The same glossary says this about code point: "A unique bit pattern defined in a code. Depending on the code, a code point can be 7-bit, 8-bit, 16-bit, or other. Code points are assigned to a graphic character in a code page."
Note the last sentence of that. Also, you earlier quoted a section of a DB2 website about "round trip conversion", including this: "Example: In ASCII CCSID 1252, the trademark symbol T is code point X'99'. In EBCDIC CCSID 37, this code point does not exist." So a code point is not just any possible combination of bits, it's a combination of bits that is assigned to a character. It is possible to say that a code point "does not exist" in a CCSID. Therefore the description of "round trip" that you quoted: "Round trip. Encoding that occurs when *every* code point in the source CCSID maps to a unique code point in the target CCSID" can be read to apply only to certain bit combinations, those to which a character is assigned, and not to all bit combinations. The glossary in the DB2 website that you referenced earlier has this for "code point": "In CDRA, a unique bit pattern that represents a character in a code page." Bill On Tue, 12 Jun 2012 21:07:51 -0700, Charles Mills wrote: >1027 was a test case and the data is arbitrary. I think the point of round >trip is supposed to be that *every* character is "recoverable." > >A good write-up in of all places <g> the Glossary of the Z Unicode manual. >Emphasis is mine. > >Round trip. Encoding that occurs when *every* code >point in the source CCSID maps to a unique code point >in the target CCSID. Using round trip tables ensure the >capability of reversing the conversion, and recovering >the complete original source datastream. > >I'm going to see what they say on the PMR. > >Charles > >-----Original Message----- >From: IBM Mainframe Discussion List [mailto:IBM-MAIN@bama.ua.edu] On Behalf >Of Bill Godfrey >Sent: Tuesday, June 12, 2012 7:12 PM >To: IBM-MAIN@bama.ua.edu >Subject: Re: Anyone a Unicode Services expert? -- roundtrip conversion > >Maybe it will turn out that "round trip" only applies to the characters that >are defined in the Source CCSID (and I'm not sure if "defined" is the right >word). When I look at a chart of CCSID 1027 here: > >ftp://ftp.software.ibm.com/software/globalization/gcoc/attachments/CP01027.p >df > >I see that all of the characters that you see being being converted to X'1A' >are either outside the chart (which starts at X'40') or have no identified >value in the chart. If your data contains these unidentified characters, >what is their purpose, and is it really appropriate to consider the data to >be associated with CCSID 1027, or just something related to but not the same >as CCSID 1027? > >Bill > >On Tue, 12 Jun 2012 16:42:02 -0700, Charles Mills wrote: > >>Not sure what you mean. Here's the PMR: >> >>Problem Details >>. >>Product or Service: Support for Unicode Component ID: 5752SCUNI . >>Operating System: z/OS >>. >>Problem title >>Round trip conversion not working as expected . >>Problem description >>My understanding of "round trip" conversion is that every code point in >>the Source CCSID should convert to a unique code point in the Target >>CCSID (so that conversion in the reverse direction will restore the >>original code points). However, when I use CUNLCNV to convert between >>CCSIDs 1027 and 1208 I see more than one character converted to x'1A' >>(UTF8 SUB). Is round trip conversion working correctly? (Both the >>documentation and CUNLINFO report that 'R' is a supported conversion >>technique for these two CCSIDs.) >> >>Characters converted to X'1A' include 3F, 41, 6A, 80, 90, etc. >> >>Thank you for your consideration. >>. >>Business impact ( BusImpact ) >>Negatively impacting product design decisions. >> >>Charles >>-----Original Message----- >>From: IBM Mainframe Discussion List [mailto:IBM-MAIN@bama.ua.edu] On >>Behalf Of Tony Harminc >>Sent: Tuesday, June 12, 2012 4:15 PM >>To: IBM-MAIN@bama.ua.edu >>Subject: Re: Anyone a Unicode Services expert? -- roundtrip conversion >> >>On 12 June 2012 18:55, Charles Mills <charl...@mcn.org> wrote: >>> I have opened a PMR. >> >>For the doc, or the behaviour of the service? Or did you choose the >>"let us decide for you" option...? >> >>Tony H. >> > >---------------------------------------------------------------------- >For IBM-MAIN subscribe / signoff / archive access instructions, send email >to lists...@bama.ua.edu with the message: INFO IBM-MAIN > >---------------------------------------------------------------------- >For IBM-MAIN subscribe / signoff / archive access instructions, >send email to lists...@bama.ua.edu with the message: INFO IBM-MAIN ---------------------------------------------------------------------- For IBM-MAIN subscribe / signoff / archive access instructions, send email to lists...@bama.ua.edu with the message: INFO IBM-MAIN
