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System Object Model (file format)
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<p>In computing, the System Object Model (SOM) is a proprietary executable <a href="/facts/File_format/qrXbwJaH">file format</a> developed by <a href="/facts/Hewlett-Packard/abuNSYNu">Hewlett-Packard</a> for its <a href="/facts/HP-UX/hIvLDdJF">HP-UX</a> and <a href="/facts/HP_Multi-Programming_Executive/sqWtI9Qh">MPE/ix</a> operating systems. In particular, SOM is the native format used for <a href="/facts/32-bit/TDMVce8s">32-bit</a> application <a href="/facts/Executable/VSst9eLA">executables</a>, <a href="/facts/Object_code/Sht3h4lW">object code</a>, and <a href="/facts/Shared_library/xRzL3P7q">shared libraries</a> running under the <a href="/facts/PA-RISC/gjDs1HEh">PA-RISC</a> family of processors. </p><p>With the introduction of <a href="/facts/64-bit/AgvkQHkM">64-bit</a> processors, Hewlett Packard adopted the <a href="/facts/Executable_and_Linkable_Format/ro2CYqso">Executable and Linkable Format</a> (ELF) format to represent the wider 64-bit program code, while still using SOM for applications running in 32-bit mode. Later, with the introduction of the <a href="/facts/Itanium/0wkjSDpe">Itanium</a> processor family, HP-UX has abandoned the SOM format in favor of ELF for both 32-bit and 64-bit application code. </p><p>In HP-UX the SOM file format is sometimes called the a.out format and is described by <a href="/facts/C_programming_language/e9JD2RRK">C programming language</a> structures in the header file "/usr/include/a.out.h". However the SOM format is technically not the same as the standard <a href="/facts/A.out/Q6Um95j8">a.out</a> format used by many other Unix operating systems. </p>