(1) A statement used to initiate an action or start a service. A command consists of the command name abbreviation, and its parameters and flags if applicable.
(2) In SDLC, a frame transmitted by a primary station. Asynchronous balanced mode stations send both commands and responses. See also response.
(3) In SNA, any field set in the transmission header (TH), request header (RH), or request unit (RU) that states an action or that starts a protocol.
(4) A request from a terminal or automated operator for the performance of an operation or service, or for the execution of a particular program.
(5) A request to perform an operation or run a program. When parameters, arguments, flags, or other operands are associated with a command, the resulting character string is a single command.