<s>
BCPL	B-Language
(	O
"	O
Basic	B-Language
Combined	I-Language
Programming	I-Language
Language	I-Language
"	O
)	O
is	O
a	O
procedural	B-Application
,	O
imperative	B-Application
,	O
and	O
structured	B-Language
programming	I-Language
language	O
.	O
</s>
<s>
Originally	O
intended	O
for	O
writing	O
compilers	B-Language
for	O
other	O
languages	O
,	O
BCPL	B-Language
is	O
no	O
longer	O
in	O
common	O
use	O
.	O
</s>
<s>
However	O
,	O
its	O
influence	O
is	O
still	O
felt	O
because	O
a	O
stripped	O
down	O
and	O
syntactically	O
changed	O
version	O
of	O
BCPL	B-Language
,	O
called	O
B	B-Language
,	O
was	O
the	O
language	O
on	O
which	O
the	O
C	B-Language
programming	I-Language
language	I-Language
was	O
based	O
.	O
</s>
<s>
BCPL	B-Language
introduced	O
several	O
features	O
of	O
many	O
modern	O
programming	O
languages	O
,	O
including	O
using	O
curly	O
braces	O
to	O
delimit	O
code	O
blocks	O
.	O
</s>
<s>
BCPL	B-Language
was	O
first	O
implemented	O
by	O
Martin	O
Richards	O
of	O
the	O
University	O
of	O
Cambridge	O
in	O
1967	O
.	O
</s>
<s>
BCPL	B-Language
was	O
designed	O
so	O
that	O
small	O
and	O
simple	O
compilers	B-Language
could	O
be	O
written	O
for	O
it	O
;	O
reputedly	O
some	O
compilers	B-Language
could	O
be	O
run	O
in	O
16	O
kilobytes	O
.	O
</s>
<s>
Furthermore	O
,	O
the	O
original	O
compiler	B-Language
,	O
itself	O
written	O
in	O
BCPL	B-Language
,	O
was	O
easily	O
portable	O
.	O
</s>
<s>
BCPL	B-Language
was	O
thus	O
a	O
popular	O
choice	O
for	O
bootstrapping	B-Application
a	O
system	O
.	O
</s>
<s>
A	O
major	O
reason	O
for	O
the	O
compiler	B-Language
's	O
portability	O
lay	O
in	O
its	O
structure	O
.	O
</s>
<s>
It	O
was	O
split	O
into	O
two	O
parts	O
:	O
the	O
front	O
end	O
parsed	O
the	O
source	O
and	O
generated	O
O-code	B-Language
,	O
an	O
intermediate	O
language	O
.	O
</s>
<s>
The	O
back	O
end	O
took	O
the	O
O-code	B-Language
and	O
translated	O
it	O
into	O
the	O
machine	O
code	O
for	O
the	O
target	O
machine	O
.	O
</s>
<s>
Only	O
of	O
the	O
compiler	B-Language
's	O
code	O
needed	O
to	O
be	O
rewritten	O
to	O
support	O
a	O
new	O
machine	O
,	O
a	O
task	O
that	O
usually	O
took	O
between	O
2	O
and	O
5	O
person-months	O
.	O
</s>
<s>
Pascal	B-Application
,	O
Java	B-Language
)	O
.	O
</s>
<s>
This	O
choice	O
later	O
proved	O
to	O
be	O
a	O
significant	O
problem	O
when	O
BCPL	B-Language
was	O
used	O
on	O
machines	O
in	O
which	O
the	O
smallest	O
addressable	O
item	O
was	O
not	O
a	O
word	O
but	O
a	O
byte	B-Application
or	O
on	O
machines	O
with	O
larger	O
word	O
sizes	O
such	O
as	O
32-bit	O
or	O
64-bit	O
.	O
</s>
<s>
The	O
mismatch	O
between	O
BCPL	B-Language
's	O
word	O
orientation	O
and	O
byte-oriented	B-General_Concept
hardware	O
was	O
addressed	O
in	O
several	O
ways	O
