| Chinese inventor [[Liang Lingzan]] built the world's first fully mechanical clock; [[water clocks]], some of them extremely accurate, had been known for centuries previous to this. This was an important technological leap forward; the earliest true computers, made a thousand years later, used technology based on that of clocks. {{Citation needed|date=July 2008}}
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| ''c.'' 850
| [[Islamic mathematics|Arab mathematician]], [[Al-Kindi]] (Alkindus), was a pioneer of [[cryptography]]. He gave the first known recorded explanation of [[cryptanalysis]] in ''A Manuscript on Deciphering Cryptographic Messages''. In particular, he is credited with developing the [[Frequency analysis (cryptanalysis)|frequency analysis]] method whereby variations in the frequency of the occurrence of letters could be analyzed and exploited to break [[encryption]] [[cipher]]s (i.e. cryptanalysis by frequency analysis).<ref>[[Simon Singh]]. ''[[The Code Book]]''. pp. 14–20</ref> The text also covers methods of cryptanalysis, [[Cipher|encipherments]], cryptanalysis of certain encipherments, and statistical analysis of letters and letter combinations in Arabic.{{Citation needed|date=May 2010}}
