Techniques used in a virtual memory system for mapping the page table for a process onto the process's virtual address space. The mappings make it possible for the virtual memory manager to compute addresses for the page table in the same fashion, regardless of the page table configuration required by the hardware. The techniques include linear mapping of a process's page table entries onto a portion of its virtual address space and self-recursive mapping of page trees onto the virtual address space. The techniques make porting an operating system to various kinds of hardware easier, reduce the size of the portion of virtual memory which must be reserved for the page table, and speed up references to the page table by the virtual memory manager. Further refinements permit creation of nodes of the mapped page table on demand and access of a second process's page table from a first process's page table.
An apparatus (20) for inflating an air bag comprises a housing (22) which includes a wall (84) having an inner surface defining a chamber (108). Ignitable gas generating material (122) is located in the chamber (108) and, upon ignition, provides combustion products including gas which flows from the housing to inflate the air bag and hot particles. A tubular filter (140) removes hot particles from the gas flow. The tubular filter (140) comprises a strip of material having a plurality of spaced openings (146) through which the gas can flow and two end portions (160, 162) which overlap. The strip of material also has a plurality of projections (142, 144) engaging the inner surface of the housing (22). The projections (142, 144) are located on the strip of material at spaced locations around the tubular filter (140). The projections (142, 144) space at least a portion (148, 150 or 152) of the tubular filter (140) away from the inner surface of the housing (22).