<s>
TopView	B-Operating_System
is	O
the	O
first	O
object-oriented	B-Language
,	O
multitasking	B-Operating_System
,	O
and	O
windowing	O
,	O
personal	B-Device
computer	I-Device
operating	B-Application
environment	I-Application
for	O
PC	B-Operating_System
DOS	I-Operating_System
developed	O
by	O
IBM	O
,	O
announced	O
in	O
August	O
1984	O
and	O
shipped	O
in	O
March	O
1985	O
.	O
</s>
<s>
TopView	B-Operating_System
provided	O
a	O
text-mode	B-Application
(	O
although	O
it	O
also	O
ran	O
in	O
graphics	O
mode	O
)	O
operating	B-Application
environment	I-Application
that	O
allowed	O
users	O
to	O
run	O
more	O
than	O
one	O
application	O
at	O
the	O
same	O
time	O
on	O
a	O
PC	O
.	O
</s>
<s>
IBM	O
demonstrated	O
an	O
early	O
version	O
of	O
the	O
product	O
to	O
key	O
customers	O
before	O
making	O
it	O
generally	O
available	O
,	O
around	O
the	O
time	O
they	O
shipped	O
their	O
new	O
PC	B-Operating_System
AT	I-Operating_System
computer	O
.	O
</s>
<s>
When	O
Microsoft	O
announced	O
Windows	B-Application
1.0	I-Application
in	O
November	O
1983	O
,	O
International	O
Business	O
Machines	O
(	O
IBM	O
)	O
,	O
Microsoft	O
's	O
important	O
partner	O
in	O
popularizing	O
MS-DOS	B-Application
for	O
the	O
IBM	B-Device
PC	I-Device
,	O
notably	O
did	O
not	O
announce	O
support	O
for	O
the	O
forthcoming	O
window	O
environment	O
.	O
</s>
<s>
IBM	O
determined	O
that	O
the	O
microcomputer	O
market	O
needed	O
a	O
multitasking	B-Operating_System
environment	O
.	O
</s>
<s>
When	O
it	O
released	O
TopView	B-Operating_System
in	O
1985	O
,	O
the	O
press	O
speculated	O
that	O
the	O
software	O
was	O
the	O
start	O
of	O
IBM	O
's	O
plan	O
to	O
increase	O
its	O
control	O
over	O
the	O
IBM	B-Device
PC	I-Device
(	O
even	O
though	O
IBM	O
published	O
the	O
specifications	O
publicly	O
)	O
by	O
creating	O
a	O
proprietary	B-Application
operating	B-General_Concept
system	I-General_Concept
for	O
it	O
,	O
similar	O
to	O
what	O
IBM	O
had	O
offered	O
for	O
years	O
on	O
its	O
larger	O
computers	O
.	O
</s>
<s>
TopView	B-Operating_System
also	O
allowed	O
IBM	O
to	O
serve	O
customers	O
who	O
were	O
surprised	O
that	O
the	O
new	O
IBM	B-Operating_System
AT	I-Operating_System
did	O
not	O
come	O
with	O
an	O
operating	B-General_Concept
system	I-General_Concept
able	O
to	O
use	O
the	O
hardware	O
multitasking	B-Operating_System
and	O
protected	B-Application
mode	I-Application
features	O
of	O
the	O
new	O
80286	B-General_Concept
CPU	B-General_Concept
,	O
as	O
DOS	B-Device
and	O
most	O
applications	O
were	O
still	O
running	O
in	O
8086/8088	O
real	B-Application
mode	I-Application
.	O
</s>
<s>
Even	O
given	O
TopView	B-Operating_System
's	O
virtual	O
memory	O
management	O
capabilities	O
,	O
hardware	O
limitations	O
still	O
held	O
the	O
new	O
environment	O
backa	O
base	O
AT	O
with	O
256	O
KB	O
of	O
RAM	O
only	O
had	O
room	O
for	O
80	O
KB	O
of	O
application	O
code	O
and	O
data	O
in	O
RAM	O
once	O
DOS	B-Device
and	O
TopView	B-Operating_System
had	O
loaded	O
