System Object Model (file format)
In computing, the System Object Model (SOM) is a proprietary file format used by the HP-UX operating system for executables, object code, and shared libraries. In particular, SOM is the native format used for 32-bit application object code running under the PA-RISC family of processors.
With the introduction of 64-bit processors, Hewlett Packard adopted the Executable and Linkable Format (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 Itanium processor family, HP-UX has abandoned the SOM format in favor of ELF for both 32-bit and 64-bit application code.