<s>
In	O
computing	O
,	O
a	O
plug	B-Device
and	I-Device
play	I-Device
(	O
PnP	O
)	O
device	O
or	O
computer	B-General_Concept
bus	I-General_Concept
is	O
one	O
with	O
a	O
specification	O
that	O
facilitates	O
the	O
recognition	O
of	O
a	O
hardware	O
component	O
in	O
a	O
system	O
without	O
the	O
need	O
for	O
physical	O
device	O
configuration	O
or	O
user	O
intervention	O
in	O
resolving	O
resource	O
conflicts	O
.	O
</s>
<s>
The	O
term	O
"	O
plug	B-Device
and	I-Device
play	I-Device
"	O
has	O
since	O
been	O
expanded	O
to	O
a	O
wide	O
variety	O
of	O
applications	O
to	O
which	O
the	O
same	O
lack	O
of	O
user	O
setup	O
applies	O
.	O
</s>
<s>
Expansion	O
devices	O
are	O
controlled	O
and	O
exchange	O
data	O
with	O
the	O
host	O
system	O
through	O
defined	O
memory	O
or	O
I/O	B-General_Concept
space	O
port	O
addresses	O
,	O
direct	B-General_Concept
memory	I-General_Concept
access	I-General_Concept
channels	O
,	O
interrupt	B-General_Concept
request	I-General_Concept
lines	O
and	O
other	O
mechanisms	O
,	O
which	O
must	O
be	O
uniquely	O
associated	O
with	O
a	O
particular	O
device	O
to	O
operate	O
.	O
</s>
<s>
Some	O
computers	O
provided	O
unique	O
combinations	O
of	O
these	O
resources	O
to	O
each	O
slot	O
of	O
a	O
motherboard	B-General_Concept
or	O
backplane	B-Architecture
.	O
</s>
<s>
Since	O
fixed	O
assignments	O
made	O
expansion	O
of	O
a	O
system	O
difficult	O
,	O
devices	O
used	O
several	O
manual	O
methods	O
for	O
assigning	O
addresses	O
and	O
other	O
resources	O
,	O
such	O
as	O
hard-wired	O
jumpers	B-Device
,	O
pins	O
that	O
could	O
be	O
connected	O
with	O
wire	O
or	O
removable	O
straps	O
,	O
or	O
switches	O
that	O
could	O
be	O
set	O
for	O
particular	O
addresses	O
.	O
</s>
<s>
As	O
microprocessors	O
made	O
mass-market	O
computers	O
affordable	O
,	O
software	O
configuration	O
of	O
I/O	B-General_Concept
devices	I-General_Concept
was	O
advantageous	O
to	O
allow	O
installation	O
by	O
non-specialist	O
users	O
.	O
</s>
<s>
Early	O
systems	O
for	O
software	O
configuration	O
of	O
devices	O
included	O
the	O
MSX	B-Operating_System
standard	O
,	O
NuBus	B-Device
,	O
Amiga	B-Device
Autoconfig	I-Device
,	O
and	O
IBM	O
Microchannel	B-Device
.	O
</s>
<s>
Initially	O
all	O
expansion	B-Device
cards	I-Device
for	O
the	O
IBM	B-Device
PC	I-Device
required	O
physical	O
selection	O
of	O
I/O	B-General_Concept
configuration	O
on	O
the	O
board	O
with	O
jumper	B-Device
straps	O
or	O
DIP	O
switches	O
,	O
but	O
increasingly	O
ISA	B-Architecture
bus	I-Architecture
devices	O
were	O
arranged	O
for	O
software	O
configuration	O
.	O
</s>
<s>
By	O
1995	O
,	O
Microsoft	B-Application
Windows	I-Application
included	O
a	O
comprehensive	O
method	O
of	O
enumerating	O
hardware	O
at	O
boot	O
time	O
and	O
allocating	O
resources	O
,	O
which	O
was	O
called	O
the	O
"	O
Plug	B-Device
and	I-Device
Play	I-Device
"	O
standard	O
.	O
</s>
<s>
Plug	B-Device
and	I-Device
play	I-Device
devices	O
can	O
have	O
resources	O
allocated	O
at	O
boot-time	O
only	O
,	O
or	O
may	O
be	O
hotplug	B-Device
