History of Operating Systems: From Batch Jobs to Unix, Windows and Cloud
An operating system (OS) is the software that manages a computer’s hardware and runs your programs. Its history explains many things sysadmins deal with every day: why Windows has drive letters, why Linux has one directory tree, why phones sandbox apps, and why the same ideas (files, processes, permissions, users) show up everywhere. This article follows the main line from having no OS at all through Unix, personal computers, Windows, Linux, mobile and the cloud.
Stage 0: no operating system (1940s to early 1950s)
Early computers were programmed directly, by wiring or by punched cards, and one person used the machine at a time. Every program had to include its own code to talk to the hardware.
Stage 1: batch systems (1950s to early 1960s)
Because computers were expensive, operators grouped jobs on tape or cards and ran them one after another, so that the machine did not sit idle. Programs such as GM-NAA I/O (1956) and IBM’s mainframe monitors handled loading and input/output. This is the origin of the idea that an OS is a supervisor that runs programs for you.
Stage 2: time-sharing and multitasking (1960s)
Batch processing made users wait hours. Time-sharing gave many users the impression of having the machine to themselves by switching between them many times a second. MIT’s CTSS (1961) and then Multics (started 1964 by MIT, GE and Bell Labs) explored this and introduced ideas still in use: hierarchical file systems, virtual memory and access control. IBM’s OS/360 (1964-66) took a different approach for business mainframes and set the pattern for large system software.
Stage 3: Unix (1969 onward)
After Bell Labs left the Multics project, Ken Thompson and Dennis Ritchie built a simpler system, Unix, starting in 1969. Its lasting ideas were:
- Everything is a file, or at least is accessed like one.
- Small programs that do one job and are combined with pipes.
- Text as the common interface.
- Portability: rewritten in C by 1973.
Unix spread through universities. The University of California, Berkeley added networking and virtual memory (BSD), and commercial versions followed (System V, Solaris, AIX, HP-UX). Later, Unix-like systems inherited the design: Linux, FreeBSD, macOS (whose core, Darwin, derives from BSD) and Android.
Stage 4: personal computers (1970s to 1980s)
- 1974-1977: CP/M was the leading OS for early 8-bit microcomputers.
- 1981: MS-DOS (PC DOS) came with the IBM PC; see the DOS article.
- 1984: Apple’s Macintosh popularised the graphical user interface (GUI) with windows, icons and a mouse, building on research at Xerox PARC.
- 1985: Microsoft Windows 1.0 arrived as a graphical shell on top of DOS.
Stage 5: Windows and the modern desktop (1990s to 2000s)
| Year | Release | Why it mattered |
|---|---|---|
| 1990-92 | Windows 3.0 and 3.1 | First widely successful Windows, still on DOS |
| 1993 | Windows NT 3.1 | A new, portable, 32-bit kernel with security and NTFS, the foundation of modern Windows |
| 1995 | Windows 95 | Start menu, taskbar, long file names; a hybrid 16/32-bit consumer OS that still booted from DOS underneath |
| 2001 | Windows XP | Merged the consumer and NT lines into one NT-based system |
| 2007-09 | Vista, then Windows 7 | UAC, driver signing, a better 64-bit story |
| 2015 | Windows 10 | Continuous updates rather than big version jumps |
| 2021 | Windows 11 | Requires UEFI firmware with Secure Boot capability, and TPM 2.0 |
Meanwhile Apple moved from the classic Mac OS to Mac OS X in 2001, based on the Unix-like Darwin, and the old system was left behind.
Stage 6: Linux and open source (1991 onward)
Linus Torvalds released the Linux kernel in 1991, and combined with GNU tools it became a free Unix-like system that could run on cheap PCs. By the 2000s it powered the web and, later, the cloud. Details are in the history of Linux.
Stage 7: mobile (2007 onward)
The iPhone (2007, iOS) and Android (2008) rebuilt the OS around touch, batteries, app stores and strong app sandboxing. Both are Unix-like inside: iOS shares its heritage with macOS, and Android uses the Linux kernel. Phones now outnumber PCs, and most people meet an OS first on a phone.
Stage 8: virtualisation, containers and cloud (2000s onward)
Hypervisors (VMware, Xen, KVM, Hyper-V) let one physical machine run many operating systems, and containers (Docker, 2013) let many isolated applications share one kernel. In the cloud, the OS is often invisible: you deploy an image or a container, and the provider manages the hardware. The kernel and user-mode split is still what makes this isolation work.
What stayed the same
- The OS manages processes, memory, files and devices.
- It enforces permissions between users and programs.
- It hides hardware differences behind a stable interface.
Common questions
What was the first operating system?
There is no single answer. GM-NAA I/O (1956) is often cited as an early one, but earlier monitors and programs performed similar tasks.
Is macOS Unix?
Yes: macOS has been certified as UNIX by The Open Group for many releases. Its core (Darwin, with the XNU kernel) has BSD heritage.
Is Windows built on DOS?
Only Windows 1.0 to Me were. Windows NT and every version since Windows XP (including 10 and 11) are built on the NT kernel.
