Computer program for implementing a modulation method and a demodulation method therefor

A computer program stored in an information recording medium for enabling a computer to implement a modulation method comprising the steps of:

• generating a 6-bit output code word in response to every 4-bit input code word by referring to a set of encoding tables, wherein the encoding tables contain output code words assigned to input code words, and contain encoding-table designation information accompanying each output code word, wherein the encoding-table designation information designates an encoding table among the encoding tables which is used next to generate an output code word immediately following the output code word accompanied with the encoding-table designation information;
• adding two redundant bits to every prescribed number of the successive generated output code words for digital-sum-variation control;
• and
• sequentially connecting the generated output code words and the added redundant bits into a redundant-bit-added output-code-word sequence which follows predetermined run length limiting rules (1, k)RLL, where “k” denotes a predetermined natural number equal to 9.