<s>
VX-REXX	B-Application
is	O
a	O
highly	O
extensible	O
REXX	B-Language
GUI	B-Application
development	O
system	O
for	O
OS/2	B-Application
developed	O
by	O
Watcom	O
and	O
initially	O
released	O
in	O
1993	O
.	O
</s>
<s>
Much	O
of	O
the	O
new	O
code	O
in	O
eComStation	B-Device
and	O
ArcaOS	B-Device
has	O
been	O
written	O
using	O
VX-REXX	B-Application
.	O
</s>
<s>
Though	O
REXX	B-Language
is	O
itself	O
a	O
3GL	O
,	O
the	O
VX-REXX	B-Application
interface	O
allows	O
you	O
to	O
build	O
REXX	B-Language
programs	O
using	O
a	O
combination	O
of	O
3GL	O
and	O
4GL	B-Language
techniques	O
;	O
its	O
drag-and-drop	O
interface	O
to	O
inserting	O
code	O
allows	O
quite	O
complex	O
programs	O
to	O
be	O
built	O
without	O
actually	O
entering	O
any	O
code	O
.	O
</s>
<s>
VX-REXX	B-Application
'	O
s	O
interface	O
is	O
itself	O
written	O
in	O
VX-REXX	B-Application
,	O
which	O
means	O
that	O
it	O
can	O
be	O
extended	O
and/or	O
modified	O
using	O
REXX	B-Language
code	O
;	O
it	O
also	O
has	O
a	O
number	O
of	O
macro	O
hooks	O
which	O
can	O
be	O
used	O
to	O
add	O
to	O
its	O
functionality	O
directly	O
.	O
</s>
<s>
Additional	O
controls	O
can	O
be	O
built	O
using	O
SOM	B-Device
and	O
distributed	O
as	O
.DLL	O
files	O
;	O
anything	O
from	O
simple	O
variants	O
of	O
existing	O
controls	O
(	O
such	O
as	O
a	O
tri-state	O
check	O
box	O
,	O
or	O
a	O
self-validating	O
entry	O
field	O
)	O
to	O
completely	O
custom-drawn	O
controls	O
(	O
for	O
example	O
,	O
a	O
self-contained	O
tic-tac-toe	O
board	O
)	O
can	O
be	O
written	O
in	O
C	O
,	O
compiled	O
,	O
and	O
added	O
to	O
a	O
VX-REXX	B-Application
project	O
.	O
</s>
