algorithm - Understanding Skiena's description of "Hashing and Strings" -

The following paragraphs in the book "Algorithm Design Manual" by Skienna 3.7 hashing and are present at the top Strings < / Strong>

Let's come to the size of the alphabet, on which the string S is written. Let's construct four (C) a function that maps each alphabet to a unique integer from 0 to α-1.

The "alphabet size" in the above paragraphs? Are not all sizes (A-Z) the same size? Apart from this, how can string S be written on alphabet α? Are not putting together to create letter string?

The alphabet size should be α, the total number of symbols can be used for the string. Depending on the situation, the characters may vary. For example, binary numbers can be represented using the alphabet {0}} (α = 2), a Latin cumiz letter {a, ..., z} (α = 26) or symbols to represent numbers in hexadecimal using code> (0, 0, ..., 9, A, ..., F} (α = 16).