A recording medium stores an information processing program that causes a computer to execute storing a compression symbol map group having a bit string indicating for each character code, presence or absence of the character code in a file group, and a Huffman tree whose leaf corresponding to the character code has a pointer to a compression symbol map of the character code, the Huffman tree converting the character code into a compression symbol of the character code; compressing sequentially and according to the Huffman tree, a character code to be compressed and described in a file of the file group; detecting access to the leaf at the compressing; identifying by a pointer in the accessed leaf, a compression symbol map of the character code to be compressed; and updating a bit that indicates presence or absence of the character code to be compressed, in the identified compression symbol map.