The Role of the Operating System

As part of the boot sequence, the operating system determines the hardware configuration of the system, finds any external devices connected to USB ports or plugged into PCI expansion slots, and initializes them, loading drivers along the way, if necessary.

Once the operating system has completed loading, the user is able to run application software. Application software may need to allocate memory or write a file to disk, and it is the operating system that handles these requests. To the user, the involvement of the operating system is largely transparent.

The operating system provides a layer of abstraction between running applications and the physical hardware. Applications typically communicate with hardware by issuing high-level requests to the operating system. Because the operating system handles these requests, the application can be completely unaware of the hardware configuration on which it is running, such as the amount of RAM installed and whether the disk storage is an internal SSD or an external USB drive.

This abstraction allows application software to be run on a wide variety of different hardware configurations without the programmer having to add support for each one, even if new hardware devices are created after the program has been released.

Application developers can often ignore many of the details of the workings of a computer system, because the operating system abstracts away the intricacies of the hardware platform on which the application is running. As a driver developer, however, the code that you write becomes part of the operating system and will interface directly with the computer's hardware; you are not immune to the inner-workings of a system. For this reason, a basic understanding of how the operating system performs its duties is necessary.