<s>
The	O
IBM	B-Device
Personal	I-Device
Computer	I-Device
(	O
model	O
5150	O
,	O
commonly	O
known	O
as	O
the	O
IBM	B-Device
PC	I-Device
)	O
is	O
the	O
first	O
microcomputer	B-Architecture
released	O
in	O
the	O
IBM	B-Device
PC	I-Device
model	O
line	O
and	O
the	O
basis	O
for	O
the	O
IBM	B-Device
PC	I-Device
compatible	O
de	O
facto	O
standard	O
.	O
</s>
<s>
The	O
machine	O
was	O
based	O
on	O
open	B-Architecture
architecture	I-Architecture
and	O
third-party	O
peripherals	O
.	O
</s>
<s>
Over	O
time	O
,	O
expansion	B-Device
cards	I-Device
and	O
software	O
technology	O
increased	O
to	O
support	O
it	O
.	O
</s>
<s>
The	O
PC	O
had	O
a	O
substantial	B-Device
influence	I-Device
on	O
the	O
personal	O
computer	O
market	O
.	O
</s>
<s>
The	O
specifications	O
of	O
the	O
IBM	B-Device
PC	I-Device
became	O
one	O
of	O
the	O
most	O
popular	O
computer	O
design	O
standards	O
in	O
the	O
world	O
.	O
</s>
<s>
The	O
only	O
significant	O
competition	O
it	O
faced	O
from	O
a	O
non-compatible	O
platform	O
throughout	O
the	O
1980s	O
was	O
from	O
the	O
Apple	O
Macintosh	B-Device
product	O
line	O
.	O
</s>
<s>
The	O
majority	O
of	O
contemporary	O
personal	O
computers	O
are	O
distant	O
descendants	O
of	O
the	O
IBM	B-Device
PC	I-Device
.	O
</s>
<s>
As	O
the	O
1980s	O
opened	O
,	O
their	O
market	O
share	O
in	O
the	O
growing	O
minicomputer	O
market	O
failed	O
to	O
keep	O
up	O
with	O
competitors	O
,	O
while	O
other	O
manufacturers	O
were	O
beginning	O
to	O
see	O
impressive	O
profits	O
in	O
the	O
microcomputer	B-Architecture
space	O
.	O
</s>
<s>
The	O
market	O
for	O
personal	O
computers	O
was	O
dominated	O
at	B-Operating_System
the	O
time	O
by	O
Tandy	O
,	O
Commodore	O
,	O
and	O
Apple	O
,	O
whose	O
machines	O
sold	O
for	O
several	O
hundred	O
dollars	O
each	O
and	O
had	O
become	O
very	O
popular	O
.	O
</s>
<s>
The	O
microcomputer	B-Architecture
market	O
was	O
large	O
enough	O
for	O
IBM	O
's	O
attention	O
,	O
with	O
$15	O
billion	O
in	O
sales	O
by	O
1979	O
and	O
projected	O
annual	O
growth	O
of	O
more	O
than	O
40%	O
during	O
the	O
early	O
1980s	O
.	O
</s>
<s>
As	O
early	O
as	O
1980	O
there	O
were	O
rumors	O
of	O
IBM	O
developing	O
a	O
personal	O
computer	O
,	O
possibly	O
a	O
miniaturized	O
version	O
of	O
the	O
IBM	B-Device
System/370	I-Device
,	O
and	O
Matsushita	O
acknowledged	O
publicly	O
that	O
it	O
had	O
discussed	O
with	O
IBM	O
the	O
possibility	O
of	O
manufacturing	O
a	O
personal	O
computer	O
in	O
partnership	O
,	O
although	O
this	O
project	O
was	O
abandoned	O
.	O
</s>
<s>
IBM	O
had	O
previously	O
produced	O
microcomputers	B-Architecture
,	O
such	O
as	O
1975	O
's	O
IBM	B-Device
5100	I-Device
,	O
but	O
targeted	O
them	O
towards	O
businesses	O
;	O
the	O
5100	O
had	O
a	O
price	O
tag	O
as	O
high	O
as	O
$	O
20,000	O
.	O
</s>
<s>
Atari	O
proposed	O
to	O
IBM	O
in	O
1980	O
that	O
it	O
act	O
as	O
original	O
equipment	O
manufacturer	O
for	O
an	O
IBM	O
microcomputer	B-Architecture
,	O
a	O
potential	O
solution	O
to	O
IBM	O
's	O
known	O
inability	O
to	O
move	O
quickly	O
to	O
meet	O
a	O
rapidly	O
changing	O
market	O
.	O
</s>
<s>
The	O
prototype	O
worked	O
poorly	O
but	O
was	O
presented	O
with	O
a	O
detailed	O
business	O
plan	O
which	O
proposed	O
that	O
the	O
new	O
computer	O
have	O
an	O
open	B-Architecture
architecture	I-Architecture
,	O
use	O
non-proprietary	O
components	O
and	O
software	O
,	O
and	O
be	O
sold	O
through	O
retail	O
stores	O
,	O
all	O
contrary	O
to	O
IBM	O
practice	O
.	O
</s>
<s>
It	O
also	O
estimated	O
sales	O
of	O
220,000	O
computers	O
over	O
three	O
years	O
,	O
more	O
than	O
IBM	O
's	O
entire	O
installed	B-Operating_System
base	I-Operating_System
.	O
</s>
