<s>
In	O
computer	B-General_Concept
science	I-General_Concept
,	O
the	O
concept	O
of	O
protected	B-Operating_System
procedure	I-Operating_System
,	O
first	O
introduced	O
as	O
protected	O
service	O
routine	O
in	O
1965	O
,	O
is	O
necessary	O
when	O
two	O
computations	O
A	O
and	O
B	O
use	O
the	O
same	O
routine	O
S	O
;	O
a	O
protected	B-Operating_System
procedure	I-Operating_System
is	O
such	O
if	O
makes	O
not	O
possible	O
for	O
a	O
malfunction	O
of	O
one	O
of	O
the	O
two	O
computation	O
to	O
cause	O
incorrect	O
execution	O
to	O
the	O
other	O
.	O
</s>
<s>
One	O
of	O
the	O
most	O
important	O
aspects	O
of	O
Dennis	O
and	O
Van	O
Horn	O
(	O
hypothetical	O
)	O
system	O
"	O
supervisor	O
"	O
was	O
the	O
inclusion	O
of	O
a	O
description	O
of	O
protected	B-Operating_System
procedure	I-Operating_System
.	O
</s>
<s>
In	O
a	O
global	O
environment	O
system	O
(	O
where	O
there	O
's	O
some	O
shared	O
variable	O
)	O
,	O
the	O
protected	B-Operating_System
procedure	I-Operating_System
mechanism	O
allows	O
the	O
enforcement	O
of	O
the	O
principle	O
of	O
least	O
privilege	O
and	O
the	O
avoidance	O
of	O
side	O
effects	O
in	O
resources	O
management	O
(	O
see	O
Denning	O
principles	O
)	O
.	O
</s>