.	O
</s>
<s>
One	O
was	O
by	O
providing	O
standard	O
library	O
routines	O
for	O
packing	O
and	O
unpacking	O
words	O
into	O
byte	B-Application
strings	O
.	O
</s>
<s>
Later	O
,	O
two	O
language	O
features	O
were	O
added	O
:	O
the	O
bit-field	O
selection	O
operator	O
and	O
the	O
infix	O
byte	B-Application
indirection	O
operator	O
(	O
denoted	O
by	O
%	O
)	O
.	O
</s>
<s>
BCPL	B-Language
handles	O
bindings	O
spanning	O
separate	O
compilation	B-Language
units	I-Language
in	O
a	O
unique	O
way	O
.	O
</s>
<s>
There	O
are	O
no	O
user-declarable	O
global	O
variables	O
;	O
instead	O
,	O
there	O
is	O
a	O
global	O
vector	O
,	O
similar	O
to	O
"	O
blank	O
common	O
"	O
in	O
Fortran	B-Application
.	O
</s>
<s>
All	O
data	O
shared	O
between	O
different	O
compilation	B-Language
units	I-Language
comprises	O
scalars	O
and	O
pointers	O
to	O
vectors	O
stored	O
in	O
a	O
pre-arranged	O
place	O
in	O
the	O
global	O
vector	O
.	O
</s>
<s>
Thus	O
,	O
the	O
header	O
files	O
(	O
files	O
included	O
during	O
compilation	B-Language
using	O
the	O
"	O
GET	O
"	O
directive	O
)	O
become	O
the	O
primary	O
means	O
of	O
synchronizing	O
global	O
data	O
between	O
compilation	B-Language
units	I-Language
,	O
containing	O
"	O
GLOBAL	O
"	O
directives	O
that	O
present	O
lists	O
of	O
symbolic	O
names	O
,	O
each	O
paired	O
with	O
a	O
number	O
that	O
associates	O
the	O
name	O
with	O
the	O
corresponding	O
numerically	O
addressed	O
word	O
in	O
the	O
global	O
vector	O
.	O
</s>
<s>
This	O
makes	O
dynamic	O
loading	O
of	O
compilation	B-Language
units	I-Language
very	O
simple	O
to	O
achieve	O
.	O
</s>
<s>
Instead	O
of	O
relying	O
on	O
the	O
link	O
loader	O
of	O
the	O
underlying	O
implementation	O
,	O
effectively	O
,	O
BCPL	B-Language
gives	O
the	O
programmer	O
control	O
of	O
the	O
linking	O
process	O
.	O
</s>
<s>
BCPL	B-Language
was	O
the	O
first	O
brace	O
programming	O
language	O
and	O
the	O
braces	O
survived	O
the	O
syntactical	O
changes	O
and	O
have	O
become	O
a	O
common	O
means	O
of	O
denoting	O
program	O
source	O
code	O
statements	O
.	O
</s>
<s>
The	O
single-line	O
//	O
comments	O
of	O
BCPL	B-Language
,	O
which	O
were	O
not	O
adopted	O
by	O
C	B-Language
,	O
reappeared	O
in	O
C++	B-Language
and	O
later	O
in	O
C99	B-Language
.	O
</s>
<s>
The	O
book	O
BCPL	B-Language
:	O
The	O
language	O
and	O
its	O
compiler	B-Language
describes	O
the	O
philosophy	O
of	O
BCPL	B-Language
as	O
follows	O
:	O
</s>
<s>
BCPL	B-Language
was	O
first	O
implemented	O
by	O
Martin	O
Richards	O
of	O
the	O
University	O
of	O
Cambridge	O
in	O
1967	O
.	O
</s>
<s>
BCPL	B-Language
was	O
a	O
response	O
to	O
difficulties	O
with	O
its	O
predecessor	O
,	O
Cambridge	O
Programming	O
Language	O
,	O
later	O
renamed	O
Combined	B-Language
