Digital data transforming method

A digital data transformation method used to transform an arbitrary bit-string data into a sequence of printable ASCII characters, the coding transformation being implemented by the computer software, characterized in:

• (1) storing the executable program module to be used to execute the coding transformation into the program storage of the computer system, and building the array R91_CH[91] of the output character set and the array φ[13] of the table denoting filling bits in the computer memory;
• (2) making the input byte-string pointer pointing to the starting address of the byte-strings to be coded, recording the length of the byte-string to be coded by using variable, making the program counting pointer pointing to the entry address of the previously described executable program module in the program storage, reading the instructions and executing coding transformation;
• (3) the coding transformation divides the input data into blocks with the length of 13 bits;
• (4) for the coding transformation of blocks, the variable set or the original image set X includes all 8192 13-bit symbols and 12 filling-bit denoting symbols φ1, . . . , φ12, totally amounting to 8204 elements;
• (5) using 91 or 92 (considering the terminating symbol “=”) printable ASCII characters in the output representation of the coding transformation;
• (6) for the coding transformation of blocks, the image set Y is the sub-set of the direct product R91×R91, wherein R91 is the set of 91 printable characters, in particular R91 excluding printable ASCII characters “−” and “=”, the reversible coding mapping relationship is
• Base91[x]=(ch1,ch2)=(R91—CH[x/91], R91—CH[x %91]) (1)
• wherein x (X, ch1,ch2 C R91, symbols “/” and “%” are the operators used in the C language, representing integral division and modulo division (remainder) respectively;
• (7) for the input data block less than 13-bit long, adding n bits to the specified side to make it become a complete block for implementing mapping, thereafter adding a block of data φn as the input data block implementing the same coding mapping, its image is in the direct product R91xR91.