<s>
Multics	B-Application
(	O
"	O
MULTiplexed	B-Application
Information	I-Application
and	I-Application
Computing	I-Application
Service	I-Application
"	O
)	O
is	O
an	O
influential	O
early	O
time-sharing	B-General_Concept
operating	I-General_Concept
system	I-General_Concept
based	O
on	O
the	O
concept	O
of	O
a	O
single-level	B-Device
memory	I-Device
.	O
</s>
<s>
Nathan	O
Gregory	O
writes	O
that	O
Multics	B-Application
"	O
has	O
influenced	O
all	O
modern	O
operating	B-General_Concept
systems	I-General_Concept
since	O
,	O
from	O
microcomputers	O
to	O
mainframes.	O
"	O
</s>
<s>
Initial	O
planning	O
and	O
development	O
for	O
Multics	B-Application
started	O
in	O
1964	O
,	O
in	O
Cambridge	O
,	O
Massachusetts	O
.	O
</s>
<s>
It	O
was	O
developed	O
on	O
the	O
GE	B-Device
645	I-Device
computer	O
,	O
which	O
was	O
specially	O
designed	O
for	O
it	O
;	O
the	O
first	O
one	O
was	O
delivered	O
to	O
MIT	O
in	O
January	O
1967	O
.	O
</s>
<s>
GE	O
offered	O
their	O
earlier	O
635	O
systems	O
with	O
an	O
early	O
timesharing	B-General_Concept
system	O
known	O
as	O
"	O
Mark	O
I	O
"	O
and	O
intended	O
to	O
offer	O
the	O
645	O
with	O
Multics	B-Application
as	O
a	O
larger	O
successor	O
.	O
</s>
<s>
Honeywell	O
offered	O
Multics	B-Application
commercially	O
,	O
but	O
with	O
limited	O
success	O
.	O
</s>
<s>
Multics	B-Application
has	O
numerous	O
features	O
intended	O
to	O
ensure	O
high	O
availability	O
so	O
that	O
it	O
would	O
support	O
a	O
computing	B-Operating_System
utility	I-Operating_System
similar	O
to	O
the	O
telephone	O
and	O
electricity	O
utilities	O
.	O
</s>
<s>
The	O
system	O
can	O
grow	O
in	O
size	O
by	O
simply	O
adding	O
more	O
of	O
the	O
appropriate	O
resource	O
,	O
be	O
it	O
computing	O
power	O
,	O
main	O
memory	B-General_Concept
,	O
or	O
disk	B-Device
storage	I-Device
.	O
</s>
<s>
Separate	O
access	O
control	O
lists	O
on	O
every	O
file	B-Operating_System
provide	O
flexible	O
information	O
sharing	O
,	O
but	O
complete	O
privacy	O
when	O
needed	O
.	O
</s>
<s>
Multics	B-Application
has	O
a	O
number	O
of	O
standard	O
mechanisms	O
to	O
allow	O
engineers	O
to	O
analyze	O
the	O
performance	O
of	O
the	O
system	O
,	O
as	O
well	O
as	O
a	O
number	O
of	O
adaptive	O
performance	O
optimization	O
mechanisms	O
.	O
</s>
<s>
Due	O
to	O
its	O
many	O
novel	O
and	O
valuable	O
ideas	O
,	O
Multics	B-Application
has	O
had	O
a	O
significant	O
influence	O
on	O
computer	B-General_Concept
science	I-General_Concept
despite	O
its	O
faults	O
.	O
</s>
<s>
Its	O
most	O
lasting	O
effect	O
on	O
the	O
computer	O
industry	O
was	O
to	O
inspire	O
the	O
creation	O
of	O
Unix	B-Application
,	O
which	O
carried	O
forward	O
many	O
Multics	B-Application
features	O
,	O
but	O
was	O
able	O
to	O
run	O
on	O
less-expensive	O
hardware	O
.	O
</s>
<s>
Unix	B-Application
was	O
developed	O
at	O
Bell	O
to	O
allow	O
their	O
Multics	B-Application
team	O
to	O
continue	O
their	O
research	O
using	O
smaller	O
