MSDOS

MS-DOS, or Microsoft Disk Operating System, is a family of operating systems for IBM PC-compatible personal computers. Released in 1981 as MS-DOS 1.0, it was developed by Microsoft and licensed from Seattle Computer Products' 86-DOS. It provided a command-line interface, a simple filesystem, and program loading capabilities that made it the standard operating system for many early PCs.

Origins trace to 86-DOS, created by Tim Paterson at SCP in 1980. Microsoft acquired the rights and rebranded it as MS-DOS for the IBM PC, yielding PC-DOS for IBM's machines. Over the 1980s, DOS evolved through versions such as 2.x and 3.x, adding subdirectories, improved memory management, support for hard disks, and basic networking. DOS 5.0 introduced a larger set of utilities and improved command processing; DOS 6.x added disk compression and maintenance tools; the final standalone release was MS-DOS 6.22 in 1994.

With the rise of Windows, the role of MS-DOS shifted from a stand-alone system to a runtime environment and compatibility layer. Windows 95 and later versions integrated MS-DOS as a bootstrap and subsystem; Windows NT-based systems provided a separate DOS compatibility layer (NTVDM) for running 16-bit DOS applications. MS-DOS remained widely used in embedded systems and legacy software environments for many years.

Technical features include the FAT12 and FAT16 file systems, conventional memory limits around 640 KB, and memory management through upper memory blocks, EMS, and XMS. It used config.sys and autoexec.bat for startup configuration and batch processing. It ran on x86 processors from the 8086 family and influenced numerous later operating systems and software ecosystems.