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Several older systems helped shape Windows and Linux, but “inspired” covers different relationships: shared interfaces, Unix influence, software combined into a system, engineering experience, and compatibility with older applications. There is no single authoritative list of six. The six below are a clearly labeled editorial selection, not six direct ancestors. One of them—Linux—may be running on a Windows PC if you have enabled and launched a Linux environment, but it is not established as a default on typical PCs.
What counts as “inspired”?
An operating system can influence another without donating its source code. The links here include an interface designed for compatibility, Unix’s influence on Linux, GNU software combined with the Linux kernel, a creator’s prior design experience informing a later project, and operating systems that ran older applications. Those are meaningful historical connections, but they are not interchangeable.
| System or project | Connection | What the evidence supports |
|---|---|---|
| CP/M | Compatibility interface | QDOS adopted a CP/M system-call interface to ease application porting; this does not make DOS a CP/M clone. |
| QDOS | DOS interface lineage | Its CP/M-compatible interface became part of the DOS history that preceded early Windows. |
| MS-DOS | Early Windows host | Microsoft describes the first Windows as a graphical interface for MS-DOS. |
| Unix | Conceptual and technical influence | Linux is Unix-like, but the cited sources do not establish that Linux copied Unix source code. |
| GNU | System components | GNU software combined with the Linux kernel forms the system commonly called GNU/Linux. |
| VAX/VMS | Design experience | Windows NT leader Dave Cutler had created VAX/VMS; this supports an influence story through experience, not source-code descent. |
| OS/2 | DOS successor and compatibility | IBM and Microsoft developed it as a DOS successor project; the cited history does not establish current Windows as a simple OS/2 descendant. |
The table includes seven names when QDOS and MS-DOS are counted separately, but treats the DOS route as one historical path among six broader entries below: CP/M and the QDOS/MS-DOS lineage are discussed together. This makes the selection explicit rather than implying a definitive six-item canon.
1. CP/M: a model for DOS compatibility
CP/M’s connection to DOS is narrower than the familiar claim that DOS was simply copied from CP/M. An OS/2 Museum historical account says Paterson implemented CP/M’s system-call interface in QDOS to make it easier to port applications. That describes a compatibility choice: a program written to use the interface could be adapted more easily.
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The same account notes an important distinction: DOS used FAT, a different disk-management scheme whose design predated the QDOS adaptation. So CP/M helps explain one interface in DOS’s history, not every part of DOS. OS/2 Museum’s account of DOS and the CP/M file system
2. QDOS and MS-DOS: the route into early Windows
QDOS carried the CP/M-compatible interface into the line of DOS systems associated with early personal computers. Microsoft’s historical timeline describes Windows 1.0 as a graphical user interface for MS-DOS. In other words, the earliest Windows was a graphical layer running in the DOS era—not the same architecture as the later Windows NT family. Microsoft’s Windows 1.0 history
This distinction matters because a system can shape another in two ways at once: DOS compatibility and operation beneath early Windows, without making every later version of Windows a DOS-based system.
3. Unix: Linux’s major point of influence
Unix began at Bell Labs in 1969. The Open Group’s history describes a 1973 rewrite in C and records the first BSD release as derived from Version 6 Unix. Linus Torvalds began Linux development in 1991, and Linux is described as Unix-like. These facts establish an important family resemblance and influence, not a claim that Linux is a direct copy of Unix code. The Open Group’s Unix history
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Outbyte Driver Updater FREEFix the driver behind crashes, sound loss and screen glitchesFind Drivers →Outbyte PC Repair FREEClear out junk files and repair common Windows errorsFree Scan →Unix is also associated with a style of composing small programs. The Open Group’s history page credits Doug McIlroy with this formulation: “This is the Unix philosophy: Write programs that do one thing and do it well. Write programs to work together. Write programs to handle text streams, because that is a universal interface.” It is a useful way to understand Unix’s lasting conceptual influence, though it is not a complete technical definition of Linux.
4. GNU: the software that joined Linux’s kernel
Linux is the kernel—the core that manages hardware and system resources—but a usable operating system also needs programs and tools around it. The GNU project says that Linux, a Unix-like kernel, was developed by Torvalds in 1991 and released as free software in 1992. Combining it with the nearly complete GNU system produced GNU/Linux. The GNU project’s explanation of Linux and GNU
This is a composition story, not a claim that GNU was an older operating system copied by Linux. The name GNU/Linux emphasizes the combination of GNU software and the Linux kernel; many people use “Linux” as shorthand for the resulting operating system.
Independent reader supportYour contribution helps us test, update, and keep practical guides available for everyone.5. VAX/VMS: experience behind Windows NT
Windows NT’s history is connected to VAX/VMS through its lead engineer. Microsoft says it hired Dave Cutler in 1988, identifies him as the creator of DEC’s VAX/VMS, and says the resulting Microsoft project became Windows NT. That supports the conclusion that Cutler’s experience informed the NT effort. It does not establish that Windows NT reused VMS source code. Microsoft’s history of Windows command-line development
6. OS/2: a DOS successor, not Windows under another name
Microsoft says it began working with IBM on OS/2 in 1985. OS/2 Museum’s history says the companies planned joint development that year and that OS/2 1.0 shipped in December 1987. OS/2 used FAT, could run DOS applications in a compatibility session, and added protected-mode multitasking and a richer API. It belongs in the history of DOS successors and compatibility, but the available account does not support describing modern Windows as OS/2 under another name. OS/2 Museum’s history of the OS/2 project
Is Linux probably running on your PC right now?
That depends on what you have installed or launched. Microsoft documents historical Windows NT compatibility subsystems and the later development of Windows Subsystem for Linux (WSL), but that does not show that a Linux distribution is installed or running by default on a typical Windows PC. If you enabled and launched a Linux environment, Linux can be running alongside Windows; the historical connections alone are not evidence that it is active on your machine. Microsoft’s Windows command-line history
Windows NT 3.1, released in 1993, supported MS-DOS, Windows, OS/2 1.3, and POSIX subsystems, according to Microsoft. Those were application-compatibility facilities for that specific release. They should not be confused with proof that Linux was bundled with Windows then—or that a Linux subsystem is present by default today.
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