In computing, SISD (single instruction, single data) is a term referring to a computer architecture in which a single processor, a uniprocessor, executes a single instruction stream, to operate on data stored in a single memory. This corresponds to the von Neumann architecture.
SISD is one of the four main classifications as defined in Flynn's taxonomy. In this system classifications are based upon the number of concurrent instructions and data streams present in the computer architecture. According to Michael J. Flynn, SISD can have concurrent processing characteristics. Instruction fetching and pipelined execution of instructions are common examples found in most modern SISD computers.