INVITATION TO CYBERSECURITY 8 Table 2.1 Example data encoding of the twelve most common letters of the English alphabet. To see how data encoding works, we can do a simple illustration using the twelve most common letters of the English alphabet: E T A O I N S H R D L U.1 To uniquely represent these twelve letters, we need a string of four 1s and 0s because a binary string of length four gives us sixteen distinct possibilities: 2 x 2 x 2 x 2 = 2⁴ = 16 Table 2.1 shows an example mapping of these letters to binary strings. Since there are more string combinations than we need, we can use the extra ones for the space character and punctuation marks or just leave them unused. Using this catalog of strings, we can unambiguously encode the twelve letters to communicate words and sentences. For example, to encode the phrase TASTE AND SEE we would write: 0001001001100001000011110010010110011111011000000000 While not nearly as efficient and easy to read as our alphabetic characters, it works! If you know the encoding, then you can read the information. What if we wanted to encode not just twelve letters but the entire alphabet? This would require twenty-six distinct binary strings. This range can be covered by a string of five 1s and 0s because this provides thirty-two possibilities, six more than are needed: 2 x 2 x 2 x 2 x 2 = 2⁵ = 32 1 This pronounceable string of letters is ordered by approximate letter frequencies in typical English text descending —E is by far the most frequently used letter.
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