<s>
DESQview	O
(	O
DV	O
)	O
is	O
a	O
text	B-Application
mode	I-Application
multitasking	B-Operating_System
operating	B-Application
environment	I-Application
developed	O
by	O
Quarterdeck	O
Office	O
Systems	O
which	O
enjoyed	O
modest	O
popularity	O
in	O
the	O
late	O
1980s	O
and	O
early	O
1990s	O
.	O
</s>
<s>
Running	O
on	O
top	O
of	O
DOS	B-Device
,	O
it	O
allows	O
users	O
to	O
run	O
multiple	O
programs	O
concurrently	O
in	O
multiple	O
windows	B-Application
.	O
</s>
<s>
Quarterdeck	O
's	O
predecessor	O
to	O
DESQview	O
was	O
a	O
task	B-Operating_System
switching	I-Operating_System
product	O
called	O
Desq	O
(	O
shipped	O
late	O
April	O
or	O
May	O
1984	O
)	O
which	O
allows	O
users	O
to	O
switch	O
between	O
running	O
programs	O
.	O
</s>
<s>
Quarterdeck	O
revamped	O
its	O
package	O
,	O
bringing	O
multitasking	B-Operating_System
in	O
,	O
and	O
adding	O
TopView	B-Operating_System
compatibility	O
.	O
</s>
<s>
DESQview	O
was	O
released	O
in	O
July	O
1985	O
,	O
four	O
months	O
before	O
Microsoft	O
released	O
the	O
first	O
version	O
of	O
Windows	B-Application
.	O
</s>
<s>
It	O
was	O
widely	O
thought	O
to	O
be	O
the	O
first	O
program	O
to	O
bring	O
multitasking	B-Operating_System
and	O
windowing	O
capabilities	O
to	O
DOS	B-Device
,	O
but	O
in	O
fact	O
there	O
was	O
a	O
predecessor	O
,	O
IBM	B-Operating_System
TopView	I-Operating_System
,	O
which	O
shipped	O
March	O
1985	O
,	O
from	O
which	O
DESQview	O
inherited	O
the	O
pop-up	O
menu	O
.	O
</s>
<s>
Under	O
DESQview	O
,	O
well-behaved	O
DOS	B-Device
programs	O
can	O
be	O
run	O
concurrently	O
in	O
resizable	O
,	O
overlapping	O
windows	B-Application
(	O
something	O
the	O
first	O
version	O
of	O
MS	B-Application
Windows	I-Application
cannot	O
do	O
)	O
.	O
</s>
<s>
DESQview	O
is	O
not	O
a	O
GUI	B-Application
(	O
Graphical	B-Application
User	I-Application
Interface	I-Application
)	O
operating	B-General_Concept
system	I-General_Concept
.	O
</s>
<s>
Rather	O
,	O
it	O
is	O
a	O
non-graphical	O
,	O
windowed	O
shell	O
that	O
runs	O
in	O
real	B-Application
mode	I-Application
on	O
top	O
of	O
DOS	B-Device
,	O
although	O
it	O
can	O
run	O
on	O
any	O
Intel	B-General_Concept
8086	I-General_Concept
-	O
or	O
Intel	O
80286-based	O
PC	O
.	O
</s>
<s>
It	O
can	O
also	O
use	O
expanded	B-Device
memory	I-Device
add-ons	O
to	O
work	O
around	O
the	O
640KB	O
RAM	B-Device
limit	I-Device
of	O
conventional	B-Device
memory	I-Device
on	O
early	O
PCs	O
.	O
</s>
<s>
DESQview	O
really	O
came	O
into	O
its	O
own	O
on	O
Intel	B-General_Concept
80386	I-General_Concept
machines	O
,	O
which	O
are	O
better	O
at	O
utilizing	O
memory	O
above	O
DOS	B-Device
's	O
limit	O
.	O
</s>
<s>
However	O
,	O
in	O
either	O
case	O
,	O
it	O
runs	O
in	O
real	B-Application
mode	I-Application
rather	O
than	O
protected	B-Application
mode	I-Application
,	O
meaning	O
that	O
a	O
misbehaving	O
program	O
can	O
still	O
crash	O
the	O
system	O
.	O
</s>
<s>
To	O
make	O
maximum	O
use	O
of	O
extended	B-Device
memory	I-Device
on	O
Intel	B-General_Concept
