Source : Free On-Line Dictionary of Computing

memory protection
     
         A system to prevent one {process}
        corrupting the memory (or other resources) of any other,
        including the {operating system}.  Memory protection usually
        relies on a combination of hardware (a {memory management
        unit}) and software to allocate memory to processes and handle
        {exceptions}.
     
        The effectiveness of memory protection varies from one
        operating system to another.  In most versions of {Unix} it is
        almost impossible to corrupt another process' memory, except
        in some archaic implementations and {Lunix} (not {Linux}!).
        Under {Microsoft Windows} (version?  hardware?) any {16 bit
        application}(?) can circumvent the memory protection, often
        leading to one or more {GPF}s.  Currently (April 1996) neither
        {Microsoft Windows} 3.1, {Windows 95}, nor {Mac OS} offer
        memory protection.  {Windows NT} has it, and Mac OS System 8
        will offer a form of memory protection.
     
        [MS DOS {EMM386} relevant?]
     
        (1996-09-10)