[1] : WordNet (r) 2.0

system call
     n : an instruction that interrupts the program being executed
         and passes control to the supervisor syn: supervisor
         call instruction
see also:
supervisor call instruction 

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

system call
     
         the mechanism used by an
        application program to request service from the operating
        system.  system calls often use a special machine code
        instruction which causes the processor to change mode e.g. to
        "supervisor mode" or "protected mode".  this allows the os
        to perform restricted actions such as accessing hardware
        devices or the memory management unit.
     
        1995-03-01
     
     
see also:
application program operating system machine code protected mode memory management unit 

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