DOS

Dos, short for Disk Operating System, refers to a family of operating systems used primarily on IBM PC compatibles in the 1980s and 1990s. They provided a simple command-line interface, basic file management, and a runtime environment for applications before graphical operating systems became dominant. The most widely known variants are MS-DOS, developed by Microsoft, and PC DOS, released by IBM.

Origins and evolution: In 1980 Microsoft licensed 86-DOS from Seattle Computer Products and adapted it for the IBM PC, marketing it as MS-DOS. IBM released PC DOS as its own branded version. MS-DOS and PC DOS shared most features and command sets, with vendor-specific updates over time. Early versions used a FAT12 file system and a simple, single-tasking design. Over the years, DOS evolved to support hard disks, subdirectories, and larger disk formats, while retaining a consistent command-line interface.

Technical characteristics: DOS primarily relied on the FAT file system (initially FAT12, later FAT16 in newer releases) and used a boot process involving system files such as IO.SYS and MSDOS.SYS. The conventional memory limit was 640 kilobytes, with additional memory managed through various schemes and memory managers. Users interacted through a command interpreter, typing commands such as DIR, COPY, DEL, and CD, often extended by external utilities. Batch files (.BAT) enabled simple automated tasks. System configuration was performed with files like CONFIG.SYS.

Decline and legacy: DOS gradually declined in mainstream use after the rise of Windows operating environments, though it persisted in Windows 95/98 as a bootable layer and found continued use in embedded systems. Open-source FreeDOS and emulation projects like DOSBox keep the environment accessible for nostalgia, software preservation, and retro computing.