80386	I-General_Concept
processors	O
,	O
by	O
transforming	O
it	O
into	O
expanded	B-Device
memory	I-Device
and	O
upper	B-Device
memory	I-Device
blocks	I-Device
(	O
UMBs	O
)	O
accessible	O
to	O
DESQview	O
and	O
other	O
real-mode	B-Application
programs	O
,	O
Quarterdeck	O
developed	O
a	O
sophisticated	O
memory	B-General_Concept
manager	I-General_Concept
.	O
</s>
<s>
Owing	O
to	O
the	O
foresight	O
of	O
its	O
marketing	O
manager	O
,	O
Quarterdeck	O
marketed	O
it	O
as	O
a	O
separate	O
product	O
,	O
QEMM-386	B-Device
(	O
Quarterdeck	B-Device
Expanded	I-Device
Memory	I-Device
Manager	I-Device
386	B-General_Concept
)	O
.	O
</s>
<s>
After	O
the	O
release	O
of	O
the	O
Intel	B-General_Concept
Pentium	I-General_Concept
processor	O
,	O
the	O
386	B-General_Concept
in	O
QEMM	B-Device
was	O
dropped	O
.	O
</s>
<s>
The	O
combination	O
package	O
of	O
DESQview	O
and	O
QEMM-386	B-Device
was	O
called	O
DESQview	O
386	B-General_Concept
(	O
DV386	O
)	O
.	O
</s>
<s>
With	O
the	O
introduction	O
of	O
the	O
80386	B-General_Concept
,	O
the	O
memory	O
management	O
features	O
were	O
enhanced	O
to	O
allow	O
the	O
system	O
to	O
shift	O
into	O
protected	B-Application
mode	I-Application
but	O
also	O
allow	O
the	O
addresses	O
to	O
be	O
configured	O
in	O
a	O
virtual	B-Application
8086	I-Application
mode	I-Application
so	O
that	O
the	O
extended	B-Device
memory	I-Device
can	O
be	O
mapped	O
into	O
addressing	O
frames	O
and	O
accessible	O
to	O
real-mode	B-Application
programs	O
such	O
as	O
DOS	B-Device
.	O
</s>
<s>
This	O
allows	O
a	O
386	B-General_Concept
to	O
implement	O
the	O
LIM	O
(	O
Lotus	O
,	O
Intel	O
,	O
Microsoft	O
)	O
EMS	O
(	O
expanded	B-Device
memory	I-Device
specification	O
)	O
.	O
</s>
<s>
The	O
memory	B-General_Concept
manager	I-General_Concept
is	O
easily	O
controlled	O
by	O
the	O
user	O
with	O
DOS	B-Device
program	O
QEMM.COM	O
.	O
</s>
<s>
DESQview	O
is	O
able	O
to	O
use	O
QEMM	B-Device
's	O
features	O
far	O
beyond	O
just	O
the	O
LIM	O
EMS	O
API	O
,	O
mapping	O
most	O
of	O
the	O
"	O
conventional	O
"	O
address	O
space	O
(	O
below	O
640KB	O
)	O
into	O
multiple	O
extended	B-Device
memory	I-Device
blocks	O
such	O
that	O
each	O
can	O
execute	O
transparently	O
during	O
its	O
context	O
.	O
</s>
<s>
The	O
main	O
copy	O
of	O
DOS	B-Device
and	O
any	O
device	O
and	O
networking	O
drivers	O
have	O
to	O
be	O
loaded	O
before	O
DESQview	O
.	O
</s>
<s>
The	O
resulting	O
space	O
is	O
the	O
largest	O
single	O
program	O
that	O
can	O
run	O
,	O
but	O
DESQview	O
under	O
QEMM	B-Device
can	O
run	O
as	O
many	O
instances	O
of	O
those	O
programs	O
as	O
the	O
EMS	O
allows	O
.	O
</s>
<s>
So	O
an	O
8MB	O
system	O
can	O
generally	O
have	O
a	O
dozen	O
full-sized	O
DOS	B-Device
programs	O
running	O
concurrently	O
;	O
a	O
16MB	O
system	O
can	O
run	O
over	O
twenty	O
,	O
and	O
so	O
on	O
.	O
</s>
<s>
DESQview	O
was	O
noteworthy	O
in	O
that	O
it	O
supported	O
all	O
common	O
DOS-compatible	O
programs	O
and	O
achieved	O
a	O
degree	O
of	O
performance	O
and	O
stability	O
that	O
was	O
remarkable	O
