library function vs system calls
- From: sophia.agnes@xxxxxxxxx
- Date: Fri, 30 Nov 2007 04:58:45 -0800 (PST)
Dear all,
I was going through peter van der linden's book expert C programming
there i found the following:-
Library call
------------
*call to a routine in a library
*linked with user program
*executes in user address space
*counts as a part of user time
*has the lower head overhead of procedure call.
system call
-----------
* call to the kernel for a service
* is an entry point to the OS
* executes in the kernel address space
* has high overhead switch to kernel and back
then the author says that , remember many routines in the C library do
their work by making system calls and system() call is
actually a library call.
then how valid is the above explanation on the differences between
library call versus system call ?
why system() call is treated as a library call ?
.
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