<s>
Presentation	B-Device
Manager	I-Device
(	O
PM	O
)	O
is	O
the	O
graphical	B-Application
user	I-Application
interface	I-Application
(	O
GUI	B-Application
)	O
that	O
IBM	O
and	O
Microsoft	O
introduced	O
in	O
version	O
1.1	O
of	O
their	O
operating	B-General_Concept
system	I-General_Concept
OS/2	B-Application
in	O
late	O
1988	O
.	O
</s>
<s>
Microsoft	O
began	O
developing	O
a	O
graphic	B-Application
user	I-Application
interface	I-Application
(	O
GUI	B-Application
)	O
in	O
1981	O
.	O
</s>
<s>
After	O
it	O
persuaded	O
IBM	O
that	O
the	O
latter	O
also	O
needed	O
a	O
GUI	B-Application
,	O
Presentation	B-Device
Manager	I-Device
(	O
PM	O
;	O
codenamed	O
Winthorn	O
)	O
was	O
co-developed	O
by	O
Microsoft	O
and	O
IBM	O
's	O
Hursley	O
Lab	O
in	O
1987-1988	O
.	O
</s>
<s>
It	O
was	O
a	O
cross	O
between	O
Microsoft	B-Application
Windows	I-Application
and	O
IBM	O
's	O
mainframe	O
graphical	O
system	O
(	O
GDDM	B-Device
)	O
.	O
</s>
<s>
Like	O
Windows	B-Application
,	O
it	O
was	O
message	O
based	O
and	O
many	O
of	O
the	O
messages	O
were	O
even	O
identical	O
,	O
but	O
there	O
were	O
a	O
number	O
of	O
significant	O
differences	O
as	O
well	O
.	O
</s>
<s>
Although	O
Presentation	B-Device
Manager	I-Device
was	O
designed	O
to	O
be	O
very	O
similar	O
to	O
the	O
upcoming	O
Windows	B-Application
2.0	I-Application
from	O
the	O
user	O
's	O
point	O
of	O
view	O
,	O
and	O
Presentation	B-Device
Manager	I-Device
application	O
structure	O
was	O
nearly	O
identical	O
to	O
Windows	B-Application
application	O
structure	O
,	O
source	O
compatibility	O
with	O
Windows	B-Application
was	O
not	O
an	O
objective	O
.	O
</s>
<s>
For	O
Microsoft	O
,	O
the	O
development	O
of	O
Presentation	B-Device
Manager	I-Device
was	O
an	O
opportunity	O
to	O
clean	O
up	O
some	O
of	O
the	O
design	O
mistakes	O
of	O
Windows	B-Application
.	O
</s>
<s>
The	O
two	O
companies	O
stated	O
that	O
Presentation	B-Device
Manager	I-Device
and	O
Windows	B-Application
2.0	I-Application
would	O
remain	O
almost	O
identical	O
.	O
</s>
<s>
One	O
of	O
the	O
most	O
significant	O
differences	O
between	O
Windows	B-Application
and	O
PM	O
was	O
the	O
coordinate	O
system	O
.	O
</s>
<s>
While	O
in	O
Windows	B-Application
the	O
0	O
,	O
0	O
coordinate	O
was	O
located	O
in	O
the	O
upper	O
left	O
corner	O
,	O
in	O
PM	O
it	O
was	O
in	O
the	O
lower	O
left	O
corner	O
.	O
</s>
<s>
Another	O
difference	O
was	O
that	O
all	O
drawing	O
operations	O
went	O
to	O
the	O
Device	O
Context	O
(	O
DC	O
)	O
in	O
Windows	B-Application
.	O
</s>
<s>
OS/2	B-Application
also	O
had	O
more	O
powerful	O
drawing	O
functions	O
in	O
its	O
Graphics	O
Programming	O
Interface	O
(	O
GPI	O
)	O
.	O
</s>
<s>
Some	O
of	O
the	O
GPI	O
concepts	O
(	O
like	O
viewing	O
transforms	O
)	O
were	O
later	O
incorporated	O
into	O
Windows	B-Device
NT	I-Device
.	O
</s>
<s>
The	O
OS/2	B-Application
programming	O
model	O
was	O
thought	O
to	O
be	O
cleaner	O
,	O
since	O
there	O
was	O
no	O
need	O
to	O
explicitly	O
export	O
the	O
window	O
procedure	O
,	O
no	O
WinMain	O
,	O
and	O
no	O
non-standard	O
function	O
prologs	O
and	O
epilogs	O
.	O
</s>
<s>
One	O
of	O
the	O
most-cited	O
reasons	O
for	O
the	O
IBM-Microsoft	O
split	O
was	O
the	O
divergence	O
of	O
the	O
APIs	B-General_Concept
between	O
Presentation	B-Device
Manager	I-Device
and	O
Windows	B-Application
,	O
which	O
was	O
probably	O
driven	O
by	O
IBM	O
.	O
</s>
<s>
Initially	O
,	O
Presentation	B-Device
Manager	I-Device
was	O
based	O
on	O
Windows	B-Application
GUI	B-Application
code	O
,	O
and	O
often	O
had	O
developments	O
performed	O
in	O
advance	O
,	O
like	O
the	O
support	O
for	O
proportional	O
fonts	O
(	O
which	O
appeared	O
in	O
Windows	B-Application
only	O
in	O
1990	O
)	O
.	O
</s>
<s>
One	O
of	O
the	O
divergences	O
regarded	O
the	O
position	O
of	O
coordinate	O
(	O
0	O
,	O
0	O
)	O
,	O
which	O
was	O
at	O
the	O
top-left	O
in	O
Windows	B-Application
,	O
but	O
at	O
bottom-left	O
(	O
as	O
in	O
Cartesian	O
coordinates	O
)	O
in	O
Presentation	B-Device
