Are some instructions in an operating system designated as privileged and executable only in kernel mode?

In an operating system, certain instructions are indeed designated as privileged, and they can only be executed in kernel mode. This is a fundamental concept in operating systems that ensures safety and stability for the system as a whole.

Kernel mode is a restricted mode of operation where the operating system has complete access to all hardware and can execute any CPU instruction, unlike user mode, where applications have limited access to resources and cannot directly interact with hardware or execute privileged instructions. Privileged instructions include things like accessing hardware devices directly, managing memory, and changing system configurations. Allowing only the kernel to execute these instructions helps to prevent user applications from crashing the system or compromising security.

This separation of modes is critical for protecting critical system resources and maintaining overall system integrity. By ensuring that only the operating system kernel can execute these privileged instructions, the system can enforce layers of protection, manage multitasking effectively, and isolate user processes from one another, thereby creating a secure and stable computing environment.