A crucial philosophical point to remember: the kernel is a computer program. It's a construct that can be rather intimidating for us lowly noobs, so it helps to remember the true nature of the beast. The casual flaws you learn about in ordinary programming can all occur in kernel code. The kernel occupies memory, just like any ordinary program, so the potential to put something where it doesn't belong and execute it exists. If this is the case, what makes the kernel so special? The kernel manages all low-level functions by interfacing the hardware of the computer and the software of the operating system. There are many, many different programs running on a modern instance of Windows and they all want to use one processor at the same time. The programs can't decide who gets how much time, and the processor dumbly completes operations – it can't decide, either. It's the kernel that functions as the cop managing all the high-level interactions with the lowest level structures of the system. The next time you're marveling at the multitasking ability of a computer that isn't actually capable of multitasking, thank the kernel for providing that illusion to you.

Windows is an example of an operating system that uses a dual-mode architecture: user and kernel (sometimes called user and supervisor). Thus, the memory space is split into two halves and user mode cannot access kernel space. Kernel mode, on the other hand, has the highest authority and can access any part of the system and hardware. The kernel is ultimately the mediator between the actual hardware and the operating system. In Windows, the interface with hardware is provided by the Hardware Abstraction Layer (HAL) which, as the name suggests, creates a layer of abstraction to, for instance, normalize differences in hardware. Kernel mode drivers provide interfaces for applications requesting access to hardware; even something taken for granted such as an application wishing to display data on the screen must work with a kernel mode driver. The beauty of these structures is they create a layer of abstraction and a single familiar environment for applications to work with. A Windows developer doesn't need to worry about the different monitors that may be displaying his or her program to the user: