<s>
Virtual	B-General_Concept
instrument	I-General_Concept
software	I-General_Concept
architecture	I-General_Concept
(	O
VISA	O
)	O
is	O
a	O
widely	O
used	O
application	B-Application
programming	I-Application
interface	I-Application
(	O
API	B-Application
)	O
in	O
the	O
test	O
and	O
measurement	O
(	O
T&M	O
)	O
industry	O
for	O
communicating	O
with	O
instruments	O
from	O
a	O
computer	O
.	O
</s>
<s>
The	O
VISA	O
standard	O
includes	O
specifications	O
for	O
communication	O
with	O
resources	O
(	O
usually	O
,	O
but	O
not	O
always	O
,	O
instruments	O
)	O
over	O
T&	O
M-specific	O
I/O	O
interfaces	O
such	O
as	O
GPIB	O
and	O
VXI	B-Architecture
.	O
</s>
<s>
There	O
are	O
also	O
some	O
specifications	O
for	O
T&	O
M-specific	O
protocols	O
over	O
PC-standard	O
I/O	O
,	O
such	O
as	O
HiSLIP	B-Architecture
or	O
VXI-11	O
(	O
over	O
TCP/IP	B-Protocol
)	O
and	O
USBTMC	O
(	O
over	O
USB	B-Protocol
)	O
.	O
</s>
<s>
The	O
VISA	O
library	O
has	O
standardized	O
the	O
presentation	O
of	O
its	O
operations	O
over	O
several	O
software	O
reuse	O
mechanisms	O
,	O
including	O
through	O
a	O
C	O
API	B-Application
exposed	O
from	O
Windows	O
DLL	O
,	O
visa32.dll	O
,	O
over	O
the	O
Microsoft	O
COM	B-Application
technology	O
,	O
and	O
through	O
a	O
.NET	B-Application
API	B-Application
.	O
</s>
