Datasheet

WHAT ARE THE FEATURES OF WINDOWS VISTA ARCHITECTURE?

The Macintosh OS is also no longer limited to special Macintosh hardware. Apple made the

interesting choice to give up that unique hardware and now you can find the Macintosh OS run-

ning on an Intel system near you. Consequently, Windows has lost a bit of its edge for running on

open hardware. There are even reports that some people have gotten Windows and the Macintosh

OS to dual boot on a single machine. Imagine that!

What Are the Features of Windows Vista Architecture?

I’ve already discussed some of the Vista architecture. In this section, I’ll analyze it a little more

closely to see what makes Vista tick and why it’s different from other operating systems.

From a programmer’s perspective, Vista is divided into two layers. These are actually two sepa-

rate operating modes. The kernel mode is where Vista performs its internal tasks and controls interac-

tion between programs and the operating system, and between programs themselves. It’s generally

protected from end users fiddling with it. The user mode, which is usually described as sitting above

the kernel mode because it’s closer to the end user, is where your applications run. The area is con-

sidered nonprotected because you have access to it through your applications.

Kernel Mode

Nothing happens in the Vista universe without the operating system knowing about it and

giving its blessing. The kernel is the core of Vista. It acts as a “gofer” between the operating sys-

tem and the computer’s processor. As such, it’s responsible for scheduling all the operating

system’s interactions with your computer. The kernel also manages all the interrelationships

between the different kernel mode operations. It does this by means of threads. A thread is a

series of instructions that are attached to a command that is executed by a program. Threads

include memory addresses, scheduling for the amount of time the process will take, and any-

thing else that describes the process.

The kernel mode is divided into three subsections: the Hardware Abstraction Layer (HAL), the

kernel, and Executive Services. Executive Services is subdivided further into its own component

parts; more on those parts shortly.

The HAL and the Kernel

The HAL controls the interaction between the kernel and the system hardware. One of the design

goals of Vista was the capability to be easily ported from one type of computer to another. To this

end, the HAL abstracts the hardware from the kernel so that the kernel doesn’t need to know what

type of hardware is installed in the computer. This abstraction extends to running multiple proces-

sors in your computer. Vista is one of the only PC-based operating systems that can take advantage

of symmetric multiprocessing. The abstraction provided by the HAL gives Vista greater stability.

Because of the abstraction provided by the HAL, software that attempts to directly access the

hardware isn’t permitted to run. The HAL, working with the kernel, stops those programs dead in

their tracks. For performance reasons, many DOS programs—particularly games—use direct hard-

ware access. Programs written for Vista don’t need to worry about how to access the hardware;

they just ask the operating system for support, and Vista takes care of the rest.

Vista does have some communication that bypasses the HAL and goes directly to the hardware.

In each of these cases, the communication is between the Executive Services and the individual

drivers for hardware devices such as the video card and network card. But the concept of hardware

abstraction is still maintained.

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