A mathematical model of computation. Named after English scientist Alan Turing, a Turing machine is a finite state machine that reads a tape divided into cells. The Turing machine examines the symbol in each cell and based on the machine's state and cell contents, changes the symbol or changes its state and moves the tape left or right. The machine does not follow instructions because the states and transitions are built into the machine for each problem to solve.
The Universal Turing Machine (UTM)
Turing also designed a machine known today as the "universal Turing machine." The UTM could simulate another Turing machine. The tape contained a description of another Turing machine and like today's computers could be programmed to perform any type of computation. See Turing test