<s>
The	O
Seventh	B-Operating_System
Edition	I-Operating_System
Unix	I-Operating_System
terminal	I-Operating_System
interface	I-Operating_System
is	O
the	O
generalized	O
abstraction	O
,	O
comprising	O
both	O
an	O
application	B-Application
programming	I-Application
interface	I-Application
for	O
programs	O
and	O
a	O
set	O
of	O
behavioural	O
expectations	O
for	O
users	O
,	O
of	O
a	O
terminal	O
as	O
historically	O
available	O
in	O
Seventh	B-Operating_System
Edition	I-Operating_System
Unix	I-Operating_System
.	O
</s>
<s>
It	O
has	O
been	O
largely	O
superseded	O
by	O
the	O
POSIX	B-Application
terminal	I-Application
interface	I-Application
.	O
</s>
<s>
The	O
terminal	O
interface	O
provided	O
by	O
Seventh	B-Operating_System
Edition	I-Operating_System
Unix	I-Operating_System
and	O
UNIX/32V	B-Operating_System
,	O
and	O
also	O
presented	O
by	O
BSD	B-Operating_System
version	O
4	O
as	O
the	O
old	O
terminal	O
driver	O
,	O
was	O
a	O
simple	O
one	O
,	O
largely	O
geared	O
towards	O
teletypewriters	O
as	O
terminals	O
.	O
</s>
<s>
From	O
a	O
programming	O
point	O
of	O
view	O
,	O
a	O
terminal	O
device	O
had	O
transmit	O
and	O
receive	O
baud	O
rates	O
,	O
"	O
erase	O
"	O
and	O
"	O
kill	O
"	O
characters	O
(	O
that	O
performed	O
line	O
editing	O
,	O
as	O
explained	O
)	O
,	O
"	O
interrupt	O
"	O
and	O
"	O
quit	O
"	O
characters	O
(	O
generating	O
signals	O
to	O
all	O
of	O
the	O
processes	O
for	O
which	O
the	O
terminal	O
was	O
a	O
controlling	O
terminal	O
)	O
,	O
"	O
start	O
"	O
and	O
"	O
stop	O
"	O
characters	O
(	O
used	O
for	O
software	O
flow	O
control	O
)	O
,	O
an	O
"	O
end	O
of	O
file	O
"	O
character	O
(	O
acting	O
like	O
a	O
carriage	O
return	O
except	O
discarded	O
from	O
the	O
buffer	O
by	O
the	O
read( )	O
system	O
call	O
and	O
therefore	O
potentially	O
causing	O
a	O
zero-length	O
result	O
to	O
be	O
returned	O
)	O
and	O
various	O
mode	O
flags	O
determining	O
whether	O
local	B-Error_Name
echo	I-Error_Name
was	O
emulated	O
by	O
the	O
kernel	O
's	O
terminal	O
driver	O
,	O
whether	O
modem	O
flow	O
control	O
was	O
enabled	O
,	O
the	O
lengths	O
of	O
various	O
output	O
delays	O
,	O
mapping	O
for	O
the	O
carriage	O
return	O
character	O
,	O
and	O
the	O
three	O
input	O
modes	O
.	O
</s>
<s>
The	O
three	O
input	O
modes	O
for	O
terminals	O
in	O
Seventh	B-Operating_System
Edition	I-Operating_System
Unix	I-Operating_System
were	O
:	O
</s>
<s>
In	O
the	O
POSIX	B-Application
terminal	I-Application
interface	I-Application
,	O
these	O
modes	O
have	O
been	O
superseded	O
by	O
a	O
system	O
of	O
just	O
two	O
input	O
modes	O
:	O
canonical	O
and	O
non-canonical	O
.	O
</s>
<s>
The	O
handling	O
of	O
signal-generating	O
special	O
characters	O
in	O
the	O
POSIX	B-Application
terminal	I-Application
interface	I-Application
is	O
independent	O
of	O
input	O
mode	O
,	O
and	O
is	O
separately	O
controllable	O
.	O
</s>
<s>
In	O
Seventh	B-Operating_System
Edition	I-Operating_System
Unix	I-Operating_System
there	O
was	O
no	O
terminal	O
job	B-Operating_System
control	I-Operating_System
and	O
a	O
process	B-Operating_System
group	I-Operating_System
was	O
considered	O
to	O
be	O
not	O
what	O
it	O
is	O
considered	O
to	O
be	O
nowadays	O
.	O
</s>
<s>
Each	O
process	B-Operating_System
in	O
the	O
system	O
had	O
either	O
a	O
single	O
controlling	O
terminal	O
,	O
or	O
no	O
controlling	O
terminal	O
at	O
all	O
.	O
</s>
<s>
A	O
process	B-Operating_System
inherits	O
its	O
controlling	O
terminal	O
from	O
its	O
parent	O
.	O
</s>
<s>
A	O
controlling	O
terminal	O
was	O
acquired	O
when	O
a	O
process	B-Operating_System
with	O
no	O
controlling	O
terminal	O
open( )	O
s	O
a	O
terminal	O
device	O
file	O
that	O
is	O
n't	O
already	O
the	O
controlling	O
terminal	O
for	O
some	O
other	O
process	B-Operating_System
.	O
</s>
<s>
All	O
of	O
the	O
processes	O
that	O
had	O
the	O
same	O
controlling	O
terminal	O
were	O
part	O
of	O
a	O
single	O
process	B-Operating_System
group	I-Operating_System
.	O
</s>
<s>
The	O
programmatic	O
interface	O
for	O
querying	O
and	O
modifying	O
all	O
of	O
these	O
modes	O
and	O
control	O
characters	O
was	O
the	O
ioctl( )	O
system	O
call	O
.	O
</s>
<s>
Although	O
the	O
"	O
erase	O
"	O
and	O
"	O
kill	O
"	O
characters	O
were	O
modifiable	O
from	O
their	O
defaults	O
of	O
and	O
,	O
for	O
many	O
years	O
after	O
Seventh	O
Edition	O
development	O
inertia	O
meant	O
that	O
they	O
were	O
the	O
pre-set	O
defaults	O
in	O
the	O
terminal	O
device	O
drivers	O
,	O
and	O
on	O
many	O
Unix	O
systems	O
,	O
which	O
only	O
altered	O
terminal	O
device	O
settings	O
as	O
part	O
of	O
the	O
login	O
process	B-Operating_System
,	O
in	O
system	O
login	O
scripts	O
that	O
ran	O
after	O
the	O
user	O
had	O
entered	O
username	O
and	O
password	O
,	O
any	O
mistakes	O
at	O
the	O
login	O
and	O
password	O
prompts	O
had	O
to	O
be	O
corrected	O
using	O
the	O
historical	O
editing	O
key	O
characters	O
inherited	O
from	O
teletypewriter	O
terminals	O
.	O
</s>
<s>
The	O
ioctl( )	O
operations	O
were	O
as	O
follows	O
:	O
</s>
<s>
Unlike	O
the	O
POSIX	B-Application
terminal	I-Application
interface	I-Application
,	O
the	O
Seventh	B-Operating_System
Edition	I-Operating_System
Unix	I-Operating_System
terminal	I-Operating_System
interface	I-Operating_System
recorded	O
input	O
and	O
output	O
baud	O
rates	O
directly	O
in	O
the	O
data	O
structure	O
.	O
</s>
