Abstract: A micro optical head, for optically reading and/or writing digital data on a recording medium in which digital data 1 and 0, corresponding to a high reflection factor and a low reflection factor, is composed of a self-coupled semiconductor laser located close to the recording medium. A bias current of the laser is determined so that it is smaller than a first threshold current, in which the medium has a low reflection factor, and is higher than a second threshold current, in which the medium has a high reflection factor. Output light of the laser is either strong stimulated emission light, corresponding to the high reflection factor, or weak spontaneous emission light, corresponding to the low reflection factor. The present head is carried on a flying slider with a spacing length less than several .mu.m which provides a small beam spot of about 1 .mu.m, and has an excellent signal to noise ratio.

Abstract: A shift register type memory having major and minor loops, wherein the number of bits of the major loop is large enough to permit data of at least two blocks to simultaneously exist in the major loop when one block is constituted of data of bits the number of which is equal to the number of the minor loops, and wherein before a particular block having been transferred out from the minor loops to the major loop is again transferred in to the minor loops after travelling round the major loop, the next block is transferred out from the minor loops to the major loop.