z/OS 3.1 is certified for UNIX 95, if this list is correct: https://www.opengroup.org/openbrand/register/index2.html https://www.opengroup.org/openbrand/regist

z/OS 3.1 is certified for UNIX 95, if this list is correct: https://www.opengroup.org/openbrand/register/index2.html https://www.opengroup.org/openbrand/register/index2.html That would include a C compiler, but yours is probably on tape somewhere. Linux has been on this list, courtesy of two Chinese companies.