Anyone a Unicode Services expert? -- roundtrip conversion

My understanding of "roundtrip conversion" is that every code point in the
from CCSID translates to a unique (possibly "meaningless") code point in the
to CCSID so that if for example a customer is so foolish as to transmit, for
example, an object deck from z/OS to a PC in "text" format, and then
transfer it back to z/OS the same way, he will have a good object deck.

I am running Kirk Wolf's excellent showtrtab with the command showtrtab -s
1027 -t 1208 -q R

The results I see include the following:

3F: 1A
40: 20
41: 1A

Several other EBCDIC code points also translate to ASCII sub, 0x1a. So the
question is if multiple EBCDIC code points all translate to 0x1a, how the
heck is this a round trip translation?

(I'm not alleging a bug in showtrtab. I am getting the same results with my
code and ran showtrtab as a reality check and a clearer example.)

Where am I going wrong?


For IBM-MAIN subscribe / signoff / archive access instructions,
send email to listserv@xxxxxxxxxxx with the message: INFO IBM-MAIN