The Kernel
- Today, all “real” operating systems have protected kernels.
The kernel resides in a well-known file: the “machine” automatically loads it into memory (boots) on power-on/reset.
Our “kernel” is called the executive in NT.
- The kernel is (mostly) a library of service procedures shared by all user programs, but the kernel is protected:
User code cannot access internal kernel data structures directly, and it can invoke the the kernel only at well-defined entry points (system calls).
- Kernel code is like user code, but the kernel is privileged:
The kernel has direct access to all hardware functions, and defines the machine entry points for interrupts and exceptions.