<s>
Several	O
CPUs	O
were	O
considered	O
,	O
including	O
the	O
Texas	B-General_Concept
Instruments	I-General_Concept
TMS9900	I-General_Concept
,	O
Motorola	B-Device
68000	I-Device
and	O
Intel	B-Device
8088	I-Device
.	O
</s>
<s>
The	O
68000	B-Device
was	O
considered	O
the	O
best	O
choice	O
,	O
but	O
was	O
not	O
production-ready	O
like	O
the	O
others	O
.	O
</s>
<s>
The	O
IBM	B-Device
801	I-Device
RISC	O
processor	O
was	O
also	O
considered	O
,	O
since	O
it	O
was	O
considerably	O
more	O
powerful	O
than	O
the	O
other	O
options	O
,	O
but	O
rejected	O
due	O
to	O
the	O
design	O
constraint	O
to	O
use	O
off-the-shelf	O
parts	O
.	O
</s>
<s>
IBM	O
chose	O
the	O
8088	B-Device
over	O
the	O
similar	O
but	O
superior	O
8086	B-General_Concept
because	O
Intel	O
offered	O
a	O
better	O
price	O
for	O
the	O
former	O
and	O
could	O
provide	O
more	O
units	O
,	O
and	O
the	O
8088	B-Device
's	O
8-bit	O
bus	O
reduced	O
the	O
cost	O
of	O
the	O
rest	O
of	O
the	O
computer	O
.	O
</s>
<s>
The	O
8088	B-Device
had	O
the	O
advantage	O
that	O
IBM	O
already	O
had	O
familiarity	O
with	O
the	O
8085	O
from	O
designing	O
the	O
IBM	B-Device
System/23	I-Device
Datamaster	I-Device
.	O
</s>
<s>
The	O
62-pin	O
expansion	B-Device
bus	I-Device
slots	O
were	O
also	O
designed	O
to	O
be	O
similar	O
to	O
the	O
Datamaster	O
slots	O
,	O
and	O
its	O
keyboard	O
design	O
and	O
layout	O
became	O
the	O
Model	B-Device
F	I-Device
keyboard	I-Device
shipped	O
with	O
the	O
PC	O
,	O
but	O
otherwise	O
the	O
PC	O
design	O
differed	O
in	O
many	O
ways	O
.	O
</s>
<s>
The	O
8088	B-Device
motherboard	B-Device
was	O
designed	O
in	O
40	O
days	O
,	O
with	O
a	O
working	O
prototype	O
created	O
in	O
four	O
months	O
,	O
demonstrated	O
in	O
January	O
1981	O
.	O
</s>
<s>
PCs	O
were	O
assembled	O
in	O
an	O
IBM	O
plant	O
in	O
Boca	O
Raton	O
,	O
with	O
components	O
made	O
at	B-Operating_System
various	O
IBM	O
and	O
third	O
party	O
factories	O
.	O
</s>
<s>
Many	O
of	O
the	O
designers	O
were	O
computer	O
hobbyists	O
who	O
owned	O
their	O
own	O
computers	O
,	O
including	O
many	O
Apple	O
II	O
owners	O
,	O
which	O
influenced	O
the	O
decisions	O
to	O
design	O
the	O
computer	O
with	O
an	O
open	B-Architecture
architecture	I-Architecture
and	O
publish	O
technical	O
information	O
so	O
others	O
could	O
create	O
compatible	O
software	O
and	O
expansion	B-Device
slot	I-Device
peripherals	O
.	O
</s>
<s>
During	O
the	O
design	O
process	O
IBM	O
avoided	O
vertical	O
integration	O
as	O
much	O
as	O
possible	O
,	O
for	O
example	O
choosing	O
to	O
license	O
Microsoft	B-Language
BASIC	I-Language
rather	O
than	O
utilizing	O
the	O
in-house	O
version	O
of	O
BASIC	O
used	O
for	O
mainframes	O
due	O
to	O
the	O
better	O
existing	O
public	O
familiarity	O
with	O
the	O
Microsoft	O
version	O
.	O
</s>
<s>
The	O
IBM	B-Device
PC	I-Device
debuted	O
on	O
August	O
12	O
,	O
1981	O
after	O
a	O
twelve-month	O
development	O
.	O
</s>
<s>
Pricing	O
started	O
at	B-Operating_System
$	O
1,565	O
for	O
a	O
configuration	O
with	O
16	O
KB	O
RAM	O
,	O
Color	B-Device
Graphics	I-Device
Adapter	I-Device
,	O
and	O
no	O
disk	O
drives	O
.	O
</s>
<s>
Sales	O
exceeded	O
IBM	O
's	O
expectations	O
by	O
as	O
much	O
as	O
800%	O
,	O
with	O
the	O
company	O
at	B-Operating_System
one	O
point	O
shipping	O
as	O
many	O
as	O
40,000	O
PCs	O
per	O
month	O
.	O
</s>
<s>
Software	O
support	O
from	O
the	O
industry	O
grew	O
rapidly	O
,	O
with	O
the	O
IBM	O
nearly	O
instantly	O
becoming	O
the	O
primary	O
target	O
for	O
most	O
microcomputer	B-Architecture
software	O
development	O
.	O
</s>
<s>
One	O
publication	O
counted	O
753	O
software	O
packages	O
available	O
a	O
year	O
after	O
the	O
PC	O
