Parity on 4.x BSD UNIX ports
C. Philip Wood
cpw%sneezy at lanl.gov
Thu Apr 14 07:06:45 AEST 1988
Apparently, 'getty' can be told, via 'gettytab' whether to do "any
parity", "even parity" or "odd parity". Depending on this setting, it
will mask off the parity bit, or honor the appropriate parity on
input. Output is another story. It appears that there are only two
choices on output, odd or even parity. However, our site has chosen to
require it's hosts to not generate parity. Most of our terminals can
be configured to "8 bit none" which means to them to mask off the high
order parity bit and output the appropriate character image. However,
there are some vendor terminals and emulators which barf on characters
with parity (odd or even) if configured to "8 bit none" mode. They
have an extended character set and actually try to output the
corresponding "graphic" for an ascii character with a parity bit set.
Note: I have been told that the other operating systems we have here
can be told to (or do) not generate parity.
So, my question(s) are:
1. Is my analysis correct. If not, please correct.
2. What can be done short of a kernel change to provide a solution?
3. If there is no easy solution. Should UNIX be modified so
that it will not (optionally) generate parity on output?
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