TYPE MANAGEMENT AND CONTROL IN AN OBJECT ORIENTED MEMORY PROTECTION MECHANISM

Access descriptors (24) include an object index (34) for selecting an object in the address space, and a rights field (35) specifying the permissible operations on a bi-paged object (38) selected by the access descriptor. An object table (42) has stored therein object descriptors for use in forming physical addresses to the page table directory object (60) which has page table descriptors stored therein for accessing page tables. A page table (44) has stored therein page table entries for use in forming physical addresses to the paged object (38). Logic compares the page rights field (81) of the page table entry with the rights field (62) of the page table descriptor in the page table directory entry and asserts a fault if the access permitted by the page rights field (50) is inconsistent with the rights field of the access descriptor in the page table directory entry. A mechanism provides for the implicit deallocation of certain objects and to prevent dangling references if access descriptors which point to objects with shorter lifetimes are stored in objects with longer lifetimes. Special Instructions provide a mechanism for the amplification or restriction of the rights of access descriptors.