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* Description: Knowledge of process mode means by system call
* Compatiablity: RDBMS 11g, 12c
* Date: 02:45 PM EST, 04/30/2017
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<1> System Call:
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     |__ The kernel is a program that constitutes the core of an operating system, and it has complete control over all resources on the system and everything that occurs on it. 
         When a user mode process (i.e., a process currently in user mode) wants to utilize a service provided by the kernel (i.e., access system resources other than the limited 
         memory space that is allocated to the user program), it must switch temporarily into kernel mode, also called system mode, by means of a system call.
		 
         Simply specking, process in user mode wants to access hardware, so it will issue a "system call" to switch to kernel mode temporarily.
		 
		 
		 
<2> Reference:
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     |__ http://www.linfo.org/system_call.html