### D.7 Other Sources

Apart from C++ and Octave language (m-files), Octave’s sources include files written in C, Fortran, M4, Perl, Unix shell, AWK, Texinfo, and TeX. There are not many rules to follow when using these other languages; some of them are summarized below. In any case, the golden rule is: if you modify a source file, try to follow any conventions you can detect in the file or other similar files.

For C you should obviously follow all C++ rules that can apply.

If you modify a Fortran file, you should stay within Fortran 77 with common extensions like `END DO`. Currently, we want all sources to be compilable with the f2c and g77 compilers, without special flags if possible. This usually means that non-legacy compilers also accept the sources.

The M4 macro language is mainly used for Autoconf configuration files. You should follow normal M4 rules when contributing to these files. Some M4 files come from external source, namely the Autoconf archive http://autoconf-archive.cryp.to.

If you give a code example in the documentation written in Texinfo with the `@example` environment, you should be aware that the text within such an environment will not be wrapped. It is recommended that you keep the lines short enough to fit on pages in the generated pdf or ps documents. Here is a ruler (in an `@example` environment) for finding the appropriate line width:

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