's	O
release	O
,	O
four	O
times	O
as	O
many	O
as	O
were	O
available	O
for	O
the	O
Macintosh	B-Device
a	O
year	O
after	O
its	O
launch	O
.	O
</s>
<s>
Hardware	O
support	O
also	O
grew	O
rapidly	O
,	O
with	O
30	O
–	O
40	O
companies	O
competing	O
to	O
sell	O
memory	O
expansion	B-Device
cards	I-Device
within	O
a	O
year	O
.	O
</s>
<s>
For	O
low	O
cost	O
and	O
a	O
quick	O
design	O
turnaround	O
time	O
,	O
the	O
hardware	O
design	O
of	O
the	O
IBM	B-Device
PC	I-Device
used	O
entirely	O
"	O
off-the-shelf	O
"	O
parts	O
from	O
third	O
party	O
manufacturers	O
,	O
rather	O
than	O
unique	O
hardware	O
designed	O
by	O
IBM	O
.	O
</s>
<s>
The	O
back	O
panel	O
houses	O
a	O
power	O
inlet	O
and	O
switch	O
,	O
a	O
keyboard	O
connector	O
,	O
a	O
cassette	B-Device
connector	O
and	O
a	O
series	O
of	O
tall	O
vertical	O
slots	O
with	O
blank	O
metal	O
panels	O
which	O
can	O
be	O
removed	O
in	O
order	O
to	O
install	O
expansion	B-Device
cards	I-Device
.	O
</s>
<s>
Internally	O
,	O
the	O
chassis	O
is	O
dominated	O
by	O
a	O
motherboard	B-Device
which	O
houses	O
the	O
CPU	O
,	O
built-in	O
RAM	O
,	O
expansion	O
RAM	O
sockets	O
,	O
and	O
slots	O
for	O
expansion	B-Device
cards	I-Device
.	O
</s>
<s>
The	O
IBM	B-Device
PC	I-Device
was	O
highly	O
expandable	O
and	O
upgradeable	O
,	O
but	O
the	O
base	O
factory	O
configuration	O
included	O
:	O
</s>
<s>
The	O
PC	O
is	O
built	O
around	O
a	O
single	O
large	O
circuit	O
board	O
called	O
a	O
motherboard	B-Device
which	O
carries	O
the	O
processor	O
,	O
built-in	O
RAM	O
,	O
expansion	B-Architecture
slots	I-Architecture
,	O
keyboard	O
and	O
cassette	B-Device
ports	O
,	O
and	O
the	O
various	O
peripheral	O
integrated	O
circuits	O
that	O
connected	O
and	O
controlled	O
the	O
components	O
of	O
the	O
machine	O
.	O
</s>
<s>
The	O
peripheral	O
chips	O
included	O
an	O
Intel	B-Device
8259	I-Device
PIC	B-Architecture
,	O
an	O
Intel	B-Device
8237	I-Device
DMA	B-General_Concept
controller	I-General_Concept
,	O
and	O
an	O
Intel	B-Device
8253	I-Device
PIT	B-Device
.	O
</s>
<s>
The	O
PIT	B-Device
provides	O
clock	O
"	O
ticks	O
"	O
and	O
dynamic	O
memory	O
refresh	O
timing	O
.	O
</s>
<s>
The	O
CPU	O
is	O
an	O
Intel	B-Device
8088	I-Device
,	O
a	O
cost-reduced	O
form	O
of	O
the	O
Intel	B-General_Concept
8086	I-General_Concept
which	O
largely	O
retains	O
the	O
8086	B-General_Concept
's	O
internal	O
16-bit	O
logic	O
,	O
but	O
exposes	O
only	O
an	O
8-bit	O
bus	O
.	O
</s>
<s>
The	O
CPU	O
is	O
clocked	O
at	B-Operating_System
4.77MHz	O
,	O
which	O
would	O
eventually	O
become	O
an	O
issue	O
when	O
clones	O
and	O
later	O
PC	O
models	O
offered	O
higher	O
CPU	O
speeds	O
that	O
broke	O
compatibility	O
with	O
software	O
developed	O
for	O
the	O
original	O
PC	O
.	O
</s>
<s>
The	O
single	O
base	O
clock	O
frequency	O
for	O
the	O
system	O
was	O
14.31818	O
MHz	O
,	O
which	O
when	O
divided	O
by	O
3	O
,	O
yielded	O
the	O
4.77	O
MHz	O
for	O
the	O
CPU	O
(	O
which	O
was	O
considered	O
close	O
enough	O
to	O
the	O
then	O
5	O
MHz	O
limit	O
of	O
the	O
8088	B-Device
)	O
,	O
and	O
when	O
divided	O
by	O
4	O
,	O
yielded	O
the	O
required	O
3.579545	O
MHz	O
for	O
the	O
NTSC	O
color	O
carrier	O
frequency	O
.	O
</s>
<s>
The	O
PC	B-Device
motherboard	I-Device
included	O
a	O
second	O
,	O
empty	O
socket	O
,	O
described	O
by	O
IBM	O
simply	O
as	O
an	O
"	O
auxiliary	O
processor	O
socket	O
"	O
,	O
although	O
the	O
most	O
obvious	O
use	O
was	O
the	O
addition	O
of	O
an	O
Intel	B-Device
8087	I-Device
math	O
coprocessor	O
,	O
which	O
improved	O
floating-point	B-Algorithm
math	I-Algorithm
performance	O
.	O
</s>
<s>
RAM	O
upgrades	O
were	O
provided	O
both	O
by	O
IBM	O
and	O
third	O
parties	O
