As a result, there are privileged instructions that do not have any corresponding trap facility.

On a modern computer a halt instruction must be a privileged instruction (see 3.5) if it is provided.

Two points should be noted in connection with supervisor mode and privileged instructions.

In supervisor state, programs are additionally able to use privileged instructions which are generally intended for supervisory functions.

Specific limitations included the inability to trap on some privileged instructions.

But back in the days of the Zilog Z80, there was no notion of privileged instructions.

Unlike virtual memory, a system virtual machine allowed the user to use privileged instructions in his code.

DCRs are typically accessed through the use of privileged instructions.

In the status register, a privileged instruction allowed one to set the current minimum interrupt level, blocking lower or equal priority interrupts.

As these are privileged instructions they must be executed by the operating system.