machines	O
,	O
first	O
a	O
PDP-7	B-Device
and	O
ultimately	O
the	O
PDP-11	B-Device
.	O
</s>
<s>
Multics	B-Application
implements	O
a	O
single-level	B-Device
store	I-Device
for	O
data	O
access	O
,	O
discarding	O
the	O
clear	O
distinction	O
between	O
files	O
(	O
called	O
segments	O
in	O
Multics	B-Application
)	O
and	O
process	B-Operating_System
memory	B-General_Concept
.	O
</s>
<s>
The	O
memory	B-General_Concept
of	O
a	O
process	B-Operating_System
consists	O
solely	O
of	O
segments	O
that	O
were	O
mapped	O
into	O
its	O
address	B-General_Concept
space	I-General_Concept
.	O
</s>
<s>
To	O
read	O
or	O
write	O
to	O
them	O
,	O
the	O
process	B-Operating_System
simply	O
uses	O
normal	O
central	B-General_Concept
processing	I-General_Concept
unit	I-General_Concept
(	O
CPU	O
)	O
instructions	O
,	O
and	O
the	O
operating	B-General_Concept
system	I-General_Concept
takes	O
care	O
of	O
making	O
sure	O
that	O
all	O
the	O
modifications	O
were	O
saved	O
to	O
disk	B-Device
.	O
</s>
<s>
In	O
POSIX	O
terminology	O
,	O
it	O
is	O
as	O
if	O
every	O
file	B-Operating_System
were	O
mmap( )	O
ed	O
;	O
however	O
,	O
in	O
Multics	B-Application
there	O
is	O
no	O
concept	O
of	O
process	B-Operating_System
memory	B-General_Concept
,	O
separate	O
from	O
the	O
memory	B-General_Concept
used	O
to	O
hold	O
mapped-in	O
files	O
,	O
as	O
Unix	B-Application
has	O
.	O
</s>
<s>
All	O
memory	B-General_Concept
in	O
the	O
system	O
is	O
part	O
of	O
some	O
segment	O
,	O
which	O
appears	O
in	O
the	O
file	B-Application
system	I-Application
;	O
this	O
includes	O
the	O
temporary	O
scratch	O
memory	B-General_Concept
of	O
the	O
process	B-Operating_System
,	O
its	O
kernel	B-Operating_System
stack	B-Application
,	O
etc	O
.	O
</s>
<s>
Segments	O
are	O
limited	O
to	O
256	O
kilowords	O
,	O
just	O
over	O
1MB	O
,	O
because	O
Multics	B-Application
hardware	O
had	O
18-bit	O
word	O
addresses	O
for	O
the	O
content	O
of	O
a	O
segment	O
.	O
</s>
<s>
The	O
256kW	O
limit	O
was	O
rarely	O
encountered	O
in	O
practice	O
,	O
because	O
at	O
the	O
time	O
,	O
one	O
megabyte	O
of	O
memory	B-General_Concept
was	O
prohibitively	O
expensive	O
.	O
</s>
<s>
Another	O
major	O
new	O
idea	O
of	O
Multics	B-Application
was	O
dynamic	O
linking	O
,	O
in	O
which	O
a	O
running	O
process	B-Operating_System
can	O
make	O
external	O
routines	O
available	O
by	O
adding	O
the	O
segments	O
containing	O
them	O
to	O
its	O
address	B-General_Concept
space	I-General_Concept
.	O
</s>
<s>
This	O
allows	O
applications	O
to	O
always	O
use	O
the	O
latest	O
version	O
of	O
any	O
external	O
routine	O
,	O
since	O
those	O
routines	O
are	O
kept	O
in	O
other	O
segments	O
,	O
which	O
are	O
dynamically	O
linked	O
only	O
when	O
a	O
process	B-Operating_System
first	O
attempts	O
to	O
begin	O
execution	O
in	O
them	O
.	O
</s>
<s>
Since	O
different	O
processes	O
can	O
use	O
different	O
search	B-Application
rules	I-Application
,	O
different	O
users	O
