Reconfigurable processor and semiconductor device

A reconfigurable processor that finely controls operation without exerting an influence upon other functions. Register groups are connected to input ports of ALUs via selectors. Data inputted to an ALU is held in a register selected by a selector under the control of a sequencer. For example, it is assumed that a register is selected for executing an application. To switch this application to a next application, a selector switches the register to another register to be used in accordance with instructions from the sequencer after the application terminates. In this case, data inputted while the application was being executed remains in the register, so the next application can be executed immediately without exporting the data after the termination of the application.