How do I get *8* data bits *no* parity?

[Gert Illemann]

In article <130 at tree.UUCP>, stever at tree.UUCP (Steve Rudek) writes:

> We're running Micrport System V/AT release 2.4 and need to change the tty
> default for incoming modem calls from the default (7 data bits even parity)
> to 8 data bits no parity ...
> ... I tried changing the standard entry: ... to:
> 1200# B1200 HUPCL CS8 CLOCAL OPOST ONLCR # B1200 HUPCL SANE IXANY TAB3 #login: #1200
> but it didn't make any significant difference.  Why not?

Because you are using SANE, that will - among other settings - give you
CS7 and PARENB

> Why does UNIX default to 7 data bits/even parity, anyway?

Most ports defaults to 7+even, because it used to be a good guess, as to what
the terminal would like. That is even today a very good guess; the majority
of terminals, used world-wide, are ASCII (more or less) based (not extended
ASCII, just plain ASCII).
As the character-width (unfortunately) still is only 8 bits in UNIX and as
it's very nice to have some measure of assurance of what you type is what the
program gets, most people prefer to use the eighth bit for parity checking.

> ...If I succeed in switching to 8 data bits will
> there be any unwanted side effects I should beware of? 

Yes ! dont use TAB3, it means "expand tabs to spaces"; normally that would
be wrong (VERY wrong sometimes) for uucp-traffic.

> I was told by one of the tech support folks at microport that the "#" in the
> center of the gettydefs record delimits line condition BEFORE login from
> line condition AFTER login.  Is this correct?

Yes, he was right there, syntax :
name# initial settings (i.e. for opening and writing the login-message) \
# final settings (i.e. sat just before login is executed) # login-message \
#next-name

>In general, I'd be fascinated
> to hear the full story of what is really going on in a gettydefs entry.
> While I can look up the supposed definition of some of these field mnemonics
> (e.g., "PARENB" or "CS7") I feel that the UNIX documentation is extremely
> inadequate in describing the available options and interactions in line
> control settings.

I wont't give you more of the story here, but, have you studied getty(1M),
termio(7), gettydefs(4), stty(1) and maybe ioctl(2), I'm sure you know what
to do.
It's more than the part-time system-administrator cares to do, I know, so
maybe you should ask your support-person(s) to do it :-)

  Gert

Gert Illemann    / gerti at ncrdk.dk  (...uunet!mcvax!dkuug!ncrdk!gerti)

				       NCR Danmark A/S, System Service Division
					Teglv{rksgade 31, DK-2100 Copenhagen O
>>DISCLAIM.ABSOLUTE<<
Nobody or -one, but I, claims to think so
as it's probably incorrect, inconsistent,
incoherent and generally untrustworthy