systems	O
such	O
as	O
USB	B-Protocol
and	O
IEEE	B-Protocol
1394	I-Protocol
(	O
FireWire	B-Protocol
)	O
.	O
</s>
<s>
Rather	O
than	O
cutting	O
and	O
soldering	O
connections	O
,	O
configuration	O
was	O
accomplished	O
by	O
jumpers	B-Device
or	O
DIP	O
switches	O
.	O
</s>
<s>
Later	O
on	O
this	O
configuration	O
process	O
was	O
automated	O
:	O
Plug	B-Device
and	I-Device
Play	I-Device
.	O
</s>
<s>
The	O
MSX	B-Operating_System
system	O
,	O
released	O
in	O
1983	O
,	O
was	O
designed	O
to	O
be	O
plug	B-Device
and	I-Device
play	I-Device
from	O
the	O
ground	O
up	O
,	O
and	O
achieved	O
this	O
by	O
a	O
system	O
of	O
slots	O
and	O
subslots	O
,	O
where	O
each	O
had	O
its	O
own	O
virtual	B-General_Concept
address	I-General_Concept
space	I-General_Concept
,	O
thus	O
eliminating	O
device	O
addressing	O
conflicts	O
in	O
its	O
very	O
source	O
.	O
</s>
<s>
No	O
jumpers	B-Device
or	O
any	O
manual	O
configuration	O
was	O
required	O
,	O
and	O
the	O
independent	O
address	O
space	O
for	O
each	O
slot	O
allowed	O
very	O
cheap	O
and	O
commonplace	O
chips	O
to	O
be	O
used	O
,	O
alongside	O
cheap	O
glue	O
logic	O
.	O
</s>
<s>
The	O
ROM	O
extensions	O
abstracted	B-Operating_System
any	I-Operating_System
hardware	I-Operating_System
differences	I-Operating_System
and	O
offered	O
standard	O
APIs	O
as	O
specified	O
by	O
ASCII	O
Corporation	O
.	O
</s>
<s>
In	O
1984	O
,	O
the	O
NuBus	B-Device
architecture	O
was	O
developed	O
by	O
the	O
Massachusetts	O
Institute	O
of	O
Technology	O
(	O
MIT	O
)	O
as	O
a	O
platform	O
agnostic	O
peripheral	O
interface	O
that	O
fully	O
automated	O
device	O
configuration	O
.	O
</s>
<s>
However	O
,	O
this	O
agnostic	O
approach	O
increased	O
interfacing	O
complexity	O
and	O
required	O
support	O
chips	O
on	O
every	O
device	O
which	O
in	O
the	O
1980s	O
was	O
expensive	O
to	O
do	O
,	O
and	O
apart	O
from	O
its	O
use	O
in	O
Apple	B-Device
Macintoshes	I-Device
and	O
NeXT	O
machines	O
,	O
the	O
technology	O
was	O
not	O
widely	O
adopted	O
.	O
</s>
<s>
In	O
1984	O
,	O
Commodore	O
developed	O
the	O
Autoconfig	B-Device
protocol	O
and	O
the	O
Zorro	O
expansion	B-Device
bus	I-Device
for	O
its	O
Amiga	B-Device
line	O
of	O
expandable	O
computers	O
.	O
</s>
<s>
Like	O
NuBus	B-Device
,	O
Zorro	O
devices	O
had	O
absolutely	O
no	O
jumpers	B-Device
or	O
DIP	O
switches	O
.	O
</s>
<s>
The	O
Zorro	O
architecture	O
did	O
not	O
spread	O
to	O
general	O
computing	O
use	O
outside	O
of	O
the	O
Amiga	B-Device
product	O
line	O
,	O
but	O
was	O
eventually	O
upgraded	O
as	O
Zorro	B-Device
II	I-Device
and	O
Zorro	B-Device
III	I-Device
for	O
the	O
later	O
iteration	O
of	O
Amiga	B-Device
computers	I-Device
.	O
</s>
<s>
In	O
1987	O
,	O
IBM	O
released	O
an	O
update	O
to	O
the	O
IBM	B-Device
PC	I-Device
known	O
as	O
the	O
Personal	B-Device
System/2	I-Device
line	O
of	O
computers	O
using	O
the	O
Micro	B-Device
Channel	I-Device
Architecture	I-Device
.	O
</s>
<s>
The	O
PS/2	B-Device
was	O
capable	O
of	O
totally	O
automatic	O
self-configuration	O
.	O
</s>
<s>
Every	O
piece	O