can	O
end	O
up	O
using	O
different	O
versions	O
of	O
external	O
routines	O
.	O
</s>
<s>
Equally	O
importantly	O
,	O
with	O
the	O
appropriate	O
settings	O
in	O
the	O
Multics	B-Application
security	O
facilities	O
,	O
the	O
code	O
in	O
the	O
other	O
segment	O
can	O
gain	O
access	O
to	O
data	O
structures	O
maintained	O
in	O
a	O
different	O
process	B-Operating_System
.	O
</s>
<s>
Dynamic	O
linking	O
in	O
Multics	B-Application
does	O
not	O
require	O
special	O
Dynamic-link	O
libraries	O
(	O
DLLs	O
)	O
;	O
a	O
program	O
can	O
dynamically	O
link	O
to	O
any	O
executable	O
segment	O
to	O
which	O
it	O
has	O
access	O
rights	O
.	O
</s>
<s>
Thus	O
,	O
to	O
interact	O
with	O
an	O
application	O
running	O
in	O
part	O
as	O
a	O
daemon	B-Operating_System
(	O
in	O
another	O
process	B-Operating_System
)	O
,	O
a	O
user	O
's	O
process	B-Operating_System
simply	O
performs	O
a	O
normal	O
procedure-call	O
instruction	O
to	O
a	O
code	O
segment	O
to	O
which	O
it	O
had	O
dynamically	O
linked	O
(	O
a	O
code	O
segment	O
that	O
implemented	O
some	O
operation	O
associated	O
with	O
the	O
daemon	B-Operating_System
)	O
.	O
</s>
<s>
The	O
code	O
in	O
that	O
segment	O
can	O
then	O
modify	O
data	O
maintained	O
and	O
used	O
in	O
the	O
daemon	B-Operating_System
.	O
</s>
<s>
When	O
the	O
action	O
necessary	O
to	O
commence	O
the	O
request	O
is	O
completed	O
,	O
a	O
simple	O
procedure	O
return	O
instruction	O
returns	O
control	O
of	O
the	O
user	O
's	O
process	B-Operating_System
to	O
the	O
user	O
's	O
code	O
.	O
</s>
<s>
Multics	B-Application
also	O
supports	O
extremely	O
aggressive	O
on-line	B-Device
reconfiguration	I-Device
:	O
central	B-General_Concept
processing	I-General_Concept
units	I-General_Concept
,	O
memory	B-General_Concept
banks	O
,	O
disk	B-Device
drives	I-Device
,	O
etc	O
.	O
</s>
<s>
At	O
the	O
MIT	O
system	O
,	O
where	B-Device
most	O
early	O
software	O
development	O
was	O
done	O
,	O
it	O
was	O
common	O
practice	O
to	O
split	O
the	O
multiprocessor	B-Operating_System
system	O
into	O
two	O
separate	O
systems	O
during	O
off-hours	O
by	O
incrementally	O
removing	O
enough	O
components	O
to	O
form	O
a	O
second	O
working	O
system	O
,	O
leaving	O
the	O
rest	O
still	O
running	O
for	O
the	O
original	O
logged-in	O
users	O
.	O
</s>
<s>
Multics	B-Application
supports	O
multiple	O
CPUs	O
;	O
it	O
is	O
one	O
of	O
the	O
earliest	O
multiprocessor	B-Operating_System
systems	O
.	O
</s>
<s>
Multics	B-Application
is	O
the	O
first	O
major	O
operating	B-General_Concept
system	I-General_Concept
to	O
be	O
designed	O
as	O
a	O
secure	O
system	O
from	O
the	O
outset	O
.	O
</s>
<s>
Despite	O
this	O
,	O
early	O
versions	O
of	O
Multics	B-Application
were	O
compromised	O
repeatedly	O
.	O
</s>
<s>
Break-ins	O
became	O
very	O
rare	O
once	O
the	O
second-generation	O
hardware	O
base	O
was	O
adopted	O
;	O
it	O
has	O
hardware	O
support	O
for	O
ring-oriented	B-Operating_System
security	I-Operating_System
