DOS stands for
disk operating system, a kind of
operating system for
computers. In particular, it is often used to refer to
MS-DOS,
PC-DOS,
DR-DOS (and also a small number of little-known compatible DOS products) which between them dominated the market for the decade between 1985 and 1995. The major DOS versions all originated, in one way or another, as outgrowths of the previous dominant operating system,
CP/M.
DOS (or
DoS, to distinguish it from the first sense) also stands for
denial of service.
In the context of
computer networking, this is the situation where a system is attacked in such a manner that "normal" network communication is blocked by excessive traffic, or the system itself is rendered non-functional due to overload or caused to crash.
This is distinct from a compromised system, which may continue to operate but is put to subversive use or exposed to illicit monitoring
In
condensed matter physics,
DOS is a common acronym for
density of states.
The density of states, N(E), for electronic energy levels in a solid is defined as follows: N(E)dE is the number of allowed energy levels per unit volume of the solid, in the energy range E to E+dE.