of	O
expansion	O
hardware	O
was	O
issued	O
with	O
a	O
floppy	O
disk	O
containing	O
a	O
special	O
file	O
used	O
to	O
auto-configure	B-Device
the	O
hardware	O
to	O
work	O
with	O
the	O
computer	O
.	O
</s>
<s>
However	O
,	O
the	O
disks	O
posed	O
a	O
problem	O
if	O
they	O
were	O
damaged	O
or	O
lost	O
,	O
as	O
the	O
only	O
options	O
at	O
the	O
time	O
to	O
obtain	O
replacements	O
were	O
via	O
postal	O
mail	O
or	O
IBM	O
's	O
dial-up	O
BBS	B-Application
service	O
.	O
</s>
<s>
Micro	B-Device
Channel	I-Device
did	O
not	O
gain	O
widespread	O
support	O
because	O
IBM	O
wanted	O
to	O
exclude	O
clone	O
manufacturers	O
from	O
this	O
next	O
generation	O
computing	O
platform	O
.	O
</s>
<s>
In	O
time	O
,	O
many	O
Industry	B-Architecture
Standard	I-Architecture
Architecture	I-Architecture
(	O
ISA	O
)	O
cards	O
incorporated	O
,	O
through	O
proprietary	O
and	O
varied	O
techniques	O
,	O
hardware	O
to	O
self-configure	O
or	O
to	O
provide	O
for	O
software	O
configuration	O
;	O
often	O
,	O
the	O
card	O
came	O
with	O
a	O
configuration	O
program	O
on	O
disk	O
that	O
could	O
automatically	O
set	O
the	O
software-configurable	O
(	O
but	O
not	O
itself	O
self-configuring	O
)	O
hardware	O
.	O
</s>
<s>
Some	O
cards	O
had	O
both	O
jumpers	B-Device
and	O
software-configuration	O
,	O
with	O
some	O
settings	O
controlled	O
by	O
each	O
;	O
this	O
compromise	O
reduced	O
the	O
number	O
of	O
jumpers	B-Device
that	O
had	O
to	O
be	O
set	O
,	O
while	O
avoiding	O
great	O
expense	O
for	O
certain	O
settings	O
,	O
e.g.	O
</s>
<s>
The	O
problems	O
of	O
required	O
jumpers	B-Device
continued	O
on	O
,	O
but	O
slowly	O
diminished	O
as	O
more	O
and	O
more	O
devices	O
,	O
both	O
ISA	O
and	O
other	O
types	O
,	O
included	O
extra	O
self-configuration	O
hardware	O
.	O
</s>
<s>
ISA	O
PnP	O
or	O
(	O
legacy	O
)	O
Plug	B-Device
&	I-Device
Play	I-Device
ISA	O
was	O
a	O
plug-and-play	B-Device
system	O
that	O
used	O
a	O
combination	O
of	O
modifications	O
to	O
hardware	O
,	O
the	O
system	O
BIOS	O
,	O
and	O
operating	O
system	O
software	O
to	O
automatically	O
manage	O
resource	O
allocations	O
.	O
</s>
<s>
It	O
was	O
superseded	O
by	O
the	O
PCI	B-Protocol
bus	I-Protocol
during	O
the	O
mid-1990s	O
.	O
</s>
<s>
The	O
PCI	B-Protocol
plug	B-Device
and	I-Device
play	I-Device
(	O
autoconfiguration	B-Device
)	O
is	O
based	O
on	O
the	O
PCI	B-Protocol
BIOS	O
Specification	O
in	O
1990s	O
,	O
the	O
PCI	B-Protocol
BIOS	O
Specification	O
is	O
superseded	O
by	O
the	O
ACPI	B-Device
in	O
2000s	O
.	O
</s>
<s>
In	O
1995	O
,	O
Microsoft	O
released	O
Windows	B-Application
95	I-Application
,	O
which	O
tried	O
to	O
automate	O
device	O
detection	O
and	O
configuration	O
as	O
much	O
as	O
possible	O
,	O
but	O
could	O
still	O
fall	O
back	O
to	O
manual	O
settings	O
if	O
necessary	O
.	O
</s>
<s>
During	O
the	O
initial	O
install	O
process	O
of	O
Windows	B-Application
95	I-Application
,	O
it	O
would	O
attempt	O
to	O
automatically	O
detect	O
all	O
devices	O
installed	O
in	O
the	O
system	O
.	O
</s>
<s>
At	O
the	O
time	O
