What is the difference between the kernel space and the user space?

Question

What is the difference between the kernel space and the user space? Do kernel space, kernel threads, kernel processes and kernel stack mean the same thing? Also, why do we n

Answer 1

Kernel space and user space is the separation of the privileged operating system functions and the restricted user applications. The separation is necessary to prevent user applications from ransacking your computer. It would be a bad thing if any old user program could start writing random data to your hard drive or read memory from another user program's memory space.

User space programs cannot access system resources directly so access is handled on the program's behalf by the operating system kernel. The user space programs typically make such requests of the operating system through system calls.

Kernel threads, processes, stack do not mean the same thing. They are analogous constructs for kernel space as their counterparts in user space.