<s>
Interactive	B-Operating_System
Application	I-Operating_System
System	I-Operating_System
(	O
IAS	O
)	O
was	O
a	O
DEC	O
operating	O
system	O
for	O
the	O
PDP-11	B-Device
.	O
</s>
<s>
It	O
was	O
a	O
fork	B-Application
from	O
RSX-11D	O
.	O
</s>
<s>
requirement	O
"	O
/later	O
"	O
Multi-user	O
"	O
(	O
with	O
RSX-11M	B-Application
Plus	O
being	O
a	O
followup	O
)	O
.	O
</s>
<s>
Another	O
description	O
,	O
rather	O
than	O
focusing	O
on	O
taking	O
away	O
overhead	O
,	O
wrote	O
"	O
IAS	O
(	O
Interactive	B-Operating_System
Application	I-Operating_System
System	I-Operating_System
)	O
was	O
created	O
by	O
adding	O
two	O
things	O
to	O
11D.	O
"	O
</s>
<s>
RSX-11	B-Application
'	O
s	O
use	O
of	O
a	O
version	O
number	O
as	O
part	O
of	O
a	O
file	O
's	O
identifier	O
:	O
MYFILE.DAT	O
;3	O
was	O
retained	O
by	O
IAS	O
.	O
</s>
<s>
The	O
batch	B-General_Concept
facility	I-General_Concept
's	O
command	O
files	O
used	O
the	O
same	O
syntax	O
as	O
the	O
indirect	O
command	O
files	O
available	O
to	O
interactive	O
users	O
;	O
multiple	O
batch	B-General_Concept
jobs	I-General_Concept
could	O
run	O
concurrently	O
.	O
</s>
<s>
Multi-User	O
shares	O
the	O
system	O
with	O
Real-Time	O
tasks	O
;	O
Timesharing	O
adds	O
effective	O
concurrent	O
use	O
of	O
batch	B-General_Concept
processing	I-General_Concept
alongside	O
"	O
noncritical	O
real-time	O
tasks	O
"	O
and	O
interactive	O
users	O
.	O
</s>
