NS if this is true or not, but it's funny! The system programmer group writing TOPS-10 use to love fancy TECO programs and had a weekly contest for them. One guru working on FORTRAN compilers would read them carefully but never enter one. They thought he was just concentrating on compilers. Then one week he submitted a macro that did FORTRAN compilation, complete with optimization. The TECO program took days to run, but it worked. Apparently he had written a PDP-10 instruction set eumlator in TECO and fed the compiler into it!