<s>
PL/C	B-Language
is	O
an	O
instructional	O
dialect	O
of	O
the	O
programming	O
language	O
PL/I	B-Language
,	O
developed	O
at	O
the	O
Department	O
of	O
Computer	O
Science	O
of	O
Cornell	O
University	O
in	O
the	O
early	O
1970s	O
in	O
an	O
effort	O
headed	O
by	O
Professor	O
Richard	O
W	O
.	O
Conway	O
and	O
graduate	O
student	O
Thomas	O
R	O
.	O
Wilcox	O
.	O
</s>
<s>
PL/C	B-Language
was	O
developed	O
with	O
the	O
specific	O
goal	O
of	O
being	O
used	O
for	O
teaching	O
programming	O
.	O
</s>
<s>
The	O
PL/C	B-Language
compiler	O
,	O
which	O
implemented	O
almost	O
all	O
of	O
the	O
large	O
PL/I	B-Language
language	O
,	O
had	O
the	O
unusual	O
capability	O
of	O
never	O
failing	O
to	O
compile	O
a	O
program	O
,	O
through	O
the	O
use	O
of	O
extensive	O
automatic	O
correction	O
of	O
many	O
syntax	O
errors	O
and	O
by	O
converting	O
any	O
remaining	O
syntax	O
errors	O
to	O
output	O
statements	O
.	O
</s>
<s>
IBM	B-Architecture
punch	I-Architecture
cards	I-Architecture
and	O
might	O
not	O
get	O
their	O
output	O
back	O
for	O
several	O
hours	O
.	O
</s>
<s>
Over	O
250	O
other	O
universities	O
adopted	O
PL/C	B-Language
;	O
as	O
one	O
late-1970s	O
textbook	O
on	O
PL/I	B-Language
noted	O
,	O
"	O
PL/C	B-Language
...	O
the	O
compiler	O
for	O
PL/I	B-Language
developed	O
at	O
Cornell	O
University	O
...	O
is	O
widely	O
used	O
in	O
teaching	O
programming.	O
"	O
</s>
<s>
Similarly	O
,	O
a	O
mid-late-1970s	O
survey	O
of	O
programming	O
languages	O
said	O
that	O
"	O
PL/C	B-Language
is	O
a	O
widely	O
used	O
dialect	O
of	O
PL/I.	O
"	O
</s>
<s>
Work	O
on	O
this	O
project	O
was	O
based	O
on	O
a	O
prior	O
Cornell	O
compiler	O
for	O
the	O
programming	O
language	O
CUPL	B-Language
,	O
which	O
in	O
turn	O
was	O
influenced	O
by	O
the	O
earlier	O
Cornell	O
language	O
implementation	O
CORC	B-Language
.	O
</s>
<s>
CORC	B-Language
had	O
been	O
used	O
at	O
Cornell	O
from	O
1962	O
to	O
1966	O
and	O
CUPL	B-Language
from	O
1965	O
to	O
1969	O
.	O
</s>
<s>
As	O
another	O
Cornell	O
computer	O
science	O
professor	O
,	O
David	O
Gries	O
,	O
wrote	O
at	O
the	O
time	O
,	O
the	O
first	O
criterion	O
effectively	O
eliminated	O
the	O
ALGOL	B-Language
family	I-Language
of	O
languages	O
and	O
the	O
second	O
criteria	O
argued	O
against	O
FORTRAN	B-Application
and	O
BASIC	O
(	O
with	O
COBOL	B-Application
not	O
even	O
being	O
considered	O
)	O
;	O
thus	O
,	O
they	O
chose	O
PL/I	B-Language
.	O
</s>
<s>
While	O
PL/I	B-Language
did	O
have	O
a	O
foothold	O
in	O
educational	B-Language
use	O
,	O
the	O
decision	O
went	O
against	O
the	O
grain	O
of	O
most	O
universities	O
,	O
where	O
one	O
survey	O
found	O
that	O
some	O
70percent	O
of	O
American	O
college	O
students	O
were	O
being	O
taught	O
with	O
FORTRAN	B-Application
.	O
</s>
<s>
However	O
,	O
Cornell	O
was	O
intent	O
on	O
having	O
a	O
language	O
useful	O
for	O
showing	O
computer	O
science	O
principles	O
and	O
best	O
engineering	O
practices	O
and	O
through	O
which	O
methods	O
such	O
as	O
structured	B-Language
programming	I-Language
and	O
stepwise	O
refinement	O
could	O
be	O
