Disc Operating System (DOS) is an operating system for personal computers(PCs). An operating system consists of a set of programs that make a computer usable in the first place. The key point in the development of a PC operating system was the most convenient operation and organization of data storage media, i.e. diskettes and disks.
The DOS operating system builds a tree-shaped directory structure on a flat data space. This structure is useful for organizing larger data sets. In addition, DOS provides simple commands and application programming interfaces( API) for application programs to run. Closely related to DOS is Basic Input/Output System( BIOS), which implements input and output functions. Starting from the version DOS 3.1 there is NetBIOS (Network Bios), which permits the input/output over network maps and represents the basis for the integration of personal computers (PC) into networks. The Disc Operating System had used a text-based user interface with command lines for a long time with the Command Line Interface( CLI). As of version 5.0, it has a graphical user interface( GUI).
DOS was developed by Microsoft. These versions are called MS-DOS. In addition, there are slightly modified versions from IBM (PC-DOS) and significant further developments from Digital Research( DR-DOS). Since Digital Research was taken over by Novell, there are own versions (Novell DOS).
DOS is a single-user operating system that supports only single tasking. This means that only one application process can be executed at the same time. This brings restrictions with it when working in the network. Therefore there is a background process in MS-DOS or PC-DOS from 3.1 on. Novell DOS 7 is a multitasking system. From MS-DOS 5.0 LAN requester for NetWare and LAN manager are integrated, from MS-DOS 6.0 there is a virus protection.