Info needed on pseudo TTYs in SysV

[Ron Natalie]

Actually, the way the System V terminal driver is set up, it is
designed to help you do this.  Unfortunately, it means driver
hacking, and you really do need a UNIX source license.  If you
can find one, look at the xt.c driver for running the BLITs and
tty5620 terminals, it is switching a packetized input stream
consisting of six virtual terminals into separate xt000 devices.

System V doesn't really have pty's at all.  The SXT (which are VR2
anyhow) devices are a kludged up version of the code for the xt
driver.  What they do is switch a single real tty line back and
forth between a set of virtual terminals.  Doing this, they achieve
something roughly equivelent to the 4.2 Job control.  The difference
is that you actually have a shell on each of the sxt virtual devices.
What you are really doing is switching your real tty to several virtual
tty "contexts."

-Ron