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.