The Windows System

Windows is a complex software system that depends on many hardware components. It uses device drivers to help programs communicate with the underlying hardware.

Unlike early Windows versions, which ran on top of MS-DOS, the modern OS is optimized for Intel processors and supports a variety of hardware devices. It also features a user-friendly interface that makes it easy for users to manage computer resources.


The windows system uses subsystems to provide different services to applications. For example, the kernel and drivers are subsystems that are responsible for interacting with hardware and software components. Other subsystems include the registry and the event log, which keep track of activities in the system.

In addition, the Linux subsystem allows users to access Windows files seamlessly from a Linux application. Similarly, Windows drives are mounted in the /mnt directory of Linux distros, making them easily accessible.

However, the Linux subsystem does have some limitations. For example, it does not support all Linux applications and only supports the Ubuntu Linux distribution at this time. Also, it does not support a graphical user interface. For these reasons, the Linux subsystem is not a substitute for a full-blown virtual machine. Instead, it provides a lightweight alternative that does not require as many computing resources as a virtual machine. It also requires less memory and storage. This makes it ideal for applications that use large amounts of data.

Kernel-Mode Drivers

When a computer runs Windows, the processor operates in two modes: user mode and kernel mode. The operating system, core components and devices execute in kernel mode; applications and other software run in user mode.

Kernel-mode drivers are a type of device driver that runs in the kernel environment. Kernel-mode drivers must delegate to the operating system APIs to perform functions such as requesting memory or accessing hardware devices. Code running in a kernel-mode driver doesn’t have private virtual address space, so any mistake by the driver can compromise data belonging to the operating system or other drivers.

To function, a kernel-mode driver must include a DriverEntry routine and Dispatch routines. It must also create and initialize required resources, objects and devices and free them when they’re no longer needed. For example, a driver might need to register an event handler for power state changes and implement synchronization mechanisms. The driver should also support the Plug and Play Manager by enabling it to respond to messages sent by the operating system to manage device additions.

Hardware Abstraction Layer

In Windows NT, the Hardware Abstraction Layer (HAL) acts as an intermediary between your computer’s physical hardware and the kernel. It hides diverse hardware structures and ensures that system hardware components communicate consistently. This allows software to be written once and run across a wide variety of hardware platforms.

HAL also provides routines that enable a single driver to support a device on multiple hardware platforms. This makes the task of writing device drivers much easier for developers.

The HAL is implemented as a set of functions that use the WIN32 API to provide user applications with an interface to system core functionality. This includes managing memory, determining the size of the kernel’s address space and coordinating context switching between different processes in the same machine. It also controls paging out and paging back in of physical memory to secondary storage and implements a parser for PE executables. It also provides an atomic memory manager that allows a process to be mapped and unmapped in a single step.


Services are programs that run in the background and perform tasks such as monitoring performance counter data, reacting to threshold values or routing network traffic. Developers can create Windows Services as Visual Studio projects, developing code that specifies what commands can be sent to the service and what actions it takes when those commands are received. You can start, pause or resume a service, and you can control how the service runs by specifying its startup type in the Services Control Manager.

Some services are essential to ensure that Windows works properly. Others are used by drivers or applications to enable connected experiences. You can change the startup type of these services to prevent them from starting at boot or running constantly, which can use up system resources. You can also disable some services if you don’t need them or want to squeeze the last bit of performance out of your PC. However, you should always use caution when editing Windows services as some of them are critical for your everyday computing needs.