<s>
A	O
Protected	B-Operating_System
Procedure	I-Operating_System
Call	I-Operating_System
(	O
PPC	O
)	O
is	O
a	O
messaging	O
facility	O
wherein	O
messages	O
are	O
sent	O
and	O
received	O
using	O
procedure	O
call	O
interfaces	O
.	O
</s>
<s>
They	O
are	O
a	O
core	O
component	O
of	O
the	O
K42	B-Operating_System
operating	O
system	O
.	O
</s>
