<s>
PRIMOS	B-General_Concept
is	O
a	O
discontinued	O
operating	B-General_Concept
system	I-General_Concept
developed	O
during	O
the	O
1970s	O
by	O
Prime	O
Computer	O
for	O
its	O
minicomputer	B-Architecture
systems	O
.	O
</s>
<s>
It	O
rapidly	O
gained	O
popularity	O
and	O
by	O
the	O
mid-1980s	O
was	O
a	O
serious	O
contender	O
as	O
a	O
mainline	O
minicomputer	B-Architecture
operating	B-General_Concept
system	I-General_Concept
.	O
</s>
<s>
With	O
the	O
advent	O
of	O
PCs	B-Device
and	O
the	O
decline	O
of	O
the	O
minicomputer	B-Architecture
industry	O
,	O
Prime	O
was	O
forced	O
out	O
of	O
the	O
market	O
in	O
the	O
early	O
1990s	O
,	O
and	O
by	O
the	O
end	O
of	O
2010	O
the	O
trademarks	O
for	O
both	O
PRIME	O
and	O
PRIMOS	B-General_Concept
no	O
longer	O
existed	O
.	O
</s>
<s>
One	O
feature	O
of	O
PRIMOS	B-General_Concept
was	O
that	O
it	O
,	O
like	O
UNIX	B-Application
,	O
was	O
largely	O
written	O
in	O
a	O
high	O
level	O
language	O
(	O
with	O
callable	O
assembly	B-Language
language	I-Language
library	O
functions	O
available	O
)	O
.	O
</s>
<s>
At	O
first	O
,	O
this	O
language	O
was	O
FORTRAN	B-Application
IV	O
,	O
which	O
was	O
an	O
odd	O
choice	O
from	O
a	O
pure	O
computer	B-General_Concept
science	I-General_Concept
standpoint	O
:	O
no	O
pointers	O
,	O
no	O
if-then-else	B-Language
,	O
no	O
native	O
string	O
type	O
,	O
etc	O
.	O
</s>
<s>
FORTRAN	B-Application
was	O
,	O
however	O
,	O
the	O
language	O
most	O
known	O
to	O
engineers	O
,	O
and	O
engineers	O
were	O
a	O
big	O
market	O
for	O
Prime	O
in	O
their	O
early	O
years	O
.	O
</s>
<s>
The	O
unusual	O
choice	O
of	O
FORTRAN	B-Application
for	O
the	O
OS	O
programming	O
language	O
had	O
to	O
do	O
with	O
the	O
people	O
who	O
founded	O
Prime	O
.	O
</s>
<s>
FORTRAN	B-Application
was	O
the	O
language	O
they	O
had	O
used	O
both	O
at	O
NASA	O
and	O
,	O
for	O
many	O
of	O
them	O
,	O
at	O
MIT	O
.	O
</s>
<s>
Honeywell	O
,	O
at	O
that	O
time	O
,	O
was	O
uninterested	O
in	O
minicomputers	B-Architecture
,	O
so	O
they	O
left	O
and	O
founded	O
Prime	O
,	O
"	O
taking	O
"	O
the	O
code	O
with	O
them	O
.	O
</s>
<s>
They	O
developed	O
hardware	O
optimized	O
to	O
run	O
FORTRAN	B-Application
,	O
including	O
machine	O
instructions	O
that	O
directly	O
implemented	O
FORTRAN	B-Application
's	O
distinctive	O
3-way	B-Language
branch	I-Language
operation	I-Language
.	O
</s>
<s>
Since	O
Prime	O
's	O
hardware	O
did	O
not	O
perform	O
byte	O
addressing	O
,	O
there	O
was	O
no	O
impetus	O
to	O
create	O
a	O
C	B-Language
compiler	O
.	O
</s>
<s>
Late	O
models	O
of	O
the	O
hardware	O
were	O
eventually	O
modified	O
to	O
support	O
I-mode	O
,	O
and	O
programs	O
compiled	O
in	O
C	B-Language
.	O
</s>
<s>
the	O
PL/P	B-Language
and	O
Modula-2	B-Language
languages	I-Language
were	O
used	O
in	O
the	O
Kernel	O
.	O
</s>
<s>
Furthermore	O
,	O
some	O
new	O
PRIMOS	B-General_Concept
utilities	O
were	O
written	O
in	O
SP/L	O
,	O
which	O
was	O
similar	O
to	O
PL/P	B-Language
.	O
</s>
<s>
The	O
source	O
code	O
to	O
PRIMOS	B-General_Concept
was	O
available	O
to	O
customers	O
and	O
,	O
thanks	O
to	O
FORTRAN	B-Application
and	O
PL/P	B-Language
,	O
customers	O
could	O
reasonably	O
modify	O
PRIMOS	B-General_Concept
as	O
needed	O
.	O
</s>
<s>
For	O
example	O
,	O
around	O
1990	O
,	O
the	O
University	O
of	O
Salford	O
in	O
the	O
UK	O
,	O
modified	O
the	O
PRIMOS	B-General_Concept
running	O
on	O
its	O
five	O
9955	O
systems	O
so	O
that	O
undergraduates	O
could	O
no	O
longer	O
use	O
the	O
MESSAGE	O
command	O
,	O
that	O
wrapped	O
the	O
PRIMOS	B-General_Concept
SMSG$( 	O
)	O
call	O
,	O
to	O
send	O
messages	O
to	O
other	O
undergraduates	O
,	O
because	O
online	O
"	O
chatting	O
"	O
using	O
that	O
