From the other side of the Iron Courtain
My first job in 1984 was a mainframe operator. We had S/360 and ICL1904 Polish made clones (R-32 and ODRA-1305). They are perfectly compatible and we were working with original Operating Systems, compilers and tools witch run without any modifications or translations.
On S/360 there were DOS/360, OS/360 MVT, HASP, Fortran and PL/1 compilers like Fortran/F, Fortran/H, PL/1 F and PL/1 Optimizing Compiler, on ICL1904 Fortran and Cobol.