up	O
.	O
</s>
<s>
This	O
was	O
the	O
maximum	O
the	O
earlier	O
IBM	B-Device
XT	I-Device
could	O
have	O
installed	O
.	O
</s>
<s>
Once	O
loaded	O
,	O
TopView	B-Operating_System
took	O
back	O
much	O
of	O
the	O
memory	O
consumed	O
by	O
DOS	B-Device
,	O
but	O
still	O
not	O
enough	O
to	O
satisfy	O
industry	O
critics	O
.	O
</s>
<s>
TopView	B-Operating_System
ran	O
in	O
real	B-Application
mode	I-Application
on	O
any	O
x86	B-Operating_System
processor	O
and	O
could	O
run	O
well	O
behaved	O
DOS	B-Device
programs	O
(	O
i.e.	O
</s>
<s>
programs	O
that	O
did	O
not	O
write	O
directly	O
to	O
the	O
screen	O
but	O
used	O
BIOS	O
int	O
10h	O
and	O
DOS	B-Device
int	O
21h	O
,	O
such	O
as	O
the	O
IBM	O
Assistant	O
Series	O
of	O
productivity	O
programs	O
)	O
in	O
an	O
arrangement	O
of	O
windows	O
.	O
</s>
<s>
Well	O
behaved	O
applications	O
would	O
use	O
standard	O
DOS	B-Device
and	O
BIOS	O
function	O
calls	O
to	O
access	O
system	O
services	O
and	O
hardware	O
.	O
</s>
<s>
such	O
as	O
programs	O
that	O
did	O
write	O
directly	O
to	O
the	O
screen	O
)	O
such	O
as	O
Lotus	O
1-2-3	O
,	O
WordStar	O
and	O
dBase	O
III	O
would	O
still	O
run	O
in	O
the	O
TopView	B-Operating_System
environment	O
,	O
but	O
would	O
consume	O
the	O
entire	O
screen	O
.	O
</s>
<s>
Object-oriented	B-Language
applications	O
were	O
written	O
using	O
the	O
TopView	B-Operating_System
API	O
.	O
</s>
<s>
TopView	B-Operating_System
was	O
developed	O
to	O
run	O
on	O
the	O
8088	O
(	O
and	O
required	O
what	O
IBM	O
referred	O
to	O
as	O
a	O
fixed	O
disk	O
)	O
and	O
later	O
the	O
80286	B-General_Concept
.	O
</s>
<s>
TopView	B-Operating_System
was	O
not	O
updated	O
to	O
make	O
use	O
of	O
the	O
virtual	B-Application
8086	I-Application
mode	I-Application
added	O
in	O
the	O
Intel	B-General_Concept
80386	I-General_Concept
processors	O
that	O
allowed	O
better	O
virtualization	B-General_Concept
.	O
</s>
<s>
Initially	O
,	O
compatibility	O
with	O
the	O
extended	O
features	O
was	O
limited	O
mainly	O
to	O
IBM	O
applications	O
,	O
along	O
with	O
a	O
few	O
third-party	O
products	O
like	O
WordPerfect	B-Application
and	O
VolksWriter	B-Protocol
.	O
</s>
<s>
Most	O
DOS	B-Device
programs	O
did	O
,	O
however	O
,	O
support	O
these	O
functions	O
and	O
did	O
allow	O
the	O
user	O
to	O
perform	O
the	O
cut	O
,	O
copy	O
,	O
and	O
paste	O
operations	O
by	O
using	O
the	O
TopView	B-Operating_System
pop-up	O
menus	O
.	O
</s>
<s>
Some	O
believed	O
that	O
IBM	O
planned	O
to	O
use	O
TopView	B-Operating_System
to	O
force	O
reliance	O
on	O
them	O
to	O
comply	O
with	O
the	O
new	O
technical	O
specifications	O
.	O
</s>
<s>
As	O
later	O
versions	O
of	O
TopView	B-Operating_System
were	O
released	O
,	O
it	O
was	O
able	O
to	O
successfully	O
make	O
more	O
challenging	O
DOS	B-Device
apps	O
run	O
in	O
a	O
multitasking	B-Operating_System
fashion	O
by	O
intercepting	O
direct	O
access	O
to	O
system	O
services	O
and	O
hardware	O
.	O
</s>
<s>
TopView	B-Operating_System
first	O