taught	O
,	O
and	O
PL/I	B-Language
was	O
a	O
more	O
expressive	O
vehicle	O
for	O
that	O
than	O
FORTRAN	B-Application
.	O
</s>
<s>
For	O
educational	B-Language
institutions	O
that	O
did	O
choose	O
to	O
use	O
the	O
language	O
,	O
the	O
production	O
IBM	O
PL/I	B-Language
F	O
compiler	O
then	O
available	O
was	O
much	O
too	O
slow	O
,	O
in	O
both	O
compile	O
time	O
and	O
execution	O
time	O
,	O
for	O
its	O
use	O
to	O
be	O
practical	O
for	O
student	O
programs	O
.	O
</s>
<s>
A	O
similar	O
situation	O
existed	O
for	O
FORTRAN	B-Application
,	O
where	O
the	O
IBM	O
FORTRAN	B-Application
IV	O
G	O
compiler	O
was	O
too	O
slow	O
and	O
the	O
University	O
of	O
Waterloo	O
's	O
WATFOR	B-Language
implementation	O
had	O
become	O
a	O
very	O
popular	O
alternate	O
solution	O
.	O
</s>
<s>
So	O
there	O
was	O
an	O
opening	O
for	O
a	O
student	O
compiler	O
for	O
PL/I	B-Language
;	O
indeed	O
,	O
IBM	O
recognized	O
this	O
and	O
contacted	O
Cornell	O
and	O
suggested	O
they	O
make	O
a	O
'	O
WATFOR	B-Language
for	O
PL/I	B-Language
'	O
.	O
</s>
<s>
Indeed	O
,	O
this	O
simile	O
would	O
be	O
made	O
explicit	O
;	O
as	O
one	O
university	O
would	O
explain	O
to	O
their	O
computer	O
center	O
users	O
,	O
"	O
PL/C	B-Language
is	O
to	O
PL/I	B-Language
what	O
WATFOR	B-Language
is	O
to	O
FORTRAN	B-Application
IV	O
,	O
a	O
fast	O
compile-and-go	O
system	O
with	O
some	O
batching	O
capabilities	O
intended	O
primarily	O
for	O
student	O
use.	O
"	O
</s>
<s>
IBM	O
supplied	O
some	O
of	O
the	O
funding	O
for	O
the	O
initial	O
PL/C	B-Language
development	O
effort	O
,	O
which	O
took	O
place	O
during	O
1968	O
and	O
1969	O
,	O
with	O
the	O
"	O
C	O
"	O
in	O
the	O
name	O
standing	O
for	O
Cornell	O
.	O
</s>
<s>
PL/C	B-Language
began	O
being	O
used	O
on	O
a	O
regular	O
basis	O
in	O
September	O
1970	O
.	O
</s>
<s>
PL/C	B-Language
,	O
a	O
large	O
subset	O
of	O
PL/I	B-Language
,	O
eliminated	O
a	O
few	O
of	O
the	O
more	O
complex	O
features	O
of	O
PL/I	B-Language
–	O
record	O
I/O	O
,	O
list	O
processing	O
,	O
multitasking	O
,	O
and	O
the	O
compile-time	O
preprocessor	O
.	O
</s>
<s>
PL/C	B-Language
was	O
upwardly	O
compatible	O
with	O
PL/I	B-Language
,	O
meaning	O
that	O
a	O
program	O
that	O
runs	O
without	O
error	O
under	O
the	O
PL/C	B-Language
compiler	O
should	O
run	O
under	O
PL/I	B-Language
and	O
produce	O
the	O
same	O
results	O
.	O
</s>
<s>
The	O
only	O
exception	O
is	O
if	O
certain	O
incompatible	O
diagnostic	O
features	O
of	O
PL/C	B-Language
were	O
used	O
.	O
</s>
<s>
The	O
PL/C	B-Language
compiler	O
had	O
the	O
unusual	O
capability	O
of	O
never	O
failing	O
to	O
compile	O
any	O
program	O
,	O
through	O
the	O
use	O
of	O
extensive	O
automatic	O
correction	O
of	O
many	O
syntax	O
errors	O
and	O
by	O
converting	O
any	O
remaining	O
syntax	O
errors	O
to	O
output	O
statements	O
.	O
</s>
<s>
PL/C	B-Language
provided	O
extensions	O
to	O
PL/I	B-Language
'	O
s	O
own	O
CHECK	O
facility	O
for	O
flow	O
tracing	O
,	O
and	O
additionally	O
provided	O
new	O
facilities	O
,	O
such	O
as	O
the	O
PUT	O
ALL	O
;	O
and	O
PUT	O
ARRAY	O
