Abstract: An operating system that provides protection domain support is arranged so to be compatible with “well behaved” threads, i.e., threads that obtain all their memory allocations from the operating system, that were written without regard for protection domains. This may be achieved by associating each protection domain with one or more pages of memory, so-called “primary memory pages”, for which the protection domain has read and write access permission. Requests by such a “protection-domain-unaware” thread to the operating system for a memory allocation, e.g., for memory in which to create a data structure, are automatically fulfilled by the operating system from the memory available in the primary memory pages of the protection domain of the requesting thread. The operating system informs the thread of the location of the created data structure, e.g., by passing to the thread a pointer to the data structure.

Abstract: Protection among threads executing in the same address space of a computer system is provided without using virtual memory techniques. This is achieved by grouping the threads into protection domains, each of the threads in a protection domain having the same rights to access memory as the other threads in that protection domain, so that each thread in a protection domain can access all the information available to the others. At least one protection domain, referred to herein as the "system" domain, which typically is the protection domain of the operating system and has unrestricted access to the entire memory, is predefined prior to execution of any threads. Prior to execution, the single address space is divided into non-overlapping pages. Each page has at least one access permission set for it. Only threads that belong to a protection domain having permission to access a page may do so.

Abstract: The availability and location of a multiplicity of multiplexed digital information streams, transmitted over one of a multiplicity of channels, are identified by transmitting a Global Channel Map which includes a version number, one Band Map Table, one Channel Map Table, and at least as many Service Map tables as there are combinations of identical service types transmitted over different channels. The Band Map Table preferably contains an entry for each frequency band used by the system, and a Band Map Table version number. A Global Channel Map Updates file is transmitted in each band. Where a plurality of channels contain similar-types of services, one Service Map Table contains relative service identification numbers for those service types. The entries for relevant channels in the Channel Map Table contain base service identification data which are combined with the relative service identification number to locate a particular service transmitted over that channel.

Abstract: The contents of a digital data file, interspersed as packets of data in a bit stream containing entertainment signals and/or other data files, are quickly identified without a high system overhead for identification of each packet. The data file is divided into packets, and sequential groups of packets making up the file are identified as segments. The first packet of each segment has a prefix containing a service identification number, a block number, a segment number, and possibly segment length information, followed by data contents. The following packets of the segment have only the service identification number and block number, followed by the data contents. Where the file data are transmitted repeatedly, often without change in many segments, receiver processing time or power can be greatly reduced by including a version number or toggle bit in the segment prefix, so that a receiver can ignore the unchanged data.