introduced	O
Program	O
Information	O
Files	O
(	O
PIF	O
files	O
)	O
,	O
which	O
defined	O
how	O
a	O
given	O
DOS	B-Device
program	O
should	O
be	O
run	O
in	O
a	O
multi-tasking	O
environment	O
,	O
notably	O
to	O
avoid	O
giving	O
it	O
unnecessary	O
resources	O
which	O
could	O
remain	O
available	O
to	O
other	O
programs	O
.	O
</s>
<s>
TopView	B-Operating_System
's	O
PIF	O
files	O
were	O
inherited	O
and	O
extended	O
by	O
Quarterdeck	O
's	O
DESQview	B-Operating_System
and	O
Microsoft	B-Application
Windows	I-Application
.	O
</s>
<s>
The	O
concept	O
of	O
Program	O
Information	O
Files	O
was	O
also	O
used	O
under	O
Digital	O
Research	O
operating	B-General_Concept
systems	I-General_Concept
such	O
as	O
Concurrent	B-Operating_System
DOS	I-Operating_System
,	O
Multiuser	B-Operating_System
DOS	I-Operating_System
,	O
Datapac	O
System	O
Manager	O
and	O
REAL/32	B-Operating_System
;	O
however	O
,	O
using	O
the	O
PIFED	O
command	O
,	O
the	O
necessary	O
program	O
information	O
got	O
directly	O
embedded	O
into	O
the	O
.EXE	O
or	O
.COM	O
executable	O
file	O
.	O
</s>
<s>
Version	O
1.1	O
,	O
introduced	O
in	O
June	O
1986	O
,	O
added	O
support	O
for	O
the	O
IBM	B-General_Concept
PC	I-General_Concept
Network	I-General_Concept
and	O
IBM	B-Operating_System
3270	I-Operating_System
terminal	B-Application
emulation	I-Application
.	O
</s>
<s>
Importantly	O
,	O
support	O
for	O
swapping	O
non-resident	O
programs	O
was	O
addedonto	O
the	O
hard	O
disk	O
on	O
all	O
computers	O
and	O
into	O
the	O
high	B-Device
memory	I-Device
area	I-Device
on	O
machines	O
equipped	O
with	O
a	O
286	B-General_Concept
CPU	B-General_Concept
.	O
</s>
<s>
The	O
initially	O
poor	O
support	O
for	O
DOS	B-Device
batch	O
files	O
was	O
improved	O
.	O
</s>
<s>
Version	O
1.12	O
,	O
introduced	O
in	O
April	O
1987	O
,	O
added	O
support	O
for	O
the	O
new	O
IBM	B-Device
PS/2	I-Device
series	I-Device
,	O
their	O
DOS	B-Device
3.30	O
operating	B-General_Concept
system	I-General_Concept
,	O
and	O
their	O
new	O
PS/2	B-Device
mice	O
.	O
</s>
<s>
TopView	B-Operating_System
sold	O
below	O
expectations	O
from	O
the	O
start	O
,	O
with	O
many	O
potential	O
users	O
already	O
satisfied	O
with	O
cheaper	O
,	O
less	O
memory-intensive	O
terminate-and-stay-resident	O
task	O
switchers	O
like	O
Ready	O
,	O
Spotlight	O
,	O
and	O
Borland	B-Application
Sidekick	I-Application
which	O
did	O
n't	O
need	O
a	O
multitasking	B-Operating_System
environment	O
.	O
</s>
<s>
TopView	B-Operating_System
ran	O
in	O
graphics	O
mode	O
(	O
TOPVIEW	B-Operating_System
/G	O
)	O
;	O
however	O
,	O
this	O
was	O
rarely	O
used	O
.	O
</s>
<s>
By	O
mid-1987	O
,	O
IBM	O
began	O
to	O
shift	O
focus	O
away	O
from	O
TopView	B-Operating_System
and	O
was	O
promoting	O
the	O
use	O
of	O
OS/2	B-Application
to	O
developers	O
and	O
end	O
users	O
alike	O
.	O
</s>
<s>
OS/2	B-Application
1.0	O
was	O
a	O
pre-emptive	O
multitasking	B-Operating_System
,	O
multithreading	O
OS	O
that	O
allowed	O
one	O
real	B-Application
