<s>
Scheme	B-Language
48	I-Language
is	O
a	O
programming	O
language	O
,	O
a	O
dialect	O
of	O
the	O
language	O
Scheme	B-Language
,	O
an	O
implementation	O
using	O
an	O
interpreter	B-Application
which	O
emits	O
bytecode	O
.	O
</s>
<s>
It	O
has	O
a	O
foreign	B-Application
function	I-Application
interface	I-Application
for	O
calling	O
functions	O
from	O
the	O
language	O
C	B-Language
and	O
comes	O
with	O
a	O
library	B-Library
for	O
regular	B-Language
expressions	I-Language
(	O
regex	B-Language
)	O
,	O
and	O
an	O
interface	O
for	O
Portable	O
Operating	O
System	O
Interface	O
(	O
POSIX	O
)	O
.	O
</s>
<s>
It	O
is	O
supported	O
by	O
the	O
portable	O
Scheme	B-Language
library	B-Library
SLIB	B-Application
,	O
and	O
is	O
the	O
basis	O
for	O
the	O
Scheme	B-Language
shell	I-Language
Scsh	B-Language
.	O
</s>
<s>
It	O
is	O
free	B-License
and	I-License
open-source	I-License
software	I-License
released	O
under	O
a	O
BSD	B-Operating_System
license	I-Operating_System
.	O
</s>
<s>
It	O
is	O
called	O
"	O
Scheme	B-Language
48	I-Language
"	O
because	O
the	O
first	O
version	O
was	O
written	O
in	O
48	O
hours	O
in	O
August	O
1986	O
.	O
</s>
<s>
Scheme	B-Language
48	I-Language
uses	O
a	O
virtual	B-Architecture
machine	I-Architecture
to	O
interpret	O
the	O
bytecode	O
,	O
which	O
is	O
written	O
in	O
a	O
restricted	O
dialect	O
of	O
Scheme	B-Language
called	O
PreScheme	B-Language
,	O
which	O
can	O
be	O
translated	O
to	O
C	B-Language
and	O
compiled	O
to	O
a	O
native	O
binary	O
.	O
</s>
<s>
PreScheme	B-Language
,	O
or	O
Pre-Scheme	B-Language
,	O
is	O
a	O
statically-typed	O
dialect	O
of	O
Scheme	B-Language
with	O
the	O
efficiency	O
and	O
low-level	O
machine	O
access	O
of	O
C	B-Language
while	O
retaining	O
many	O
of	O
the	O
desirable	O
features	O
of	O
Scheme	B-Language
.	O
</s>
