An apparatus for performing a desired logical function comprises a logic circuit including signal lines, a storage device storing information which determines whether each of the signal lines is to be sensitized or desensitized, and a device for selectively sensitizing or desensitizing the signal lines on the basis of the information stored in the storage device. The apparatus can be repeatedly and easily programmed by altering information stored in the storage device. Moreover, it can be formed as a highly integrated circuit.