<s>
S3	B-Language
is	O
a	O
structured	B-Language
,	O
imperative	B-Application
high-level	B-Language
computer	B-General_Concept
programming	I-General_Concept
language	O
.	O
</s>
<s>
It	O
was	O
developed	O
by	O
the	O
UK	O
company	O
International	O
Computers	O
Limited	O
(	O
ICL	O
)	O
for	O
its	O
2900	B-Device
Series	I-Device
mainframes	O
.	O
</s>
<s>
It	O
is	O
a	O
system	B-Language
programming	I-Language
language	I-Language
with	O
syntax	O
influenced	O
by	O
ALGOL	B-Language
68	I-Language
but	O
with	O
data	O
types	O
and	O
operators	O
aligned	O
to	O
those	O
offered	O
by	O
the	O
2900	B-Device
Series	I-Device
.	O
</s>
<s>
It	O
was	O
the	O
implementation	O
language	O
of	O
the	O
operating	B-General_Concept
system	I-General_Concept
VME	B-General_Concept
.	O
</s>
<s>
A	O
rare	O
example	O
of	O
an	O
S3	B-Language
program	O
available	O
in	O
the	O
public	O
domain	O
is	O
the	O
implementation	O
of	O
Kermit	B-Protocol
developed	O
at	O
the	O
South-West	O
Universities	O
Regional	O
Computer	B-General_Concept
Centre	O
,	O
and	O
archived	O
in	O
the	O
Columbia	O
University	O
archive	O
of	O
Kermit	B-Protocol
implementations	O
.	O
</s>
<s>
Mode	O
is	O
the	O
Algol	B-Language
68	I-Language
term	O
for	O
a	O
type	O
.	O
</s>
<s>
The	O
final	O
type	O
declared	O
here	O
is	O
a	O
STRUCT	B-Language
,	O
specifically	O
a	O
tuple	O
containing	O
two	O
integers	O
.	O
</s>
<s>
Procedure	O
calls	O
prefixed	O
CTM	O
are	O
calls	O
to	O
the	O
"	O
Compiler	O
Target	O
Machine	O
"	O
,	O
an	O
API	B-General_Concept
offered	O
by	O
the	O
VME	B-General_Concept
operating	B-General_Concept
system	I-General_Concept
.	O
</s>
<s>
"	O
JSV	O
"	O
means	O
"	O
job	O
space	O
variable	O
"	O
,	O
VME	B-General_Concept
's	O
term	O
for	O
an	O
environment	O
variable	O
,	O
and	O
the	O
call	O
on	O
CTM_JS_READ	O
reads	O
the	O
value	O
of	O
the	O
variable	O
.	O
</s>
<s>
This	O
is	O
called	O
indirectly	O
via	O
the	O
operating	B-General_Concept
system	I-General_Concept
CTM_JS_CALL	O
,	O
similar	O
to	O
an	O
exec( )	O
call	O
on	O
Unix	O
systems	O
;	O
this	O
ensures	O
clean	O
failure	O
handling	O
and	O
tidying	O
up	O
of	O
any	O
resources	O
in	O
the	O
event	O
of	O
a	O
fatal	O
error	O
.	O
</s>