as	O
expansion	B-Device
cards	I-Device
,	O
and	O
could	O
upgrade	O
the	O
machine	O
to	O
a	O
maximum	O
of	O
256	O
KB	O
on	O
the	O
motherboard	B-Device
,	O
and	O
640	O
KB	O
total	O
.	O
</s>
<s>
The	O
BIOS	O
is	O
the	O
firmware	O
of	O
the	O
IBM	B-Device
PC	I-Device
,	O
occupying	O
one	O
8	O
KB	O
chip	O
on	O
the	O
motherboard	B-Device
.	O
</s>
<s>
While	O
most	O
home	O
computers	O
had	O
built-in	O
video	O
output	O
hardware	O
,	O
IBM	O
took	O
the	O
unusual	O
approach	O
of	O
offering	O
two	O
different	O
graphics	O
options	O
,	O
the	O
MDA	B-Device
and	O
CGA	B-Device
cards	O
.	O
</s>
<s>
CGA	B-Device
used	O
the	O
same	O
scan	O
rate	O
as	O
NTSC	O
television	O
,	O
allowing	O
it	O
to	O
provide	O
a	O
composite	O
video	O
output	O
which	O
could	O
be	O
used	O
with	O
any	O
compatible	O
television	O
or	O
composite	O
monitor	O
,	O
as	O
well	O
as	O
a	O
direct-drive	O
TTL	O
output	O
suitable	O
for	O
use	O
with	O
any	O
RGBI	O
monitor	O
using	O
an	O
NTSC	O
scan	O
rate	O
.	O
</s>
<s>
IBM	O
also	O
sold	O
the	O
5153	O
color	O
monitor	O
for	O
this	O
purpose	O
,	O
but	O
it	O
was	O
not	O
available	O
at	B-Operating_System
release	O
and	O
was	O
not	O
released	O
until	O
March	O
1983	O
.	O
</s>
<s>
MDA	B-Device
scanned	O
at	B-Operating_System
a	O
higher	O
frequency	O
and	O
required	O
a	O
proprietary	O
monitor	O
,	O
the	O
IBM	B-Device
5151	I-Device
.	O
</s>
<s>
The	O
card	O
also	O
included	O
a	O
built-in	O
printer	B-Device
port	I-Device
.	O
</s>
<s>
For	O
instance	O
,	O
AutoCAD	B-Algorithm
,	O
Lotus	B-Application
1-2-3	I-Application
and	O
other	O
software	O
allowed	O
use	O
of	O
a	O
CGA	B-Device
Monitor	O
for	O
graphics	O
and	O
a	O
separate	O
monochrome	B-Device
monitor	I-Device
for	O
text	O
menus	O
.	O
</s>
<s>
Third	O
parties	O
went	O
on	O
to	O
provide	O
an	O
enormous	O
variety	O
of	O
aftermarket	O
graphics	O
adapters	O
,	O
such	O
as	O
the	O
Hercules	B-Device
Graphics	I-Device
Card	I-Device
.	O
</s>
<s>
The	O
software	O
and	O
hardware	O
of	O
the	O
PC	O
,	O
at	B-Operating_System
release	O
,	O
was	O
designed	O
around	O
a	O
single	O
8-bit	O
adaptation	O
of	O
the	O
ASCII	O
character	O
set	O
,	O
now	O
known	O
as	O
code	O
page	O
437	O
.	O
</s>
<s>
The	O
two	O
bays	O
in	O
the	O
front	O
of	O
the	O
machine	O
could	O
be	O
populated	O
with	O
one	O
or	O
two	O
5.25	O
″	O
floppy	B-Device
disk	I-Device
drives	I-Device
,	O
storing	O
160	O
KB	O
per	O
disk	O
side	O
for	O
a	O
total	O
of	O
320	O
KB	O
of	O
storage	O
on	O
one	O
disk	O
.	O
</s>
<s>
The	O
floppy	B-Device
drives	I-Device
require	O
a	O
controller	O
card	O
inserted	O
in	O
an	O
expansion	B-Device
slot	I-Device
,	O
and	O
connect	O
with	O
a	O
single	O
ribbon	O
cable	O
with	O
two	O
edge	O
connectors	O
.	O
</s>
<s>
The	O
IBM	O
floppy	B-Device
controller	O
card	O
provides	O
an	O
external	O
37-pin	O
D-sub	O
connector	O
for	O
attachment	O
of	O
an	O
external	O
disk	O
drive	O
,	O
although	O
IBM	O
did	O
not	O
offer	O
one	O
for	O
purchase	O
until	O
1986	O
.	O
</s>
<s>
As	O
was	O
common	O
for	O
home	O
computers	O
of	O
the	O
era	O
,	O
the	O
IBM	B-Device
PC	I-Device
offered	O
a	O
port	O
for	O
connecting	O
a	O
cassette	B-Device
data	I-Device
recorder	I-Device
.	O
</s>
<s>
Unlike	O
the	O
typical	O
home	O
computer	O
however	O
,	O
this	O
was	O
never	O
a	O
major	O
avenue	O
for	O
software	O
distribution	O
,	O
probably	O
because	O
very	O
few	O
PCs	O
were	O
sold	O
without	O
floppy	B-Device
drives	I-Device
.	O
</s>
<s>
The	O
port	O
was	O
removed	O
on	O
the	O
very	O
next	O
PC	O
model	O
,	O
the	O
XT	B-Device
.	O
</s>
<s>
At	B-Operating_System
release	O
,	O
IBM	O
did	O
not	O
offer	O
any	O
hard	O
disk	O
drive	O
option	O
and	O
adding	O
