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We know that system calls are requests by a process for a service from an operating system's kernel.[1] I'm asking this question because I wanted to know if a process can really generate a signal on its own, ask the CPU for arithmetic operations directly, or read/write to files, and the like; OR does a process really just requests these to the operating system.

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2 Answers 2

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"Signals" and "files" only exist within the context of an operating system, so applications must ask the kernel to operate on them on its behalf. Arithmetic operations are preformed by the CPU, so applications can perform them directly.

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Furthermore, functions within libraries (such as Windows DLLs, etc.) do not HAVE to use system calls. It's possible for a developer to create/use one or more libraries merely to contain a certain category of code/functions that don't directly interact with the OS at all. Physically loading and linking a library function in object form from a file into RAM does always involve a system call though. –  ultrasawblade Jan 12 '13 at 1:16

I failed to realize that the string library functions in string.h don't make any use of system calls.

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This is not an answer, update your OP or add a comment to add this content –  Shekhar Jan 11 '13 at 23:35
    
This does not provide an answer to the question. To critique or request clarification from an author, leave a comment below their post. –  Shekhar Jan 11 '13 at 23:35
    
I'm sorry but I did not intend to "critique or request clarification from an author". –  WikiWitz Jan 12 '13 at 3:17
    
Ok those are my standard comments to answers that dont look like a real answer,I did not realize it was your own question. If you feel you have find your answer, try to post an explanatory answer so that its helpful for other too, also mark is as an accepted answer. –  Shekhar Jan 12 '13 at 17:53

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