Definition – What does DOS mean?
Disk Operating System (DOS) was the command-line-based first operating system that is used by IBM- computers originally available in two versions that were basically the same but marketed under two different names such as PC-DOS and MS-DOS. PC-DOS (Personal Computer Disk Operating System) was the version created by IBM and sold to the first IBM-compatible manufacturers. MS-DOS (Microsoft Disk Operating System) was the version that Microsoft bought the rights to the first versions of Windows.
Glossary Web explains DOS
DOS (Disk Operating System) uses a text-based or command-line interface that enables the user to type commands to perform functions. By typing simple commands such as pwd and cd, the user can browse the files on the hard disk drive, open files, and run functions. In order to use the operating system, the user must need to know all the basic commands to use DOS effectively. This made the operating system tough for novices to use that is why Microsoft later exchange the graphic-based Windows operating system with DOS.
Actually, the first versions of the Microsoft Windows ran on the DOS operating system. This is why many DOS-related files and functions are still used by Windows. However, the Windows OS was rewritten for Windows New Technology that allows Windows to run on its own, without using DOS. Disk Operating System is still included with Windows OS but is run from the Windows operating system instead of the other way around.