<s>
IMP	B-Language
is	O
an	O
early	O
systems	B-Language
programming	I-Language
language	I-Language
that	O
was	O
developed	O
by	O
Edgar	O
T	O
.	O
Irons	O
in	O
the	O
late	O
1960s	O
through	O
early	O
1970s	O
,	O
at	O
the	O
National	O
Security	O
Agency	O
(	O
NSA	O
)	O
.	O
</s>
<s>
Unlike	O
most	O
other	O
systems	O
languages	O
,	O
IMP	B-Language
supports	O
syntax-extensible	O
programming	O
.	O
</s>
<s>
Even	O
though	O
,	O
IMP	B-Language
excludes	O
many	O
defining	O
features	O
of	O
that	O
language	O
,	O
while	O
supporting	O
a	O
very	O
non-ALGOL-like	O
one	O
:	O
syntax	O
extensibility	O
.	O
</s>
<s>
A	O
compiler	B-Language
for	O
IMP	B-Language
existed	O
as	O
early	O
as	O
1965	O
and	O
was	O
used	O
to	O
program	O
the	O
CDC	B-Device
6600	I-Device
time-sharing	B-General_Concept
system	I-General_Concept
,	O
which	O
was	O
in	O
use	O
at	O
the	O
Institute	O
for	O
Defense	O
Analyses	O
since	O
1967	O
.	O
</s>
<s>
Although	O
the	O
compiler	B-Language
is	O
slower	O
than	O
comparable	O
ones	O
for	O
non-extensible	O
languages	O
,	O
it	O
has	O
been	O
used	O
for	O
practical	O
production	O
work	O
.	O
</s>
<s>
IMP	B-Language
compilers	B-Language
were	O
developed	O
for	O
the	O
CDC	B-Device
6600	I-Device
,	O
Cray	O
,	O
PDP-10	B-Device
and	O
PDP-11	B-Device
computers	O
.	O
</s>
<s>
Important	O
IMP	B-Language
versions	O
were	O
IMP65	O
,	O
IMP70	O
,	O
and	O
IMP72	B-Language
.	O
</s>
<s>
Being	O
an	O
extensible	B-Application
syntax	O
programming	O
language	O
,	O
IMP	B-Language
allows	O
a	O
programmer	O
to	O
extend	O
its	O
syntax	O
,	O
although	O
no	O
specific	O
means	O
are	O
provided	O
to	O
add	O
new	O
data	O
types	O
or	O
structures	O
to	O
it	O
.	O
</s>
<s>
To	O
achieve	O
its	O
syntax-extensibility	O
,	O
IMP	B-Language
uses	O
a	O
powerful	O
parse	O
algorithm	O
based	O
on	O
a	O
syntax	O
graph	O
and	O
several	O
connectivity	O
matrices	O
.	O
</s>
<s>
IMP72	B-Language
's	O
syntax	O
is	O
extended	O
by	O
means	O
of	O
extended-BNF	O
syntax	O
statements	O
included	O
in	O
a	O
source	O
code	O
program	O
.	O
</s>
<s>
The	O
mechanism	O
is	O
so	O
powerful	O
,	O
that	O
it	O
allowed	O
the	O
implementation	O
of	O
the	O
language	O
by	O
itself	O
,	O
i.e.	O
,	O
by	O
an	O
IMP72	B-Language
source	O
file	O
consisting	O
entirely	O
of	O
syntax	O
statements	O
,	O
which	O
was	O
input	O
to	O
a	O
trivial	O
compiler	B-Language
which	O
was	O
initially	O
able	O
to	O
translate	O
the	O
simplest	O
case	O
of	O
the	O
syntax	O
statement	O
.	O
</s>
<s>
Basically	O
,	O
the	O
syntax	O
statement	O
is	O
an	O
augmented	O
BNF	O
production	O
with	O
associated	O
semantics	B-Application
added	O
on	O
the	O
right	O
:	O
</s>
<s>
with	O
the	O
semantics	B-Application
that	O
INCREMENT	O
V	O
should	O
translate	O
to	O
V	O
←	O
V	O
+	O
1	O
,	O
the	O
programmer	O
would	O
only	O
need	O
to	O
insert	O
the	O
following	O
IMP	B-Language
statement	O
:	O
</s>
<s>
DEWOP	O
is	O
a	O
semantic	O
routine	O
which	O
respectively	O
takes	O
as	O
its	O
arguments	O
a	O
PDP-10	B-Device
machine	O
language	O
opcode	B-Language
,	O
a	O
register	O
object	O
,	O
and	O
any	O
other	O
object	O
,	O
and	O
produces	O
an	O
object	O
whose	O
value	O
is	O
the	O
result	O
of	O
executing	O
the	O
designated	O
machine	O
instruction	O
using	O
as	O
address	O
field	O
the	O
object	O
which	O
is	O
its	O
last	O
argument	O
.	O
</s>
<s>
In	O
this	O
example	O
,	O
the	O
opcode	B-Language
214B	O
designates	O
the	O
Load	O
Magnitude	O
instruction	O
,	O
and	O
thus	O
the	O
result	O
of	O
the	O
above	O
syntax	O
statement	O
will	O
be	O
to	O
compile	B-Language
code	O
to	O
compute	O
the	O
absolute	O
value	O
of	O
A	O
.	O
</s>
<s>
IMP	B-Language
was	O
the	O
language	O
used	O
on	O
NSA	O
's	O
homegrown	O
time-sharing	B-General_Concept
operating	I-General_Concept
system	I-General_Concept
named	O
Folklore	O
.	O
</s>