,	O
there	O
could	O
be	O
a	O
mix	O
of	O
devices	O
in	O
a	O
system	O
,	O
some	O
capable	O
of	O
automatic	O
configuration	O
,	O
and	O
some	O
still	O
using	O
fully	O
manual	O
settings	O
via	O
jumpers	B-Device
and	O
DIP	O
switches	O
.	O
</s>
<s>
The	O
old	O
world	O
of	O
DOS	O
still	O
lurked	O
underneath	O
Windows	B-Application
95	I-Application
,	O
and	O
systems	O
could	O
be	O
configured	O
to	O
load	O
devices	O
three	O
different	O
ways	O
:	O
</s>
<s>
Microsoft	O
could	O
not	O
assert	O
full	O
control	O
over	O
all	O
device	O
settings	O
,	O
so	O
configuration	O
files	O
could	O
include	O
a	O
mix	O
of	O
driver	O
entries	O
inserted	O
by	O
the	O
Windows	B-Application
95	I-Application
automatic	O
configuration	O
process	O
,	O
and	O
could	O
also	O
include	O
driver	O
entries	O
inserted	O
or	O
modified	O
manually	O
by	O
the	O
computer	O
users	O
themselves	O
.	O
</s>
<s>
The	O
Windows	B-Application
95	I-Application
Device	O
Manager	O
also	O
could	O
offer	O
users	O
a	O
choice	O
of	O
several	O
semi-automatic	O
configurations	O
to	O
try	O
to	O
free	O
up	O
resources	O
for	O
devices	O
that	O
still	O
needed	O
manual	O
configuration	O
.	O
</s>
<s>
Also	O
,	O
although	O
some	O
later	O
ISA	O
devices	O
were	O
capable	O
of	O
automatic	O
configuration	O
,	O
it	O
was	O
common	O
for	O
PC	O
ISA	O
expansion	B-Device
cards	I-Device
to	O
limit	O
themselves	O
to	O
a	O
very	O
small	O
number	O
of	O
choices	O
for	O
interrupt	B-General_Concept
request	I-General_Concept
lines	O
.	O
</s>
<s>
The	O
hardware	O
of	O
PC	O
computers	O
additionally	O
limited	O
device	O
expansion	O
options	O
because	O
interrupts	O
could	O
not	O
be	O
shared	O
,	O
and	O
some	O
multifunction	O
expansion	B-Device
cards	I-Device
would	O
use	O
multiple	O
interrupts	O
for	O
different	O
card	O
functions	O
,	O
such	O
as	O
a	O
dual-port	O
serial	O
card	O
requiring	O
a	O
separate	O
interrupt	O
for	O
each	O
serial	O
port	O
.	O
</s>
<s>
This	O
led	O
to	O
device	O
conflicts	O
within	O
Windows	B-Application
95	I-Application
,	O
resulting	O
in	O
devices	O
which	O
were	O
supposed	O
to	O
be	O
fully	O
self-configuring	O
failing	O
to	O
work	O
.	O
</s>
<s>
The	O
unreliability	O
of	O
the	O
device	O
installation	O
process	O
led	O
to	O
Plug	B-Device
and	I-Device
Play	I-Device
being	O
sometimes	O
referred	O
to	O
as	O
Plug	B-Device
and	I-Device
Pray	I-Device
.	O
</s>
<s>
Until	O
approximately	O
2000	O
,	O
PC	O
computers	O
could	O
still	O
be	O
purchased	O
with	O
a	O
mix	O
of	O
ISA	O
and	O
PCI	B-Protocol
slots	I-Protocol
,	O
so	O
it	O
was	O
still	O
possible	O
that	O
manual	O
ISA	O
device	O
configuration	O
might	O
be	O
necessary	O
.	O
</s>
<s>
Although	O
both	O
FireWire	B-Protocol
and	O
USB	B-Protocol
have	O
bandwidth	O
that	O
must	O
be	O
shared	O
by	O
all	O
devices	O
,	O
most	O
modern	O
operating	O
systems	O
are	O
unable	O
to	O
monitor	O
and	O
report	O
the	O
amount	O
of	O
bandwidth	O
being	O
used	O
or	O
available	O
,	O
or	O
to	O
identify	O
which	O
devices	O
are	O
currently	O
using	O
the	O
interface	O
.	O
</s>
