<s>
When	O
a	O
process	O
is	O
created	O
(	O
initialized	O
or	O
installed	O
)	O
,	O
the	O
operating	O
system	O
creates	O
a	O
corresponding	O
process	B-Operating_System
control	I-Operating_System
block	I-Operating_System
.	O
</s>
<s>
In	O
multitasking	B-Operating_System
operating	I-Operating_System
systems	I-Operating_System
,	O
the	O
PCB	O
stores	O
data	O
needed	O
for	O
correct	O
and	O
efficient	O
process	O
management	O
.	O
</s>
<s>
Process	O
identification	O
data	O
include	O
a	O
unique	O
identifier	O
for	O
the	O
process	O
(	O
almost	O
invariably	O
an	O
integer	O
)	O
and	O
,	O
in	O
a	O
multiuser-multitasking	O
system	O
,	O
data	O
such	O
as	O
the	O
identifier	O
of	O
the	O
parent	O
process	O
,	O
user	O
identifier	O
,	O
user	O
group	O
identifier	O
,	O
etc	O
.	O
</s>
<s>
The	O
process	B-Operating_System
id	I-Operating_System
is	O
particularly	O
relevant	O
since	O
it	O
is	O
often	O
used	O
to	O
cross-reference	O
the	O
tables	O
defined	O
above	O
,	O
e.g.	O
</s>
<s>
This	O
always	O
includes	O
the	O
content	O
of	O
general-purpose	O
CPU	B-General_Concept
registers	O
,	O
the	O
CPU	B-General_Concept
process	O
status	O
word	O
,	O
stack	B-General_Concept
and	O
frame	O
pointers	O
,	O
etc	O
.	O
</s>
<s>
During	O
context	B-Operating_System
switch	I-Operating_System
,	O
the	O
running	O
process	O
is	O
stopped	O
and	O
another	O
process	O
runs	O
.	O
</s>
<s>
Process	O
scheduling	O
state	O
–	O
The	O
state	O
of	O
the	O
process	O
in	O
terms	O
of	O
"	O
ready	O
"	O
,	O
"	O
suspended	O
"	O
,	O
etc.	O
,	O
and	O
other	O
scheduling	O
information	O
as	O
well	O
,	O
such	O
as	O
priority	O
value	O
,	O
the	O
amount	O
of	O
time	O
elapsed	O
since	O
the	O
process	O
gained	O
control	O
of	O
the	O
CPU	B-General_Concept
or	O
since	O
it	O
was	O
suspended	O
.	O
</s>
<s>
Process	O
Number	O
(	O
PID	O
)	O
–	O
unique	O
identification	O
number	O
for	O
each	O
process	O
(	O
also	O
known	O
as	O
Process	B-Operating_System
ID	I-Operating_System
)	O
;	O
</s>
<s>
CPU	B-General_Concept
Registers	O
–	O
register	O
set	O
where	O
process	O
needs	O
to	O
be	O
stored	O
for	O
execution	O
for	O
running	O
state	O
;	O
</s>
<s>
CPU	B-General_Concept
Scheduling	O
Information	O
–	O
information	O
scheduling	O
CPU	B-General_Concept
time	O
;	O
</s>
<s>
Accounting	O
Information	O
–	O
amount	O
of	O
CPU	B-General_Concept
used	O
for	O
process	O
execution	O
,	O
time	O
limits	O
,	O
execution	O
ID	O
etc	O
.	O
</s>
<s>
In	O
some	O
operating	O
systems	O
the	O
PCB	O
is	O
placed	O
at	O
the	O
bottom	O
of	O
the	O
process	B-General_Concept
stack	I-General_Concept
.	O
</s>
