<s>
The	O
man	B-Language
or	I-Language
boy	I-Language
test	I-Language
was	O
proposed	O
by	O
computer	O
scientist	O
Donald	O
Knuth	O
as	O
a	O
means	O
of	O
evaluating	O
implementations	O
of	O
the	O
ALGOL	B-Language
60	I-Language
programming	I-Language
language	I-Language
.	O
</s>
<s>
The	O
aim	O
of	O
the	O
test	O
was	O
to	O
distinguish	O
compilers	B-Language
that	O
correctly	O
implemented	O
"	O
recursion	O
and	O
non-local	O
references	O
"	O
from	O
those	O
that	O
did	O
not	O
.	O
</s>
<s>
In	O
ALGOL	B-Language
60	I-Language
:	O
</s>
<s>
Even	O
modern	O
machines	O
quickly	O
run	O
out	O
of	O
stack	B-General_Concept
space	O
for	O
larger	O
values	O
of	O
k	O
,	O
which	O
are	O
tabulated	O
below	O
(	O
)	O
.	O
</s>
<s>
There	O
are	O
three	O
Algol	O
features	O
used	O
in	O
this	O
program	O
that	O
can	O
be	O
difficult	O
to	O
implement	O
properly	O
in	O
a	O
compiler	B-Language
:	O
</s>
<s>
This	O
is	O
straightforward	O
in	O
the	O
Algol	O
descendant	O
Pascal	B-Application
,	O
but	O
not	O
possible	O
in	O
the	O
other	O
major	O
Algol	O
descendant	O
C	B-Language
(	O
without	O
manually	O
simulating	O
the	O
mechanism	O
by	O
using	O
C	B-Language
's	O
address-of	O
operator	O
,	O
passing	O
around	O
pointers	O
to	O
local	O
variables	O
between	O
the	O
functions	O
)	O
.	O
</s>
<s>
Function	B-Application
references	I-Application
:	O
The	O
B	O
in	O
the	O
recursive	O
call	O
A(k, B, x1, x2, x3, x4 )	O
is	O
not	O
a	O
call	O
to	O
B	O
,	O
but	O
a	O
reference	O
to	O
B	O
,	O
which	O
will	O
be	O
called	O
only	O
when	O
k	O
is	O
greater	O
than	O
zero	O
.	O
</s>
<s>
This	O
is	O
straightforward	O
in	O
standard	O
Pascal	B-Application
(	O
ISO	O
7185	O
)	O
,	O
and	O
also	O
in	O
C	B-Language
.	O
Some	O
variants	O
of	O
Pascal	B-Application
(	O
e.g.	O
</s>
<s>
older	O
versions	O
of	O
Turbo	B-Application
Pascal	I-Application
)	O
do	O
not	O
support	O
procedure	O
references	O
,	O
but	O
when	O
the	O
set	O
of	O
functions	O
that	O
may	O
be	O
referenced	O
is	O
known	O
beforehand	O
(	O
in	O
this	O
program	O
it	O
is	O
only	O
B	O
)	O
,	O
this	O
can	O
be	O
worked	O
around	O
.	O
</s>
<s>
A	O
"	O
boy	O
"	O
compiler	B-Language
might	O
,	O
for	O
example	O
,	O
instead	O
compile	B-Language
the	O
program	O
so	O
that	O
B	O
always	O
accesses	O
the	O
topmost	O
A	O
call	O
frame	O
.	O
</s>
