Introduction to the Windows XP Architecture.ppt

Week of Feb 4 WIN133 Introduction to the Windows XP Architecture WIN133 Today… Examining the structure of the Windows 2000/XP OS Processes and Threads The programmer’s perspective on how XP works How programs work in XP Questions: What does “Architecture” mean? What does it mean in computers? Windows 2000/XP’s Architecture XP’s Key Design Items: Layered design Abstraction Object-oriented Client/Server Architecture – Layers Windows XP is built in Layers… User mode – layer closest to the person Applications that you run (Word, Netscape) Support programs for applications - the Windows XP Subsystems Kernel mode – layer closest to hardware Programs that help software running on our system use the computer’s hardware Device drivers (software interfaces to hardware) Layers (con’t) It all begins with your hardware Windows XP was designed to work on almost any type of hardware. Instead of writing a different version of XP for every hardware platform, MS created HAL The Hardware Abstraction Layer is a piece of software that sits between XP and your hardware. XP doesn’t actually know anything about your hardware. It leaves that up to HAL. Whenever XP needs to do something with your hardware it asks HAL how to do it. Layers (con’t) On top of HAL sits the XP Kernel Kernel mode programs are “Trusted” programs that get to do privileged activities with the computer’s hardware (CPU, RAM, etc.) Components provided (mostly) by MS Manufacturers of hardware devices also provide device driver software This software must pass a rigorous test Microkernel At the heart of the kernel is the Microkernel The Microkernel is very small On its own it can’t do much But it is important because it provides building-blocks for all the Executive Services running in the Kernel Windows XP Executive Services Provides services for applications (e.g., draws the GUI on the screen, checks security rights, performs disk I/O) Relies on the Microkernel to do everything Together, the Microkernel and Exec