;	O
statements	O
for	O
printing	O
the	O
values	O
of	O
every	O
scalar	O
and	O
every	O
array	O
variable	O
at	O
that	O
point	O
in	O
the	O
program	O
.	O
</s>
<s>
PL/C	B-Language
also	O
provided	O
pseudo-comments	O
,	O
which	O
could	O
be	O
used	O
to	O
conditionally	O
turn	O
on	O
code	O
based	O
on	O
options	O
supplied	O
in	O
the	O
PL/C	B-Language
job	O
control	O
card	O
:	O
</s>
<s>
Pseudo-comments	O
also	O
provided	O
a	O
way	O
to	O
use	O
PL/C	B-Language
-specific	O
statements	O
in	O
an	O
upwardly	O
compatible	O
way	O
with	O
PL/I	B-Language
,	O
as	O
in	O
the	O
second	O
case	O
,	O
since	O
the	O
PL/I	B-Language
compiler	O
would	O
see	O
them	O
as	O
comments	O
only	O
.	O
</s>
<s>
PL/C	B-Language
handles	O
floating	B-Algorithm
point	I-Algorithm
arithmetic	I-Algorithm
by	O
computing	O
all	O
single-precision	O
values	O
as	O
double	O
precision	O
,	O
which	O
can	O
complicate	O
attempts	O
by	O
the	O
programmer	O
to	O
validate	O
rounding	O
behavior	O
of	O
particular	O
computations	O
.	O
</s>
<s>
A	O
simple	O
example	O
of	O
PL/C	B-Language
'	O
s	O
error	O
repair	O
has	O
been	O
presented	O
as	O
:	O
</s>
<s>
There	O
were	O
several	O
other	O
education-related	O
PL/I	B-Language
compilers	O
,	O
including	O
PLAGO	O
from	O
the	O
Polytechnic	O
Institute	O
of	O
Brooklyn	O
and	O
SP/k	B-Language
from	O
the	O
University	O
of	O
Toronto	O
,	O
however	O
they	O
tended	O
to	O
use	O
much	O
more	O
restricted	O
subsets	O
of	O
PL/I	B-Language
,	O
whereas	O
PL/C	B-Language
supported	O
almost	O
the	O
entire	O
language	O
.	O
</s>
<s>
And	O
PL/C	B-Language
was	O
the	O
only	O
PL/I	B-Language
educational	B-Language
dialect	O
mentioned	O
in	O
languages	O
expert	O
Jean	O
E	O
.	O
Sammet	O
's	O
extensive	O
survey	O
of	O
programming	O
languages	O
in	O
use	O
for	O
1976	O
–	O
77	O
.	O
</s>
<s>
The	O
implementation	O
of	O
the	O
PL/C	B-Language
compiler	O
itself	O
was	O
done	O
in	O
IBM	B-Device
360	I-Device
Assembly	I-Device
Language	I-Device
,	O
with	O
a	O
heavy	O
use	O
of	O
assembly	O
language	O
macros	O
.	O
</s>
<s>
It	O
was	O
done	O
as	O
a	O
three-pass	B-Application
compiler	I-Application
,	O
with	O
the	O
first	O
pass	O
doing	O
syntax	B-Language
analysis	I-Language
and	O
error	O
correction	O
of	O
syntactical	O
mistakes	O
,	O
the	O
second	O
pass	O
doing	O
semantic	O
analysis	O
and	O
further	O
error	O
correction	O
,	O
and	O
the	O
third	O
pass	O
doing	O
code	B-Application
generation	I-Application
.	O
</s>
<s>
PL/C	B-Language
needed	O
to	O
avoid	O
the	O
longstanding	O
problem	O
of	O
"	O
cascading	O
diagnostics	O
"	O
,	O
wherein	O
one	O
error	O
is	O
internally	O
but	O
often	O
mistakenly	O
"	O
fixed	O
"	O
by	O
the	O
compiler	O
,	O
resulting	O
in	O
a	O
secondary	O
,	O
tertiary	O
and	O
additional	O
series	O
of	O
unhelpful	O
error	O
messages	O
.	O
</s>
<s>
The	O
design	O
of	O
the	O
intermediate	O
language	O
used	O
between	O
the	O
passes	O
and	O
of	O
the	O
accompanying	O
symbol	B-Application
table	I-Application
was	O
tailored	O
towards	O
,	O
and	O
key	O
to	O
the	O
achievement	O
of	O
,	O
the	O
error-repair	O
