<s>
The	O
Visual	B-Library
Component	I-Library
Library	I-Library
(	O
VCL	O
)	O
is	O
a	O
visual	O
component-based	O
object-oriented	B-Language
framework	B-Architecture
for	O
developing	O
the	O
user	O
interface	O
of	O
Microsoft	B-Application
Windows	I-Application
applications	O
.	O
</s>
<s>
It	O
is	O
written	O
in	O
Object	B-Language
Pascal	I-Language
.	O
</s>
<s>
The	O
VCL	O
was	O
developed	O
by	O
Borland	O
for	O
use	O
in	O
,	O
and	O
is	O
tightly	O
integrated	O
with	O
,	O
its	O
Delphi	B-Language
and	O
C++Builder	B-Language
RAD	O
tools	O
.	O
</s>
<s>
In	O
1995	O
Borland	O
released	O
Delphi	B-Language
,	O
its	O
first	O
release	O
of	O
an	O
Object	B-Language
Pascal	I-Language
IDE	O
and	O
language	O
.	O
</s>
<s>
Up	O
until	O
that	O
point	O
,	O
Borland	O
's	O
Turbo	O
Pascal	O
for	O
DOS	O
and	O
Windows	O
was	O
largely	O
a	O
procedural	O
language	O
,	O
with	O
minimal	O
object-oriented	B-Language
features	O
,	O
and	O
building	O
UI	O
frameworks	O
with	O
the	O
language	O
required	O
using	O
frameworks	O
like	O
Turbo	B-Application
Vision	I-Application
and	O
Object	B-Language
Windows	I-Language
Library	I-Language
.	O
</s>
<s>
OWL	O
,	O
a	O
similar	O
framework	B-Architecture
to	O
MFC	B-Language
,	O
required	O
writing	O
code	O
to	O
create	O
UI	O
objects	O
.	O
</s>
<s>
A	O
key	O
aim	O
of	O
the	O
VCL	O
combined	O
with	O
the	O
Delphi	B-Language
language	I-Language
was	O
to	O
change	O
the	O
requirements	O
of	O
building	O
a	O
user	O
interface	O
.	O
</s>
<s>
(	O
For	O
context	O
,	O
the	O
Delphi	B-Language
variant	O
of	O
Pascal	O
had	O
a	O
number	O
of	O
innovative	O
object-oriented	B-Language
features	O
,	O
such	O
as	O
properties	O
and	O
runtime	O
type	O
information	O
,	O
inspired	O
by	O
Modula	O
and	O
Smalltalk	B-Application
.	O
)	O
</s>
<s>
The	O
combination	O
of	O
the	O
Delphi	B-Language
language	I-Language
and	O
the	O
VCL	O
framework	B-Architecture
written	O
in	O
that	O
language	O
addressed	O
these	O
by	O
:	O
</s>
<s>
In	O
other	O
words	O
,	O
this	O
creates	O
"	O
custom	O
behaviours	O
through	O
delegation	O
instead	O
of	O
inheritance	B-Language
"	O
.	O
</s>
<s>
With	O
the	O
release	O
of	O
C++	B-Language
Builder	I-Language
,	O
the	O
Delphi	B-Language
compiler	O
could	O
emit	O
C++	O
header	O
files	O
for	O
compiled	O
Delphi-language	O
units	O
,	O
and	O
so	O
the	O
flexibility	O
of	O
the	O
streaming	O
,	O
visually	O
designed	O
UI	O
framework	B-Architecture
became	O
available	O
for	O
C++	O
.	O
</s>
<s>
VCL	O
components	O
can	O
in	O
fact	O
be	O
written	O
in	O
C++	O
,	O
but	O
ultimately	O
inherit	O
from	O
Delphi	B-Language
ancestors	O
,	O
since	O
the	O
C++Builder	B-Language
compiler	O
and	O
linker	O
can	O
consume	O
object	O
and	O
header	O
files	O
produced	O
by	O
Delphi	B-Language
.	O
</s>
<s>
This	O
was	O
one	O
of	O
the	O
first	O
examples	O
of	O
cross-language	O
compatibility	O
,	O
something	O
unseen	O
until	O
.Net	B-Application
.	O
</s>
<s>
Today	O
the	O
VCL	O
includes	O
several	O
hundred	O
visual	O
and	O
non-visual	O
components	O
,	O
usable	O
in	O
both	O
the	O
Delphi	B-Language
and	O
C++	O
languages	O
.	O
</s>
<s>
VCL	O
forms	O
a	O
class	O
hierarchy	O
with	O
a	O
common	O
ancestor	B-Language
,	O
the	O
TComponent	O
class	O
(	O
which	O
inherits	B-Language
