A teaching operating system from 1987 now hides inside most Intel chips
MINIX was written in 1987 as a stripped-down version of UNIX so students could study how operating systems work. It went on to inspire Linux, and since 2008 it has quietly run on controllers inside most Intel processors. Millions of people carry a classroom project around without ever seeing it.
An operating system is the layer of software that shares out a computer's resources among the programs running on it. It decides which application gets processor time and memory, walls programs off so one crash or security hole does not spread, and offers a common set of services for disks and networks, so software need not be rewritten for each machine. Virtual memory is one of its conjuring tricks, giving programs the impression of far more memory than the hardware holds. The part that is always running is called the kernel.
The earliest computers of the late 1940s had nothing of the kind; programmers wired plugboards or fed in punch cards, and human operators scheduled jobs by hand. IBM's System/360 family of the 1960s all ran one system, OS/360, millions of lines of assembly code with thousands of bugs, but it was the first popular system to let the processor switch to another job while one waited for input or output. MULTICS aimed to let hundreds of users share one large machine and is sometimes seen as a forerunner of cloud computing. UNIX began as a single-user offshoot of it, and because its source code circulated freely, it spawned many variants, including AT&T's System V and Berkeley's BSD.
Personal computers brought new players. CP/M led for about five years from around 1980, until IBM bought a disk operating system from Microsoft, sold by IBM as PC DOS and by Microsoft as MS-DOS. Apple's Macintosh popularised the graphical interface, prompting Microsoft to layer Windows on top of DOS. The rewritten Windows NT borrowed so heavily from another system, VAX/VMS, that a large legal settlement followed. On phones, Symbian gave way to BlackBerry and the iPhone, then to Android, launched in 2008 on a Linux kernel.
By November 2025, Android ran on 38 percent of devices and Windows on 33 percent. At the other extreme, embedded systems for appliances and smart cards can fit in under 10 kilobytes, and real-time systems in aircraft and factories must respond at exact moments.
Source: Operating system