and	O
diagnostic	O
reporting	O
capabilities	O
of	O
PL/C	B-Language
.	O
</s>
<s>
While	O
a	O
number	O
of	O
these	O
techniques	O
dated	O
from	O
the	O
Cornell	O
CORC	B-Language
and	O
CUPL	B-Language
efforts	O
,	O
here	O
they	O
were	O
being	O
used	O
for	O
the	O
first	O
time	O
on	O
large	O
programming	O
language	O
with	O
a	O
full	O
set	O
of	O
commercial-grade	O
features	O
.	O
</s>
<s>
This	O
was	O
especially	O
notable	O
given	O
that	O
the	O
PL/I	B-Language
language	O
was	O
notoriously	O
challenging	O
for	O
compilers	O
to	O
deal	O
with	O
.	O
</s>
<s>
The	O
compilation	O
speed	O
of	O
PL/C	B-Language
was	O
quite	O
good	O
–	O
some	O
10,000	O
–	O
20,000	O
sources	O
lines	O
of	O
code	O
per	O
minute	O
on	O
an	O
IBM	B-Device
System/360	I-Device
Model	I-Device
65	I-Device
.	O
</s>
<s>
The	O
work	O
done	O
on	O
PL/C	B-Language
was	O
described	O
in	O
a	O
paper	O
presented	O
at	O
an	O
AFIPS	O
joint	O
conference	O
in	O
Spring	O
1971	O
.	O
</s>
<s>
More	O
prominent	O
was	O
the	O
paper	O
"	O
Design	O
and	O
Implementation	O
of	O
a	O
Diagnostic	O
Compiler	O
for	O
PL/I	B-Language
"	O
by	O
Conway	O
and	O
Wilcox	O
,	O
published	O
in	O
the	O
March	O
1973	O
issue	O
of	O
the	O
flagship	O
journal	O
Communications	O
of	O
the	O
ACM	O
,	O
which	O
gave	O
the	O
project	O
considerable	O
visibility	O
within	O
the	O
computer	O
science	O
world	O
.	O
</s>
<s>
PL/C	B-Language
was	O
implemented	O
as	O
a	O
compile	O
and	O
go	O
system	O
,	O
similar	O
to	O
WATFOR	B-Language
.	O
</s>
<s>
It	O
ran	O
on	O
the	O
IBM	B-Application
System/360	I-Application
and	O
System/370	B-Device
under	O
OS	B-Application
and	O
HASP	B-Application
.	O
</s>
<s>
As	O
such	O
,	O
it	O
was	O
designed	O
to	O
run	O
within	O
a	O
128K	O
byte	O
partition	O
,	O
where	O
the	O
PL/C	B-Language
software	O
and	O
the	O
generated	O
object	O
code	O
took	O
a	O
maximum	O
of	O
100K	O
bytes	O
.	O
</s>
<s>
Error	O
correction	O
was	O
attempted	O
at	O
runtime	O
as	O
well	O
,	O
with	O
the	O
PL/C	B-Language
execution	O
supervisor	O
trapping	O
or	O
otherwise	O
detecting	O
use	O
of	O
uninitialized	O
variables	O
,	O
division	O
by	O
zero	O
,	O
out-of-range	O
array	O
indexes	O
,	O
and	O
the	O
like	O
,	O
by	O
issuing	O
a	O
diagnostic	O
and	O
making	O
some	O
adjustment	O
to	O
allow	O
the	O
program	O
to	O
keep	O
running	O
.	O
</s>
<s>
Overall	O
,	O
use	O
of	O
PL/C	B-Language
significantly	O
reduced	O
the	O
severity	O
of	O
the	O
wait-times-for-batch-runs	O
problem	O
(	O
although	O
Cornell	O
itself	O
developed	O
a	O
job	O
entry	O
system	O
for	O
turning	O
around	O
most	O
student	O
batch	O
jobs	O
very	O
quickly	O
)	O
.	O
</s>
<s>
As	O
soon	O
as	O
it	O
was	O
ready	O
,	O
PL/C	B-Language
was	O
distributed	O
beyond	O
Cornell	O
itself	O
,	O
in	O
the	O
form	O
of	O
magnetic	B-Architecture
tapes	I-Architecture
sent	O
to	O
interested	O
parties	O
.	O
</s>
<s>
For	O
instance	O
,	O
PL/C	B-Language
was	O
first	O
used	O
at	O
the	O
University	O
of	O
Michigan	O
in	O
the	O
Fall	O
1970	O
semester	O
.	O
</s>
<s>
The	O
PL/C	B-Language
project	O
was	O
considered	O
a	O
research	O
