIN subscribe / signoff / archive access instructions, send email > to [email protected] with the message: INFO IBM-MAIN > > ---------------------------------------------------------------------- > For IBM-MAIN subscribe / signoff / archive access instructions, > send email to [email protected] with the message: INFO IBM-MAIN > -- Mike A Schwab, Springfield IL USA Where do Forest Rangers go to get away from it all? ---------------------------------------------------------------------- For IBM-MAIN subscribe / signoff / archive access instructions, send email to [email protected] with the message: INFO IBM-MAIN