,	O
given	O
the	O
constraints	O
of	O
its	O
host	O
operating	B-General_Concept
system	I-General_Concept
.	O
</s>
<s>
Pressing	O
the	O
Alt	O
key	O
by	O
itself	O
brings	O
up	O
the	O
DESQview	O
menu	O
allowing	O
access	O
to	O
the	O
program	O
's	O
features	O
:	O
start	O
new	O
tasks	O
,	O
switch	O
among	O
them	O
,	O
mark	O
text	O
on	O
the	O
screen	O
,	O
paste	O
text	O
as	O
input	O
into	O
the	O
current	O
task	O
,	O
resize	O
or	O
move	O
the	O
text	O
windows	B-Application
,	O
configure	O
new	O
menu	O
items	O
,	O
etc	O
.	O
</s>
<s>
In	O
one	O
area	O
,	O
however	O
,	O
DESQview	O
was	O
a	O
lasting	O
success	O
:	O
many	O
multiuser	O
bulletin	B-Application
board	I-Application
systems	I-Application
were	O
based	O
on	O
it	O
,	O
thanks	O
to	O
its	O
modest	O
hardware	O
requirements	O
,	O
robust	O
multitasking	B-Operating_System
,	O
and	O
superlative	O
handling	O
of	O
multiple	O
communication	O
ports	O
.	O
</s>
<s>
Most	O
free	O
or	O
inexpensive	O
BBS	O
software	O
of	O
the	O
time	O
ran	O
as	O
a	O
single-node	O
,	O
single-tasking	O
DOS	B-Device
program	O
.	O
</s>
<s>
DESQview	O
does	O
not	O
provide	O
a	O
graphical	B-Application
user	I-Application
interface	I-Application
(	O
GUI	B-Application
)	O
.	O
</s>
<s>
Microsoft	O
released	O
MS	B-Application
Windows	I-Application
version	O
3.0	O
with	O
its	O
own	O
memory	O
management	O
and	O
multitasking	B-Operating_System
features	O
.	O
</s>
<s>
While	O
DESQview	O
was	O
far	O
faster	O
,	O
smaller	O
,	O
and	O
more	O
stable	O
,	O
it	O
was	O
more	O
expensive	O
and	O
did	O
n't	O
include	O
support	O
for	O
the	O
graphical	O
features	O
of	O
MS	B-Application
Windows	I-Application
.	O
</s>
<s>
The	O
decline	O
of	O
QEMM	B-Device
started	O
with	O
the	O
bundling	O
of	O
a	O
memory	B-General_Concept
manager	I-General_Concept
in	O
Digital	O
Research	O
's	O
DR	O
DOS	B-Device
5.0	O
,	O
released	O
in	O
1990	O
.	O
</s>
<s>
To	O
catch	O
on	O
,	O
Microsoft	O
included	O
its	O
own	O
EMM386	B-Device
in	O
MS-DOS	O
5.0	O
,	O
while	O
previously	O
the	O
memory	O
management	O
functionality	O
was	O
only	O
available	O
with	O
Windows	B-Application
.	O
</s>
<s>
QEMM	B-Device
could	O
still	O
be	O
used	O
instead	O
,	O
notably	O
with	O
Windows	B-Application
3.1x	I-Application
,	O
but	O
only	O
for	O
incremental	O
benefit	O
.	O
</s>
<s>
Sales	O
of	O
QEMM	B-Device
declined	O
.	O
</s>
<s>
As	O
users	O
moved	O
from	O
DESQview	O
to	O
other	O
platforms	O
,	O
notably	O
Windows	B-Application
3.x	O
and	O
OS/2	O
,	O
third	O
party	O
utility	O
authors	O
wrote	O
utility	O
programs	O
that	O
emulated	O
some	O
DESQview	O
API	O
functions	O
to	O
allow	O
suitably	O
equipped	O
DOS	B-Device
programs	O
to	O
co-operate	O
with	O
these	O
OS	O
.	O
</s>
<s>
The	O
most	O
notable	O
are	O
TAME	O
(	O
for	O
Windows	B-Application
)	O
and	O
OS/2SPEED	O
(	O
for	O
OS/2	O
)	O
.	O
</s>
<s>
Quarterdeck	O
eventually	O
also	O
released	O
a	O
product	O
named	O
DESQview/X	O
(	O
DVX	O
)	O
,	O
which	O
is	O
an	O
X	B-Operating_System
Window	I-Operating_System
System	I-Operating_System