one	O
was	O
difficult	O
-	O
the	O
PC	O
's	O
stock	O
power	O
supply	O
had	O
inadequate	O
power	O
to	O
run	O
a	O
hard	O
drive	O
,	O
the	O
motherboard	B-Device
did	O
not	O
support	O
BIOS	O
expansion	O
ROMs	O
which	O
was	O
needed	O
to	O
support	O
a	O
hard	O
drive	O
controller	O
,	O
and	O
both	O
PC	B-Operating_System
DOS	I-Operating_System
and	O
the	O
BIOS	O
had	O
no	O
support	O
for	O
hard	O
disks	O
.	O
</s>
<s>
After	O
the	O
XT	B-Device
was	O
released	O
,	O
IBM	O
altered	O
the	O
design	O
of	O
the	O
5150	O
to	O
add	O
most	O
of	O
these	O
capabilities	O
,	O
except	O
for	O
the	O
upgraded	O
power	O
supply	O
.	O
</s>
<s>
At	B-Operating_System
this	O
point	O
adding	O
a	O
hard	O
drive	O
was	O
possible	O
,	O
but	O
required	O
the	O
purchase	O
of	O
the	O
IBM	O
5161	O
Expansion	O
Unit	O
,	O
which	O
contained	O
a	O
dedicated	O
power	O
supply	O
and	O
included	O
a	O
hard	O
drive	O
.	O
</s>
<s>
Although	O
official	O
hard	O
drive	O
support	O
did	O
not	O
exist	O
,	O
the	O
third	O
party	O
market	O
did	O
provide	O
early	O
hard	O
drives	O
that	O
connected	O
to	O
the	O
floppy	B-Device
disk	I-Device
controller	O
,	O
but	O
required	O
a	O
patched	O
version	O
of	O
PC	B-Operating_System
DOS	I-Operating_System
to	O
support	O
the	O
larger	O
disk	O
sizes	O
.	O
</s>
<s>
The	O
only	O
option	O
for	O
human	B-General_Concept
interface	I-General_Concept
provided	O
in	O
the	O
base	O
PC	O
was	O
the	O
built-in	O
keyboard	O
port	O
,	O
meant	O
to	O
connect	O
to	O
the	O
included	O
Model	B-Device
F	I-Device
keyboard	I-Device
.	O
</s>
<s>
The	O
Model	B-Device
F	I-Device
was	O
initially	O
developed	O
for	O
the	O
IBM	B-Device
Datamaster	I-Device
,	O
and	O
was	O
substantially	O
better	O
than	O
the	O
keyboards	O
provided	O
with	O
virtually	O
all	O
home	O
computers	O
on	O
the	O
market	O
at	B-Operating_System
that	O
time	O
in	O
many	O
regards	O
-	O
number	O
of	O
keys	O
,	O
reliability	O
and	O
ergonomics	O
.	O
</s>
<s>
While	O
some	O
home	O
computers	O
of	O
the	O
time	O
utilized	O
chiclet	B-Device
keyboards	I-Device
or	O
inexpensive	O
mechanical	O
designs	O
,	O
the	O
IBM	O
keyboard	O
provided	O
good	O
ergonomics	O
,	O
reliable	O
and	O
positive	O
tactile	O
key	O
mechanisms	O
and	O
flip-up	O
feet	O
to	O
adjust	O
its	O
angle	O
.	O
</s>
<s>
Public	O
reception	O
of	O
the	O
keyboard	O
was	O
extremely	O
positive	O
,	O
with	O
some	O
sources	O
describing	O
it	O
as	O
a	O
major	O
selling	O
point	O
of	O
the	O
PC	O
and	O
even	O
as	O
"	O
the	O
best	O
keyboard	O
available	O
on	O
any	O
microcomputer.	O
"	O
</s>
<s>
At	B-Operating_System
release	O
,	O
IBM	O
provided	O
a	O
Game	B-Protocol
Control	I-Protocol
Adapter	I-Protocol
which	O
offered	O
a	O
15-pin	O
port	O
intended	O
for	O
the	O
connection	O
of	O
up	O
to	O
two	O
joysticks	O
,	O
each	O
having	O
two	O
analog	O
axes	O
and	O
two	O
buttons	O
.	O
</s>
<s>
Connectivity	O
to	O
other	O
computers	O
and	O
peripherals	O
was	O
initially	O
provided	O
through	O
serial	B-Protocol
and	O
parallel	B-Device
ports	I-Device
.	O
</s>
<s>
IBM	O
provided	O
a	O
serial	B-Protocol
card	I-Protocol
based	O
on	O
an	O
8250	B-Device
UART	I-Device
.	O
</s>
<s>
The	O
BIOS	O
supports	O
up	O
to	O
two	O
serial	B-Protocol
ports	I-Protocol
.	O
</s>
<s>
IBM	O
provided	O
two	O
different	O
options	O
for	O
connecting	O
Centronics-compatible	O
parallel	B-Device
printers	O
.	O
</s>
<s>
One	O
was	O
the	O
IBM	O
Printer	O
Adapter	O
,	O
and	O
the	O
other	O
was	O
integrated	O
into	O
the	O
MDA	B-Device
as	O
the	O
IBM	O
Monochrome	B-Device
Display	I-Device
and	I-Device
Printer	I-Device
Adapter	I-Device
.	O
</s>
<s>
The	O
expansion	O
capability	O
of	O
the	O
IBM	B-Device
PC	I-Device
was	O
very	O
