Being able to simply replace a part with something else without issue is what makes Linux great.But your distribution constantly asks you to update your kernel.When the CPU is in kernel mode, it is assumed to be executing trusted software, and thus it can execute any instructions and reference any memory addresses (i.e., locations in memory).The kernel (which is the core of the operating system and has complete control over everything that occurs in the system) is trusted software, but all other programs are considered untrusted software.Keep that on mind if you will execute anything which would take less time.
The other is user mode, a non-privileged mode for user programs, that is, for everything other than the kernel.
I always assumed it was just used so that it didn't scare end users into thinking their PC was about to crash.
When I started reading more into improving the efficiency of your code I understood what it was for but how much of an effect does Turning off screen updating will only make a difference to execution time if the code interacts with Excel in a way that causes changes to the screen content.
As part of the kernel's functionality, device drivers control the hardware; "mainlined" device drivers are also meant to be very stable.
However, the interface between the kernel and loadable kernel modules (LKMs), unlike in many other kernels and operating systems, is not meant to be very stable by design.