,	O
a	O
multilevel	O
refinement	O
of	O
the	O
concept	O
of	O
master	O
mode	O
.	O
</s>
<s>
A	O
US	O
Air	O
Force	O
tiger	O
team	O
project	O
tested	O
Multics	B-Application
security	O
in	O
1973	O
under	O
the	O
codeword	O
ZARF	O
.	O
</s>
<s>
Multics	B-Application
is	O
the	O
first	O
operating	B-General_Concept
system	I-General_Concept
to	O
provide	O
a	O
hierarchical	B-Application
file	I-Application
system	I-Application
,	O
and	O
file	B-Operating_System
names	O
can	O
be	O
of	O
almost	O
arbitrary	O
length	O
and	O
syntax	O
.	O
</s>
<s>
A	O
given	O
file	B-Operating_System
or	O
directory	O
can	O
have	O
multiple	O
names	O
(	O
typically	O
a	O
long	O
and	O
short	O
form	O
)	O
,	O
and	O
symbolic	O
links	O
between	O
directories	O
are	O
also	O
supported	O
.	O
</s>
<s>
Multics	B-Application
is	O
the	O
first	O
to	O
use	O
the	O
now-standard	O
concept	O
of	O
per-process	O
stacks	B-Application
in	O
the	O
kernel	B-Operating_System
,	O
with	O
a	O
separate	O
stack	B-Application
for	O
each	O
security	O
ring	O
.	O
</s>
<s>
It	O
is	O
also	O
the	O
first	O
to	O
have	O
a	O
command	O
processor	O
implemented	O
as	O
ordinary	O
user	O
code	O
–	O
an	O
idea	O
later	O
used	O
in	O
the	O
Unix	B-Application
shell	I-Application
.	O
</s>
<s>
It	O
is	O
also	O
one	O
of	O
the	O
first	O
written	O
in	O
a	O
high-level	O
language	O
(	O
Multics	B-Application
PL/I	B-Language
)	O
,	O
after	O
the	O
Burroughs	B-Application
MCP	I-Application
system	O
written	O
in	O
ESPOL	B-Language
,	O
an	O
expanded	O
version	O
of	O
ALGOL	B-Language
.	O
</s>
<s>
The	O
deployment	O
of	O
Multics	B-Application
into	O
secure	O
computing	O
environments	O
also	O
spurred	O
the	O
development	O
of	O
innovative	O
supporting	O
applications	O
.	O
</s>
<s>
Thus	O
,	O
a	O
random	O
word	O
generator	O
was	O
researched	O
and	O
then	O
developed	O
in	O
PL/I	B-Language
.	O
</s>
<s>
Instead	O
of	O
being	O
based	O
on	O
phonemes	B-Language
,	O
the	O
system	O
employed	O
phonemic	O
segments	O
(	O
second	O
order	O
approximations	O
of	O
English	O
)	O
and	O
other	O
rules	O
to	O
enhance	O
pronounceability	O
and	O
randomness	O
,	O
which	O
was	O
statistically	O
modeled	O
against	O
other	O
approaches	O
.	O
</s>
<s>
A	O
descendant	O
of	O
this	O
generator	O
was	O
added	O
to	O
Multics	B-Application
during	O
Project	O
Guardian	O
.	O
</s>
<s>
In	O
1964	O
,	O
Multics	B-Application
was	O
developed	O
initially	O
for	O
the	O
GE-645	B-Device
mainframe	O
,	O
a	O
36-bit	O
system	O
.	O
</s>
<s>
GE	O
's	O
computer	O
business	O
,	O
including	O
Multics	B-Application
,	O
was	O
taken	O
over	O
by	O
Honeywell	O
in	O
1970	O
;	O
around	O
1973	O
,	O
Multics	B-Application
is	O
supported	O
on	O
the	O
Honeywell	B-Device
6180	I-Device
machines	O
,	O
which	O
included	O
security	O
improvements	O
including	O
hardware	O
support	O
for	O
protection	B-Operating_System
rings	I-Operating_System
.	O
</s>
<s>
Bell	O
Labs	O
pulled	O
out	O
of	O
the	O
project	O
in	O
1969	O
;	O
some	O
of	O
the	O
people	O
who	B-Application
had	O
worked	O
on	O
it	O
there	O
went	O
on	O
to	O
create	O
the	O
Unix	B-Application
system	I-Application
.	O
</s>
<s>
Multics	B-Application
development	O
continued	O
at	O
MIT	O
and	O
General	O
Electric	O
.	O
</s>
<s>
At	O
MIT	O
in	O
1975	O
,	O
use	O
of	O
Multics	B-Application
was	O
declining	O
and	O
did	O
not	O
recover	O
by	O
1976	O
to	O
prior	O
levels	O
.	O
</s>
<s>
Finally	O
by	O
slashing	O
prices	O
,	O
MIT	O
managed	O
to	O
lure	O
users	O
back	O
to	O
Multics	B-Application
in	O
1978	O
.	O
</s>
<s>
After	O
Honeywell	O
stopped	O
supporting	O
Multics	B-Application
,	O
users	O
migrated	O
to	O
other	O
systems	O
like	O
Unix	B-Application
.	O
</s>
<s>
In	O
1985	O
,	O
Multics	B-Application
was	O
issued	O
certification	O
as	O
a	O
B2	O
level	O
secure	O
operating	B-General_Concept
system	I-General_Concept
using	O
the	O
Trusted	O
Computer	O
System	O
Evaluation	O
Criteria	O
from	O
the	O
National	O
Computer	O
Security	O
Center	O
(	O
NCSC	O
)	O
a	O
division	O
of	O
the	O
NSA	O
,	O
the	O
first	O
operating	B-General_Concept
system	I-General_Concept
evaluated	O
to	O
this	O
level	O
.	O
</s>
<s>
Multics	B-Application
was	O
distributed	O
from	O
1975	O
to	O
2000	O
by	O
Groupe	O
Bull	O
in	O
Europe	O
,	O
and	O
by	O
Bull	O
HN	O
Information	O
Systems	O
Inc	O
.	O
in	O
the	O
United	O
States	O
.	O
</s>
<s>
In	O
2006	O
,	O
Bull	O
SAS	O
released	O
the	O
source	O
code	O
of	O
Multics	B-Application
versions	O
MR10.2	O
,	O
MR11.0	O
,	O
MR12.0	O
,	O
MR12.1	O
,	O
MR12.2	O
,	O
MR12.3	O
,	O
MR12.4	O
&	O
MR12.5	O
under	O
a	O
free	B-Application
software	I-Application
license	O
.	O
</s>
<s>
The	O
last	O
known	O
Multics	B-Application
installation	O
running	O
natively	B-Language
on	O
Honeywell	O
hardware	O
was	O
shut	O
down	O
on	O
October	O
30	O
,	O
2000	O
,	O
at	O
the	O
Canadian	O
Department	O
of	O
National	O
Defence	O
in	O
Halifax	O
,	O
Nova	O
Scotia	O
,	O
Canada	O
.	O
</s>
<s>
In	O
2006	O
Bull	O
HN	O
released	O
the	O
source	O
code	O
for	O
MR12.5	O
,	O
the	O
final	O
1992	O
Multics	B-Application
release	O
,	O
to	O
MIT	O
.	O
</s>
<s>
Most	O
of	O
the	O
system	O
is	O
now	O
available	O
as	O
free	B-Application
software	I-Application
with	O
the	O
exception	O
of	O
some	O
optional	O
pieces	O
such	O
as	O
TCP/IP	B-Protocol
.	O
</s>
<s>
In	O
2014	O
,	O
Multics	B-Application
was	O
successfully	O
run	O
on	O
current	O
hardware	O
using	O
an	O
emulator	O
.	O
</s>
<s>
Release	O
12.6f	O
of	O
Multics	B-Application
accompanies	O
the	O
1.0	O
release	O
of	O
the	O
emulator	O
,	O
and	O
adds	O
a	O
few	O
new	O
features	O
,	O
including	O
command	B-Application
line	I-Application
recall	O
and	O
editing	O
using	O
the	O
video	O
system	O
.	O
</s>
<s>
The	O
following	O
is	O
a	O
list	B-General_Concept
of	O
programs	O
and	O
commands	B-Application
for	O
common	O
computing	O
tasks	O
that	O
are	O
supported	O
by	O
the	O
Multics	B-Application
command-line	B-Application
interface	I-Application
.	O
</s>
<s>
Peter	O
H	O
.	O
Salus	O
,	O
author	O
of	O
a	O
book	O
covering	O
Unix	B-Application
's	O
early	O
years	O
,	O
stated	O
one	O
position	O
:	O
"	O
With	O
Multics	B-Application
they	O
tried	O
to	O
have	O
a	O
much	O
more	O
versatile	O
and	O
flexible	O
operating	B-General_Concept
system	I-General_Concept
,	O
and	O
it	O
failed	O
miserably	O
"	O
.	O
</s>
<s>
This	O
position	O
,	O
however	O
,	O
is	O
said	O
to	O
have	O
been	O
discredited	O
in	O
the	O
computing	O
community	O
because	O
many	O
of	O
Multics	B-Application
 '	O
technical	O
innovations	O
are	O
used	O
in	O
modern	O
commercial	O
computing	O
systems	O
.	O
</s>
<s>
The	O
permanently	O
resident	O
kernel	B-Operating_System
of	O
Multics	B-Application
,	O
a	O
system	O
derided	O
in	O
its	O
day	O
as	O
being	O
too	O
large	O
and	O
complex	O
,	O
was	O
135KB	O
of	O
code	O
.	O
</s>
<s>
The	O
first	O
MIT	O
GE-645	B-Device
had	O
512	O
kilowords	O
of	O
memory	B-General_Concept
(	O
2MiB	O
)	O
,	O
a	O
truly	O
enormous	O
amount	O
at	O
the	O
time	O
,	O
and	O
the	O
kernel	B-Operating_System
used	O
a	O
moderate	O
portion	O
of	O
Multics	B-Application
main	O
memory	B-General_Concept
.	O
</s>
<s>
The	O
entire	O
system	O
,	O
including	O
the	O
operating	B-General_Concept
system	I-General_Concept
and	O
the	O
complex	O
PL/I	B-Language
compiler	B-Language
,	O
user	O
commands	B-Application
,	O
and	O
subroutine	O
libraries	O
,	O
consists	O
of	O
about	O
1500	O
source	O
modules	O
.	O
</s>
<s>
These	O
average	O
roughly	O
200	O
lines	O
of	O
source	O
code	O
each	O
,	O
and	O
compile	B-Language
to	O
a	O
total	O
of	O
roughly	O
4.5MiB	O
of	O
procedure	O
code	O
,	O
which	O
was	O
fairly	O
large	O
by	O
the	O
standards	O
of	O
the	O
day	O
.	O
</s>
<s>
Multics	B-Application
compilers	B-Language
generally	O
optimise	O
more	O
for	O
code	O
density	O
than	O
CPU	O
performance	O
,	O
for	O
example	O
using	O
small	O
sub-routines	O
called	O
operators	O
for	O
short	O
standard	O
code	O
sequences	O
,	O
which	O
makes	O
comparison	O
of	O
object	O
code	O
size	O
with	O
modern	O
systems	O
less	O
useful	O
.	O
</s>
<s>
High	O
code	O
density	O
is	O
a	O
good	O
optimisation	O
choice	O
for	O
Multics	B-Application
as	O
a	O
multi-user	B-Operating_System
system	I-Operating_System
with	O
expensive	O
main	O
memory	B-General_Concept
.	O
</s>
<s>
During	O
its	O
commercial	O
product	O
history	O
,	O
it	O
was	O
often	O
commented	O
internally	O
that	O
the	O
Honeywell	O
Information	O
Systems	O
(	O
HIS	O
)	O
(	O
later	O
Honeywell-Bull	O
)	O
sales	O
and	O
marketing	O
staff	O
were	O
more	O
familiar	O
with	O
and	O
comfortable	O
making	O
the	O
business	O
case	O
for	O
Honeywell	O
’s	O
other	O
computer	O
line	O
,	O
the	O
DPS	O
6	O
running	O
GCOS	B-Application
.	O
</s>
<s>
The	O
DPS-6	O
and	O
GCOS	B-Application
was	O
a	O
well-regarded	O
and	O
reliable	O
platform	O
for	O
inventory	O
,	O
accounting	O
,	O
word	O
processing	O
,	O
and	O
vertical	O
market	O
applications	O
,	O
such	O
as	O
banking	O
,	O
where	B-Device
it	O
had	O
a	O
sizeable	O
customer	O
base	O
.	O
</s>
<s>
In	O
contrast	O
,	O
the	O
full	O
potential	O
of	O
Multics’	O
flexibility	O
for	O
even	O
mundane	O
tasks	O
was	O
not	O
easy	O
to	O
comprehend	O
in	O
that	O
era	O
and	O
its	O
features	O
were	O
generally	O
outside	O
the	O
skill	O
set	O
of	O
contemporary	O
business	O
analysts	O
.	O
</s>
<s>
When	O
asked	O
when	O
the	O
process	B-Operating_System
could	O
be	O
completed	O
,	O
the	O
Multician	O
replied	O
,	O
"	O
It	O
's	O
done.	O
"	O
</s>
<s>
The	O
design	O
and	O
features	O
of	O
Multics	B-Application
slightly	O
influenced	O
the	O
Unix	B-Application
operating	I-Application
system	I-Application
,	O
which	O
was	O
originally	O
written	O
by	O
two	O
Multics	B-Application
programmers	O
,	O
Ken	O
Thompson	O
and	O
Dennis	O
Ritchie	O
.	O
</s>
<s>
Influence	O
of	O
Multics	B-Application
on	O
Unix	B-Application
is	O
evident	O
in	O
many	O
areas	O
,	O
including	O
the	O
hierarchical	B-Application
file	I-Application
system	I-Application
,	O
redirection	B-Device
,	O
the	O
shell	B-Operating_System
,	O
and	O
the	O
naming	O
of	O
some	O
commands	B-Application
.	O
</s>
<s>
But	O
the	O
internal	O
design	O
philosophy	O
is	O
quite	O
different	O
,	O
focusing	O
on	O
keeping	O
the	O
system	O
small	O
and	O
simple	O
,	O
and	O
so	O
correcting	O
some	O
perceived	O
deficiencies	O
of	O
Multics	B-Application
because	O
of	O
its	O
high	O
resource	O
demands	O
on	O
the	O
limited	O
computer	O
hardware	O
of	O
the	O
time	O
.	O
</s>
<s>
The	O
name	O
Unix	B-Application
(	O
originally	O
Unics	O
)	O
is	O
itself	O
a	O
pun	O
on	O
Multics	B-Application
.	O
</s>
<s>
The	O
U	O
in	O
Unix	B-Application
is	O
rumored	O
to	O
stand	O
for	O
uniplexed	O
as	O
opposed	O
to	O
the	O
multiplexed	O
of	O
Multics	B-Application
,	O
further	O
underscoring	O
the	O
designers	O
 '	O
rejections	O
of	O
Multics	B-Application
 '	O
complexity	O
in	O
favor	O
of	O
a	O
more	O
straightforward	O
and	O
workable	O
approach	O
for	O
smaller	O
computers	O
.	O
</s>
<s>
(	O
Garfinkel	O
and	O
Abelson	O
cite	O
an	O
alternative	O
origin	O
:	O
Peter	O
Neumann	O
at	O
Bell	O
Labs	O
,	O
watching	O
a	O
demonstration	O
of	O
the	O
prototype	O
,	O
suggested	O
the	O
pun	O
name	O
UNICS	O
–	O
pronounced	O
"	O
eunuchs	O
"	O
–	O
as	O
a	O
"	O
castrated	O
Multics	B-Application
"	O
,	O
although	O
Dennis	O
Ritchie	O
is	O
said	O
to	O
have	O
denied	O
this	O
.	O
)	O
</s>
<s>
Ken	O
Thompson	O
,	O
in	O
a	O
transcribed	O
2007	O
interview	O
with	O
Peter	O
Seibel	O
refers	O
to	O
Multics	B-Application
as	O
"	O
overdesigned	O
and	O
overbuilt	O
and	O
over	O
everything	O
.	O
</s>
<s>
On	O
the	O
influence	O
of	O
Multics	B-Application
on	O
Unix	B-Application
,	O
Thompson	O
stated	O
that	O
"	O
the	O
things	O
that	O
I	O
liked	O
enough	O
(	O
about	O
Multics	B-Application
)	O
to	O
actually	O
take	O
were	O
the	O
hierarchical	B-Application
file	I-Application
system	I-Application
and	O
the	O
shell	B-Operating_System
—	O
a	O
separate	O
process	B-Operating_System
that	O
you	O
can	O
replace	O
with	O
some	O
other	O
process	B-Operating_System
"	O
.	O
</s>
<s>
Dennis	O
Ritchie	O
wrote	O
that	O
the	O
design	O
of	O
UNIX	B-Application
was	O
influenced	O
by	O
CTSS	B-Operating_System
.	O
</s>
<s>
The	O
Prime	O
Computer	B-General_Concept
operating	I-General_Concept
system	I-General_Concept
,	O
PRIMOS	B-General_Concept
,	O
was	O
referred	O
to	O
as	O
"	O
Multics	B-Application
in	O
a	O
shoebox	O
"	O
by	O
William	O
Poduska	O
,	O
a	O
founder	O
of	O
the	O
company	O
.	O
</s>
<s>
Poduska	O
later	O
moved	O
on	O
to	O
found	O
Apollo	O
Computer	O
,	O
whose	O
AEGIS	O
and	O
later	O
Domain/OS	B-Application
operating	B-General_Concept
systems	I-General_Concept
,	O
sometimes	O
called	O
"	O
Multics	B-Application
in	O
a	O
matchbox	O
"	O
,	O
extends	O
the	O
Multics	B-Application
design	O
to	O
a	O
networked	O
graphics	O
workstation	O
environment	O
.	O
</s>
<s>
The	O
Stratus	B-General_Concept
VOS	I-General_Concept
operating	B-General_Concept
system	I-General_Concept
of	O
Stratus	B-General_Concept
Computer	I-General_Concept
(	O
now	O
Stratus	B-General_Concept
Technologies	I-General_Concept
)	O
is	O
very	O
strongly	O
influenced	O
by	O
Multics	B-Application
,	O
and	O
both	O
its	O
external	O
user	B-Application
interface	I-Application
and	O
internal	O
structure	O
bear	O
many	O
close	O
resemblances	O
to	O
the	O
older	O
project	O
.	O
</s>
<s>
The	O
high-reliability	O
,	O
availability	O
,	O
and	O
security	O
features	O
of	O
Multics	B-Application
are	O
extended	O
in	O
Stratus	B-General_Concept
VOS	I-General_Concept
to	O
support	O
a	O
new	O
line	O
of	O
fault	B-General_Concept
tolerant	I-General_Concept
computer	O
systems	O
supporting	O
secure	O
,	O
reliable	O
transaction	B-General_Concept
processing	I-General_Concept
.	O
</s>
<s>
Stratus	B-General_Concept
VOS	I-General_Concept
is	O
the	O
most	O
directly-related	O
descendant	O
of	O
Multics	B-Application
still	O
in	O
active	O
development	O
and	O
production	O
usage	O
today	O
.	O
</s>
<s>
The	O
protection	O
architecture	O
of	O
Multics	B-Application
,	O
restricting	O
the	O
ability	O
of	O
code	O
at	O
one	O
level	O
of	O
the	O
system	O
to	O
access	O
resources	O
at	O
another	O
,	O
was	O
adopted	O
as	O
the	O
basis	O
for	O
the	O
security	O
features	O
of	O
ICL	O
's	O
VME	B-General_Concept
operating	B-General_Concept
system	I-General_Concept
.	O
</s>
<s>
The	O
Edinburgh	B-Application
Multiple	I-Application
Access	I-Application
System	I-Application
(	O
EMAS	O
)	O
draws	O
particularly	O
on	O
the	O
one-level	O
store	O
concept	O
used	O
by	O
Multics	B-Application
,	O
providing	O
access	O
to	O
files	O
only	O
by	O
mapping	O
them	O
into	O
memory	B-General_Concept
.	O
</s>
<s>
All	O
memory	B-General_Concept
space	O
is	O
associated	O
with	O
a	O
segment	O
.	O
</s>