significant	O
to	O
its	O
success	O
in	O
the	O
market	O
.	O
</s>
<s>
The	O
motherboard	B-Device
includes	O
five	O
62-pin	O
card	O
edge	O
connectors	O
which	O
are	O
connected	O
to	O
the	O
CPU	O
's	O
I/O	O
lines	O
.	O
</s>
<s>
IBM	O
referred	O
to	O
these	O
as	O
"	O
I/O	O
slots	O
,	O
"	O
but	O
after	O
the	O
expansion	O
of	O
the	O
PC	O
clone	O
industry	O
they	O
became	O
retroactively	O
known	O
as	O
the	O
ISA	B-Architecture
bus	I-Architecture
.	O
</s>
<s>
At	B-Operating_System
the	O
back	O
of	O
the	O
machine	O
is	O
a	O
metal	O
panel	O
,	O
integrated	O
into	O
the	O
steel	O
chassis	O
of	O
the	O
system	O
unit	O
,	O
with	O
a	O
series	O
of	O
vertical	O
slots	O
lined	O
up	O
with	O
each	O
card	O
slot	O
.	O
</s>
<s>
Most	O
expansion	B-Device
cards	I-Device
have	O
a	O
matching	O
metal	O
bracket	O
which	O
slots	O
into	O
one	O
of	O
these	O
openings	O
,	O
serving	O
two	O
purposes	O
.	O
</s>
<s>
The	O
PC	O
expansion	B-Architecture
slots	I-Architecture
can	O
accept	O
an	O
enormous	O
variety	O
of	O
expansion	O
hardware	O
,	O
adding	O
capabilities	O
such	O
as	O
:	O
</s>
<s>
Another	O
was	O
that	O
there	O
were	O
only	O
five	O
expansion	B-Architecture
slots	I-Architecture
,	O
which	O
tended	O
to	O
get	O
filled	O
up	O
by	O
essential	O
hardware	O
-	O
a	O
PC	O
with	O
a	O
graphics	O
card	O
,	O
memory	O
expansion	O
,	O
parallel	B-Device
card	O
and	O
serial	B-Protocol
card	I-Protocol
was	O
left	O
with	O
only	O
one	O
open	O
slot	O
,	O
for	O
instance	O
.	O
</s>
<s>
IBM	O
rectified	O
these	O
problems	O
in	O
the	O
later	O
XT	B-Device
,	O
which	O
included	O
more	O
slots	O
and	O
support	O
for	O
an	O
internal	O
hard	O
drive	O
,	O
but	O
at	B-Operating_System
the	O
same	O
time	O
released	O
the	O
5161	O
Expansion	O
Unit	O
,	O
which	O
could	O
be	O
used	O
with	O
either	O
the	O
XT	B-Device
or	O
the	O
original	O
PC	O
.	O
</s>
<s>
The	O
5161	O
connected	O
to	O
the	O
PC	O
system	O
unit	O
using	O
a	O
cable	O
and	O
a	O
card	O
plugged	O
into	O
an	O
expansion	B-Device
slot	I-Device
,	O
and	O
provided	O
a	O
second	O
system	O
chassis	O
with	O
more	O
expansion	B-Architecture
slots	I-Architecture
and	O
a	O
hard	O
drive	O
.	O
</s>
<s>
IBM	O
initially	O
announced	O
intent	O
to	O
support	O
multiple	O
operating	O
systems	O
:	O
CP/M	B-Operating_System
-86	I-Operating_System
,	O
UCSD	B-Language
p-System	I-Language
,	O
and	O
an	O
in-house	O
product	O
called	O
IBM	B-Operating_System
PC	I-Operating_System
DOS	I-Operating_System
,	O
developed	O
by	O
Microsoft	O
.	O
</s>
<s>
In	O
practice	O
,	O
IBM	O
's	O
expectation	O
and	O
intent	O
was	O
for	O
the	O
market	O
to	O
primarily	O
use	O
PC	B-Operating_System
DOS	I-Operating_System
,	O
CP/M	B-Operating_System
-86	I-Operating_System
was	O
not	O
available	O
for	O
six	O
months	O
after	O
the	O
PC	O
's	O
release	O
and	O
received	O
extremely	O
few	O
orders	O
once	O
it	O
was	O
,	O
and	O
p-System	B-Language
was	O
also	O
not	O
available	O
at	B-Operating_System
release	O
.	O
</s>
<s>
PC	B-Operating_System
DOS	I-Operating_System
rapidly	O
established	O
itself	O
as	O
the	O
standard	O
OS	O
for	O
the	O
PC	O
and	O
remained	O
the	O
standard	O
for	O
over	O
a	O
decade	O
,	O
with	O
a	O
variant	O
being	O
sold	O
by	O
Microsoft	O
themselves	O
as	O
MS-DOS	B-Application
.	O
</s>
<s>
Its	O
ROM	O
BASIC	O
supported	O
the	O
cassette	B-Device
tape	I-Device
interface	O
,	O
but	O
PC	B-Operating_System
DOS	I-Operating_System
did	O
not	O
,	O
limiting	O
use	O
of	O
that	O
interface	O
to	O
BASIC	O
only	O
.	O
</s>
<s>
PC	B-Operating_System
DOS	I-Operating_System
version	O
1.00	O
supported	O
only	O
160KB	O
SSDD	O
floppies	B-Device
,	O
but	O
version	O
1.1	O
,	O
which	O
was	O
