Providing capability architectures with memory tagging features

The problem of tagging memory architectures is examined and a solution portions based on in capability tagged memory segments is presented. Each segment of this kind implements an object of a speci fic abstract type: besides the segment length. the segment includes the specification of the type of the object, together with its internal representation. Object types are classified into machine and predefined types. A machine type is a type whose operations are implemented by machine instructions, whereas the operations of a predefined type are implemented by software routines. So only the class of machine types is wired in the machine design. The resulting architecture is characterized by interesting performance indexes. In particular, it allows both considerable memory space savings (with respect to traditional tagged archi tectures), as well as considerable processing time savings (compared to classical capabili ty environments). I~oreover, the facilities provided for obj ect type redefinition make it possible to orient a given machine towards a specific application environment. Indeed, several environments may coexist on the same machine, and the efficiency of the mechanisms for environment switching is such that a switch may even be performed corresponding to each process scheduling operation.