Operating Systems: Kernel mode operations
<p>I would appreciate help with determining which of the following operations should be performed/done only in the kernel mode. I tried finding the answer in Silberschatz "Operating System Concepts" but it is still unclear to me. 
Here is the list of operations to decide whether they should be done in the kernel mode or the user mode:</p>

<pre><code>(1) disable interrupts detection
(2) clear memory
(3) switch from the user mode to the kernel mode
(4) read the state of the clock/timer
(5) determine/program timer. 
</code></pre>