<s>
In	O
computing	O
,	O
the	O
System	B-Application
Object	I-Application
Model	I-Application
(	O
SOM	O
)	O
is	O
a	O
proprietary	O
executable	B-Application
file	I-Application
format	I-Application
developed	O
by	O
Hewlett-Packard	O
for	O
its	O
HP-UX	B-Application
and	O
MPE/ix	B-Operating_System
operating	O
systems	O
.	O
</s>
<s>
In	O
particular	O
,	O
SOM	O
is	O
the	O
native	O
format	O
used	O
for	O
32-bit	O
application	O
executables	B-Application
,	O
object	B-Language
code	I-Language
,	O
and	O
shared	O
libraries	O
running	O
under	O
the	O
PA-RISC	B-Device
family	I-Device
of	O
processors	O
.	O
</s>
<s>
With	O
the	O
introduction	O
of	O
64-bit	B-Device
processors	I-Device
,	O
Hewlett	O
Packard	O
adopted	O
the	O
Executable	B-Application
and	O
Linkable	O
Format	O
(	O
ELF	O
)	O
format	O
to	O
represent	O
the	O
wider	O
64-bit	B-Device
program	O
code	O
,	O
while	O
still	O
using	O
SOM	O
for	O
applications	O
running	O
in	O
32-bit	O
mode	O
.	O
</s>
<s>
Later	O
,	O
with	O
the	O
introduction	O
of	O
the	O
Itanium	B-General_Concept
processor	I-General_Concept
family	I-General_Concept
,	O
HP-UX	B-Application
has	O
abandoned	O
the	O
SOM	O
format	O
in	O
favor	O
of	O
ELF	O
for	O
both	O
32-bit	O
and	O
64-bit	B-Device
application	O
code	O
.	O
</s>
<s>
In	O
HP-UX	B-Application
the	O
SOM	O
file	O
format	O
is	O
sometimes	O
called	O
the	O
a.out	O
format	O
and	O
is	O
described	O
by	O
C	B-Language
programming	I-Language
language	I-Language
structures	O
in	O
the	O
header	O
file	O
"	O
/usr/include/a.out.h	O
"	O
.	O
</s>
<s>
Numeric	O
fields	O
are	O
stored	O
in	O
big	O
endian	O
byte	O
order	O
,	O
the	O
native	O
byte	O
order	O
of	O
the	O
PA-RISC	B-Device
,	O
with	O
most	O
being	O
32-bit	O
wide	O
.	O
</s>
<s>
Character	O
strings	O
are	O
generally	O
encoded	O
in	O
8-bit	O
ASCII	B-Protocol
and	O
both	O
prefixed	O
with	O
a	O
32-bit	O
length	O
indicator	O
as	O
well	O
as	O
being	O
null-terminated	B-Data_Structure
,	O
like	O
C	B-Language
strings	I-Language
.	O
</s>
