<s>
The	O
PL/I	B-Language
preprocessor	I-Language
is	O
the	O
preprocessor	B-General_Concept
for	O
the	O
PL/I	B-Language
computer	O
programming	O
language	O
.	O
</s>
<s>
The	O
preprocessor	B-General_Concept
interprets	O
a	O
subset	O
of	O
the	O
full	O
PL/I	B-Language
language	O
to	O
perform	O
source	O
file	O
inclusion	O
,	O
conditional	B-Application
compilation	I-Application
,	O
and	O
macro	O
expansion	O
.	O
</s>
<s>
The	O
preprocessor	B-General_Concept
language	O
has	O
a	O
PL/I	B-Language
-like	O
syntax	O
with	O
preprocessor	B-General_Concept
statements	O
and	O
preprocessor	B-General_Concept
procedures	O
prefixed	O
with	O
a	O
percent	O
symbol	O
( %	O
)	O
.	O
</s>
<s>
Listing-control	O
statements	O
,	O
which	O
supply	O
formatting	O
commands	O
for	O
the	O
compiler	B-Language
listing	O
,	O
are	O
usually	O
considered	O
preprocessor	B-General_Concept
statements	O
and	O
also	O
begin	O
with	O
%	O
.	O
</s>
<s>
Preprocessor	B-General_Concept
statements	O
are	O
imbedded	O
in	O
and	O
operate	O
on	O
input	O
text	O
.	O
</s>
<s>
The	O
input	O
text	O
is	O
normally	O
a	O
PL/I	B-Language
program	O
,	O
but	O
is	O
agnostic	O
to	O
the	O
grammar	O
of	O
PL/I	B-Language
,	O
so	O
the	O
preprocessor	B-General_Concept
can	O
also	O
be	O
used	O
independently	O
to	O
process	O
other	O
kinds	O
of	O
text	O
files	O
.	O
</s>
<s>
The	O
preprocessor	B-General_Concept
is	O
not	O
specified	O
as	O
part	O
of	O
standard	O
PL/I	B-Language
,	O
but	O
most	O
PL/I	B-Language
implementations	O
accept	O
the	O
language	O
of	O
the	O
IBM	O
preprocessor	B-General_Concept
.	O
</s>
<s>
The	O
%INCLUDE	O
preprocessor	B-General_Concept
statement	O
is	O
used	O
to	O
include	O
the	O
text	O
of	O
another	O
file	O
,	O
which	O
may	O
also	O
contain	O
preprocessor	B-General_Concept
directives	O
.	O
</s>
<s>
The	O
latest	O
IBM	O
compilers	B-Language
also	O
provide	O
an	O
%XINCLUDE	O
directive	O
,	O
which	O
has	O
the	O
effect	O
of	O
including	O
the	O
specified	O
file	O
only	O
if	O
it	O
has	O
not	O
already	O
been	O
included	O
.	O
</s>
<s>
%INSCAN	O
and	O
%XINSCAN	O
operate	O
similarly	O
,	O
except	O
that	O
the	O
name	O
of	O
the	O
file	O
to	O
be	O
included	O
is	O
specified	O
by	O
a	O
preprocessor	B-General_Concept
expression	O
.	O
</s>
<s>
Listing	O
control	O
statements	O
provide	O
instructions	O
for	O
formatting	O
both	O
the	O
listing	O
generated	O
by	O
the	O
preprocessor	B-General_Concept
and	O
the	O
listing	O
generated	O
by	O
the	O
compiler	B-Language
.	O
</s>
<s>
The	O
preprocessor	B-General_Concept
operates	O
by	O
scanning	O
the	O
input	O
text	O
and	O
recognizing	O
declared	O
preprocessor	B-General_Concept
names	O
,	O
also	O
called	O
preprocessor	B-General_Concept
identifiers	O
.	O
</s>
<s>
The	O
text	O
is	O
copied	O
to	O
the	O
preprocessor	B-General_Concept
output	O
with	O
the	O
preprocessor	B-General_Concept
names	O
replaced	O
with	O
their	O
current	O
values	O
.	O
</s>
<s>
The	O
name	O
may	O
represent	O
a	O
call	O
to	O
a	O
preprocessor	B-General_Concept
procedure	O
(	O
macro	O
)	O
.	O
</s>
<s>
Replacement	O
text	O
may	O
be	O
rescanned	O
by	O
the	O
preprocessor	B-General_Concept
for	O
possible	O
additional	O
replacement	O
.	O
</s>
<s>
Preprocessor	B-General_Concept
data	O
may	O
be	O
declared	O
to	O
be	O
CHARACTER	O
,	O
a	O
