What is a major difference between a monolithic kernel and a microkernel?

The distinction made in the correct response highlights that a monolithic kernel encompasses all core system services within a single, large executable block. This design means that essential functionalities such as device drivers, file system management, and system calls are all executed in kernel space. This approach allows for efficient communication and execution, as functions can directly call each other without the overhead of inter-process communication, which is often necessary in a microkernel architecture.

In contrast, a microkernel only includes the most fundamental services, such as low-level address space management, thread management, and inter-process communication, pushing other services like device drivers and file systems into user space. This modular approach typically enhances system stability and security, as issues in user space processes do not compromise the entire kernel. Understanding this key difference is crucial for grasping the implications of kernel design on operating system performance, security, and manageability.