command	O
was	O
becoming	O
rife	O
,	O
tying	O
up	O
terminals	O
from	O
the	O
limited	O
pool	O
available	O
.	O
</s>
<s>
Very	O
early	O
versions	O
of	O
PRIMOS	B-General_Concept
(	O
revision	O
6	O
)	O
were	O
originally	O
called	O
DOS	O
(	O
PRIMOS	B-General_Concept
2	I-General_Concept
)	O
and	O
later	O
DOSVM	O
(	O
PRIMOS	B-General_Concept
3	I-General_Concept
)	O
,	O
but	O
starting	O
with	O
PRIMOS	B-General_Concept
4	I-General_Concept
,	O
on	O
the	O
P400	O
system	O
,	O
PRIMOS	B-General_Concept
was	O
the	O
name	O
that	O
stuck	O
.	O
</s>
<s>
There	O
were	O
many	O
major	O
releases	O
of	O
PRIMOS	B-General_Concept
.	O
</s>
<s>
By	O
this	O
time	O
,	O
a	O
company	O
called	O
Peritus	O
(	O
which	O
employed	O
a	O
number	O
of	O
ex-Prime	O
engineers	O
)	O
was	O
maintaining	O
PRIMOS	B-General_Concept
.	O
</s>
<s>
From	O
Revision	O
19	O
,	O
major	O
portions	O
of	O
PRIMOS	B-General_Concept
were	O
written	O
in	O
the	O
languages	O
SPL	O
and	O
Modula-2	B-Language
,	O
the	O
usage	O
of	O
the	O
Prime	O
Macro	O
Assembler	B-Language
_(PMA )	O
,	O
FORTRAN	B-Application
IV	O
and	O
PL/P	B-Language
declined	O
considerably	O
around	O
this	O
time	O
.	O
</s>
<s>
In	O
the	O
versions	O
of	O
PRIMOS	B-General_Concept
ca	O
.	O
</s>
<s>
1977	O
and	O
later	O
,	O
the	O
filesystem	B-Application
included	O
a	O
distinctive	O
construct	O
known	O
as	O
the	O
Segment	O
Directory	O
.	O
</s>
<s>
Segment	O
Directories	O
were	O
used	O
in	O
their	O
Keyed-Index/Direct	O
Access	O
(	O
KI/DA	O
)	O
file	B-Application
access	I-Application
system	O
and	O
in	O
later	O
versions	O
of	O
the	O
system	O
loader	O
.	O
</s>
<s>
Indexed	O
data	O
could	O
be	O
stored	O
in	O
a	O
MIDAS	O
file	O
:	O
Multi-Indexed	O
Data	O
Access	O
System	O
and	O
be	O
accessed	O
via	O
COBOL	B-Application
or	O
FORTRAN	B-Application
.	O
</s>
<s>
third	O
party	O
tools	O
was	O
a	O
package	O
named	O
Queo	O
,	O
which	O
was	O
more	O
powerful	O
than	O
COBOL	B-Application
despite	O
being	O
less	O
verbose	O
.	O
</s>
<s>
The	O
PRIMOS	B-General_Concept
character	O
set	O
was	O
basically	O
ASCII	B-Protocol
but	O
with	O
the	O
8th	O
bit	O
inverted	O
.	O
</s>
<s>
The	O
original	O
7-bit	O
standard	O
for	O
ASCII	B-Protocol
left	O
the	O
8th	O
bit	O
unspecified	O
,	O
but	O
on	O
the	O
commonly	O
available	O
Teletype	B-Application
Model	I-Application
33	I-Application
ASR	O
,	O
the	O
bit	O
was	O
customarily	O
set	O
to	O
1	O
,	O
and	O
this	O
became	O
Prime	O
's	O
standard	O
.	O
</s>
<s>
This	O
is	O
vital	O
to	O
realize	O
when	O
transferring	O
data	O
from	O
PRIMOS	B-General_Concept
to	O
almost	O
any	O
other	O
system	O
.	O
</s>
<s>
By	O
the	O
time	O
of	O
Prime	O
Computer	O
's	O
demise	O
,	O
a	O
list	O
of	O
languages	O
supported	O
by	O
Primos	B-General_Concept
included	O
:	O
</s>
<s>
Late	O
versions	O
of	O
PRIMOS	B-General_Concept
included	O
a	O
scripting	B-Language
language	I-Language
,	O
CPL	O
(	O
Command	O
Processing	O
Language	O
)	O
that	O
ESRI	O
used	O
as	O
a	O
basis	O
for	O
its	O
platform-independent	O
scripting	B-Language
languages	I-Language
AML	O
(	O
for	O
ArcInfo	B-Application
)	O
and	O
SML	O
(	O
PC-ARC/INFO	B-Application
)	O
.	O
</s>
<s>
it	O
enabled	O
high-speed	O
Local	B-General_Concept
Area	I-General_Concept
Networking	I-General_Concept
.	O
</s>
<s>
In	O
1985	O
,	O
Prime	O
's	O
port	O
of	O
T	O
's	O
UNIX	B-Operating_System
System	I-Operating_System
V	I-Operating_System
,	O
called	O
Primix	O
,	O
became	O
available	O
with	O
Primos	B-General_Concept
Release	O
19.4.2	O
that	O
was	O
modified	O
to	O
include	O
Unix	B-Application
functions	O
.	O
</s>
<s>
It	O
co-existed	O
with	O
PRIMOS	B-General_Concept
,	O
allowing	O
users	O
to	O
switch	O
back	O
and	O
forth	O
.	O
</s>
