Ma'anar ƙamus na "Disk Operating System" (DOS) shine tsarin aiki na kwamfuta wanda ake lodawa daga faifai kuma yana samar da layin umarni don sarrafa fayiloli da gudanar da shirye-shirye. An yi amfani da DOS sosai a farkon zamanin sarrafa kwamfuta, musamman akan kwamfutoci masu jituwa na IBM PC, kuma sun ba da hanya mai sauƙi da sauƙi don mu'amala da kwamfutar. DOS an maye gurbinsa da mafi yawan tsarin aiki na zamani kamar Windows, macOS, da Linux, amma har yanzu yana da wuri a wasu aikace-aikace na musamman kuma a matsayin kayan aiki ga masu sha'awar kwamfuta da masana tarihi.