Manager	I-Device
.	O
</s>
<s>
In	O
practice	O
it	O
became	O
impossible	O
to	O
recompile	O
a	O
GUI	B-Application
program	O
to	O
run	O
on	O
the	O
other	O
system	O
;	O
an	O
automated	O
source	O
code	O
conversion	O
tool	O
was	O
promised	O
at	O
some	O
point	O
.	O
</s>
<s>
Both	O
companies	O
were	O
hoping	O
that	O
at	O
some	O
point	O
users	O
would	O
migrate	O
to	O
OS/2	B-Application
.	O
</s>
<s>
In	O
1990	O
,	O
version	O
3.0	O
of	O
Windows	B-Application
was	O
beginning	O
to	O
sell	O
in	O
volume	O
,	O
and	O
Microsoft	O
began	O
to	O
lose	O
interest	O
in	O
OS/2	B-Application
especially	O
since	O
,	O
even	O
earlier	O
,	O
market	O
interest	O
in	O
OS/2	B-Application
was	O
always	O
much	O
smaller	O
than	O
in	O
Windows	B-Application
.	O
</s>
<s>
Microsoft	O
took	O
OS/2	B-Application
3.0	O
,	O
which	O
it	O
renamed	O
Windows	B-Device
NT	I-Device
;	O
as	O
such	O
,	O
it	O
inherited	O
certain	O
characteristics	O
of	O
Presentation	B-Device
Manager	I-Device
.	O
</s>
<s>
IBM	O
continued	O
to	O
develop	O
Presentation	B-Device
Manager	I-Device
.	O
</s>
<s>
In	O
subsequent	O
versions	O
of	O
OS/2	B-Application
,	O
and	O
derivatives	O
such	O
as	O
ArcaOS	B-Device
,	O
it	O
was	O
used	O
as	O
a	O
base	O
for	O
the	O
object-oriented	O
interface	O
Workplace	B-Device
Shell	I-Device
.	O
</s>
<s>
There	O
is	O
a	O
significant	O
integration	O
of	O
the	O
GUI	B-Application
layer	O
with	O
the	O
rest	O
of	O
the	O
system	O
,	O
but	O
it	O
is	O
still	O
possible	O
to	O
run	O
certain	O
parts	O
of	O
OS/2	B-Application
from	O
a	O
text-console	O
or	O
X	B-Operating_System
window	I-Operating_System
,	O
and	O
it	O
is	O
possible	O
to	O
boot	O
OS/2	B-Application
into	O
a	O
command-line	O
environment	O
without	O
Presentation	B-Device
Manager	I-Device
(	O
e.g.	O
</s>
<s>
In	O
the	O
late	O
1980s	O
,	O
Hewlett-Packard	O
and	O
Microsoft	O
collaborated	O
on	O
an	O
implementation	O
of	O
Presentation	B-Device
Manager	I-Device
for	O
Unix	B-Application
systems	I-Application
running	O
the	O
X11	B-Operating_System
windowing	O
system	O
.	O
</s>
<s>
The	O
port	O
consisted	O
of	O
two	O
separate	O
pieces	O
of	O
software	O
-	O
a	O
toolkit	O
,	O
window	O
manager	O
and	O
style	O
guide	O
named	O
CXI	O
(	O
Common	O
X	B-Operating_System
Interface	O
)	O
and	O
an	O
implementation	O
of	O
the	O
Presentation	B-Device
Manager	I-Device
API	B-General_Concept
for	O
Unix	B-Application
named	O
PM/X	O
.	O
</s>
<s>
Both	O
CXI	O
and	O
PM/X	O
were	O
submitted	O
to	O
the	O
Open	B-Application
Software	I-Application
Foundation	I-Application
for	O
consideration	O
as	O
OSF	O
's	O
new	O
user	O
interface	O
standard	O
for	O
Unix	B-Application
,	O
which	O
eventually	O
became	O
Motif	B-Application
.	O
</s>
<s>
OSF	O
ultimately	O
selected	O
CXI	O
,	O
but	O
used	O
Digital	O
Equipment	O
Corporation	O
's	O
XUI	O
API	B-General_Concept
instead	O
of	O
PM/X	O
.	O
</s>
<s>
Microsoft	O
and	O
HP	O
continued	O
the	O
development	O
of	O
PM/X	O
for	O
some	O
time	O
after	O
the	O
release	O
of	O
Motif	B-Application
,	O
but	O
it	O
was	O
ultimately	O
abandoned	O
.	O
</s>
<s>
PM	O
follows	O
the	O
Common	B-General_Concept
User	I-General_Concept
Access	I-General_Concept
interface	O
conventions	O
.	O
</s>
<s>
An	O
important	O
problem	O
was	O
that	O
of	O
the	O
single	O
input	B-Operating_System
queue	I-Operating_System
:	O
a	O
non-responsive	O
application	O
could	O
block	O
the	O
processing	O
of	O
user-interface	O
messages	O
,	O
thus	O
freezing	O
the	O
graphical	B-Application
interface	I-Application
.	O
</s>
<s>
This	O
problem	O
has	O
been	O
solved	O
in	O
Windows	B-Device
NT	I-Device
,	O
where	O
such	O
an	O
application	O
would	O
just	O
become	O
a	O
dead	O
rectangle	O
on	O
the	O
screen	O
;	O
in	O
later	O
versions	O
it	O
became	O
possible	O
to	O
move	O
or	O
hide	O
it	O
.	O
</s>
<s>
In	O
OS/2	B-Application
it	O
was	O
solved	O
in	O
a	O
FixPack	O
,	O
using	O
a	O
timer	O
to	O
determine	O
when	O
an	O
application	O
was	O
not	O
responding	O
to	O
events	O
.	O
</s>