released	O
nine	O
months	O
after	O
the	O
PC	O
's	O
introduction	O
,	O
supported	O
160KB	O
SSDD	O
and	O
320KB	O
DSDD	O
floppies	B-Device
.	O
</s>
<s>
Reception	O
of	O
the	O
IBM	B-Device
PC	I-Device
was	O
extremely	O
positive	O
.	O
</s>
<s>
Praise	O
was	O
directed	O
at	B-Operating_System
the	O
build	O
quality	O
of	O
the	O
PC	O
,	O
in	O
particular	O
its	O
keyboard	O
,	O
IBM	O
's	O
decision	O
to	O
use	O
open	O
specifications	O
to	O
encourage	O
third	O
party	O
software	O
and	O
hardware	O
development	O
,	O
their	O
speed	O
at	B-Operating_System
delivering	O
documentation	O
and	O
the	O
quality	O
therein	O
,	O
the	O
quality	O
of	O
the	O
video	O
display	O
,	O
and	O
the	O
use	O
of	O
commodity	O
components	O
from	O
established	O
suppliers	O
in	O
the	O
electronics	O
industry	O
.	O
</s>
<s>
Two	O
years	O
after	O
its	O
release	O
,	O
Byte	O
magazine	O
retrospectively	O
concluded	O
that	O
the	O
PC	O
had	O
succeeded	O
both	O
because	O
of	O
its	O
features	O
–	O
an	O
80-column	O
screen	O
,	O
open	B-Architecture
architecture	I-Architecture
,	O
and	O
high-quality	O
keyboard	O
–	O
and	O
the	O
failure	O
of	O
other	O
computer	O
manufacturers	O
to	O
achieve	O
these	O
features	O
first	O
:	O
</s>
<s>
Creative	B-General_Concept
Computing	I-General_Concept
that	O
year	O
named	O
the	O
PC	O
the	O
best	O
desktop	O
computer	O
between	O
$	O
2,000	O
and	O
$4	O
,	O
000	O
,	O
praising	O
its	O
vast	O
hardware	O
and	O
software	O
selection	O
,	O
manufacturer	O
support	O
,	O
and	O
resale	O
value	O
.	O
</s>
<s>
Many	O
IBM	B-Device
PCs	I-Device
remained	O
in	O
service	O
long	O
after	O
their	O
technology	O
became	O
largely	O
obsolete	O
.	O
</s>
<s>
For	O
instance	O
,	O
as	O
of	O
June	O
2006	O
(	O
23	O
–	O
25	O
years	O
after	O
release	O
)	O
IBM	B-Device
PC	I-Device
and	O
XT	B-Device
models	O
were	O
still	O
in	O
use	O
at	B-Operating_System
the	O
majority	O
of	O
U.S.	O
National	O
Weather	O
Service	O
upper-air	O
observing	O
sites	O
,	O
processing	O
data	O
returned	O
from	O
radiosondes	O
attached	O
to	O
weather	O
balloons	O
.	O
</s>
<s>
Due	O
to	O
its	O
status	O
as	O
the	O
first	O
entry	O
in	O
the	O
extremely	O
influential	O
PC	O
industry	O
,	O
the	O
original	O
IBM	B-Device
PC	I-Device
remains	O
valuable	O
as	O
a	O
collector	O
's	O
item	O
.	O
</s>
<s>
The	O
name	O
was	O
not	O
used	O
for	O
several	O
years	O
before	O
being	O
reused	O
for	O
the	O
IBM	B-Device
PC	I-Device
Series	I-Device
in	O
the	O
90s	O
and	O
early	O
2000s	O
.	O
</s>
<s>
+The	O
IBM	B-Device
PC	I-Device
line	O
Model	O
nameModel	O
#IntroducedDiscontinuedCPUFeatures	O
PC5150August	O
1981April	O
19878088Floppy	O
disk	O
or	O
cassette	B-Device
system.IBM	O
did	O
not	O
offer	O
own	O
brand	O
cassette	B-Device
recorders	O
,	O
but	O
the	O
5150	O
had	O
a	O
cassette	B-Device
player	O
jack	O
,	O
and	O
IBM	O
anticipated	O
that	O
entry-level	O
home	O
users	O
would	O
connect	O
their	O
own	O
cassette	B-Device
recorders	O
for	O
data	O
storage	O
instead	O
of	O
using	O
the	O
more	O
expensive	O
floppy	B-Device
drives	I-Device
(	O
and	O
use	O
their	O
existing	O
TV	O
sets	O
as	O
monitors	O
)	O
;	O
to	O
this	O
end	O
,	O
IBM	O
initially	O
offered	O
the	O
5150	O
in	O
a	O
basic	O
configuration	O
without	O
any	O
floppy	B-Device
drives	I-Device
or	O
monitor	O
at	B-Operating_System
the	O
price	O
of	O
$1	O
,	O
565	O
,	O
whereas	O
they	O
offered	O
a	O
system	O
with	O
a	O
monitor	O
and	O
single	O
floppy	B-Device
drive	I-Device
for	O
an	O
initial	O
$	O
3,005	O
.	O
</s>
<s>
Few	O
if	O
any	O
users	O
however	O
bought	O
IBM	B-Device
5150	I-Device
PCs	I-Device
without	O
floppy	B-Device
drives	I-Device
.	O
</s>
<s>
One	O
or	O
two	O
internal	O