effort	O
,	O
not	O
a	O
commercial	O
endeavor	O
;	O
however	O
,	O
those	O
installations	O
who	O
wanted	O
to	O
use	O
PL/C	B-Language
were	O
asked	O
to	O
pay	O
a	O
"	O
research	O
grant	O
"	O
in	O
exchange	O
.	O
</s>
<s>
Cornell	O
's	O
further	O
development	O
work	O
on	O
PL/C	B-Language
was	O
partly	O
funded	O
by	O
these	O
payments	O
.	O
</s>
<s>
PL/C	B-Language
quickly	O
became	O
the	O
most	O
popular	O
of	O
any	O
education	O
version	O
of	O
PL/I	B-Language
;	O
in	O
1970	O
–	O
71	O
alone	O
,	O
it	O
was	O
sent	O
to	O
100	O
different	O
institutions	O
,	O
resulting	O
in	O
60	O
of	O
them	O
purchasing	O
it	O
.	O
</s>
<s>
By	O
1976	O
,	O
there	O
were	O
more	O
than	O
200	O
sites	O
around	O
the	O
world	O
that	O
had	O
installed	O
PL/C	B-Language
.	O
</s>
<s>
There	O
was	O
also	O
some	O
interest	O
in	O
PL/C	B-Language
from	O
non-academic	O
entities	O
,	O
thus	O
resulting	O
in	O
PL/C	B-Language
adding	O
support	O
for	O
some	O
business-oriented	O
features	O
such	O
as	O
PICTURE	O
variables	O
.	O
</s>
<s>
A	O
survey	O
conducted	O
by	O
New	O
Mexico	O
State	O
University	O
in	O
1972	O
looked	O
at	O
various	O
possibilities	O
for	O
teaching	O
languages	O
and	O
implementations	O
and	O
concluded	O
regarding	O
PL/C	B-Language
:	O
</s>
<s>
"	O
PL/C	B-Language
seems	O
praiseworthy	O
.	O
</s>
<s>
It	O
has	O
all	O
of	O
the	O
built-in	O
functions	O
PL/I	B-Language
has	O
,	O
is	O
much	O
faster	O
in	O
both	O
compilation	O
and	O
execution	O
,	O
and	O
runs	O
in	O
86K	O
of	O
a	O
100K	O
partition	O
leaving	O
14K	O
for	O
the	O
student	O
program	O
.	O
</s>
<s>
The	O
PL/C	B-Language
compiler	O
not	O
only	O
diagnoses	O
errors	O
,	O
but	O
often	O
corrects	O
them	O
properly	O
.	O
</s>
<s>
If	O
PL/C	B-Language
finds	O
a	O
statement	O
completely	O
unrecognizable	O
it	O
deletes	O
it	O
and	O
attempts	O
execution	O
anyway.	O
"	O
</s>
<s>
Some	O
universities	O
,	O
including	O
Washington	O
State	O
University	O
,	O
found	O
success	O
in	O
teaching	O
an	O
introductory	O
class	O
that	O
used	O
PL/C	B-Language
first	O
and	O
then	O
Fortran	B-Application
(	O
using	O
WATFIV	B-Language
)	O
second	O
,	O
which	O
was	O
found	O
to	O
be	O
a	O
beneficial	O
order	O
in	O
terms	O
of	O
student	O
learning	O
.	O
</s>
<s>
PL/C	B-Language
release	O
numbers	O
were	O
to	O
some	O
extent	O
synchronized	O
to	O
releases	O
of	O
the	O
IBM	O
PL/I	B-Language
F	O
compiler	O
,	O
so	O
that	O
for	O
instance	O
Release	O
4	O
of	O
PL/C	B-Language
was	O
intended	O
to	O
match	O
Version	O
4	O
of	O
the	O
IBM	O
F	O
compiler	O
in	O
terms	O
of	O
upward	O
compatibility	O
.	O
</s>
<s>
In	O
terms	O
of	O
some	O
instances	O
of	O
PL/C	B-Language
distributions	O
,	O
Release	O
4	O
was	O
available	O
by	O
January	O
1971	O
;	O
Release	O
6	O
by	O
August	O
1971	O
;	O
Release	O
6.5	O
by	O
November	O
1973	O
;	O
Release	O
7.1	O
in	O
March	O
1975	O
;	O
and	O
Release	O
7.5	O
in	O
March	O
1976	O
.	O
</s>
<s>
The	O
last	O
version	O
of	O
PL/C	B-Language
appears	O
to	O
have	O
been	O
Release	O
7.6	O
,	O
put	O
out	O
in	O
1977	O
.	O
</s>
<s>
Within	O
the	O
computer	O
