Operating Systems (OS)

What is an Operating System

• The original meaning (and still used by hardware engineering): a basic set of functions to control the hardware and manage things like task scheduling and system calls.
• The modern terminology used by software developers, the collection of these functions is usually referred to as a kernel, while an operating system is expected to have a more extensive set of programs.

You may have seen the term GNU/Linux, Linux is the kernel, GNU is the toolset on top of that.

OS = kernel + drivers + software

Read more about Linux and GNU

Popular Operating Systems

• Unix-like
  • Linux
    • Android
    • ChromeOS
    • HarmonyOS (鸿蒙): https://consumer.huawei.com/en/harmonyos/
  • BSD
    • Darwin: macOS, iOS, ipadOS, watchOS, tvOS. Based on XNU ("X is Not Unix"). Hybrid kernel.
    • QNX: a commercial Unix-like real-time operating system aimed primarily at the embedded systems market (Used by Audi, BMW, Ford, etc). Microkernel. Acquired by BlackBerry in 2010.
• Windows
• Fuchsia:
  • https://fuchsia.dev/

Monolithic Kernel vs Microkernel

• Microkernel provides the most basic functionalities: low-level address space management, thread management, IPC, etc.
• Device drivers, file systems, protocol stacks are included in Monolithic kernels, but are NOT in Microkernels, instead they run in user mode.

Examples:

• Linux is Monolithic.
• Google's Fuchsia, is based on a microkernel named Zircon. Fuchsia is NOT Linux.

Tanenbaum, the creator of Minix, arguing that microkernels are superior to monolithic kernels:

https://en.wikipedia.org/wiki/Tanenbaum%E2%80%93Torvalds_debate

Fuchsia OS

Fuchsia OS has effectively replaced the role of Android Things in Google's ecosystem. Android Things was officially discontinued by Google. The developer console stopped accepting new projects in January 2021, and the service was fully shut down in January 2022. Android Things, which was based on the Linux kernel, was generally considered too heavy, requiring too much memory and processing power for the majority of small, low-cost IoT devices. It never gained significant traction outside of a few smart displays.

There is no official timeline or commitment from Google to replace Wear OS with Fuchsia. However, Wear OS is considered a strong candidate for an eventual "under-the-hood" replacement due to its smaller ecosystem and specific challenges.