mode	I-Application
and	O
multiple	O
16-bit	O
protected	B-Application
mode	I-Application
sessions	O
to	O
run	O
at	O
the	O
same	O
time	O
on	O
the	O
PC/AT	B-Operating_System
based	O
80286	B-General_Concept
and	O
provided	O
as	O
a	O
DOS	B-Device
alternative	O
announced	O
in	O
April	O
1987	O
and	O
made	O
available	O
later	O
that	O
December	O
.	O
</s>
<s>
A	O
graphical	O
user	O
interface	O
(	O
Presentation	B-Device
Manager	I-Device
)	O
was	O
added	O
with	O
OS/2	B-Application
1.1	O
in	O
October	O
1988	O
.	O
</s>
<s>
1.1	O
could	O
run	O
with	O
or	O
without	O
Presentation	B-Device
Manager	I-Device
as	O
well	O
as	O
an	O
embedded	B-Architecture
system	I-Architecture
with	O
no	O
screen	O
,	O
keyboard	O
or	O
mouse	O
interface	O
required	O
.	O
</s>
<s>
IBM	O
officially	O
stopped	O
marketing	O
the	O
final	O
release	O
of	O
TopView	B-Operating_System
,	O
version	O
1.12	O
,	O
on	O
3	O
July	O
1990	O
.	O
</s>
<s>
TopView	B-Operating_System
's	O
concept	O
was	O
carried	O
forward	O
by	O
other	O
DOS	B-Device
multitaskers	O
,	O
most	O
notably	O
Quarterdeck	O
's	O
DESQview	B-Operating_System
,	O
which	O
retained	O
TopView	B-Operating_System
's	O
user	O
interface	O
and	O
many	O
features	O
,	O
plus	O
added	O
more	O
features	O
such	O
as	O
support	O
for	O
the	O
special	O
features	O
of	O
the	O
80286	B-General_Concept
,	O
80386	B-General_Concept
and	O
compatible	O
processors	O
,	O
and	O
,	O
with	O
DESQview/X	O
(	O
released	O
in	O
June	O
1992	O
)	O
,	O
a	O
true	O
GUI	O
interface	O
running	O
on	O
DOS	B-Device
.	O
</s>
<s>
A	O
variety	O
of	O
similar	O
programs	O
to	O
TopView	B-Operating_System
were	O
also	O
available	O
,	O
including	O
one	O
from	O
Dynamical	O
Systems	O
called	O
Mondrian	O
,	O
which	O
Microsoft	O
bought	O
in	O
1986	O
with	O
the	O
stated	O
intention	O
of	O
implementing	O
TopView	B-Operating_System
API	O
compatibility	O
into	O
Windows	O
which	O
never	O
happened	O
.	O
</s>
<s>
Later	O
in	O
April	O
1992	O
,	O
IBM	O
introduced	O
OS/2	B-Application
2.0	O
which	O
included	O
virtual	B-Application
8086	I-Application
mode	I-Application
and	O
full	O
32-bit	O
support	O
of	O
the	O
Intel	B-General_Concept
80386	I-General_Concept
superseding	O
even	O
DESQview	B-Operating_System
and	O
other	O
similar	O
environments	O
.	O
</s>
<s>
OS/2	B-Application
2.0	O
was	O
a	O
priority	O
based	O
preemptive	O
multitasking	B-Operating_System
multithreading	O
OS	O
including	O
32	O
levels	O
of	O
priority	O
(	O
from	O
time	O
critical	O
to	O
idle	O
time	O
)	O
for	O
the	O
386	B-General_Concept
.	O
</s>
<s>
TopView	B-Operating_System
requires	O
IBM	B-Operating_System
PC	I-Operating_System
DOS	I-Operating_System
versions	O
2.0	O
to	O
5.0	O
or	O
MS-DOS	B-Application
2.0	O
to	O
6.0	O
,	O
and	O
will	O
not	O
run	O
with	O
later	O
releases	O
.	O
</s>
<s>
Key	O
contributors	O
to	O
TopView	B-Operating_System
included	O
David	O
Morrill	O
(	O
the	O
"	O
father	O
of	O
TopView	B-Operating_System
"	O
code-named	O
"	O
Orion	O
"	O
