<s>
In	O
computer	B-General_Concept
programming	I-General_Concept
,	O
a	O
Visual	B-Library
Basic	I-Library
Extension	I-Library
(	O
commonly	O
abbreviated	O
VBX	B-Library
)	O
or	O
custom	O
control	O
,	O
was	O
the	O
component	O
model	O
used	O
in	O
Microsoft	O
Visual	B-Language
Basic	I-Language
versions	O
1.0	O
to	O
3.0	O
.	O
</s>
<s>
VBX	B-Library
has	O
also	O
been	O
supported	O
in	O
the	O
first	O
,	O
16-bit	O
version	O
of	O
Borland	B-Language
Delphi	I-Language
.	O
</s>
<s>
The	O
VBX	B-Library
specification	O
was	O
created	O
so	O
that	O
developers	O
could	O
extend	O
Visual	B-Language
Basic	I-Language
.	O
</s>
<s>
Since	O
at	O
the	O
time	O
Visual	B-Language
Basic	I-Language
was	O
an	O
interpreted	B-Application
language	I-Application
with	O
limited	O
speed	O
,	O
VBXs	O
,	O
which	O
were	O
most	O
often	O
written	O
in	O
C	O
or	O
C++	O
,	O
provided	O
the	O
ability	O
to	O
create	O
very	O
powerful	O
and	O
efficient	O
user	O
interface	O
sub-components	O
which	O
could	O
be	O
assembled	O
into	O
applications	O
using	O
Visual	B-Language
Basic	I-Language
as	O
the	O
glue	O
.	O
</s>
<s>
Visual	B-Language
Basic	I-Language
4.0	O
added	O
support	O
for	O
the	O
newer	O
OLE	O
Controls	O
or	O
OCXs	O
(	O
which	O
became	O
ActiveX	O
controls	O
)	O
,	O
implicitly	O
deprecating	O
VBX	B-Library
controls	O
.	O
</s>
<s>
OCXs	O
are	O
based	O
on	O
the	O
Component	B-Application
Object	I-Application
Model	I-Application
.	O
</s>
<s>
Each	O
version	O
of	O
Visual	B-Language
Basic	I-Language
has	O
come	O
with	O
many	O
controls	O
.	O
</s>
<s>
By	O
incorporating	O
VBX	B-Library
controls	O
into	O
Visual	B-Language
Basic	I-Language
,	O
Microsoft	O
spawned	O
the	O
first	O
commercially	O
viable	O
market	O
for	O
reusable	O
software	O
components	O
.	O
</s>
<s>
Third	B-General_Concept
parties	I-General_Concept
have	O
created	O
a	O
large	O
market	O
of	O
custom	B-Library
controls	I-Library
for	O
resale	O
.	O
</s>
<s>
VBX	B-Library
components	O
were	O
called	O
"	O
custom	B-Library
controls	I-Library
"	O
because	O
the	O
Microsoft	O
development	O
team	O
envisioned	O
them	O
as	O
visual	O
"	O
control	O
"	O
components	O
like	O
a	O
toggle	O
switch	O
or	O
button	O
.	O
</s>
<s>
Enterprising	O
third	B-General_Concept
party	I-General_Concept
software	I-General_Concept
component	I-General_Concept
developers	O
saw	O
opportunities	O
to	O
use	O
the	O
VBX	B-Library
specification	O
for	O
non-visual	O
components	O
,	O
such	O
as	O
components	O
for	O
creating	O
ZIP	B-General_Concept
files	I-General_Concept
,	O
manipulating	O
low-level	O
system	O
settings	O
and	O
communicating	O
with	O
TCP/IP	B-Protocol
.	O
</s>
