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system calls in operating system

kuntilanak
kuntilanak asked
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Last Modified: 2013-12-17
what is the purpose of a system call in an OS?
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Commented:
It's not homework at all.. I just started a class in operating system and I just don't get it.. is it like a call to a program?
Did you read the above article?  Do you have further/specific questions?

In essence, a system call is a request made to the operating system to perform some generally low-level operation, such as access to underlying hardware, file systems, network protocols, etc.

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Commented:
is it the same basically to ask the operating system to have certain access/features that the kernel mode supplies?

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Commented:
Can you give me an example of an system call in windows?
From:

http://msdn.microsoft.com/en-us/library/bb540534(VS.85).aspx

Which has sample code using CreateFile, ReadFile, and WriteFile
HANDLE hFile; 
 
hFile = CreateFile(argv[1],               // file to open
                   GENERIC_READ,          // open for reading
                   FILE_SHARE_READ,       // share for reading
                   NULL,                  // default security
                   OPEN_EXISTING,         // existing file only
                   FILE_ATTRIBUTE_NORMAL, // normal file
                   NULL);                 // no attr. template

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