character	O
string	O
with	O
no	O
maximum	O
length	O
,	O
or	O
FIXED	O
an	O
integer	O
number	O
of	O
up	O
to	O
five	O
decimal	O
digits	O
.	O
</s>
<s>
A	O
preprocessor	B-General_Concept
builtin	O
is	O
a	O
predefined	O
procedure	O
operating	O
on	O
preprocessor	B-General_Concept
data	O
.	O
</s>
<s>
A	O
preprocessor	B-General_Concept
expression	O
is	O
an	O
expression	O
consisting	O
only	O
of	O
preprocessor	B-General_Concept
names	O
,	O
references	O
to	O
preprocessor	B-General_Concept
procedures	O
or	O
builtins	O
,	O
and	O
decimal	O
or	O
character	O
constants	O
.	O
</s>
<s>
All	O
PL/I	B-Language
operators	O
are	O
allowed	O
except	O
exponentiation	O
.	O
</s>
<s>
establishes	O
an	O
identifier	O
as	O
a	O
preprocessor	B-General_Concept
variable	O
,	O
either	O
or	O
.	O
</s>
<s>
%assignment	O
assigns	O
a	O
value	O
to	O
a	O
preprocessor	B-General_Concept
identifier	O
.	O
</s>
<s>
makes	O
a	O
preprocessor	B-General_Concept
identifier	O
active	O
,	O
that	O
is	O
,	O
eligible	O
for	O
replacement	O
when	O
encountered	O
in	O
the	O
input	O
text	O
.	O
</s>
<s>
makes	O
a	O
preprocessor	B-General_Concept
ineligible	O
for	O
replacement	O
.	O
</s>
<s>
heads	O
a	O
preprocessor	B-General_Concept
-group	O
,	O
which	O
is	O
used	O
to	O
group	O
statements	O
and	O
possibly	O
specify	O
iteration	O
.	O
</s>
<s>
A	O
preprocessor	B-General_Concept
-group	O
can	O
contain	O
any	O
combination	O
of	O
preprocessor	B-General_Concept
statements	O
and	O
input	O
text	O
.	O
</s>
<s>
heads	O
a	O
preprocessor	B-General_Concept
procedure	O
,	O
a	O
set	O
of	O
preprocessor	B-General_Concept
statements	O
that	O
functions	O
as	O
a	O
macro	O
returning	O
a	O
value	O
when	O
its	O
name	O
is	O
encountered	O
in	O
the	O
input	O
text	O
.	O
</s>
<s>
heads	O
a	O
preprocessor	B-General_Concept
-group	O
.	O
</s>
<s>
terminates	O
a	O
preprocessor	B-General_Concept
-group	O
,	O
-group	O
,	O
or	O
preprocessor	B-General_Concept
procedure	O
.	O
</s>
<s>
(	O
or	O
)	O
causes	O
the	O
preprocessor	B-General_Concept
to	O
continue	O
its	O
scan	O
at	O
the	O
specified	O
preprocessor	B-General_Concept
label	O
,	O
either	O
a	O
preprocessor	B-General_Concept
statement	O
or	O
an	O
arbitrary	O
point	O
in	O
the	O
input	O
text	O
.	O
</s>
<s>
controls	O
the	O
flow	O
of	O
the	O
preprocessor	B-General_Concept
scan	O
according	O
to	O
the	O
value	O
of	O
a	O
preprocessor	B-General_Concept
expression	O
.	O
</s>
<s>
The	O
preprocessor-units	O
can	O
be	O
any	O
single	O
preprocessor	B-General_Concept
statement	O
or	O
a	O
preprocessor	B-General_Concept
-group	O
.	O
</s>
<s>
transfers	O
control	O
to	O
the	O
of	O
the	O
containing	O
preprocessor	B-General_Concept
-group	O
,	O
ending	O
the	O
current	O
iteration	O
and	O
beginning	O
the	O
next	O
if	O
needed	O
.	O
</s>
<s>
terminates	O
any	O
remaining	O
iterations	O
of	O
the	O
containing	O
preprocessor	B-General_Concept
-group	O
transfers	O
control	O
to	O
the	O
.	O
</s>
<s>
generates	O
a	O
user-specified	O
preprocessor	B-General_Concept
diagnostic	O
message	O
.	O
</s>
<s>
is	O
a	O
preprocessor	B-General_Concept
statement	O
consisting	O
only	O
of	O
an	O
optional	O
statement	O
label	O
and	O
a	O
semicolon	O
(	O
)	O
.	O
</s>
<s>
The	O
name	O
does	O
not	O
have	O
to	O
be	O
a	O
declared	O
preprocessor	B-General_Concept
