[1] : The Free On-line Dictionary of Computing (27 SEP 03)

extended memory
     
         memory above the first megabyte of address space
        in an ibm pc with an 80286 or later processor.
     
        extended memory is not directly available in real mode, only
        through ems, umb, xms, or hma; only applications
        executing in protected mode can use extended memory
        directly.  in this case, the extended memory is provided by a
        supervising protected-mode operating system such as
        microsoft windows.  the processor makes this memory
        available through a system of global descriptor tables and
        local descriptor tables.  the memory is "protected" in the
        sense that memory assigned a local descriptor cannot be
        accessed by another program without causing a hardware trap.
        this prevents programs running in protected mode from
        interfering with each other's memory.
     
        a protected-mode operating system such as windows can also
        run real-mode programs and provide expanded memory to
        them.  dos protected mode interface is microsoft's
        prescribed method for an ms-dos program to access extended
        memory under a multitasking environment.
     
        having extended memory does not necessarily mean that you have
        more than one megabyte of memory since the reserved memory
        area may be partially empty.  in fact, if your 386 or higher
        uses extended memory as expanded memory then that part is not
        in excess of 1mb.
     
        see also conventional memory.
     
        1996-01-10
     
     
see also:
megabyte address space ibm pc 80286 real mode ems 
umb xms hma protected mode protected-mode 
operating system microsoft windows global descriptor tables local descriptor tables trap 
real-mode expanded memory dos protected mode interface microsoft ms-dos 
multitasking conventional memory 

Extended Memory >> E Words
Extended Memory, definition of term: Extended Memory
extended+memory_pag1.html

Extended >> E Words
Extended, definition of term: Extended
extended_pag1.html

Memory >> M Words
Memory, definition of term: Memory
memory_pag1.html

Memory Manageme >> M Words
Memory Manageme, definition of term: Memory Manageme
memory+manageme_pag1.html

Memory Device >> M Words
Memory Device, definition of term: Memory Device
memory+device_pag1.html

Memory Loss >> M Words
Memory Loss, definition of term: Memory Loss
memory+loss_pag1.html

Extended C >> E Words
Extended C, definition of term: Extended C
extended+c_pag1.html

Extended Family >> E Words
Extended Family, definition of term: Extended Family
extended+family_pag1.html

Memory Protecti >> M Words
Memory Protecti, definition of term: Memory Protecti
memory+protecti_pag1.html

Memory Farts >> M Words
Memory Farts, definition of term: Memory Farts
memory+farts_pag1.html

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