IBM maintained full compatibility with the past, so that programs developed in the sixties can still run under z/VSE (if developed for DOS/360) or z/OS (if developed for MFT or MVT) with no change.
IBM palaiko pilną suderinamumą su praeitimi, taigi programos sukurtos septintame dešimtmetyje gali vis dar veikti po z/VSEŪ(jei jie sukurti DOS/360) ir z/OS(jei jie sukurti OS/MFT ir OS/MVT) be pakeitimų.