ion coding or alphanumerical symbols. This reserve would be adequate to code other symbols, such as lower-case a-z characters, characters with accents and alterations (é, è, à, ä, ç, ú, ü, ...), space and punctuation characters, parentheses and quotes, math operands and symbols X, , the decimals 0-9, and other special characters (*, %, \, [, ], {, }, $, €, £, @ ). This whole character bank forms our computer-keyboard alphabet, to be completed with several other computer commands. It can, thus, be theoretically coded through 100 decimal numbers (00 to 99). But such a decimal coding has never been of any practical use, except in the early times of cryptography, with the unique character-decimal correspondence representing the "secret code."4 A second and more powerful coding approach consists in converting the whole key- board alphabet into binary codewords. The advantage is that the latter can be processed by computers, without any other form of encoding. Since we have 27 = 128, we observe that codewords of only seven-bit length are more than sufficient to cover a full keyboard- symbol alphabet. This is the reason why most computers use ASCI,5 a standard code invented in 1961 and based on seven-bit codewords. Note that ASCII is not the only possible code for computers: indeed, EBCDIC6 is another standard based on eight-bit codewords, or bytes. The extra bit of EBCDIC makes it possible to code twice as many alphabet characters as in ASCII, namely 28 = 256 codewords. In the 1970s, ASCII was, in fact, extended to eight-bit codewords, which, in particular, makes it possible to include all language-specific characters. The correspondence table between ASCII and keyboard characters can be found on the Internet. 7 Table 8.1 illustrates the correspondence for the most commonly used keyboard characters. For instance, the letter A is coded as 1000001, the letter b is coded as 1100010, and the character @ is coded as 1000000. We observe from the table that all alphabetical characters or letters (lower or upper case) begin wi