science	O
department	O
at	O
Cornell	O
there	O
was	O
a	O
sense	O
of	O
pride	O
about	O
PL/C	B-Language
being	O
associated	O
with	O
the	O
university	O
,	O
and	O
there	O
were	O
several	O
variants	O
of	O
PL/C	B-Language
worked	O
on	O
by	O
Conway	O
,	O
other	O
faculty	O
members	O
,	O
and	O
graduate	O
students	O
.	O
</s>
<s>
In	O
1974	O
,	O
the	O
PL/CT	O
variant	O
of	O
PL/C	B-Language
,	O
for	O
use	O
on	O
interactive	O
terminals	O
rather	O
than	O
in	O
batch	O
job	O
submissions	O
,	O
was	O
first	O
made	O
available	O
at	O
Cornell	O
.	O
</s>
<s>
PL/CT	O
primarily	O
ran	O
on	O
an	O
IBM	B-Device
System/370	I-Device
under	O
VM/CMS	B-Application
;	O
it	O
could	O
also	O
run	O
in	O
the	O
IBM	B-Application
TSO	I-Application
environment	O
.	O
</s>
<s>
A	O
variant	O
under	O
development	O
by	O
1976	O
was	O
PL/CS	B-Language
,	O
which	O
was	O
a	O
far	O
more	O
restricted	O
subset	O
of	O
PL/I	B-Language
than	O
regular	O
PL/C	B-Language
and	O
which	O
provided	O
direct	O
language	O
support	O
for	O
assertions	O
.	O
</s>
<s>
The	O
subset	O
was	O
enough	O
,	O
however	O
,	O
that	O
PL/CS	B-Language
would	O
still	O
be	O
suitable	O
for	O
teaching	O
introductory	O
programming	O
classes	O
.	O
</s>
<s>
It	O
was	O
implemented	O
as	O
an	O
alternate	O
lexical	O
and	O
syntactic	O
analyzer	O
that	O
then	O
plugged	O
into	O
the	O
common	O
PL/C	B-Language
code	O
generator	O
and	O
runtime	O
system	O
.	O
</s>
<s>
PL/CS	B-Language
was	O
also	O
used	O
in	O
research	O
on	O
the	O
formal	B-Application
semantics	I-Application
of	I-Application
programming	I-Application
languages	I-Application
.	O
</s>
<s>
A	O
different	O
implementation	O
of	O
the	O
PL/CS	B-Language
definition	O
came	O
with	O
Professor	O
Tim	O
Teitelbaum	O
and	O
his	O
pioneering	O
Cornell	O
Program	O
Synthesizer	O
work	O
.	O
</s>
<s>
This	O
early	O
instance	O
of	O
an	O
integrated	B-Application
development	I-Application
environment	I-Application
was	O
developed	O
in	O
1978	O
for	O
the	O
PDP-11/60	O
,	O
and	O
contained	O
a	O
structured	B-Application
editor	I-Application
for	O
PL/CS	B-Language
along	O
with	O
an	O
incremental	B-Application
compiler	I-Application
as	O
well	O
as	O
an	O
interpreter	B-Application
.	O
</s>
<s>
The	O
Cornell	O
Program	O
Synthesizer	O
was	O
soon	O
adapted	O
for	O
the	O
Terak	B-Device
desktop	I-Device
workstation	I-Device
,	O
an	O
early	O
personal	O
computer	O
,	O
which	O
was	O
based	O
on	O
the	O
LSI-11	O
processor	O
.	O
</s>
<s>
The	O
Terak	O
computer	O
found	O
popularity	O
for	O
instructional	O
use	O
at	O
Cornell	O
and	O
at	O
other	O
universities	O
,	O
as	O
did	O
the	O
PL/CS	B-Language
available	O
on	O
it	O
.	O
</s>
<s>
In	O
addition	O
,	O
Cornell	O
built	O
a	O
link	O
between	O
the	O
Terak	O
and	O
their	O
IBM	B-Device
370	I-Device
mainframe	O
,	O
that	O
would	O
allow	O
batch-mode	O
execution	O
of	O
programs	O
under	O
PL/C	B-Language
and	O
the	O
obtaining	O
of	O
results	O
on	O
printers	O
.	O
</s>
<s>
PL/CV	O
used	O
PL/CS	B-Language
as	O
part	O
of	O
what	O
it	O
did	O
,	O
and	O
indeed	O
Constable	O
had	O
participated	O
