<s>
HAL/S	B-Language
(	O
High-order	O
Assembly	O
Language/Shuttle	O
)	O
is	O
a	O
real-time	B-General_Concept
aerospace	O
programming	O
language	O
compiler	O
and	O
cross-compiler	O
for	O
avionics	O
applications	O
used	O
by	O
NASA	O
and	O
associated	O
agencies	O
(	O
JPL	O
,	O
etc	O
.	O
)	O
.	O
</s>
<s>
It	O
has	O
been	O
used	O
in	O
many	O
U.S.	O
space	O
projects	O
since	O
1973	O
and	O
its	O
most	O
significant	O
use	O
was	O
in	O
the	O
Space	O
Shuttle	O
program	O
(	O
approximately	O
85%	O
of	O
the	O
Shuttle	O
software	O
was	O
coded	O
in	O
HAL/S	B-Language
)	O
.	O
</s>
<s>
HAL/S	B-Language
is	O
written	O
in	O
XPL	B-Language
,	O
a	O
dialect	O
of	O
PL/I	B-Language
.	O
</s>
<s>
Although	O
HAL/S	B-Language
is	O
designed	O
primarily	O
for	O
programming	O
on-board	O
computers	O
,	O
it	O
is	O
general	O
enough	O
to	O
meet	O
nearly	O
all	O
the	O
needs	O
in	O
the	O
production	O
,	O
verification	O
,	O
and	O
support	O
of	O
aerospace	O
and	O
other	O
real-time	B-General_Concept
applications	I-General_Concept
.	O
</s>
<s>
According	O
to	O
documentation	O
from	O
2005	O
,	O
it	O
was	O
being	O
maintained	O
by	O
the	O
HAL/S	B-Language
project	O
of	O
United	O
Space	O
Alliance	O
.	O
</s>
<s>
The	O
three	O
key	O
principles	O
in	O
designing	O
the	O
language	O
were	O
reliability	O
,	O
efficiency	O
,	O
and	O
machine-independence	B-Architecture
.	O
</s>
<s>
The	O
language	O
is	O
designed	O
to	O
allow	O
aerospace-related	O
tasks	O
(	O
such	O
as	O
vector/matrix	O
arithmetic	O
)	O
to	O
be	O
accomplished	O
in	O
a	O
way	O
that	O
is	O
easily	O
understandable	O
by	O
people	O
who	O
have	O
spaceflight	O
knowledge	O
,	O
but	O
may	O
not	O
necessarily	O
have	O
proficiency	O
with	O
computer	O
programming	O
.	O
</s>
<s>
HAL/S	B-Language
was	O
designed	O
not	O
to	O
include	O
some	O
constructs	O
that	O
were	O
thought	O
to	O
be	O
the	O
cause	O
of	O
errors	O
.	O
</s>
<s>
The	O
language	O
provides	O
special	O
support	O
for	O
real-time	B-General_Concept
execution	O
environments	O
.	O
</s>
<s>
Some	O
features	O
,	O
such	O
as	O
"	O
GOTO	B-Application
"	O
were	O
provided	O
chiefly	O
to	O
ease	O
mechanical	O
translations	O
from	O
other	O
languages	O
.	O
</s>
<s>
On	O
the	O
Preface	O
page	O
of	O
the	O
HAL/S	B-Language
Language	O
Specification	O
,	O
it	O
says	O
,	O
</s>
<s>
A	O
proposal	O
for	O
a	O
NASA	O
standard	O
ground-based	O
version	O
of	O
HAL	O
named	O
HAL/G	O
for	O
"	O
ground	O
"	O
was	O
proposed	O
,	O
but	O
the	O
coming	O
emergence	O
of	O
the	O
soon	O
to	O
be	O
named	O
Ada	B-Language
programming	I-Language
language	I-Language
contributed	O
to	O
Intermetrics	O
 '	O
lack	O
of	O
interest	O
in	O
continuing	O
this	O
work	O
.	O
</s>
<s>
Host	O
compiler	O
systems	O
have	O
been	O
implemented	O
on	O
an	O
IBM	B-Application
360/370	I-Application
,	O
Data	B-Device
General	I-Device
Eclipse	I-Device
,	O
and	O
the	O
Modcomp	O
IV/Classic	O
computers	O
.	O
</s>
<s>
Target	O
computer	O
systems	O
have	O
included	O
IBM	B-Application
360/370	I-Application
,	O
IBM	B-Device
AP-101	I-Device
(	O
space	O
shuttle	O
avionics	O
computer	O
)	O
,	O
Sperry	O
1819A/1819B	O
,	O
Data	B-Device
General	I-Device
Nova	I-Device
and	O
Eclipse	O
,	O
CII	O
Mitra	O
125	O
,	O
Modcomp	O
II	O
and	O
IV	O
,	O
NASA	O
Std	O
.	O
</s>
<s>
Spacecraft	O
Computer-l	O
and	O
Computer-2	O
,	O
ITEK	O
ATAC	O
16M	O
(	O
Galileo	O
Project	O
)	O
,	O
and	O
since	O
1978	O
the	O
RCA	B-General_Concept
CDP1802	I-General_Concept
COSMAC	I-General_Concept
microprocessor	O
(	O
Galileo	O
Project	O
and	O
others	O
)	O
.	O
</s>
<s>
HAL/S	B-Language
is	O
a	O
mostly	O
free-form	B-Language
language	I-Language
:	O
statements	O
may	O
begin	O
anywhere	O
on	O
a	O
line	O
and	O
may	O
spill	O
over	O
the	O
next	O
lines	O
,	O
and	O
multiple	O
statements	O
may	O
be	O
fitted	O
onto	O
the	O
same	O
line	O
if	O
required	O
.	O
</s>
<s>
One	O
particularly	O
interesting	O
feature	O
of	O
HAL/S	B-Language
is	O
that	O
it	O
supports	O
,	O
in	O
addition	O
to	O
a	O
normal	O
single	O
line	O
text	O
format	O
,	O
an	O
optional	O
three-line	O
input	O
format	O
in	O
which	O
three	O
source	O
code	O
lines	O
are	O
used	O
for	O
each	O
statement	O
.	O
</s>
<s>
The	O
multi-line	O
format	O
was	O
designed	O
to	O
permit	O
writing	O
of	O
HAL/S	B-Language
code	O
that	O
is	O
similar	O
to	O
mathematical	O
notation	O
.	O
</s>
<s>
Exponentiation	O
is	O
denoted	O
by	O
two	O
asterisks	B-Language
,	O
as	O
in	O
PL/I	B-Language
and	O
Fortran	B-Application
.	O
</s>
<s>
The	O
following	O
is	O
a	O
simple	O
HAL/S	B-Language
program	O
.	O
</s>
<s>
HAL/S	B-Language
has	O
native	O
support	O
for	O
integers	O
,	O
floating	B-Algorithm
point	I-Algorithm
scalars	O
,	O
vector	O
,	O
matrices	B-Architecture
,	O
booleans	O
and	O
strings	O
of	O
8-bit	O
characters	O
,	O
limited	O
to	O
a	O
maximum	O
length	O
of	O
255	O
.	O
</s>
