The paper presents a direct data control method of an AC to AC thyristor converter for induction heating by a minicomputer. The details of the hardware of the interface between the converter and a minicomputer, and of the software for the following two purposes are described. (1) Programmed output power control by variations of thyristor1s switching function given by the computer, and by the ON/OFF control of capacitors under instructions of the computer. (2) To use this system for the purpose of data acquisition by the computer which is necessary for designing this converter, such as the worst case turn-off time margin of the thyristor, optimal switching function pattern for power control, max. and min. output power, stability, etc.