A magnetic tape recorder is removably secured to an electronic digital information processing apparatus of the portable type for storing digital information and audio information. The digital information stored in the magnetic tape recorder is let out from the magnetic tape recorder in response to commands introduced through a keyboard means included in the electronic digital information processing apparatus and is displayed on a digital display secured on the electronic digital information processing apparatus. In a preferred form, another keyboard means is removably associated with the electronic digital information processing apparatus, whereby many kinds of information can be stored in the magnetic tape recorder.