from	O
TObject	O
,	O
the	O
root	O
class	O
in	O
Delphi	B-Language
Object	B-Language
Pascal	I-Language
)	O
.	O
</s>
<s>
This	O
is	O
a	O
common	O
approach	O
shared	O
by	O
the	O
Java	B-Language
programming	I-Language
language	I-Language
,	O
Smalltalk	B-Application
,	O
C#	B-Application
and	O
many	O
other	O
object-oriented	B-Language
programming	I-Language
languages	I-Language
.	O
</s>
<s>
VCL	O
components	O
cover	O
Windows	O
controls	O
like	O
windows	O
(	O
TForm	O
class	O
)	O
,	O
controls	O
(	O
e.g.	O
,	O
TButton	O
,	O
TCheckBox	O
,	O
TLabel	O
classes	O
)	O
as	O
well	O
as	O
database	O
access	O
(	O
e.g.	O
,	O
ADO	O
or	O
IBX	O
components	O
)	O
or	O
Internet	O
connections	O
(	O
Indy	B-Language
components	O
)	O
.	O
</s>
<s>
There	O
is	O
a	O
large	O
number	O
of	O
free	O
and	O
commercial	B-Application
component	O
packages	O
.	O
</s>
<s>
While	O
not	O
all	O
VCL	O
components	O
are	O
thread-safe	B-Operating_System
,	O
VCL	O
supports	O
multi-threading	B-Operating_System
too	O
.	O
</s>
<s>
One	O
example	O
is	O
the	O
built	O
in	O
multi-threading	B-Operating_System
support	O
of	O
the	O
OpenWire	B-Language
VCL	O
library	O
.	O
</s>
<s>
VCL	O
provides	O
native	O
support	O
for	O
PME	O
(	O
properties	O
,	O
methods	O
and	O
events	O
)	O
model	O
at	O
the	O
.NET	B-Application
level	O
.	O
</s>
<s>
Much	O
of	O
the	O
.NET	B-Application
design	O
,	O
especially	O
WinForms	O
,	O
is	O
modeled	O
after	O
the	O
VCL	O
.	O
</s>
<s>
One	O
of	O
the	O
main	O
architects	O
of	O
the	O
first	O
Delphi	B-Language
versions	O
,	O
Anders	O
Hejlsberg	O
,	O
was	O
hired	O
by	O
Microsoft	O
and	O
became	O
one	O
of	O
the	O
main	O
architects	O
of	O
.NET	B-Application
.	O
</s>
<s>
According	O
to	O
delphi.about.com,	O
the	O
bonus	O
was	O
three	O
million	O
dollars	O
in	O
Anders	O
 '	O
case	O
.	O
</s>
<s>
Many	O
Delphi	B-Language
developers	O
find	O
C#	B-Application
quite	O
familiar	O
,	O
due	O
to	O
the	O
design	O
similarities	O
.	O
</s>
<s>
A	O
cross-platform	B-Operating_System
equivalent	O
of	O
the	O
VCL	O
,	O
called	O
CLX	B-Language
(	O
Component	B-Language
Library	I-Language
for	I-Language
Cross	I-Language
Platform	I-Language
)	O
,	O
was	O
later	O
developed	O
for	O
use	O
in	O
Delphi	B-Language
,	O
C++Builder	B-Language
and	O
Kylix	B-Application
in	O
2000	O
–	O
2001	O
.	O
</s>
<s>
A	O
second	O
cross-platform	B-Operating_System
framework	B-Architecture
,	O
FireMonkey	B-Language
,	O
was	O
integrated	O
into	O
Delphi	B-Language
and	O
C++Builder	B-Language
XE2	O
in	O
2011	O
.	O
</s>
<s>
FireMonkey	B-Language
is	O
a	O
vector-based	O
WPF-like	O
framework	B-Architecture
for	O
UIs	O
on	O
Windows	O
,	O
OSX	O
,	O
iOS	B-Application
and	O
Android	B-Application
.	O
</s>
<s>
The	O
Lazarus	B-Language
project	O
has	O
a	O
portable	O
( *	O
nix	O
,	O
OS/X	O
,	O
Win32/64	O
+wince	O
)	O
equivalent	O
called	O
LCL	O
,	O
which	O
was	O
already	O
working	O
when	O
Kylix	B-Application
and	O
CLX	B-Language
emerged	O
.	O
</s>
<s>
The	O
project	O
maintained	O
its	O
course	O
and	O
ignored	O
Kylix	B-Application
(	O
and	O
later	O
FMX	O
)	O
.	O
</s>
<s>
OpenOffice.org	B-Application
and	O
thus	O
LibreOffice	B-Application
contain	O
an	O
unrelated	O
graphic	O
library	O
called	O
Visual	O
Class	O
Library	O
(	O
VCL	O
)	O
.	O
</s>
