Abstract: The present invention relates to an apparatus for modulating input data by encoding the data to a run length limited (RLL) code data satisfying the (d,k,m,n) condition and decoding the modulated data, in which d is a minimum run length, k is a maximum run length, m is the bit number of input code data, n is the bit number of transmission code data, and the encoding and decoding apparatus according to the present invention comprises a look-up table (LUT) for encoding input parallel m-bit code data to r-bit code data in which r is not less than m and less than n, a post-encoder for encoding the encoded r-bit data to an n-bit transmission code data, a pre-decoder for decoding the input n-bit transmission code data to the r-bit code data according to the minimum run length condition, and a LUT for decoding the decoded r-bit code data to the original m-bit code data, by which the transmission code length is shortened according to the minimum run length condition so that the memory size required for encoding and de