What is an operating system?

Every device runs a government, and the operating system is it: the layer that administers physical resources — processor, memory, disk, network — arbitrates between applications demanding them simultaneously, and provides the common services everything else leans on, from files and windows to permissions and security. The families a company meets are few. Windows on most office workstations, with the Home versus Pro distinction that matters far more than people assume, since the professional editions carry exactly the business tooling: full-disk encryption, directory joining, centrally applied policies. macOS across creative and management seats. Linux, invisible but dominant on servers, running most of the world’s web hosting and cloud infrastructure and free of licence cost, which is a large part of why. And in pockets, Android and iOS with their fleets of company phones. The decisions this puts on a manager’s desk are concrete. Lifecycle and updates first: every system has an end-of-support date, after which newly discovered vulnerabilities stay open permanently, and the ancient machine kept alive beside the till because it still works is among the most exploited doors in small business. Then licensing, since pirated copies on company machines are a legal and a security liability at once. Then standardisation of the fleet, so problems get solved once rather than ten times, and mobile device management so company data on phones stays separable and remotely erasable. And finally application compatibility, because Windows-only local business software frequently settles the whole question on its own.