In x86-based computers, user applications have very limited privileges, where certain tasks can only be performed by the operating system code.
In this type of architecture, the OS and the CPU work together to restrict what a user level program can do in the system.
As illustrated in the following diagram, there are four privilege levels that start from 0 (Most privileged) to 3 (Least privileged) and there are three important resources that are protected, which are memory, I/O ports, and ability to run certain machine-level instructions:
It's important to remember that even having a root account means that ...
