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System Object Model (file format)
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<h2 id="overview-of-the-som-file-format">Overview of the SOM file format</h2> <p>A SOM file consists of a fixed-size header record followed by a number of sections, some of which are optional. The header always appears at the beginning of the file and contains the byte offsets and sizes of where the other sections are located within the file. Except for the header the other sections may appear anywhere in the file, although the typical layout of a SOM file (assuming all sections are present) is as follows: </p> <ul><li>Header Record</li> <li>Auxiliary Header Record</li> <li>Space Records</li> <li>Subspace Records</li> <li>Loader Fixup Records</li> <li>Space Strings</li> <li>Symbol Records</li> <li>Fixup Records</li> <li>Symbol Strings</li> <li>Compiler Records</li> <li>Data for Loadable Spaces</li> <li>Data for Unloadable Spaces</li></ul> <p>Numeric fields are stored in <a href="/facts/Endianness/wbrQnyu3">big endian</a> byte order, the native byte order of the PA-RISC, with most being 32-bit wide. Character strings are generally encoded in 8-bit <a href="/facts/ASCII/vGUI33Qu">ASCII</a> and both prefixed with a 32-bit length indicator as well as being <a href="/facts/Null-terminated_string/Vt75UxVG">null-terminated</a>, like <a href="/facts/C_string_handling/V0AYCYR2">C strings</a>. Most records are word-aligned (start at even-byte offsets) with padding introduced as necessary. </p> <h2 id="see-also">See also</h2> <ul><li><a href="/facts/Comparison_of_executable_file_formats/uobPt1yC">Comparison of executable file formats</a></li></ul> <h2 id="external-links">External links</h2> <ul><li><a href="http://docs.hp.com/en/B2355-90696/a.out.4.html"><i>HP-UX a.out(4) manual page</i></a>, Hewlett-Packard</li> <li><a href="https://web.archive.org/web/20050502101134/http://devresource.hp.com/drc/STK/docs/archive/rad_11_0_32.pdf"><i>The 32-bit PA-RISC Run-time Architecture Document, HP-UX 11.0 Version 1.0</i></a>, Hewlett-Packard, 1997</li> <li><a href="https://web.archive.org/web/20050502102352/http://devresource.hp.com/drc/STK/docs/archive/rad_10_20.pdf"><i>The 32-bit PA-RISC Run-time Architecture Document, HP-UX 10.20 version 3.0</i></a>, Hewlett-Packard, 1997. Also available at <a href="http://ftp.parisc-linux.org/docs/arch/pa-runtime-32-SOM.pdf">parisc-linux.org</a></li> <li><a href="https://web.archive.org/web/20070722155126/http://devrsrc1.external.hp.com/STK/gloss.html#SOM"><i>HP-UX Software Transition Kit Glossary</i></a>, Hewlett-Packard (online)</li> <li><a href="http://www.parisc-linux.org/documentation/index.html#pa11">PA-RISC 1.1 Architecture Specifications</a></li></ul>