Operating System
OS Families
Windows Family
- NT kernel (1993) is the foundation for all modern Windows
- DOS-based Windows (3.x, 95, 98) is a separate pre-NT lineage
- Dave Cutler: Lead architect of the Windows NT kernel
| OS | Kernel / Base | Who uses it / Key traits |
|---|
| Windows | NT kernel | Enterprise, gaming, consumer desktop; most-used desktop OS |
| Windows Server | NT kernel | Enterprise servers; Active Directory, IIS, .NET workloads |
| FreeDOS | DOS-compatible | Legacy DOS apps, BIOS flashing, retro computing; pre-NT lineage |
Unix-like Family
- Linux and BSDs share Unix ancestry but are clean reimplementations - no original Unix code, no official Unix certification
- BSD started as “Unix + UC Berkeley improvements” (1977)
- legally cleaned up after AT&T lawsuit
- all modern BSDs descend from this clean version
- Ken Thompson: Unix co-creator
- Dennis Ritchie: Unix co-creator and creator of
C
- Linus Torvalds: Creator of the Linux kernel
| OS | Kernel / Base | Who uses it / Key traits |
|---|
| Linux | Linux (monolithic) | Servers, cloud, embedded; See Flavors of Linux |
| FreeBSD | FreeBSD kernel | Netflix CDN, PlayStation OS, high-performance networking |
| OpenBSD | OpenBSD kernel | Security-critical systems, firewalls; origin of OpenSSH |
| NetBSD | NetBSD kernel | Extreme portability; mostly academic / niche hardware |
Apple (BSD-derived)
- macOS and iOS/iPadOS run on the
XNU kernel (Mach microkernel + FreeBSD userland)
- Partially open-sourced by Apple under the Darwin name but not usable as a standalone OS
- Despite BSD roots, Apple holds official Unix certification from The Open Group - a paid trademark, not a measure of heritage
| OS | Kernel / Base | Who uses it / Key traits |
|---|
| macOS | XNU | Apple desktops/laptops; devs, creatives |
| iOS / iPadOS | XNU | iPhones, iPads; same kernel as macOS, heavily sandboxed |
graph TD
UNIX["Unix<br/>(AT&T Bell Labs, 1969)"]
BSD["BSD<br/>(UC Berkeley, 1977)"]
MINIX["MINIX<br/>(Tanenbaum, 1987)"]
FREEBSD["FreeBSD (1993)"]
NETBSD["NetBSD (1993)"]
OPENBSD["OpenBSD (1995)"]
DARWIN["Darwin / XNU<br/>(Apple, 1996)"]
MACOS["macOS"]
IOS["iOS / iPadOS"]
LINUX["Linux kernel<br/>(Torvalds, 1991)"]
UNIX --> BSD
UNIX -.->|inspired| MINIX
BSD --> FREEBSD
BSD --> NETBSD
BSD --> DARWIN
NETBSD -->|forked| OPENBSD
DARWIN --> MACOS
MACOS --> IOS
MINIX -.->|inspired| LINUX
RTOS
- not full OSes; they are libraries that run on microcontrollers
- no HDD, CD-ROM, or UEFI BIOS concept
- use simulators like
Wokwi for development
- See Realtime_OS
| OS | Kernel / Base | Who uses it / Key traits |
|---|
| VxWorks | VxWorks kernel | Aerospace, defense, NASA rovers; Wind River Systems |
| QNX | QNX microkernel | Automotive ADAS, medical devices; BlackBerry-owned |
| FreeRTOS | FreeRTOS | IoT, industrial sensors, consumer electronics; AWS-backed |
| Zephyr | Zephyr kernel | Wearables, automotive; Linux Foundation project |
Mainframe
- built for extreme reliability, uptime, and transactional throughput. Not general-purpose computing
- AIX is Unix-family (System V, Unix-certified) but grouped here as it serves the same IBM enterprise world as z/OS
| OS | Kernel / Base | Who uses it / Key traits |
|---|
| IBM z/OS | z/Architecture | Banks, credit card processors, airline reservation systems |
| AIX | AIX (System V) | IBM POWER servers; banking, insurance, legacy enterprise |
| OpenVMS | VMS kernel | Power grids, nuclear facilities, railways; legendary uptime |
Hobby / Research
- not production OSes — built to explore ideas or as personal projects
| OS | Kernel / Base | Who uses it / Key traits |
|---|
| HaikuOS | Haiku kernel | BeOS revival; multimedia-focused desktop |
| TempleOS | HolyC | Terry Davis; Ring-0 only, intentionally minimal |
| Redox OS | Redox (microkernel) | Rust-based; modern Unix-like research OS |