in	O
the	O
creation	O
of	O
PL/CS	B-Language
,	O
especially	O
working	O
with	O
Conway	O
and	O
Gries	O
on	O
the	O
adding	O
of	O
assertions	O
.	O
</s>
<s>
In	O
the	O
early	O
1970s	O
,	O
three	O
cross	B-Application
compilers	I-Application
based	O
on	O
PL/C	B-Language
were	O
created	O
at	O
the	O
University	O
of	O
North	O
Carolina	O
;	O
in	O
these	O
,	O
the	O
host	O
platform	O
was	O
the	O
IBM	B-Application
360	I-Application
,	O
and	O
the	O
target	O
machine	O
was	O
one	O
of	O
several	O
minicomputers	O
in	O
use	O
at	O
the	O
time	O
.	O
</s>
<s>
The	O
PL/C	B-Language
language	O
subset	O
was	O
used	O
in	O
these	O
cross	B-Application
compilers	I-Application
,	O
as	O
was	O
the	O
PL/C	B-Language
compiler	O
's	O
first	O
two	O
passes	O
for	O
syntax	O
and	O
semantic	O
analysis	O
.	O
</s>
<s>
However	O
the	O
IBM	B-Application
360	I-Application
code	B-Application
generation	I-Application
pass	O
and	O
storage	O
allocation	O
modules	O
were	O
replaced	O
by	O
ones	O
specific	O
to	O
the	O
target	O
architecture	O
.	O
</s>
<s>
The	O
first	O
of	O
these	O
cross	B-Application
compilers	I-Application
was	O
PLCV	O
(	O
not	O
to	O
be	O
confused	O
with	O
the	O
PL/CV	O
verifier	O
)	O
,	O
a	O
cross	B-Application
compiler	I-Application
for	O
Varian	O
Data	O
Machines	O
minicomputers	O
,	O
specifically	O
the	O
620/i	O
and	O
620/f	O
,	O
and	O
was	O
created	O
around	O
1971	O
.	O
</s>
<s>
The	O
second	O
,	O
PLCI	O
,	O
was	O
targeted	O
at	O
the	O
Interdata	B-Device
Model	O
3	O
;	O
it	O
also	O
had	O
a	O
revised	O
version	O
around	O
the	O
same	O
time	O
.	O
</s>
<s>
The	O
third	O
was	O
PLCD	O
,	O
used	O
to	O
target	O
the	O
Digital	O
Equipment	O
Corporation	O
's	O
PDP-11/45	B-Device
minicomputer	O
,	O
which	O
came	O
out	O
in	O
1973	O
.	O
</s>
<s>
Again	O
,	O
PLCD	O
used	O
PL/C	B-Language
but	O
with	O
the	O
IBM	B-Application
360	I-Application
code	O
generator	O
replaced	O
by	O
one	O
for	O
PDP-11/45	B-Device
.	O
</s>
<s>
The	O
University	O
of	O
North	O
Carolina	O
used	O
these	O
cross	B-Application
compilers	I-Application
for	O
real	O
projects	O
,	O
not	O
just	O
education	O
;	O
in	O
particular	O
,	O
PLCD	O
was	O
used	O
in	O
support	O
of	O
a	O
graphical	B-Language
programming	I-Language
environment	O
that	O
would	O
use	O
the	O
same	O
programming	O
language	O
for	O
both	O
a	O
general	O
purpose	O
mainframe	O
and	O
a	O
graphical	O
support	O
minicomputer	O
,	O
thereby	O
allowing	O
easier	O
shifting	O
of	O
code	O
from	O
one	O
to	O
the	O
other	O
.	O
</s>
<s>
The	O
IBM	O
PL/I	B-Language
F	O
compiler	O
was	O
used	O
on	O
the	O
mainframe	O
,	O
with	O
programmers	O
restricting	O
themselves	O
to	O
the	O
PL/C	B-Language
subset	O
of	O
the	O
language	O
,	O
and	O
PLCD	O
was	O
used	O
to	O
generate	O
code	O
for	O
the	O
PDP-11/45	B-Device
.	O
</s>
<s>
The	O
textbook	O
An	O
Introduction	O
to	O
Programming	O
:	O
A	O
Structured	B-Language
Approach	O
Using	O
PL/I	B-Language
and	O
PL/C	B-Language
was	O
written	O
by	O
Conway	O
and	O
Gries	O
using	O
PL/C	B-Language
as	O
the	O
programming	O
language	O
and	O
was	O
published	O