server	O
running	O
under	O
DOS	B-Device
and	O
DESQview	O
and	O
thus	O
provides	O
a	O
GUI	B-Application
to	O
which	O
X	B-Operating_System
software	O
(	O
mostly	O
Unix	B-Application
)	O
could	O
be	O
ported	O
.	O
</s>
<s>
DESQview/X	O
had	O
three	O
window	O
managers	O
that	O
it	O
launched	O
with	O
,	O
X/Motif	B-Device
,	O
OPEN	B-Operating_System
LOOK	I-Operating_System
,	O
and	O
twm	B-Language
.	O
</s>
<s>
The	O
default	O
package	O
contained	O
only	O
twm	B-Language
,	O
the	O
others	O
were	O
costly	O
optional	O
extras	O
,	O
as	O
was	O
the	O
ability	O
to	O
interact	O
on	O
TCP/IP	B-Protocol
networks	I-Protocol
.	O
</s>
<s>
Mosaic	B-Application
was	O
ported	O
to	O
DVX	O
.	O
</s>
<s>
DVX	O
itself	O
can	O
serve	O
DOS	B-Device
programs	O
and	O
the	O
16-bit	O
Windows	B-Application
environment	O
across	O
the	O
network	O
as	O
X	B-Operating_System
programs	O
,	O
which	O
made	O
it	O
useful	O
for	O
those	O
who	O
wished	O
to	O
run	O
DOS	B-Device
and	O
Windows	B-Application
programs	O
from	O
their	O
Unix	B-Application
workstations	O
.	O
</s>
<s>
Internetworking	O
company	O
Novell	O
developed	O
a	O
product	O
called	O
NetWare	B-Application
Access	I-Application
Server	I-Application
(	O
NAS	O
)	O
incorporating	O
features	O
of	O
DESQview	O
386	B-General_Concept
and	O
pcAnywhere	B-Protocol
.	O
</s>
<s>
The	O
DESQview	O
multitasking	B-Operating_System
support	O
was	O
used	O
to	O
create	O
an	O
environment	O
into	O
which	O
up	O
to	O
16	O
PC	O
and	O
Macintosh	O
clients	O
can	O
login	O
remotely	O
to	O
access	O
NetWare	O
services	O
and	O
run	O
DOS	B-Device
applications	O
.	O
</s>
<s>
DESQview	O
development	O
continued	O
in	O
parallel	O
with	O
DESQview/X	O
.	O
</s>
<s>
After	O
ceasing	O
development	O
on	O
DESQview/X	O
,	O
another	O
version	O
of	O
DESQview	O
was	O
released	O
.	O
</s>
<s>
QEMM	B-Device
was	O
still	O
developed	O
after	O
the	O
discontinuation	O
of	O
DESQview	O
,	O
and	O
a	O
version	O
compatible	O
with	O
Windows	B-Device
98	I-Device
was	O
released	O
.	O
</s>
<s>
In	O
the	O
mid-1990s	O
,	O
Quarterdeck	O
tried	O
to	O
recast	O
itself	O
as	O
an	O
Internet	O
company	O
,	O
releasing	O
a	O
version	O
of	O
the	O
Mosaic	B-Application
web	I-Application
browser	I-Application
.	O
</s>
<s>
BYTE	B-Application
in	O
1984	O
stated	O
that	O
DesQ	O
's	O
application	O
compatibility	O
was	O
the	O
highest	O
of	O
the	O
five	O
window	O
managers	O
tested	O
.	O
</s>
<s>
The	O
magazine	O
's	O
Jerry	O
Pournelle	O
in	O
1989	O
noted	O
that	O
"	O
while	O
MultiFinder	O
does	O
n't	O
work	O
very	O
well	O
yet	O
,	O
DESQView	O
on	O
a	O
big	O
80386	B-General_Concept
machine	O
certainly	O
does	O
"	O
.	O
</s>
<s>
The	O
magazine	O
that	O
year	O
listed	O
version	O
3.0	O
as	O
among	O
the	O
"	O
Distinction	O
"	O
winners	O
of	O
the	O
BYTE	B-Application
Awards	O
,	O
stating	O
that	O
"	O
unlike	O
OS/2	O
,	O
DESQview	O
lets	O
you	O
run	O
the	O
programs	O
you	O
've	O
already	O
paid	O
for	O
…	O
Many	O
users	O
will	O
find	O
that	O
DESQview	O
is	O
all	O
they	O
need	O
"	O
.	O
</s>
