* first cstool -- Segmentation fault: 11
* Modify the format of output.
* Preprocess the input from user. The result of converting looks right but the disassembly is not unsatisfactory.
* Skip the character not in set A = {'a'~'f','A'~'F','0'~'9'}.
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* delete cstool binary
* using isxdigit() to tests for any hexadecimal-digit character
* write README
* final version 1.0 for cstool