identifier	O
.	O
</s>
<s>
A	O
preprocessor	B-General_Concept
procedure	O
is	O
a	O
subroutine	O
executed	O
by	O
the	O
preprocessor	B-General_Concept
.	O
</s>
<s>
The	O
procedure	O
is	O
delimited	O
by	O
%PROCEDURE	O
and	O
%END	O
statements	O
and	O
can	O
contain	O
only	O
preprocessor	B-General_Concept
statements	O
,	O
without	O
the	O
leading	O
%	O
.	O
</s>
<s>
It	O
is	O
invoked	O
as	O
a	O
function	O
reference	O
from	O
open	O
code	O
,	O
outside	O
of	O
any	O
preprocessor	B-General_Concept
procedure	O
,	O
or	O
from	O
another	O
preprocessor	B-General_Concept
procedure	O
,	O
and	O
returns	O
a	O
CHARACTER	O
or	O
FIXED	O
value	O
.	O
</s>
<s>
These	O
are	O
the	O
built-ins	O
for	O
IBM	O
's	O
PL/I	B-Language
for	O
MVS	O
and	O
VM	O
compiler	B-Language
.	O
</s>
<s>
There	O
can	O
be	O
considerable	O
difference	O
in	O
the	O
built-ins	O
provided	O
among	O
preprocessors	B-General_Concept
of	O
various	O
PL/I	B-Language
compilers	B-Language
.	O
</s>
<s>
returns	O
the	O
date	O
and	O
time	O
of	O
compilation	B-Language
as	O
a	O
character	O
string	O
such	O
as	O
"	O
15	O
SEP	O
12	O
15:30:00	O
"	O
for	O
September	O
15	O
,	O
2012	O
3:30PM	O
(	O
local	O
time	O
)	O
.	O
</s>
<s>
same	O
as	O
PL/I	B-Language
builtin	O
.	O
</s>
<s>
same	O
as	O
PL/I	B-Language
builtin	O
.	O
</s>
<s>
returns	O
if	O
the	O
argument	O
was	O
set	O
in	O
the	O
current	O
call	O
to	O
this	O
preprocessor	B-General_Concept
procedure	O
,	O
otherwise	O
.	O
</s>
<s>
same	O
as	O
PL/I	B-Language
builtin	O
.	O
</s>
<s>
The	O
following	O
example	O
for	O
IBM	O
PL/I	B-Language
for	O
OS/2	O
illustrates	O
the	O
use	O
of	O
a	O
preprocessor	B-General_Concept
procedure	O
to	O
implement	O
a	O
C-like	O
write	O
statement	O
for	O
PL/I	B-Language
.	O
</s>
<s>
A	O
1964	O
report	O
on	O
"	O
NPL	O
"	O
,	O
as	O
PL/I	B-Language
was	O
called	O
at	O
the	O
time	O
,	O
provided	O
that	O
macro	O
procedures	O
,	O
identified	O
by	O
the	O
keyword	O
MACRO	O
,	O
could	O
use	O
the	O
complete	O
facilities	O
of	O
the	O
language	O
.	O
</s>
<s>
The	O
following	O
compile-time	O
statements	O
were	O
allowed	O
in	O
open	O
code	O
:	O
</s>
<s>
In	O
1965	O
an	O
update	O
to	O
IBM	O
's	O
PL/I	B-Language
Language	O
specification	O
defined	O
an	O
even	O
less	O
ambitious	O
preprocessor	B-General_Concept
language	O
.	O
</s>
<s>
All	O
mention	O
of	O
preprocessor	B-General_Concept
procedures	O
was	O
omitted	O
.	O
</s>
<s>
The	O
following	O
compile-time	O
statements	O
were	O
specified	O
:	O
</s>
<s>
This	O
language	O
specification	O
was	O
again	O
never	O
implemented	O
,	O
however	O
a	O
1966	O
revision	O
of	O
this	O
manual	O
restored	O
preprocessor	B-General_Concept
procedures	O
with	O
the	O
now-current	O
syntax	O
and	O
brought	O
the	O
specification	O
close	O
to	O
what	O
was	O
actually	O
included	O
in	O
PL/I	B-Language
( F	O
)	O
.	O
</s>
<s>
RETURN	O
in	O
a	O
compile-time	O
procedure	O
only	O
.	O
</s>
<s>
A	O
single	O
compile-time	O
builtin	O
,	O
SUBSTR	O
,	O
was	O
added	O
.	O
</s>
<s>
Also	O
in	O
1966	O
Robert	O
Rosin	O
published	O
a	O
pair	O
of	O
articles	O
discussing	O
development	O
of	O
the	O
preprocessor	B-General_Concept
.	O
</s>
<s>
Rosin	O
credits	O
MAD	B-Language
as	O
the	O
only	O
previous	O
example	O
of	O
a	O
macro	O
processor	O
in	O
a	O
high-level	O
language	O
.	O
</s>