in	O
1973	O
.	O
</s>
<s>
It	O
presented	O
top-down	O
design	O
,	O
and	O
stressed	O
the	O
discipline	O
of	O
structured	B-Language
programming	I-Language
throughout	O
,	O
becoming	O
one	O
of	O
the	O
most	O
prominent	O
textbooks	O
to	O
do	O
so	O
.	O
</s>
<s>
The	O
book	O
had	O
a	O
potential	O
market	O
at	O
any	O
university	O
using	O
PL/C	B-Language
,	O
and	O
Conway	O
later	O
said	O
that	O
the	O
book	O
had	O
sold	O
very	O
well	O
.	O
</s>
<s>
Besides	O
reorganizing	O
some	O
material	O
on	O
the	O
development	O
and	O
testing	O
of	O
computer	O
programs	O
,	O
it	O
incorporated	O
changes	O
due	O
to	O
Release	O
7	O
of	O
the	O
PL/C	B-Language
compiler	O
.	O
</s>
<s>
A	O
third	O
edition	O
was	O
published	O
in	O
1979	O
and	O
,	O
besides	O
pitching	O
the	O
textbook	O
material	O
at	O
a	O
somewhat	O
higher	O
level	O
to	O
reflect	O
that	O
many	O
college	O
students	O
had	O
previous	O
programming	O
exposure	O
in	O
high	O
school	O
,	O
incorporated	O
additions	O
to	O
reflect	O
the	O
PL/CT	O
and	O
PL/CS	B-Language
variants	O
of	O
PL/C	B-Language
.	O
</s>
<s>
An	O
Introduction	O
to	O
Programming	O
:	O
A	O
Structured	B-Language
Approach	O
was	O
used	O
as	O
the	O
basis	O
for	O
several	O
offshoot	O
textbooks	O
,	O
sometimes	O
with	O
additional	O
co-authors	O
,	O
that	O
were	O
either	O
aimed	O
at	O
a	O
more	O
beginning	O
level	O
or	O
that	O
covered	O
other	O
languages	O
or	O
dialects	O
.	O
</s>
<s>
PL/C	B-Language
was	O
still	O
in	O
use	O
at	O
the	O
beginning	O
of	O
the	O
1980s	O
.	O
</s>
<s>
However	O
,	O
by	O
then	O
the	O
Pascal	B-Application
programming	I-Application
language	I-Application
was	O
beginning	O
to	O
come	O
to	O
the	O
fore	O
as	O
a	O
teaching	O
language	O
,	O
and	O
the	O
move	O
of	O
student	O
access	O
towards	O
smaller	O
and	O
more	O
distributed	O
computer	O
systems	O
than	O
IBM	O
mainframes	O
also	O
continued	O
.	O
</s>
<s>
And	O
PL/I	B-Language
itself	O
never	O
gained	O
the	O
dominance	O
its	O
designers	O
had	O
hoped	O
for	O
in	O
either	O
the	O
business	O
or	O
scientific	O
programming	O
fields	O
.	O
</s>
<s>
At	O
Cornell	O
itself	O
,	O
the	O
switch	O
to	O
using	O
Pascal	B-Application
in	O
its	O
introductory	O
computer	O
programming	O
classes	O
took	O
place	O
during	O
1984	O
.	O
</s>
<s>
Conway	O
has	O
said	O
he	O
does	O
not	O
know	O
how	O
long	O
PL/C	B-Language
remained	O
in	O
use	O
at	O
the	O
various	O
sites	O
where	O
it	O
was	O
installed	O
.	O
</s>
<s>
In	O
2012	O
,	O
an	O
effort	O
was	O
ongoing	O
to	O
resurrect	O
the	O
popular	O
Michigan	B-Application
Terminal	I-Application
System	I-Application
and	O
the	O
software	O
that	O
ran	O
on	O
it	O
as	O
part	O
of	O
an	O
archival	O
effort	O
on	O
IBM	O
360/370	O
simulators	O
.	O
</s>
<s>
Among	O
the	O
things	O
they	O
requested	O
was	O
permission	O
to	O
run	O
the	O
PL/C	B-Language
object	O
code	O
,	O
which	O
was	O
informally	O
granted	O
by	O
those	O
staff	O
associated	O
with	O
it	O
who	O
were	O
still	O
at	O
Cornell	O
.	O
</s>
<s>
,	O
the	O
source	O
for	O
PL/C	B-Language
appears	O
to	O
have	O
been	O
lost	O
.	O
</s>
