Encoding and decoding method of a prml code for a high-density data storage apparatus, especially in connection with magnetically recording and reproducing digital data without interference between signals

PURPOSE: An encoding and decoding method of a PRML(Partial Response Maximum Likelihood) code for a high-density data storage apparatus is provided to increase an encoding rate for influencing various signal distortions or noise, thereby improving a recording/reproducing function of data while realizing an optimized input and output for encoding and decoding block codes. CONSTITUTION: A system generates a codeword having an 8/9 encoding rate and satisfying a condition of a maximum transition run being 3(S100). The system generates a codeword satisfying a condition of a maximum continuous zero value being 7(S200). The system decides whether the fifth bit of 9-bit codewords is 0(S300). If so, the system maps the first 4 bits and the last 4 bits of input 8-bit user data with the first 4 bits and the last 4 bits of the codewords without changing(S400). The system prepares an input/output code book between the input 8-bit user data and the 9-bit codewords, and simplifies into a Karnaugh map(S600).