Programming	I-Language
Language	I-Language
(	O
CPL	B-Language
)	O
,	O
which	O
was	O
designed	O
during	O
the	O
early	O
1960s	O
.	O
</s>
<s>
Richards	O
created	O
BCPL	B-Language
by	O
"	O
removing	O
those	O
features	O
of	O
the	O
full	O
language	O
which	O
make	O
compilation	B-Language
difficult	O
"	O
.	O
</s>
<s>
The	O
first	O
compiler	B-Language
implementation	O
,	O
for	O
the	O
IBM	B-Device
7094	I-Device
under	O
Compatible	B-Operating_System
Time-Sharing	I-Operating_System
System	I-Operating_System
,	O
was	O
written	O
while	O
Richards	O
was	O
visiting	O
Project	O
MAC	O
at	O
the	O
Massachusetts	O
Institute	O
of	O
Technology	O
in	O
the	O
spring	O
of	O
1967	O
.	O
</s>
<s>
BCPL	B-Language
has	O
been	O
rumored	O
to	O
have	O
originally	O
stood	O
for	O
"	O
Bootstrap	O
Cambridge	O
Programming	O
Language	O
"	O
,	O
but	O
CPL	B-Language
was	O
never	O
created	O
since	O
development	O
stopped	O
at	O
BCPL	B-Language
,	O
and	O
the	O
acronym	O
was	O
later	O
reinterpreted	O
for	O
the	O
BCPL	B-Language
book	O
.	O
</s>
<s>
BCPL	B-Language
is	O
the	O
language	O
in	O
which	O
the	O
original	O
"	O
Hello	O
,	O
World	O
!	O
"	O
</s>
<s>
The	O
first	O
MUD	B-Application
was	O
also	O
written	O
in	O
BCPL	B-Language
(	O
MUD1	B-Protocol
)	O
.	O
</s>
<s>
Several	O
operating	B-General_Concept
systems	I-General_Concept
were	O
written	O
partially	O
or	O
wholly	O
in	O
BCPL	B-Language
(	O
for	O
example	O
,	O
TRIPOS	B-Operating_System
and	O
the	O
earliest	O
versions	O
of	O
AmigaDOS	B-Operating_System
)	O
.	O
</s>
<s>
BCPL	B-Language
was	O
also	O
the	O
initial	O
language	O
used	O
in	O
the	O
Xerox	O
PARC	O
Alto	B-Device
project	O
,	O
the	O
first	O
modern	O
personal	B-Device
computer	I-Device
;	O
among	O
other	O
projects	O
,	O
the	O
Bravo	B-Application
document	B-General_Concept
preparation	I-General_Concept
system	I-General_Concept
was	O
written	O
in	O
BCPL	B-Language
.	O
</s>
<s>
An	O
early	O
compiler	B-Language
,	O
bootstrapped	O
in	O
1969	O
,	O
by	O
starting	O
with	O
a	O
paper	O
tape	O
of	O
the	O
O-code	B-Language
of	O
Richards	O
's	O
Atlas	B-Device
2	I-Device
compiler	B-Language
,	O
targeted	O
the	O
ICT	B-Device
1900	I-Device
series	I-Device
.	O
</s>
<s>
The	O
two	O
machines	O
had	O
different	O
word-lengths	O
(	O
48	O
vs	O
24	O
bits	O
)	O
,	O
different	O
character	O
encodings	O
,	O
and	O
different	O
packed	O
string	O
representations	O
—	O
and	O
the	O
successful	O
bootstrapping	B-Application
increased	O
confidence	O
in	O
the	O
practicality	O
of	O
the	O
method	O
.	O
</s>
<s>
By	O
late	O
1970	O
,	O
implementations	O
existed	O
for	O
the	O
Honeywell	B-Device
635	I-Device
and	I-Device
Honeywell	I-Device
645	I-Device
,	O
IBM	B-Application
360	I-Application
,	O
PDP-10	B-Device
,	O
TX-2	B-Device
,	O
CDC	O
6400	O
,	O
UNIVAC	O
1108	O
,	O
PDP-9	B-Device
,	O
KDF	B-Device
9	I-Device
and	O
Atlas	B-Device
2	I-Device
.	O
</s>
<s>
In	O
1974	O
a	O
dialect	O
of	O
BCPL	B-Language
was	O
implemented	O
at	O
BBN	O
without	O
using	O
the	O
intermediate	O
O-code	B-Language
.	O
</s>
<s>
The	O
initial	O
implementation	O
was	O
a	O
cross-compiler	B-Application
hosted	O
on	O
BBN	O
's	O
TENEX	B-Operating_System
PDP-10s	B-Device
,	O
and	O
directly	O
targeted	O
the	O
PDP-11s	B-Device
used	O
in	O
BBN	O
's	O
implementation	O
of	O
the	O
second	O
generation	O
IMPs	B-Protocol
used	O
in	O
the	O
ARPANET	O
.	O
</s>
<s>
There	O
was	O
also	O
a	O
version	O
produced	O
for	O
the	O
BBC	B-Device
Micro	I-Device
in	O
the	O
mid-1980s	O
,	O
by	O
Richards	O
Computer	O
Products	O
,	O
a	O
company	O
started	O
by	O
John	O
Richards	O
,	O
the	O
brother	O
of	O
Martin	O
Richards	O
.	O
</s>
<s>
The	B-Device
BBC	I-Device
Domesday	I-Device
Project	I-Device
made	O
use	O
of	O
the	O
language	O
.	O
</s>
<s>
Versions	O
of	O
BCPL	B-Language
for	O
the	O
Amstrad	B-Device
CPC	I-Device
and	O
Amstrad	B-Device
PCW	I-Device
computers	O
were	O
also	O
released	O
in	O
1986	O
by	O
UK	O
software	O
house	O
Arnor	O
Ltd	O
.	O
MacBCPL	O
was	O
released	O
for	O
the	O
Apple	O
Macintosh	O
in	O
1985	O
by	O
Topexpress	O
Ltd	O
,	O
of	O
Kensington	O
,	O
England	O
.	O
</s>
<s>
Both	O
the	O
design	O
and	O
philosophy	O
of	O
BCPL	B-Language
strongly	O
influenced	O
B	B-Language
,	O
which	O
in	O
turn	O
influenced	O
C	B-Language
.	O
Programmers	O
at	O
the	O
time	O
debated	O
whether	O
an	O
eventual	O
successor	O
to	O
C	B-Language
would	O
be	O
called	O
"	O
D	B-Application
"	O
,	O
the	O
next	O
letter	O
in	O
the	O
alphabet	O
,	O
or	O
"	O
P	O
"	O
,	O
the	O
next	O
letter	O
in	O
the	O
parent	O
language	O
name	O
.	O
</s>
<s>
The	O
language	O
most	O
accepted	O
as	O
being	O
C	B-Language
's	O
successor	O
is	O
C++	B-Language
(	O
with	O
++	O
being	O
C	B-Language
's	O
increment	O
operator	O
)	O
,	O
although	O
meanwhile	O
,	O
a	O
D	B-Application
programming	I-Application
language	I-Application
also	O
exists	O
.	O
</s>
<s>
In	O
1979	O
,	O
implementations	O
of	O
BCPL	B-Language
existed	O
for	O
at	O
least	O
25	O
architectures	O
;	O
the	O
language	O
gradually	O
fell	O
out	O
of	O
favour	O
as	O
C	B-Language
became	O
popular	O
on	O
non-Unix	O
systems	O
.	O
</s>
<s>
Martin	O
Richards	O
maintains	O
a	O
modern	O
version	O
of	O
BCPL	B-Language
on	O
his	O
website	O
,	O
last	O
updated	O
in	O
2018	O
.	O
</s>
<s>
He	O
continues	O
to	O
program	O
in	O
it	O
,	O
including	O
for	O
his	O
research	O
on	O
musical	O
automated	O
score	B-Application
following	I-Application
.	O
</s>
<s>
A	O
common	O
informal	O
MIME	B-Application
type	I-Application
for	O
BCPL	B-Language
is	O
.	O
</s>
