<div dir="ltr"><span style="font-family:arial,sans-serif;font-size:13px">I am not sure if I understand your question correctly. But If you are referring to user mode and kernel mode in the concept of operating system, developers use system calls to complete the transition from user to kernel mode. Kernel mode or "kernel code" operates with system critical data structures, direct memory access, hardware manipulation and so on. In my opinion, "user code" should be safer than "kernel code". So I'm just guessing, defining the security issues(levels) of a system is how they draw the line between kernel mode and user mode.</span><div style="font-family:arial,sans-serif;font-size:13px"><br><div><a href="http://stackoverflow.com/questions/1311402/differences-between-user-and-kernel-modes" target="_blank">http://stackoverflow.com/questions/1311402/differences-between-user-and-kernel-modes</a></div></div></div><div class="gmail_extra"><br><div class="gmail_quote">On Mon, Sep 8, 2014 at 10:49 PM, <a href="mailto:xxu15@stevens.edu">xxu15@stevens.edu</a> <span dir="ltr"><<a href="mailto:xxu15@stevens.edu" target="_blank">xxu15@stevens.edu</a>></span> wrote:<br><blockquote class="gmail_quote" style="margin:0 0 0 .8ex;border-left:1px #ccc solid;padding-left:1ex"><u></u>
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<div>Hi,</div>
<div style="TEXT-INDENT:2em">How to defferentiate between user code and kernel
code ?</div>
<div style="TEXT-INDENT:2em">Is there a standard to defferentiate the boundry
of the two ? Or just the Unix designers/engineers defined the boundry ?</div>
<div style="TEXT-INDENT:2em">Thank you.</div>
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<div>Sincerely,</div>
<div>Xiang Xu (徐祥) </div>
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