floppy	B-Device
drives	I-Device
were	O
optional.XT5160March	O
1983April	O
19878088First	O
IBM	B-Device
PC	I-Device
to	O
come	O
with	O
an	O
internal	O
hard	O
drive	O
as	O
standard	O
.	O
</s>
<s>
XT/3705160/588October	O
1983April	O
198780885160	O
with	O
XT/370	O
Option	O
Kit	O
and	O
3277	O
Emulation	O
Adapter.3270	O
PC5271October	O
1983April	O
19878088With	O
3270	B-Operating_System
terminal	I-Operating_System
emulation	O
,	O
20	O
function	O
key	O
keyboardPCjr4860November	O
1983March	O
19858088Floppy-based	O
home	O
computer	O
,	O
but	O
also	O
used	O
ROM	O
cartridges	O
;	O
infrared	O
keyboard.Portable5155February	O
1984April	O
19868088Floppy-based	O
portableAT5170August	O
1984April	O
198780286Faster	O
processor	O
,	O
faster	O
system	O
bus	O
(	O
6	O
MHz	O
,	O
later	O
8	O
MHz	O
,	O
vs	O
4.77	O
MHz	O
)	O
,	O
jumperless	B-Device
configuration	O
,	O
real-time	O
clock	O
.	O
</s>
<s>
AT/3705170/599October	O
1984April	O
1987802865170	O
with	O
AT/370	O
Option	O
Kit	O
and	O
3277	O
Emulation	O
Adapter	O
.	O
</s>
<s>
3270	B-Operating_System
AT5281June	O
1985Scott	O
Mueller	O
,	O
Upgrading	O
and	O
Repairing	O
PCs	O
,	O
2nd	O
Ed	O
,	O
Que	O
Books	O
1992	O
,,	O
page	O
94April	O
198780286With	O
3270	B-Operating_System
terminal	I-Operating_System
emulation.Convertible5140April	O
1986August	O
198980C88Microfloppy	O
laptop	B-Device
portable	B-Device
XT	B-Device
2865162September	O
1986April	O
198780286Slow	O
hard	O
disk	O
,	O
but	O
zero	O
wait	B-Device
state	I-Device
memory	O
on	O
the	O
motherboard	B-Device
.	O
</s>
<s>
This	O
6	O
MHz	O
model	O
is	O
faster	O
than	O
the	O
8	O
MHz	O
AT	B-Operating_System
models	O
(	O
when	O
using	O
planar	O
memory	O
)	O
because	O
of	O
its	O
zero	O
wait	B-Device
state	I-Device
memory	O
.	O
</s>
<s>
As	O
with	O
all	O
PC-derived	O
systems	O
,	O
all	O
IBM	B-Device
PC	I-Device
models	O
are	O
nominally	O
software-compatible	O
,	O
although	O
some	O
timing-sensitive	O
software	O
will	O
not	O
run	O
correctly	O
on	O
models	O
with	O
faster	O
CPUs	O
.	O
</s>
<s>
Because	O
the	O
IBM	B-Device
PC	I-Device
was	O
based	O
on	O
commodity	O
hardware	O
rather	O
than	O
unique	O
IBM	O
components	O
,	O
and	O
because	O
its	O
operation	O
was	O
extensively	O
documented	O
by	O
IBM	O
,	O
creating	O
machines	O
that	O
were	O
fully	O
compatible	O
with	O
the	O
PC	O
offered	O
few	O
challenges	O
other	O
than	O
the	O
creation	O
of	O
a	O
compatible	O
BIOS	O
ROM	O
.	O
</s>
<s>
Simple	O
duplication	O
of	O
the	O
IBM	B-Device
PC	I-Device
BIOS	O
was	O
a	O
direct	O
violation	O
of	O
copyright	O
law	O
,	O
but	O
soon	O
into	O
the	O
PC	O
's	O
life	O
the	O
BIOS	O
was	O
reverse-engineered	O
by	O
companies	O
like	O
Compaq	O
,	O
Phoenix	O
Software	O
Associates	O
,	O
American	O
Megatrends	O
and	O
Award	O
,	O
who	O
either	O
built	O
their	O
own	O
computers	O
that	O
could	O
run	O
the	O
same	O
software	O
and	O
use	O
the	O
same	O
expansion	O
hardware	O
as	O
the	O
PC	O
,	O
or	O
sold	O
their	O
BIOS	O
code	O
to	O
other	O
manufacturers	O
who	O
wished	O
to	O
build	O
their	O
own	O
machines	O
.	O
</s>
<s>
These	O
machines	O
became	O
known	O
as	O
IBM	O
compatibles	O
or	O
"	O
clones	O
"	O
,	O
and	O
software	O
was	O
widely	O
marketed	O
as	O
compatible	O
with	O
"	O
IBM	B-Device
PC	I-Device
or	O
100%	O
compatible	O
"	O
.	O
</s>
<s>
Shortly	O
thereafter	O
,	O
clone	O
manufacturers	O
began	O
to	O
make	O
improvements	O
and	O
extensions	O
to	O
the	O
hardware	O
,	O
such	O
as	O
by	O
using	O
faster	O
processors	O
like	O
the	O
NEC	B-Device
V20	I-Device
,	O
which	O
executed	O
the	O
same	O
software	O
as	O
the	O
8088	B-Device
at	B-Operating_System
a	O
higher	O
speed	O
up	O
to	O
10	O
MHz	O
.	O
</s>
