Windows is a software system that provides functionality like graphical user interface, preemptive multitasking, virtual memory and file management. It also provides device drivers for standardized hardware interaction, and services to support applications.
The first version of windows was released in 1985 as an add-on to MS-DOS and allowed users to navigate a graphical desktop, opening graphical “windows” that displayed the contents of electronic folders and files.
Hardware Abstraction Layer (HAL)
HAL provides a standard interface for hardware devices to operate with the operating system. This allows developers to write applications and software that are independent of the specific hardware devices, allowing them to run on many different types of hardware.
The HAL interface translates standardized functions into low-level instructions that the hardware can understand, ensuring that the application runs correctly. This enables the application to function smoothly regardless of the specific hardware, enhancing compatibility and portability across platforms.
Since HAL is deeply integrated into the operating system, updates typically come bundled with operating system updates. However, developers should test the HAL to ensure that it is implementing commands properly. This testing can include verifying that the HAL is handling interrupts, analyzing CAN communication, or simulating hardware errors like invalid parameters and high-frequency interrupts.
Kernel
The kernel is the program that sits at the heart of an operating system. It’s the first program to start when the computer boots up and controls all other programs. It manages a computer’s hardware resources by controlling and coordinating operations between applications and other software modules.
The operating system kernel also implements sandboxing techniques to provide a secure execution environment for application processes. It can control when and how much a process uses a hardware resource such as a CPU or memory.
The kernel supports standardized hardware interfaces and uniform program user interfaces. It can also communicate with other computers through network sockets. A kernel can perform low-level hardware tasks using a library that hides the details from application programs. These are called system calls.
User Interface (UI)
UIs display important information and updates to users. They also allow users to interact with interface elements through various means, such as a mouse or keyboard. For example, a menu-driven interface lets users select options to navigate a program or website. Online shopping sites exemplify this type of interface.
Unlike MS-DOS, which used a text prompt for most tasks, Windows allowed users to visually navigate a desktop and open graphical “windows” that displayed the contents of electronic folders and files with a click of a button, rather than typing commands and directory paths at a terminal window. Likewise, Windows allowed users to execute several graphical programs at once through cooperative multitasking.
Microsoft also incorporated multilingual support, with users able to change the interface language through the Region and Language Control Panel. Third-party software developers can create programs that work with Windows, allowing users to install a wide variety of apps for personal use and business.
Device Drivers
Device drivers are software programs that enable your computer to communicate with hardware devices like printers and keyboards. They translate operating system instructions into commands for the hardware devices, and vice versa. They operate in the kernel layer and require low-level access to hardware operations.
There are several different types of device drivers. Kernel mode drivers load into RAM and run along with the operating system. They are the most general and include drivers for standard external devices like printers and keyboards.
Class drivers are more specific and work for a class of devices with similar functionality, such as all USB-connected printers. Miniport drivers are add-ons to class drivers that implement a hardware or function-specific subset of the full driver functionality. Layered drivers (also called filter drivers) receive data from lower-level drivers in a driver stack and change the format of the data before sending it to a device.
File System
File systems store and retrieve data from physical storage. They also maintain metadata about each file, such as its size, type and creation or modification date.
There are several file systems that operate in Windows, each with its own advantages and disadvantages. For example, NTFS was developed by Microsoft for its NT line of operating systems in 1993 and is the default file system for internal hard drives. It offers advanced features like permissions, encryption and journaling. FAT32 is commonly used for external devices and memory cards due to its simplicity and compatibility, but it has significant size limitations.
Other file systems include ext (Extended File System), HFS+ (Hierarchical File System) and APFS, which was introduced in macOS. Each provides a different balance of features, performance and reliability.