<s>
ALGOL	B-Language
W	I-Language
is	O
a	O
programming	O
language	O
.	O
</s>
<s>
It	O
is	O
based	O
on	O
a	O
proposal	O
for	O
ALGOL	B-Language
X	I-Language
by	O
Niklaus	O
Wirth	O
and	O
Tony	O
Hoare	O
as	O
a	O
successor	O
to	O
ALGOL	B-Language
60	I-Language
.	O
</s>
<s>
ALGOL	B-Language
W	I-Language
is	O
a	O
relatively	O
simple	O
upgrade	O
of	O
the	O
original	O
ALGOL	B-Language
60	I-Language
,	O
adding	O
string	O
,	O
bitstring	O
,	O
complex	O
number	O
and	O
reference	O
to	O
record	O
data	O
types	O
and	O
call-by-result	O
passing	O
of	O
parameters	O
,	O
introducing	O
the	O
while	O
statement	O
,	O
replacing	O
switch	O
with	O
the	O
case	O
statement	O
,	O
and	O
generally	O
tightening	O
up	O
the	O
language	O
.	O
</s>
<s>
Wirth	O
's	O
entry	O
was	O
considered	O
too	O
little	O
of	O
an	O
advance	O
over	O
ALGOL	B-Language
60	I-Language
,	O
and	O
the	O
more	O
complex	O
entry	O
from	O
Adriaan	O
van	O
Wijngaarden	O
was	O
selected	O
in	O
a	O
highly	O
contentious	O
meeting	O
.	O
</s>
<s>
Wirth	O
later	O
published	O
his	O
version	O
as	O
A	O
contribution	O
to	O
the	O
development	O
of	O
ALGOL	B-Language
.	O
</s>
<s>
With	O
a	O
number	O
of	O
small	O
additions	O
,	O
this	O
eventually	O
became	O
ALGOL	B-Language
W	I-Language
.	O
</s>
<s>
Wirth	O
supervised	O
a	O
high	O
quality	O
implementation	O
for	O
the	O
IBM	B-Application
System/360	I-Application
at	O
Stanford	O
University	O
that	O
was	O
widely	O
distributed	O
.	O
</s>
<s>
The	O
implementation	O
was	O
written	O
in	O
PL360	B-Language
,	O
an	O
ALGOL-like	B-Language
assembly	B-Language
language	I-Language
designed	O
by	O
Wirth	O
.	O
</s>
<s>
ALGOL	B-Language
W	I-Language
served	O
as	O
the	O
basis	O
for	O
the	O
Pascal	B-Application
language	I-Application
,	O
and	O
the	O
syntax	O
of	O
ALGOL	B-Language
W	I-Language
will	O
be	O
immediately	O
familiar	O
to	O
anyone	O
with	O
Pascal	B-Application
experience	O
.	O
</s>
<s>
The	O
key	O
differences	O
are	O
improvements	O
to	O
record	O
handling	O
in	O
Pascal	B-Application
,	O
and	O
,	O
oddly	O
,	O
the	O
loss	O
of	O
ALGOL	B-Language
W	I-Language
's	O
ability	O
to	O
define	O
the	O
length	O
of	O
an	O
array	O
at	O
runtime	O
,	O
which	O
is	O
one	O
of	O
Pascal	B-Application
's	O
most-complained-about	O
features	O
.	O
</s>
<s>
ALGOL	B-Language
W	I-Language
's	O
syntax	O
is	O
built	O
on	O
a	O
subset	O
of	O
the	O
EBCDIC	B-Language
character	B-General_Concept
encoding	I-General_Concept
set	O
.	O
</s>
<s>
In	O
ALGOL	B-Language
60	I-Language
,	O
reserved	O
words	O
are	O
distinct	O
lexical	B-Language
items	O
,	O
but	O
in	O
ALGOL	B-Language
W	I-Language
they	O
are	O
only	O
sequences	O
of	O
characters	O
,	O
and	O
do	O
not	O
need	O
to	O
be	O
stropped	B-Application
.	O
</s>
<s>
In	O
these	O
ways	O
ALGOL	B-Language
W	I-Language
's	O
syntax	O
resembles	O
that	O
of	O
Pascal	B-Application
and	O
later	O
languages	O
.	O
</s>
<s>
The	O
ALGOL	B-Language
W	I-Language
Language	O
Description	O
defines	O
ALGOL	B-Language
W	I-Language
in	O
an	O
affix	O
grammar	O
that	O
resembles	O
Backus	O
–	O
Naur	O
form	O
(	O
BNF	O
)	O
.	O
</s>
<s>
This	O
formal	O
grammar	O
was	O
a	O
precursor	O
of	O
the	O
Van	B-Application
Wijngaarden	I-Application
grammar	I-Application
.	O
</s>
<s>
Much	O
of	O
ALGOL	B-Language
W	I-Language
's	O
semantics	O
is	O
defined	O
grammatically	O
:	O
</s>
<s>
Identifiers	O
are	O
distinguished	O
by	O
their	O
definition	O
within	O
the	O
current	O
scope	B-Language
.	O
</s>
<s>
For	O
example	O
,	O
a	O
⟨procedure	O
identifier⟩	O
is	O
an	O
identifier	O
that	O
has	O
been	O
defined	O
by	O
a	O
procedure	O
declaration	O
,	O
a	O
⟨label	O
identifier⟩	O
is	O
an	O
identifier	O
that	O
is	O
being	O
used	O
as	O
a	O
goto	B-Application
label	O
.	O
</s>
<s>
For	O
example	O
⟨τ	O
function	O
identifier⟩	O
is	O
the	O
syntactic	O
entity	O
for	O
a	O
function	O
that	O
returns	O
a	O
value	O
of	O
type	O
τ	O
,	O
if	O
an	O
identifier	O
has	O
been	O
declared	O
as	O
an	O
integer	O
function	O
in	O
the	O
current	O
scope	B-Language
then	O
that	O
is	O
expanded	O
to	O
⟨integer	O
function	O
identifier⟩	O
.	O
</s>
<s>
This	O
demonstrates	O
ALGOL	B-Language
W	I-Language
's	O
record	O
type	O
facility	O
.	O
</s>
