<s>
Virtue	O
is	O
a	O
virtual	O
session	O
manager	O
running	O
under	O
IBM	O
's	O
VM	B-Application
.	O
</s>
<s>
Virtue	O
,	O
"	O
virtual	O
tube	O
"	O
,	O
was	O
the	O
first	O
session	O
manager	O
commercially	O
available	O
for	O
the	O
VM	B-Application
environment	O
on	O
IBM	O
mainframes	B-Architecture
.	O
</s>
<s>
The	O
product	O
allows	O
users	O
to	O
use	O
a	O
standard	O
3270	B-Operating_System
monitor	O
to	O
control	O
multiple	O
sessions	O
,	O
whether	O
VM/CMS	B-Application
,	O
DOS/VSE	B-Application
,	O
z/VSE	B-Application
MVS	B-Application
,	O
z/OS	B-Application
,	O
or	O
other	O
operating	B-General_Concept
systems	I-General_Concept
or	O
applications	B-Application
such	O
as	O
CICS	B-Application
,	O
Westi	B-Application
,	O
or	O
DUCS	B-Application
sessions	O
.	O
</s>
<s>
Virtue	O
runs	O
as	O
a	O
highly	O
privileged	O
CMS	B-Operating_System
task	B-General_Concept
,	O
designed	O
to	O
accommodate	O
model	O
IBM	B-Operating_System
3270	I-Operating_System
monitors	O
and	O
their	O
descendants	O
.	O
</s>
<s>
Although	O
the	O
package	O
nominally	O
ran	O
as	O
a	O
highly	O
privileged	O
CMS	B-Operating_System
session	O
and	O
utilized	O
CMS	B-Operating_System
services	O
,	O
it	O
deployed	O
an	O
internal	O
multitasking	O
mechanism	O
called	O
a	O
"	O
subvisor	O
"	O
,	O
which	O
queued	O
and	O
prioritized	O
tasks	O
to	O
be	O
done	O
.	O
</s>
<s>
Macintosh	B-Device
versions	O
prior	O
to	O
macOS	B-Application
and	O
IBM	O
's	O
OS/2	B-Application
came	O
to	O
use	O
similar	O
mechanisms	O
for	O
task	B-General_Concept
control	O
.	O
</s>
<s>
Broad	O
range	O
in-depth	O
testing	O
was	O
conducted	O
at	O
IBM	O
's	O
data	B-Operating_System
center	I-Operating_System
in	O
Tampa	O
,	O
Florida	O
and	O
the	O
IBM	O
lab	O
in	O
Böblingen	O
,	O
Germany	O
.	O
</s>
<s>
The	O
concept	O
found	O
its	O
way	O
onto	O
early	O
PC	O
platforms	O
at	O
the	O
time	O
,	O
notably	O
Apple	O
Computer	O
's	O
Switcher	O
for	O
the	O
Macintosh	B-Device
and	O
subsequent	O
products	O
for	O
the	O
IBM	B-Device
PC	I-Device
.	O
</s>
