IMProved Mercury autocode(IMP) A version of {Autocode} used to program the {Edinburgh Multi Access System} (EMAS), one of the first {operating systems} written in a {high-level language}, apparently predating {Unix}. Luis Damas' {Prolog} {interpreter} in IMP for EMAS led to {C-Prolog}. [Papers in J. {British Computer Society}]. (1996-04-07)