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 for shared memory
From The Free On-line Dictionary of Computing (30 December 2018) :

  shared memory
     1. Memory in a parallel computer, usually RAM, which can
     be accessed by more than one processor, usually via a shared
     bus or network.
     It usually takes longer for a processor to access shared
     memory than to access its own private memory because of
     contention for the processor-to-memory connections and because
     of other overheads associated with ensuring synchronised
     access.  Computers using shared memory usually have some kind
     of local cache on each processor to reduce the number of
     accesses to shared memory.  This requires a cache
     consistency protocol to ensure that one processor's cached
     copy of a shared memory location is invalidated when another
     processor writes to that location.
     The alternative to shared memory is message passing where
     all memory is private to some particular processor and
     processors communicate by sending messages down special
     links.  This is usually slower than shared memory but it
     avoids the problems of contention for memory and can be
     implemented more cheaply.
     2. Memory which can be access by more than one process in a
     multitasking operating system with memory protection.
     Some Unix variants, e.g. SunOS provide this kind of shared
     Unix manual pages: shmop(2), shmctl(2), shmget(2).

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