The process hierarchy is a labeled directed graph

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Unformatted text preview: via a trapping instruction called INT Ò, where Ò can be the index of any of the 256 entries in the exception table. Historically, systems calls are provided through exception 128 (0x80). Aside: A note on terminology. The terminology for the various classes of exceptions varies from system to system. Processor macro-architecture specifications often distinguish between asynchronous “interrupts” and synchronous “exceptions”, yet provide no umbrella term to refer to these very similar concepts. To avoid having to constantly refer to “exceptions and interrupts” and “exceptions or interrupts”, we use the word “exception” as the general term and distinguish between asynchronous exceptions (interrupts) and synchronous exceptions (traps, faults, and aborts) only when it is appropriate. As we have noted, the basic ideas are the same for every system, but you should be aware that some manufacturers’ manuals use the word “exception” to refer only to those changes in...
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