once	O
the	O
GLASS	O
project	O
was	O
moved	O
to	O
Boca	O
Raton	O
)	O
,	O
Dennis	O
McKinley	O
(	O
tasking	O
)	O
,	O
Ross	O
Cook	O
(	O
memory	O
management	O
)	O
,	O
Bob	O
Hobbs	O
(	O
TopView	B-Operating_System
Toolkit	O
)	O
and	O
Neal	O
Whitten	O
(	O
product	O
manager	O
)	O
.	O
</s>
<s>
Bill	O
Gates	O
,	O
Steve	O
Ballmer	O
,	O
Gordon	O
Letwin	O
and	O
other	O
key	O
Microsoft	O
executives	O
accepted	O
an	O
invitation	O
from	O
IBM	O
executive	O
Don	O
Estridge	O
to	O
IBM	O
Boca	O
Raton	O
to	O
see	O
a	O
special	O
demonstration	O
of	O
TopView	B-Operating_System
.	O
</s>
<s>
Gates	O
was	O
disturbed	O
that	O
Windows	O
did	O
not	O
have	O
the	O
multitasking	B-Operating_System
(	O
Windows	O
used	O
a	O
cooperative	B-Operating_System
method	O
to	O
share	O
the	O
CPU	B-General_Concept
)	O
and	O
windowing	O
capabilities	O
(	O
i.e.	O
</s>
<s>
that	O
TopView	B-Operating_System
had	O
.	O
</s>
<s>
Gates	O
witnessed	O
TopView	B-Operating_System
running	O
multiple	O
copies	O
of	O
the	O
Microsoft	O
BASIC	O
interpreter	O
running	O
in	O
windows	O
(	O
overlapping	O
and	O
side-by-side	O
)	O
in	O
a	O
multitasking	B-Operating_System
fashion	O
.	O
</s>
<s>
Microsoft	O
later	O
released	O
a	O
multitasking	B-Operating_System
version	O
of	O
MS-DOS	B-Application
4.0	I-Application
(	O
multitasking	B-Operating_System
)	O
from	O
what	O
it	O
learned	O
from	O
the	O
meeting	O
.	O
</s>
<s>
Even	O
though	O
there	O
was	O
no	O
joint	O
development	O
agreement	O
with	O
Microsoft	O
for	O
the	O
development	O
of	O
TopView	B-Operating_System
,	O
Estridge	O
asked	O
and	O
later	O
told	O
Whitten	O
(	O
against	O
Whitten	O
's	O
and	O
the	O
TopView	B-Operating_System
team	O
's	O
wishes	O
)	O
to	O
turn	O
over	O
all	O
source	O
code	O
and	O
documentation	O
of	O
TopView	B-Operating_System
to	O
Microsoft	O
.	O
</s>
<s>
This	O
led	O
to	O
a	O
Joint	O
Development	O
Agreement	O
with	O
Microsoft	O
(	O
an	O
agreement	O
that	O
previously	O
only	O
included	O
DOS	B-Device
)	O
to	O
co-develop	O
OS/2	B-Application
(	O
an	O
agreement	O
that	O
lasted	O
until	O
1990	O
)	O
.	O
</s>
<s>
InfoWorld	O
in	O
1985	O
described	O
TopView	B-Operating_System
as	O
"	O
bland	O
,	O
plain	O
vanilla	O
software	O
that	O
hogs	O
far	O
too	O
much	O
memory	O
"	O
.	O
</s>
<s>
BYTE	B-Application
also	O
criticized	O
TopView	B-Operating_System
's	O
memory	O
usage	O
,	O
but	O
stated	O
that	O
"	O
you	O
will	O
find	O
that	O
most	O
software	O
written	O
for	O
the	O
IBM	B-Device
PC	I-Device
is	O
TopView-compatible	O
"	O
.	O
</s>
<s>
Noting	O
the	O
low	O
price	O
and	O
"	O
innovative	O
multitasking	B-Operating_System
features	O
"	O
,	O
the	O
magazine	O
predicted	O
that	O
the	O
software	O
"	O
will	O
attract	O
a	O
lot	O
of	O
takers	O
"	O
.	O
</s>
<s>
In	O
1985	O
,	O
Digital	O
Research	O
positioned	O
their	O
multitasking	B-Operating_System
Concurrent	B-Operating_System
DOS	I-Operating_System
4.1	O
with	O
GEM	B-Application
as	O
alternative	O
for	O
TopView	B-Operating_System
.	O
</s>
