<s>
X	B-Language
Toolkit	I-Language
Intrinsics	I-Language
(	O
also	O
known	O
as	O
Xt	O
,	O
for	O
X	B-Language
toolkit	I-Language
)	O
is	O
a	O
library	B-Library
that	O
implements	O
an	O
API	B-Application
to	O
facilitate	O
the	O
development	O
of	O
programs	O
with	O
a	O
graphical	B-Application
user	I-Application
interface	I-Application
(	O
GUI	B-Application
)	O
for	O
the	O
X	B-Operating_System
Window	I-Operating_System
System	I-Operating_System
.	O
</s>
<s>
It	O
can	O
be	O
used	O
in	O
the	O
C	B-Language
or	O
C++	B-Language
languages	I-Language
.	O
</s>
<s>
The	O
low-level	O
library	B-Library
Xlib	B-Language
is	O
the	O
client-side	O
implementation	O
of	O
the	O
X11	B-Device
protocol	I-Device
.	O
</s>
<s>
It	O
communicates	O
with	O
an	O
X	B-Operating_System
server	O
,	O
but	O
does	O
not	O
provide	O
any	O
function	O
for	O
implementing	O
graphical	O
control	O
elements	O
(	O
"	O
widgets	O
"	O
)	O
,	O
such	O
as	O
buttons	O
or	O
menus	O
.	O
</s>
<s>
The	O
Xt	O
library	B-Library
provides	O
support	O
for	O
creating	O
widget	O
types	O
,	O
but	O
does	O
not	O
provide	O
any	O
itself	O
.	O
</s>
<s>
A	O
programmer	O
could	O
use	O
the	O
Xt	O
library	B-Library
to	O
create	O
and	O
use	O
a	O
new	O
type	O
of	O
widget	O
.	O
</s>
<s>
Since	O
the	O
graphical	B-Application
user	I-Application
interface	I-Application
of	O
applications	O
typically	O
requires	O
a	O
number	O
of	O
widget	O
types	O
,	O
most	O
developers	O
are	O
reluctant	O
to	O
write	O
their	O
own	O
,	O
and	O
instead	O
prefer	O
to	O
use	O
libraries	O
such	O
as	O
Xaw	B-Library
,	O
Motif	B-Application
and	O
OLIT	B-Library
that	O
provide	O
a	O
set	O
of	O
widgets	O
.	O
</s>
<s>
Most	O
widely	O
used	O
toolkits	O
such	O
as	O
GTK	B-Application
and	O
Qt	B-Language
do	O
not	O
use	O
the	O
Xt	O
library	B-Library
.	O
</s>
<s>
Rather	O
,	O
they	O
use	O
Xlib	B-Language
or	O
XCB	B-Language
directly	O
.	O
</s>
