1. 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 greater than N and each of said N-bit data words 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, in the M-bit data word, of boundaries between adjacent "1" and "0" bits, 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 bounded on both sides by "0" and "1" bits, respectively, 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; 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; converting said N-bit data words to said respective assigned M-bit data words; and recording on a record medium said M-bit data words to which said N-bit data words are converted so as to minimize DC components of the recorded digital information signal and to concentrate the frequency spectrum.
3. The method according to claim 1; in which said number of isolated "1" and "0" bits is weighted by a factor of one and the number of isolated pairs of "1" and "0" bits is weighted by a factor of two, wherein said third value for each M-bit data word is obtained by adding the number of isolated "1" and "0" bits to twice the number of isolated pairs of "1" and "0" bits.