14. In a method of recording a digital information signal comprised of a plurality of N-bit data words by means of a recording apparatus which imperfectly transmits DC components of said digital information signal, the steps of: selectively generating M-bit data words in which M is an even integer larger than N and each of said N-bit and M-bit data words is comprised of a plurality of logic level "1" bits and logic level "0" bits; weighting each of said M-bit data words on the basis of a first value corresponding to a number of boundaries between adjacent "1" and "0" bits in the M-bit data word, a second value corresponding to the number of said "1" bits in the M-bit data word, and a third value corresponding to the numbers, in the M-bit data word, of isolated "1" and "0" bits and of isolated pairs of "1" and "0" bits bounded on both sides by "0" and "1" bits, respectively; grouping the weighted M-bit data words in accordance with the run length of data thereof; classifying the grouped M-bit data words into a first group consisting of said M-bit data words which have an equal number of said "1" and "0" bits, a second group consisting of said M-bit data words which have a number of said "1" bits greater than the number of said "0" bits, and a third group consisting of said M-bit data words which have a number of said "0" bits greater than the number of said "1" bits; assigning each of said N-bit data words to at least a respective one of said M-bit data words in accordance with the generation frequencies of said N-bit data words so that the run lengths of the assigned M-bit data words will vary generally inversely in respect to the generation frequencies of the respective N-bit data words, with some of said N-bit data words being assigned alternately to said M-bit data words of said second and third groups and the remainder of said N-bit data words being assigned to said M-bit data words of said first group; converting said N-bit data words to said respective assigned M-bit data words so as to minimize DC components of the digital information signal, as converted, and to concentrate its frequency spectrum; and recording on a record medium said M-bit data words to which said N-bit data words have been converted.
14. In a method of recording a digital information signal comprised of a plurality of N-bit data words by means of a recording apparatus which imperfectly transmits DC components of said digital information signal, the steps of: selectively generating M-bit data words in which M is an even integer larger than N and each of said N-bit and M-bit data words is comprised of a plurality of logic level "1" bits and logic level "0" bits; weighting each of said M-bit data words on the basis of a first value corresponding to a number of boundaries between adjacent "1" and "0" bits in the M-bit data word, a second value corresponding to the number of said "1" bits in the M-bit data word, and a third value corresponding to the numbers, in the M-bit data word, of isolated "1" and "0" bits and of isolated pairs of "1" and "0" bits bounded on both sides by "0" and "1" bits, respectively; grouping the weighted M-bit data words in accordance with the run length of data thereof; classifying the grouped M-bit data words into a first group consisting of said M-bit data words which have an equal number of said "1" and "0" bits, a second group consisting of said M-bit data words which have a number of said "1" bits greater than the number of said "0" bits, and a third group consisting of said M-bit data words which have a number of said "0" bits greater than the number of said "1" bits; assigning each of said N-bit data words to at least a respective one of said M-bit data words in accordance with the generation frequencies of said N-bit data words so that the run lengths of the assigned M-bit data words will vary generally inversely in respect to the generation frequencies of the respective N-bit data words, with some of said N-bit data words being assigned alternately to said M-bit data words of said second and third groups and the remainder of said N-bit data words being assigned to said M-bit data words of said first group; converting said N-bit data words to said respective assigned M-bit data words so as to minimize DC components of the digital information signal, as converted, and to concentrate its frequency spectrum; and recording on a record medium said M-bit data words to which said N-bit data words have been converted. 17. The method according to claim 14; further comprising the step of mapping said first and second groups into a first coding map and mapping said first and third groups into a second coding map.